Comprehensive Physiology Wiley Online Library

Regulation of Extramuscular Fuel Sources During Exercise

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Abstract

The sections in this article are:

1 Fuel Requirements of the Working Muscle
1.1 Effect of Exercise Duration
1.2 Effect of Exercise Intensity
2 Exercise Responses of Hormones and Nerves Involved in Acute Metabolic Regulation
2.1 Insulin Response
2.2 Glucagon Response
2.3 Catecholamine Responses
3 Extramuscular Fuel Sources
4 NEFA Mobilization from Adipose Tissue
4.1 Basic Mechanisms that Influence NEFA Availability
4.2 Regulatory Factors
5 Hepatic Glucose Production
5.1 Exercise Response
5.2 Regulation by the Endocrine Pancreas
5.3 Role of Epinephrine
5.4 Role of Sympathetic Nerve Activity and Norepinephrine
5.5 Role of Cortisol
5.6 Regulation during High‐Intensity Exercise
6 Hepatic Fat Metabolism: Oxidation and Triglyceride Synthesis
6.1 Regulation of Ketogenesis
6.2 Triglyceride Synthesis
7 Splanchnic Bed Amino Acid Metabolism
7.1 Protein Breakdown
7.2 Amino Acids as a Carbon Source for Gluconeogenesis and Oxidation
7.3 Uptake of Nitrogenous Compounds by the Splanchnic Bed
7.4 Fate of Nitrogenous Compounds in the Liver
8 Gastrointestinal Tract as a Source of Glucose: Effect of Carbohydrate Ingestion
8.1 Importance
8.2 Determinants of the Metabolic Availability of Ingested Carbohydrates
8.3 Effect of Carbohydrate Ingestion on Endogenous Substrates
9 Training‐Induced Adaptations in Extramuscular Fuel Mobilization
9.1 Endocrine Adaptations to Physical Training
9.2 Adaptations of Extramuscular Fuel Sources to Physical Training
10 Summary
Figure 1. Figure 1.

The effect of the absolute exercise intensity (expressed as O2 uptake) on limb glucose uptake (A) and hepatic glycogenolysis and gluconeogenesis (B) in untrained subjects. The increase in limb glucose uptake and hepatic glucose production per increase in work intensity is greater at higher work rates. The increase in hepatic glucose production is due strictly to an increase in hepatic glycogenolysis (see HEPATIC GLUCOSE PRODUCTION). All measurements were made at 40 min of exercise.

Modified from the data of Wahren et al.
Figure 2. Figure 2.

Mechanisms that have been proposed to control the secretion of hormones involved in acute metabolic regulation and the activity of sympathetic nerves during exercise. Glucagon and insulin are secreted from the pancreas into the portal vein after which a percentage is extracted by the liver before reaching the systemic circulation. Sympathetic nerve activity is increased to specific target organs where norepinephrine is released into the synaptic cleft. Norepinephrine levels in the blood represent mainly that which escapes reuptake and spills over from the synaptic cleft.

Figure 3. Figure 3.

Pathways involved in the regulation of NEFA mobilization and availability to working muscle. Substrate cycling occurs due to concurrent lipolysis in adipocytes and re‐esterification in liver (see HEPATIC FAT METABOLISM: OXIDATION AND TRIGLYCERIDE SYNTHESIS) and adipocytes. These cycles increase the sensitivity of NEFA fluxes to regulatory factors. TG refers to triglycerides.

Adapted from Wolfe and George
Figure 4. Figure 4.

Gluconeogenic regulation during exercise. Gluconeogenesis is increased during exercise as accelerated rates of protein degradation, lipolysis, and glycolysis lead to increased rates of amino acid, glycerol, lactate, and pyruvate production and subsequent delivery to the liver. The hepatic extraction of gluconeogenic precursors is enhanced by exercise, as is the efficiency of intrahepatic conversion of precursors into glucose. The importance of each of these regulatory sites is determined by the intensity and duration of exercise and the absorptive state of the subject.

Modified from Cherrington
Figure 5. Figure 5.

Schematic representation of the minimal glycogenolytic and maximal gluconeogenic contributions to total glucose production during rest, exercise, and recovery. These responses are based on studies in the overnight‐fasted dog .

From Wasserman and Cherrington
Figure 6. Figure 6.

Role of the exercise‐induced increase in glucagon in gluconeogenic regulation. Effect of exercise alone (shaded area), exercise with somatostatin + simulated glucagon and insulin (solid line) and somatostatin + basal glucagon and simulated insulin (dashed line) on (A) gluconeogenic conversion from alanine; (B) intrahepatic gluconeogenic efficiency from alanine; and (C) hepatic fractional alanine extraction. The exercise‐induced increment in glucagon increases gluconeogenesis by stimulating the gluconeogenic precursor extraction by the liver and channeling into glucose within the liver. Data are mean ± SE.

Modified from Wasserman et al.
Figure 7. Figure 7.

Schematic representation of the rise in glucose production during moderate‐intensity exercise and the impact of the fall in insulin and rise in glucagon and the role of the increase in epinephrine on this response.

Modified from Wasserman and Cherrington
Figure 8. Figure 8.

Proposed pathways for amino acid metabolism in the splanchnic bed. Amino acids, primarily alanine and glutamine, are released by working muscle. Glutamine (GLN) is deaminated in the gastrointestinal tract forming glutamate (GLT), which is released or oxidized. Amino acids are released from the gastrointestinal tract as a result of proteolysis. The liver takes up amino acids where they are converted into glucose, oxidized, or incorporated into protein. Only the branched chain amino acids (leucine, isoleucine, valine) are consistently released from the splanchnic bed in a net sense. Nitrogen released during metabolism of amino acids may be converted to urea.

Figure 9. Figure 9.

Rate of appearance of plasma glucose at rest and during exercise before (closed circles) and after 10 days (open circles) and 12 weeks (open squares) of endurance training. Subjects were exercised at 60% of their pretraining maximum oxygen uptakes. Significantly different than before training (P<0.05). Significantly different than before training (P<0.001).

Modified from Mendenhall et al.
Figure 10. Figure 10.

Summary of hormones and nerves involved in the regulation of glucose from the liver and NEFA from adipose tissue during moderate‐intensity exercise.



Figure 1.

The effect of the absolute exercise intensity (expressed as O2 uptake) on limb glucose uptake (A) and hepatic glycogenolysis and gluconeogenesis (B) in untrained subjects. The increase in limb glucose uptake and hepatic glucose production per increase in work intensity is greater at higher work rates. The increase in hepatic glucose production is due strictly to an increase in hepatic glycogenolysis (see HEPATIC GLUCOSE PRODUCTION). All measurements were made at 40 min of exercise.

Modified from the data of Wahren et al.


Figure 2.

Mechanisms that have been proposed to control the secretion of hormones involved in acute metabolic regulation and the activity of sympathetic nerves during exercise. Glucagon and insulin are secreted from the pancreas into the portal vein after which a percentage is extracted by the liver before reaching the systemic circulation. Sympathetic nerve activity is increased to specific target organs where norepinephrine is released into the synaptic cleft. Norepinephrine levels in the blood represent mainly that which escapes reuptake and spills over from the synaptic cleft.



Figure 3.

Pathways involved in the regulation of NEFA mobilization and availability to working muscle. Substrate cycling occurs due to concurrent lipolysis in adipocytes and re‐esterification in liver (see HEPATIC FAT METABOLISM: OXIDATION AND TRIGLYCERIDE SYNTHESIS) and adipocytes. These cycles increase the sensitivity of NEFA fluxes to regulatory factors. TG refers to triglycerides.

Adapted from Wolfe and George


Figure 4.

Gluconeogenic regulation during exercise. Gluconeogenesis is increased during exercise as accelerated rates of protein degradation, lipolysis, and glycolysis lead to increased rates of amino acid, glycerol, lactate, and pyruvate production and subsequent delivery to the liver. The hepatic extraction of gluconeogenic precursors is enhanced by exercise, as is the efficiency of intrahepatic conversion of precursors into glucose. The importance of each of these regulatory sites is determined by the intensity and duration of exercise and the absorptive state of the subject.

Modified from Cherrington


Figure 5.

Schematic representation of the minimal glycogenolytic and maximal gluconeogenic contributions to total glucose production during rest, exercise, and recovery. These responses are based on studies in the overnight‐fasted dog .

From Wasserman and Cherrington


Figure 6.

Role of the exercise‐induced increase in glucagon in gluconeogenic regulation. Effect of exercise alone (shaded area), exercise with somatostatin + simulated glucagon and insulin (solid line) and somatostatin + basal glucagon and simulated insulin (dashed line) on (A) gluconeogenic conversion from alanine; (B) intrahepatic gluconeogenic efficiency from alanine; and (C) hepatic fractional alanine extraction. The exercise‐induced increment in glucagon increases gluconeogenesis by stimulating the gluconeogenic precursor extraction by the liver and channeling into glucose within the liver. Data are mean ± SE.

Modified from Wasserman et al.


Figure 7.

Schematic representation of the rise in glucose production during moderate‐intensity exercise and the impact of the fall in insulin and rise in glucagon and the role of the increase in epinephrine on this response.

Modified from Wasserman and Cherrington


Figure 8.

Proposed pathways for amino acid metabolism in the splanchnic bed. Amino acids, primarily alanine and glutamine, are released by working muscle. Glutamine (GLN) is deaminated in the gastrointestinal tract forming glutamate (GLT), which is released or oxidized. Amino acids are released from the gastrointestinal tract as a result of proteolysis. The liver takes up amino acids where they are converted into glucose, oxidized, or incorporated into protein. Only the branched chain amino acids (leucine, isoleucine, valine) are consistently released from the splanchnic bed in a net sense. Nitrogen released during metabolism of amino acids may be converted to urea.



Figure 9.

Rate of appearance of plasma glucose at rest and during exercise before (closed circles) and after 10 days (open circles) and 12 weeks (open squares) of endurance training. Subjects were exercised at 60% of their pretraining maximum oxygen uptakes. Significantly different than before training (P<0.05). Significantly different than before training (P<0.001).

Modified from Mendenhall et al.


Figure 10.

Summary of hormones and nerves involved in the regulation of glucose from the liver and NEFA from adipose tissue during moderate‐intensity exercise.

References
 1. Abumrad, N. N., P. E. Williams, M. Frexes‐Steed, R. Geer, P. Flakoll, E. Cersosimo, L. L. Brown, I. Melki, N. Bulus, H. Hourani, M. Hubbard, and F. Ghishan. Inter‐organ metabolism of amino acids in vivo. Diabetes Metab. Rev. 5: 213–226, 1989.
 2. Adopo, E., F. Peronnet, D. Masicotte, G. R. Brisson, and C. Hillaire‐Marccl. Respective of oxidation of exogenous glucose and fructose given in the same drink during exercise. J. Appl. Physiol. 76: 1014–1019, 1994.
 3. Ahlborg, G., and P. Felig. Influence of glucose ingestion on fuel‐hormone response during prolonged exercise. J. Appl. Physiol. 41: 683–688, 1976.
 4. Ahlborg, G., and P. Felig. Substrate utilization during prolonged exercise preceded by ingestion of glucose. Am. J. Physiol. 233 (Endocrinol. Metab. Gastrointest. Physiol. 2): E188–E194, 1977.
 5. Ahlborg, G., and P. Felig. Lactate and glucose exchange across the forearm, legs, and splanchnic bed during after prolonged leg exercise. J. Clin. Invest. 69: 45–54, 1982.
 6. Ahlborg, G., P. Felig, L. Hagenfeldt, R. Hendler, and J. Wahren. Substrate turnover during prolonged exercise in man. J. Clin. Invest. 53: 1080–1090, 1974.
 7. Arnall, D. A., J. C. Marker, R. K. Conlee, and W. W. Winder. Effect of infusing epinephrine on liver and muscle glycogenolysis during exercise. Am. J. Physiol. 250 (Endocrinol. Metab. 13): E641–E649, 1986.
 8. Arner, P., E. Kriegholm, P. Engfeldt, and J. Bolinder. Adrenergic regulation of lipolysis in situ at rest and during exercise. J. Clin. Invest. 85: 893–898, 1990.
 9. Arogyasami, J., T. L. Sellers, J. P. Jones, C. Duan, and W. W. Winder. Insulin‐induced hypoglycemia in fed and fasted exercising rats. J. Appl. Physiol. 72: 1992–1998, 1989.
 10. Askew, E. W., A. L. Hecker, V. G. Coppes, and F. B. Stifel. Cyclic AMP metabolism in adipose tissue of exercise‐trained rats. J. Lipid. Res. 19: 729–736, 1978.
 11. Askew, E. W., R. L. Huston, C. G. Plopper, and A. L. Hecker. Adipose tissue cellularity and lipolysis: response to exercise and Cortisol treatment. J. Clin. Invest. 56: 521–529, 1975.
 12. Balon, T. W., A. Zorzano, J. L. Treadway, M. N. Goodman, and N. B. Ruderman. Effect of insulin on protein synthesis and degradation in skeletal muscle after exercise. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E92–E97, 1990.
 13. Barakat, H. A., G. J. Kasperek, and G. L. Dohm. Progressive changes in fatty acid metabolism in rat liver and muscle during exercise. Biochem. Med. 29: 298–306, 1983.
 14. Barclay, G. R., and L. A. Turnberg. Effect of moderate exercise on salt and water transport in the human jejunum. Gut 29: 816–820, 1988.
 15. Begum, N., R. L. Terjung, H. M. Tepperman, and J. Tepperman. Effect of acute exercise on insulin generation of pyruvate dehydrogenase activator by rat liver and rat adipocyte plasma membranes. Diabetes 35: 785–790, 1986.
 16. Benade, A. J. S., C. H. Wyndham, C. R. Jansen, G. G. Rogers, and E. J. P. Debruin. Plasma insulin and carbohydrate metabolism after sucrose ingestion during rest and prolonged exercise. Pflugers Arch. 342: 207–218, 1973.
 17. Bennet, W. M., and M. W. Haymond. Plasma pool source for fibrinogen synthesis in postabsorptive conscious dogs. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E581–E587, 1991.
 18. Berger, C. M., P. J. Sharis, D. P. Bracy, D. B. Lacy, and D. H. Wasserman. Sensitivity of the exercise‐induced increments in hepatic glycogenolysis and gluconeogenesis to glucose supply and demand. Am. J. Physiol. 267 (Endocrinol. Metab. 30): E411–E421, 1994.
 19. Berger, M., P. Berchtold, H. J. Kuppers, H. Drost, H. K. Kley, W. A. Muller, W. Wiegelmann, H. Zimmerman‐Telschow, F. A. Gries, H. L. Kruskemper, and H. Zimmerman. Metabolic and hormonal effects of muscular exercise in juvenile type diabetics. Diabetologia 13: 355–365, 1977.
 20. Bergstrom, J., L. Hermansen, E. Hultman, and B. Saltin. Diet, muscle glycogen and physical performance. Acta Physiol. Scand. 71: 140–150, 1967.
 21. Bjorkman, O., P. Miles, D. H. Wasserman, L. Lickley, and M. Vranic. Muscle glucose uptake during exercise in total insulin deficiency: No effect of beta‐adrenergic blockade. J. Clin. Invest. 81: 1759–1767, 1988.
 22. Bjorkman, O., K. Sahlin, L. Hagenfeldt, and J. Wahren. Influence of glucose and fructose ingestion on the capacity for long‐term exercise in well‐trained men. Clin. Physiol. 4: 483–494, 1984.
 23. Bjorntorp, P. The effect of lactic acid on adipose tissue metabolism in vitro. Acta Med. Scand. 178: 253–258, 1965.
 24. Bjorntorp, P., K. Dejounge, L. Sjostrom, and L. Sullivan. The effect of physical training on insulin production in obesity. Metabolism 19: 631–638, 1970.
 25. Bobyleva‐Guarriero, V., and H. Lardy. The effect of different types of physical exercise on glucose and citrulline synthesis in isolated rat liver parenchymal cells. FEBS Lett. 194: 56–59, 1986.
 26. Bolinder, J., L. Kager, J. Ostman, and P. Arner. Differences at the receptor and post‐receptor levels between human omental and subcutaneous adipose tissue in the action of insulin on lipolysis. Diabetes 32: 117–129, 1983.
 27. Bonen, A., P. A. Clune, and M. H. Tan. Chronic exercise increases insulin binding in muscles but not liver. Am. J. Physiol. 251 (Endocrinol. Metab. 14): E196–E203, 1986.
 28. Boyd, A. E., S. R. Giamber, M. Mager, and H. E. Lebovitz. Lactate inhibition of lipolysis in exercising man. Metabolism 23: 531–542, 1974.
 29. Brenner, W., T. R. Hendrix, and P. R. McHugh. Regulation of the gastric emptying of glucose. Gastroenterology 85: 76–82, 1983.
 30. Brockman, R. P. Effect of somatostatin on plasma glucagon and insulin, and glucose turnover in exercising sheep. J. Appl. Physiol. 47: 273–278, 1979.
 31. Brooks, B., J. R. S. Arch, and E. A. Newsholme. Effects of hormones on the rate of the triacylglycerol/fatty acid substrate cycle in adipocytes and and epididymal fat pads. FEBS Lett. 146: 327–330, 1982.
 32. Brooks, G. A., and C. M. Donovan. Effect of endurance training on glucose kinetics during exercise. Am. J. Physiol. 244 (Endocrinol. Metab. 7): E505–E512, 1983.
 33. Brooks, G. A., E. E. Wolfel, B. M. Groves, P. R. Bender, G. E. Butterfield, A. Cymerman, R. S. Mazzeo, J. R. Sutton, R. R. Wolfe, and J. T. Reeves. Muscle accounts for glucose disposal but not blood lactate appearance during exercise after acclimatization to 4,300 m. J. Appl. Physiol. 72: 2435–2445, 1992.
 34. Bukowiecki, L., J. Lupien, N. Follea, D. Paradis, D. Richard, and J. Leblanc. Mechanism of enhanced lipolysis in adipose tissue of exercise‐trained rat. Am. J. Physiol. 239 (Endocrinol. Metab. 2): E422–E429, 1980.
 35. Buttrose, M., D. McKellar, and T. C. Welbourne. Gut‐liver interaction in glutamine homeostasis: portal ammonia role in uptake and metabolism. Am. J. Physiol. 252 (Endocrinol. Metab. 15): E746–E750, 1987.
 36. Calles, J., J. J. Cunningham, L. Nelson, N. Brown, E. Nadel, R. S. Sherwin, and P. Felig. Glucose turnover during recovery from intensive exercise. Diabetes 32: 734–738, 1983.
 37. Calles‐Escandon, J., J. J. Cunningham, P. Snyder, R. Jacob, G. Huszar, J. Loke, and P. Felig. Influence of exercise on urea, creatinine, and 3‐methylhistidine excretion in normal human subjects. Am. J. Physiol. 246 (Endocrinol. Metab. 15): E334–E339, 1984.
 38. Cammack, J., N. W. Read, P. A. Cann, B. Greenwood, and A. M. Holgate. Effect of prolonged exercise on the pasage of a solid meal through the stomach and small intestine. Gut 23: 957–961, 1982.
 39. Campbell, J. M. H., G. O. Mitchell, and A. T. W. Powell. The influence of exercise on digestion. Guy's Hosp. Rep. 78: 279–293, 1928.
 40. Carlson, K. I., J. C. Marker, D. A. Arnall, M. L. Terry, H. T. Yang, L. G. Lindsay, M. E. Bracken, and W. W. Winder. Epinephrine is unessential for stimulation of liver glycogenolysis during exercise. J. Appl. Physiol. 58: 544–548, 1985.
 41. Carlson, L. A., and F. Mossfeldt. Acute effects of prolonged, heavy exercise on the concentration of plasma lipids and lipoproteins in man. Acta Physiol. Scand. 62: 51–59, 1964.
 42. Carraro, F., W. H. Hartl, C. A. Stuart, D. K. Layman, F. Jahoor, and R. R. Wolfe. Whole body and plasma protein synthesis in exercise and recovery in human subjects. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E821–E831, 1990.
 43. Carraro, F., T. D. Kimbrough, and R. R. Wolfe. Urea kinetics in humans at two levels of exercise intensity. J. Appl. Physiol. 75: 1180–1185, 1993.
 44. Carraro, F., A. Naldini, J. M. Weber, and R. R. Wolfe. Alanine kinetics in humans during low‐intensity exercise. Med. Sci. Sports Exerc. 26: 348–353, 1994.
 45. Carraro, F., C. A. Stuart, W. H. Hartl, J. Rosenblatt, and R. R. Wolfe. Effect of exercise and recovery on muscle protein synthesis in human subjects. Am. J. Physiol. 259 (Endocrinol. Metab. 22): E470–E476, 1990.
 46. Cersosimo, E., P. E. Williams, R. J. Geer, T. Lairmore, F. Ghishan, and N. N. Abumrad. Importance of ammonium ions in regulating hepatic glutamine synthesis during fasting. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E514–E519, 1989.
 47. Cherrington, A. D. Gluconeogenesis: its regulation by glucagon and insulin. In: Diabetes Mellitus, edited by M. Brownlee, New York: Garland, 1981.
 48. Cherrington, A. D., H. Fuchs, R. W. Stevenson, P. E. Williams, K. G. M. M. Alberti, and K. E. Steiner. Effect of epinephrine on glycogenolysis and gluconeogenesis in conscious overnight‐fasted dogs. Am. J. Physiol. 247 (Endocrinol. Metab. 10): E137–E144, 1984.
 49. Cherrington, A. D., W. W. Lacy, and J. L. Chiasson. Effect of glucagon on glucose production during insulin deficiency in the dog. J. Clin. Invest. 62: 664–677, 1978.
 50. Cherrington, A. D., J. E. Liljenquist, G. I. Shulman, P. E. Williams, and W. W. Lacy. Importance of hypoglycemia‐induced glucose production during isolated glucagon deficiency. Am. J. Physiol. 236 (Endocrinol. Metab. Gastroin‐test. Physiol. 5): E263–E271, 1979.
 51. Chisholm, D. J., A. B. Jenkins, D. E. James, and E. W. Kraegan. The effect of hyperinsulinemia on glucose homeostasis during moderate exercise in man. Diabetes 31: 603–608, 1982.
 52. Christensen, N. J., and H. Galbo. Sympathetic nerve activity during exercise. Annu. Rev. Physiol. 45: 139–153, 1983.
 53. Coggan, A. R., and E. F. Coyle. Reversal of fatigue during prolonged exercise by carbohydrate infusion or ingestion. J. Appl. Physiol. 63: 2388–2395, 1987.
 54. Coggan, A. R., and E. F. Coyle. Metabolism and performance following carbohydrate ingestion late in exercise. Med. Sci. Sports Exerc. 21: 59–65, 1989.
 55. Coggan, A. R., and E. F. Coyle. Carbohyrate ingestion during prolonged exercise: effects on metabolism and performance. Exerc. Sports Sci. Rev. 19: 1–40, 1991.
 56. Coggan, A. R., W. M. Kohrt, R. J. Spina, D. M. Bier, and J. O. Holloszy. Endurance training decreases plasma glucose turnover and oxidation during moderate intensity exercise in men. J. Appl. Physiol. 68: 990–996, 1990.
 57. Cooper, D. M., T. J. Barstow, A. Bergner, and W. P. Lee. Blood glucose turnover during high‐ and low‐intensity exercise. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E405–E412, 1989.
 58. Cooper, D. M., D. H. Wasserman, M. Vranic, and K. Wasserman. Glucose turnover in response to exercise during high‐ and low‐FiO2 breathing in humans. Am. J. Physiol. 14 (Endocrinol. Metab. 14): E209–E214, 1986.
 59. Cordain, L., R. W. Latin, and J. J. Behnke. The effects of an aerobic running programme on bowel transit time. J. Sports Med. 26: 101–104, 1986.
 60. Costill, D. L., A. Bennett, G. Branam, and D. Eddy. Glucose ingestion at rest and during prolonged exercise. J. Appl. Physiol. 34: 764–769, 1973.
 61. Costill, D. L., E. Coyle, G. P. Dalsky, W. Evans, W. Fink, and D. Hoopes. Effects of elevated plasma FFA and insulin on muscle glycogen usage during exercise. J. Appl. Physiol. 43: 695–699, 1977.
 62. Costill, D. L., W. F. Kammer, and A. Fisher. Fluid ingestion during distance running. Arch. Environ. Health 21: 520–525, 1970.
 63. Costill, D. L., and B. Saltin. Factors limiting gastric emptying. J. Appl. Physiol. 37: 679–683, 1974.
 64. Coyle, E. F., A. R. Coggin, M. K. Hemmert, and J. L. Ivy. Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate. J. Appl. Physiol. 61: 165–172, 1986.
 65. Craig, B. W., G. T. Hammons, S. M. Garthwaite, L. Jarett, and J. O. Holloszy. Adaptation of fat cells to exercise: response of glucose uptake and oxidation to insulin. J. Appl. Physiol. 51: 1500–1506, 1981.
 66. Crampes, F., M. Beauville, D. Riviere, and M. Garrigues. Effect of physical training in humans on the response of isolated fat cells to epinephrine. J. Appl. Physiol. 61: 25–29, 1986.
 67. Danforth, W. H. Glycogen synthetase activity in skeletal muscle: interconversion of two forms and control of glycogen synthesis. J. Biol. Chem. 2: 588–593, 1965.
 68. Decombaz, J., P. Reinhardt, K. Anantharaman, G. V. Glutz, and J. R. Poortsman. Biochemical changes in a 100 km run: free amino acids, urea, and creatinine. Eur. J. Appl. Physiol. 41: 61–72, 1979.
 69. Decombaz, J., D. Sartori, M. J. Arnaud, A. L. Thelin, P. Schurch, and H. Howald. Oxidation of metabolic effects of glucose ingested before exercise. Int. J. Sports Med. 6: 282–286, 1985.
 70. Deibert, D. C., and R. A. Defronzo. Epinephrine‐induced insulin resistance in man. J. Clin. Invest. 65: 717–721, 1980.
 71. Dill, D. B., H. T. Edwards, and J. H. Talbott. Studies in muscular activity. VII. Factors limiting the capacity to work. J. Physiol. 77: 49–62, 1932.
 72. Dohm, G. L., R. G. Israel, R. L. Breedlove, R. T. Williams, and E. W. Askew. Biphasic changes in 3‐methylhistidine excretion in humans after exercise. Am. J. Physiol. 248 (Endocrinol. Metab. 11): E588–E592, 1985.
 73. Dohm, G. L., G. J. Kasperek, and H. A. Barakat. Time course of changes in gluconeogenic enzyme activities during exercise and recovery. Am. J. Physiol. 249 (Endocrinol. Metab. 12): E6–E11, 1985.
 74. Dohm, G. L., and E. A. Newsholme. Metabolic control of hepatic gluconeogenesis during exercise. Biochem. J. 212: 633–639, 1983.
 75. Dohm, G. L., S. N. Pennington, and H. Barakat. Effect of exercise training on adenylyl cyclase and phosphodiesterase in skeletal muscle, heart, and liver. Biochem. Med. 16: 138–142, 1976.
 76. Dohm, G. R., G. J. Kasperek, E. B. Tapscott, and G. R. Beecher. Effect of exercise on synthesis and degradation of muscle protein. Biochem. J. 188: 255–262, 1985.
 77. Donovan, C. M., and K. D. Sumida. Training improves glucose homeostasis in rats during exercise via glucose production. Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol. 27): R770–R776, 1990.
 78. Erikson, M. A., R. J. Schwarzkopf, and R. D. McKenzie. Effects of caffeine, fructose, and glucose ingestion on muscle glycogen utilization during exercise. Med. Sci. Sports Exerc. 19: 579–583, 1987.
 79. Eriksson, L. S., S. Broberg, O. Bjorkman, and J. Wahren. Ammonia metabolism during exercise in man. Clin. Physiol. 5: 325–336, 1985.
 80. Euler, U. S. V. Adrenal Medullary Secretion and its Neural Control. New York: Academic Press, 1967.
 81. Evans, D. F., G. E. Foster, and J. D. Hardcastle. Does exercise affect small bowel motility in man? Gut 24: A1012, 1989.
 82. Exton, J. H., and S. C. Harper. Role of cyclic‐AMP in the actions of the catecholamines in hepatic carbohydrate metabolism. Adv. Cyclic Nucleotide Res. 5: 519–532, 1975.
 83. Feldman, M., and J. V. Nixon. Effect of exercise on postprandial gastic secretion and emptying in humans. J. Appl. Physiol. 53: 851–854, 1982.
 84. Felig, P., and J. Wahren. Amino acid metabolism in exercising man. J. Clin. Invest. 50: 2703–2711, 1971.
 85. Fery, F., and E. O. Balasse. Response of ketone body metabolism to exercise during transition from post‐absorptive to fasted state. Am. J. Physiol. 250 (Endocrinol. Metab. 13): E495–E501, 1986.
 86. Fielding, R. A., D. L. Costill, W. J. Fink, D. S. King, M. Hargreaves, and J. E. Kovaleski. Effect of carbohydrate feeding frequency and dosage on muscle glycogen use during exercise. Med. Sci. Sports Exerc. 17: 472–476, 1985.
 87. Fordtran, J. S., and B. Saltin. Gastric emptying and intestinal absorption during prolonged severe exercise. J. Appl. Physiol. 23: 555–559, 1967.
 88. Foster, C., D. L. Costill, and W. J. Fink. Effects of pre‐exercise feedings on endurance performance. Med. Sci. Sports Exerc. 11: 1–5, 1979.
 89. Foster, C., D. L. Costill, and W. J. Fink. Gastric emptying characteristics of glucose and glucose polymer solution. Med. Sci. Sports Exerc. 51: 299–305, 1980.
 90. Franckson, J. R. M., R. Vanroux, R. Leclercq, H. Brunengraber, and H. A. Ooms. Labelled insulin catabolism and pancreatic responsiveness during long‐term exercise in man. Horm. Metab. Res. 3: 366–373, 1979.
 91. Friedman, J. E. Role of glucocorticoids in activation of hepatic PEPCK gene transcription during exercise. Am. J. Physiol. 266 (Endocrinol. Metab. 29): E560–E566, 1994.
 92. Galbo, H. Hormonal Adaptations to Exercise. New York: Thieme‐Stratton, Inc., 1983.
 93. Galbo, H., N. J. Christensen, and J. J. Hoist. Catecholamines and pancreatic hormones during autonomic blockade in exercising man. Acta Physiol. Scand. 101: 428–437, 1977.
 94. Galbo, H., N. J. Christensen, and J. J. Hoist. Glucose‐induced decrease in glucagon and epinephrine responses to exercise in man. J. Appl. Physiol. 42: 525–530, 1977.
 95. Galbo, H., N. J. Christensen, K. J. Mikines, B. Sonne, J. Hilsted, C. Hagen, and J. Fahrenkrug. The effect of fasting on the hormonal response to graded exercise. J. Clin. Endocrinol. Metab. 52: 1106–1112, 1981.
 96. Galbo, H., C. J. Hedeskov, K. Capito, and J. Vinten. The effect of physical training on insulin secretion of rat pancreatic islets. Acta Physiol. Scand. 111: 75–79, 1981.
 97. Galbo, H., J. J. Hoist, and N. J. Christensen. Glucagon and plasma catecholamine responses to graded and prolonged exercise in man. J. Appl. Physiol. 38: 70–76, 1975.
 98. Galbo, H., J. J. Hoist, and N. J. Christensen. The effect of different diets and of insulin on the hormonal response to prolonged exercise in man. Acta Physiol. Scand. 107: 19–32, 1979.
 99. Garceau, D., N. Yamaguchi, R. Goyer, and F. Guitard. Correlation between endogenous noradrenaline and glucose released from the liver upon hepatic sympathetic nerve stimulation in anesthetized dogs. Can. J. Physiol. Pharmacol. 62: 1086–1091, 1984.
 100. Geer, R. J., P. E. Williams, T. Lairmore, and N. N. Abumrad. Glucagon: an important stimulator of gut and hepatic glutamine metabolism. Surg. Forum 38: 27–29, 1987.
 101. Girardier, L., J. Seydoux, M. Berger, and A. Veicsteinas. Selective pancreatic nerve section. An investigation of neural control of glucagon release in the conscious unrestrained dog. J. Physiol. (Paris) 74: 731–735, 1978.
 102. Goldstein, R. E., G. W. Reed, D. H. Wasserman, P. E. Williams, D. B. Lacy, R. Buckspan, N. N. Abumrad, and A. D. Cherrington. The effects of acute elevations in plasma Cortisol on alanine metabolism in the conscious dog. Metabolism 41: 1295–1303, 1992.
 103. Gollnick, P. D., R. G. Soule, A. W. Taylor, C. Williams, and C. D. Ianuzzo. Exercise‐induced glycogenolysis and lipol‐ysis in the rat: hormonal influences. Am. J. Physiol. 219: 729–733, 1970.
 104. Greenway, C. V., and R. D. Stark. Hepatic vascular bed. Physiol. Rev. 51: 23–65, 1971.
 105. Gregg, S. G., M. Kern, and G. A. Brooks. Acute anemia results in an increased glucose dependence during sustained exercise. J. Appl. Physiol. 66: 1874–1880, 1989.
 106. Gue, M., T. Peeters, I. Depoortere, G. Vantrappen, and L. Bueno. Stress induced changes in gastric emptying motilitly and plasma gut hormone levels in dogs. Gastroenterology 97: 1101–1107, 1989.
 107. Guezennec, C. Y., P. Satapin, F. Duforez, D. Merino, F. Peronnet, and J. Koziet. Oxidation of corn starch, glucose, and fructose ingested before exercise. Med. Sci. Sports Exerc. 21: 45–50, 1989.
 108. Hagg, S. A., E. L. Morse, and S. A. Adibi. Effect of exercise on rates of oxidation, turnover, and plasma clearance of leucine in human subjects. Am. J. Physiol. 242 (Endocrinol. Metab. 5): E407–E410, 1982.
 109. Haralambie, G., and L. Senser. Metabolic changes in man during long‐distance swimming. Eur. J. Appl. Physiol. 43: 115–125, 1980.
 110. Harber, V. J., and J. R. Sutton. Endorphins and exercise. Sports Med. 1: 154–174, 1984.
 111. Hargreaves, M., and C. A. Briggs. Effect of carbohydrate ingestion on exercise metabolism. J. Appl. Physiol. 65: 1553–1555, 1988.
 112. Hargreaves, M., D. Costill, A. Coggan, W. J. Fink, and D. Nishibata. Effect of carbohydrate feeding on muscle glycogen utilization and exercise performance. Med. Sci. Sports Exerc. 16: 219–222, 1984.
 113. Hartmann, H., K. Beckh, and K. Jungermann. Direct control of glycogen metabolism in the perfused rat liver by the sympathetic innervation. Eur. J. Biochem. 123: 521–526, 1982.
 114. Harvey, W. D., G. R. Faloona, and R. H. Unger. The effect of adrenergic blockade on exercise‐induced hyperglucago‐nemia. Endocrinology 94: 1254–1258, 1974.
 115. Haussinger, D., W. Gerok, and H. Sies. Regulation of flux through glutaminase and glutamine synthetase in isolated perfused rat liver. Biochim. Biophys. Acta 755: 272–278, 1983.
 116. Hawley, J. A., S. C. Dennis, and T. D. Noakes. Oxidation of carbohydrate ingested during prolonged endurance exercise. Sports Med. 14: 27–42, 1992.
 117. Hellebrandt, F. A., and R. H. Tepper. Studies on the influence of exercise on the digestive work of the stomach. II. Its effect on emptying time. Am. J. Physiol. 107: 355–363, 1934.
 118. Hems, D. A., and P. D. Whitton. Control of hepatic glycogenolysis. Physiol. Rev. 60: 1–50, 1980.
 119. Henderson, S. A., A. L. Black, and G. A. Brooks. Leucine turnover and oxidation in trained rats during exercise. Am. J. Physiol. 249 (Endocrinol. Metab. 12): E137–E144, 1985.
 120. Hermansen, L., E. Hultman, and B. Saltin. Muscle glycogen during prolonged severe exercise. Acta Physiol. Scand. 71: 129–139, 1967.
 121. Hilsted, J., H. Galbo, B. Sonne, T. Schwartz, J. Fahrenkrug, O. B. S. D. Muckadell, K. B. Launtsen, and B. Tronier. Gastroenteropancreatic hormonal changes during exercise. Am. J. Physiol. 239 (Gastrointest. Liver Physiol. 2): G136–G140, 1980.
 122. Hirsh, I. B., J. C. Marker, L. J. Smith, R. Spina, C. A. Parvin, J. O. Holloszy, and P. E. Cryer. Insulin and glucagon in the prevention of hypoglycemia during exercise in humans. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E695–E704, 1991.
 123. Hirshman, M. F., L. J. Wardzala, L. J. Goodyear, S. P. Fuller, E. D. Horton, and F. S. Horton. Exercise training increases the number of glucose transporters in rat adipose cells. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E520–E530, 1989.
 124. Hoelzer, D. R., G. P. Dalsky, W. E. Clutter, S. D. Shah, J. O. Holloszy, and P. E. Cryer. Glucoregulation during exercise: hypoglycemia is prevented by redundant gluco‐regulatory systems, sympathochromaffin activation, and changes in islet hormone secretion. J. Clin. Invest. 77: 212–221, 1986.
 125. Hoelzer, D. R., G. P. Dalsky, N. S. Schwartz, W. E. Clutter, S. D. Shah, J. O. Holloszy, and P. E. Cryer. Epinephrine is not critical to prevention of hypoglycemia during exercise in humans. Am. J. Physiol. 251 (Endocrinol. Metab. 14): E104–E110, 1986.
 126. Holloszy, J. O., and E. Coyle. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. J. Appl. Physiol. 56: 831–838, 1984.
 127. Hood, D. A., and R. L. Terjung. Leucine metabolism in perfused rat skeletal muscle during contractions. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E636–E647, 1987.
 128. Hourani, H., P. E. Williams, J. A. Morris, M. E. May, and N. N. Abumrad. Effect of insulin‐induced hypoglycemia on protein metabolism in vivo. Am. J. Physiol. 259 (Endocrinol. Metab. 22): E342–E350, 1990.
 129. Hunt, J. N., J. L. Smith, and C. L. Jiang. Effect of meal volume and energy density on the gastric emptying of carbohydrates. Gastroenterology 89: 1326–1330, 1985.
 130. Huston, R. L., P. C. Weiser, G. L. Dohm, E. W. Askew, and J. B. Boyd. Effect of training, exercise, and diet on muscle glycogenolysis and liver gluconeogenesis. Life Sci. 17: 369–376, 1975.
 131. Huttunen, J. K., and D. Steinberg. Activation and phosphorylation of purified adipose tissue hormonse‐sensitive lipase by cyclic AMP‐dependent protein kinase. Biochim. Biophys. Acta 239: 411–427, 1971.
 132. Huttunen, J. K., D. Steinberg, and S. E. Mayer. ATP‐de‐pendent and cyclic AMP‐dependent activation of rat adipose tissue lipase by protein kinase from rabbit skeletal muscle. Proc. Natl. Acad. Sci. U. S. A. 67: 290–295, 1970.
 133. Issekutz, B. Role of beta‐adrenergic receptors in mobilization of energy sources in exercising dogs. J. Appl. Physiol. 44: 869–876, 1978.
 134. Issekutz, B. The role of hypoinsulinemia in exercise metabolism. Diabetes 29: 629–635, 1980.
 135. Issekutz, B. Effects of glucose infusion on hepatic and muscle glycogenolysis in exercising dogs. Am. J. Physiol. 240 (Endocrinol. Metab. 3): E451–E457, 1981.
 136. Issekutz, B., W. A. S. Shaw, and T. B. Issekutz. Effect of lactate on FFA and glycerol turnover in resting and exercising dogs. J. Appl. Physiol. 39: 349–353, 1975.
 137. Issekutz, B., and M. Vranic. Significance of glucagon in the control of glucose production during exercise. Am. J. Physiol. 238 (Endocrinol. Metab. 1): E13–E20, 1980.
 138. Ivy, J. L., W. Miller, V. Dover, L. J. Goodyear, W. M. Sherman, S. Farrell, and H. Williams. Endurance improved by ingestion of a glucose polymer supplement. Med. Sci. Sports Exerc. 15: 466–471, 1983.
 139. Izawa, T., T. Komabayashi, T. Mochizuki, K. Suda, and M. Tsuboi. Enhanced coupling of adenylate cyclase to lipolysis in permeabilized adipocytes from trained rats. J. Appl. Physiol. 71: 23–29, 1991.
 140. Izawa, T., T. Komabayashi, M. Tsuboi, E. Koshimizu, and K. Suda. Augmentation of catecholamine‐stimulated [3H] GDP release in adipocyte membranes from exercise‐trained rats. Jpn. J. Physiol. 36: 1039–1045, 1986.
 141. James, D. E., K. M. Burleigh, E. W. Kraegen, and D. J. Chisholm. Effect of acute exercise and prolonged training on insulin response to intravenous glucose in vivo in rat. J. Appl. Physiol. 55: 1660–1664, 1983.
 142. James, D. E., E. W. Kraegen, and D. J. Chisholm. Effect of exercise training on in vivo insulin action in individual tissues of the rat. J. Clin. Invest. 76: 657–666, 1985.
 143. Jandrain, B. J., G. Krzentowski, F. Pirnay, F. Morosa, A. J. Scheen, and P. J. Lefebvre. Metabolic availability of glucose ingested 3 h before prolonged exercise in humans. Eur. J. Appl. Physiol. 56: 1314–1319, 1984.
 144. Jandrain, B. J., F. Pirnay, M. Lacroix, F. Morosa, A. J. Sheen, and P. J. Lefebvre. Effect of osmolality on availability of glucose ingested during prolonged exercise in humans. J. Appl. Physiol. 67: 76–92, 1989.
 145. Jarhult, J., and J. J. Hoist. The role of the adrenergic innervation to the pancreatic islets in the control of insulin release during exercise in man. Pflugers Arch. 383: 41–45, 1979.
 146. Jenkins, A. B., D. J. Chisholm, K. Y. Ho, and E. W. Kraegen. Exercise induced hepatic glucose output is precisely sensitive to the rate of systemic glucose supply. Metabolism 34: 431–434, 1985.
 147. Jenkins, A. B., S. M. Furler, D. J. Chisholm, and E. W. Kraegen. Regulation of hepatic glucose output during exercise by circulating glucose and insulin in humans. Am. J. Physiol. 250 (Regulatory Integrative Comp. Physiol. 19): R411–R417, 1986.
 148. Jensen, M. D., M. W. Haymond, R. A. Rizza, P. E. Oyer, and J. M. Miles. Influence of body fat distribution on free fatty acid metabolism in obesity. J. Clin. Invest. 83: 1168–1173, 1989.
 149. Ji, L. L., D. F. Lennon, R. G. Kochan, F. J. Nagle, and H. A. Lardy. Enzymatic adaptation to physical training under β‐blockade in the rat. Evidence of a β2‐adrenergic mechanism in skeletal muscle. J. Clin. Invest. 78: 771–778, 1986.
 150. John‐Adler, H. B., R. M. McAllister, and R. L. Terjung. Reduced running endurance in gluconeogenesis‐inhibited rats. Am. J. Physiol. 251 (Regulatory Integrative Comp. Physiol. 14): R137–R142, 1986.
 151. Jones, N. L., G. J. F. Heigenhauser, A. Kuksis, C. G. Matsos, J. R. Sutton, and C. J. Toews. Fat metabolism during heavy exercise. Clin. Sci. 59: 469–478, 1980.
 152. Juhlin‐Dannfeldt, A., G. Ahlborg, L. Hagenfeldt, L. Jor‐feldt, and P. Felig. Influence of ethanol on splanchnic and skeletal muscle substrate turnover during prolonged exercise in man. Am. J. Physiol. 233 (Endocrinol. Metab. Gas‐trointest. Physiol. 2): E195–E202, 1977.
 153. Kanaley, J. A., P. E. Cryer, and M. D. Jensen. Fatty acid kinetic responses to exercise. Effects of obesity, body fat distribution, and energy‐restricted diet. J. Clin. Invest. 92: 255–261, 1993.
 154. Karlsson, J., and B. Saltin. Lactate, ATP, and CP in working muscles during exhaustive exercise in man. J. Appl. Physiol. 29: 598–602, 1970.
 155. Kasperek, G. J., G. R. Conway, D. S. Krayeski, and J. J. Lohne. A re‐examination of the effect of exercise on rate of muscle protein degradation. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E1144–E1150, 1992.
 156. Kasperek, G. J., G. L. Dohm, H. A. Barakat, P. H. Straus‐bauch, D. W. Barnes, and R. D. Snider. The role of lysosomes in exercise‐induced hepatic protein loss. Biochem. J. 202: 281–288, 1982.
 157. Kasperek, G. J., G. L. Dohm, E. B. Tapscott, and T. Powell. Effect of exercise on liver protein loss and lysosomal enzyme levels in fed and fasted rats. Proc. Soc. Exp. Biol. Med. 164: 430–434, 1980.
 158. Kasperek, G. J., and R. D. Snider. Effect of exercise intensity and starvation on activation of branched‐chain keto acid dehydrogenase by exercise. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E33–E37, 1987.
 159. Kasperek, G. J., and R. D. Snider. Total and myofibrillar protein degradation in isolated soleus muscle after exercise. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E1–E5, 1989.
 160. Kather, H., F. Schroeder, B. Simon, and G. Schlierf. Human fat cell adenylate cyclase: Regional differences in hormone sensitivity. Eur. J. Clin. Invest. 7: 595–597, 1977.
 161. Katz, A., S. Broberg, K. Sahlin, and J. Wahren. Leg glucose uptake during maximal dynamic exercise in humans. Am. J. Physiol. 251 (Endocrinol. Metab. 14): E65–E70, 1986.
 162. Katz, A., and K. Sahlin. Effect of hypoxia on glucose metabolism in human skeletal muscle during exercise. Acta Physiol. Scand. 136: 377–382, 1989.
 163. Keller, U., P. P. G. Gerber, and W. Stauffacher. Fatty acid‐independent inhibition of hepatic ketone body production in humans. Am. J. Physiol. 254 (Endocrinol. Metab. 17): E694–E699, 1988.
 164. Kenno, K. A., J. L. Durstine, and R. E. Shepherd. Distribution of cyclic AMP phosphodiesterase in adipose tissue from trained rats. J. Appl. Physiol. 56: 845–848, 1986.
 165. King, D. S., G. P. Dalsky, W. E. Clutter, D. A. Young, M. A. Staten, P. E. Cryer, and J. O. Holloszy. Effects of lack of exercise on insulin secretion and action in trained subjects. Am. J. Physiol. 254 (Endocrinol. Metab. 17): E537–E542, 1988.
 166. Kjaer, M., K. Engfred, A. Fernandez, N. Secher, and H. Galbo. Regulation of hepatic glucose production during exercise in humans: role of sympathoadrenergic activity. Am. J. Physiol. 265 (Endocrinol. Metab. 28): E275–E283, 1993.
 167. Kjaer, M., K. Engfred, H. Galbo, B. Sonne, K. Rasmussen, and S. Keiding. Hepatic glucose production during exercise in liver‐transplanted subjects (Abstract). Scand. J. Gastroenterol. 26 (Suppl.): 46A, 1991.
 168. Kjaer, M., and H. Galbo. Effect of physical training on the capacity to secrete epinephrine. J. Appl. Physiol. 64: 11–16, 1988.
 169. Kjaer, M., K. J. Mikines, N. J. Christensen, B. Tronier, J. Vinten, B. Sonne, E. A. Richter, and H. Galbo. Glucose turnover and hormonal changes during insulin‐induced hypoglycemia in trained men. J. Appl. Physiol. 57: 21–27, 1984.
 170. Kjaer, M., N. H. Secher, F. W. Bach, and H. Galbo. Role of motor center activity for hormonal changes and substrate mobilization in humans. Am. J. Physiol. 253 (Regulatory Integrative Comp. Physiol. 22): R687–R695, 1987.
 171. Kjaer, M., N. H. Secher, F. W. Bach, S. Sheikh, and H. Galbo. Hormonal and metabolic responses to exercise in humans: effect of sensory nervous blockade. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E95–E101, 1989.
 172. Koivisto, V. A., M. Harkonen, S. Karonen, P. H. Groop, R. Elovaino, E. Ferrannini, L. Sacca, and R. A. Defronzo. Glycogen depletion during prolonged exercise: influence of glucose fructose, or placebo. J. Appl. Physiol. 58: 731–737, 1985.
 173. Koivisto, V. A., S. Karonen, and E. A. Nikkila. Carbohydrate ingestion before exercise: comparison of glucose, fructose, and sweet placebo. J. Appl. Physiol. 51: 783–787, 1981.
 174. Koivisto, V. A., and H. Yki‐Jarvinen. Effect of exercise on insulin binding and glucose transport in adipocytes of normal humans. J. Appl. Physiol. 63: 1319–1323, 1987.
 175. Koranyi, L. I., R. E. Bourey, C. A. Slentz, and J. O. Holloszy. Coordinate reduction of rat pancreatic islet gluco‐kinase and proinsulin mRNA by exercise training. Diabetes 40: 401–404, 1991.
 176. Kozlowski, S., K. Nazar, Z. Brzezinska, D. Stephens, H. Kaciuba‐Uscitko, and A. Kobryn. Mechanism of sympathetic activation during prolonged physical exercise in dogs. Pflugers Arch. 399: 63–67, 1983.
 177. Krotkiewski, M., and J. Groski. Effect of muscular exercise on plasma C‐peptide and insulin in obese non‐diabetics and diabetics, type II. Clin. Physiol. 6: 499–506, 1986.
 178. Krzentowski, G., F. Pirnay, N. Pallikarakis, A. S. Luyckx, M. Lacroix, F. Mosora, and P. J. Lelfebvre. Glucose utilization during exercise in normal and diabetic subjects. The role of insulin. Diabetes 30: 983–989, 1981.
 179. Krzentowski, G. B., B. Jandrain, F. Pirnay, F. Morosa, A. S. Lacroix, and P. Lefebvre. Availability of glucose given orally during exercise. J. Appl. Physiol. 56: 315–320, 1984.
 180. Lautt, W. Afferent and efferent neural roles in liver function. Prog. Neurobiol. 21: 323–348, 1983.
 181. Lautt, W. W., and C. Wong. Hepatic glucose balance in response to direct stimulation of sympathetic nerves in the intact liver of cats. Can. J. Physiol. Pharmacol. 56: 1022–1028, 1978.
 182. Lavoie, J. M., S. Cardin, and B. Doiron. Influence of hepatic vagus nerve on pancreatic hormone secretion. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E855–E859, 1989.
 183. Leclerq‐Meyer, V., J. Marchand, and R. Leclerq. Studies on the molecular forms of glucagon immunoreactivity (GLI) released by the in vitro perfused pancreas. Diabetologia 19: 294–300, 1980.
 184. Leuenberger, U., L. Sinoway, S. Gubin, L. Gaul, D. Davis, and R. Zelis. Effects of exercise intensity and duration on norepinephrine spillover and clearance in humans. Am. J. Physiol. 75: 668–674, 1993.
 185. Lickley, H. L. A., F. W. Kemmer, D. E. Gray, N. Kovacevic, T. W. Hatton, G. Perez, and M. Vranic. Chromatographic pattern of extrapancreatic glucagon and glucagon‐like immunoreactivity before and during stimulation by epinephrine, and participation of glucagon in epinephrine‐induced hepatic glucose overproduction. Surgery 90: 186–194, 1981.
 186. Liljenquist, J. E., G. L. Mueller, A. D. Cherrington, U. Keller, J. L. Chiasson, J. M. Perry, W. W. Lacy, and D. Rabinowitz. Evidence for an important role of glucagon in the regulation of hepatic glucose production in normal man. J. Clin. Invest. 59: 369–374, 1977.
 187. Lobley, G. E., V. Milne, J. M. Lovie, P. J. Reeds, and K. Pennie. Whole body and tissue protein synthesis in cattle. Br. J. Nutr. 43: 491–502, 1980.
 188. Luyckx, A. S., and P. J. Lefebvre. Mechanisms involved in the exercise‐induced increase in glucagon secretion in rats. Diabetes 23: 81–93, 1974.
 189. Luyckx, A. S., F. Pirnay, and P. J. Lefebvre. Effect of glucose on plasma glucagon and free fatty acids during prolonged exercise. Eur. J. Appl. Physiol. 39: 53–61, 1978.
 190. Macleod, J. J. R., H. E. Magee, and C. B. Purves. Selective absorption of carbohydrates. J. Physiol. (Lond.) 70: 404–413, 1930.
 191. Marker, J. C., D. A. Arnall, R. K. Conlee, and W. W. Winder. Effect of adrenodemedullation on metabolic responses to high‐intensity exercise. Am. J. Physiol. 251 (Regulatory Integrative Comp. Physiol. 20): R552–R559, 1986.
 192. Marker, J. C., I. B. Hirsh, L. J. Smith, C. A. Parvin, J. O. Holloszy, and P. E. Cryer. Catecholamines in prevention of hypoglycemia during exercise in humans. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E705–E712, 1991.
 193. Marliss, E. B., E. Simantirakis, C. Purdon, R. Gougeon, C. J. Field, J. B. Halter, and M. Vranic. Glucoregulatory and hormonal responses to repeated bouts of intense exercise in normal male subjects. J. Appl. Physiol. 71: 924–933, 1991.
 194. Martin, W. H., E. F. Coyle, M. Joyner, D. Santesusanio, A. A. Ehsani, and J. O. Holloszy. Effect of stopping exercise training on epinephrine‐stimulated lipolysis in humans. J. Appl. Physiol. 56: 845–848, 1984.
 195. Massicotte, D., F. Peronnet, C. Allah, C. Hillaire‐Marcel, M. Ledoux, and G. Brisson. Metabolic response of to [13C]‐glucose and [13C]‐fructose ingestion during exercise. J. Appl. Physiol. 61: 1180–1184, 1986.
 196. Massicotte, D., F. Peronnet, G. Brisson, K. Bakkouch, and C. Hillaire‐Marcel. Oxidation of glucose polymer during exercise: comparison with glucose or fructose. J. Appl. Physiol. 66: 179–183, 1989.
 197. Massicotte, D., F. Peronnet, G. Brisson, L. Boivin, and C. Hillaire‐Marcel. Oxidation of exogenous carbohydrate during prolonged exercise in fed and fasted conditions. Int. J. Sports Med. 11: 253–258, 1990.
 198. Matchinsky, F. M. Glucokinase as glucose sensor and metabolic signal generator in pancreatic B‐cells and hepatocytes. Diabetes 39: 647–652, 1990.
 199. Maughan, R. J., J. B. Leiper, and A. McGaw. Effects of exercise intensity on absorption of ingested fluids in man. Exp. Physiol. 75: 419–421, 1990.
 200. May, M. E., and M. G. Buse. Effects of branched chain amino acids on protein turnover. Diabetes Metab. Rev. 5: 227–245, 1989.
 201. McGarry, J. D., and D. W. Foster. Regulation of hepatic fatty acid oxidation and ketone body production. Annu. Rev. Biochem. 49: 395–420, 1980.
 202. McNurlan, M. A., and P. J. Garlick. Contribution of liver and gastrointestinal tract to whole‐body protein synthesis in the rat. Biochem. J. 186: 381–383, 1980.
 203. Meister, A. Enzymology of glutamine metabolism. In: Glutamine Metabolism in Mammalian Tissues, edited by D. Haussinger and H. Sies, New York: Springer‐Verlag, 1984.
 204. Mendenhall, L. A., S. C. Swanson, D. L. Habash, and A. R. Coggan. Ten days of exercise training reduces glucose production and utilization during moderate‐intensity exercise. Am. J. Physiol. 266 (Endocrinol. Metab. 29): E136–E143, 1994.
 205. Meshkinpour, H., C. Kemp, and R. Fairster. The effect of aerobic exercise on mouth to cecum transit time. Gastroenterology 96: 938–941, 1989.
 206. Meyer, R. A., and R. L. Terjung. Differences in ammonia and adenylate metabolism in contracting fast and slow muscle. Am. J. Physiol. 237 (Cell Physiol. 6): C111–C118, 1979.
 207. Mikines, K. J., B. Sonne, P. A. Farrell, B. Tronier, and H. Galbo. Effect of training on the dose‐response relationship for insulin action in men. J. Appl. Physiol. 66: 695–703, 1989.
 208. Miles, J. M., M. W. Haymond, S. L. Nissen, and J. E. Gerich. Effects of free fatty acid availability, glucagon excess, and insulin deficiency on ketone body production in postabsorptive man. J. Clin. Invest. 71: 1554–1561, 1983.
 209. Mitchell, J. B., D. L. Costill, J. A. Houmard, W. J. Fink, R. A. Robergs, and J. A. Davis. Influence of carbohydrate dosage on exercise performance and glycogen metabolism. J. Appl. Physiol. 67: 1843–1849, 1989.
 210. Moates, J. M., D. B. Lacy, A. D. Cherrington, R. E. Goldstein, and D. H. Wasserman. The metabolic role of the exercise‐induced increment in epinephrine. Am. J. Physiol. 255 (Endocrinol. Metab. 18): E428–E436, 1988.
 211. Mondon, C. E., C. B. Dolkas, and G. M. Reaven. Site of enhanced insulin sensitivity in exercise‐trained rats at rest. Am. J. Physiol. 239 (Endocrinol. Metab. 2): E169–E177, 1980.
 212. Mortimore, G. E., A. R. Poso, and B. R. Lardeux. Mechanism and regulation of protein degradation in liver. Diabetes Metab. Rev. 5: 49–70, 1989.
 213. Moses, F. M., C. Ryan, J. Debolt, and B. Smoak. Oral cecal transit time during a 2 h run with ingestion of water of glucose polymer. Am. J. Gastroenterol. 83: 1055–1061, 1988.
 214. Moses, F. M., A. Singh, V. V. Nueva, B. Kelsey, and B. Smoak. Lactate absorption and transit during prolonged exercise. Am. J. Gastroenterol. 84: 1192–1201, 1989.
 215. Murray, R., G. L. Paul, J. G. Siefert, D. E. Eddy, and G. L. Halaby. The effects of of glucose, fructose, and sucrose ingestion during exercise. Med. Sci. Sports Exerc. 21: 275–282, 1989.
 216. Murray, R. K., D. K. Granner, P. A. Mayes, and V. W. Rodwell. Harper's Biochemistry. Englewood Cliffs, NJ: Prentice Hall, 1990.
 217. Neufer, P. D., D. L. Costill, W. J. Fink, J. P. Kirwin, R. A. Fielding, and M. G. Flynn. Effects of exercise and carbohydrate composition on gastric emptying. Med. Sci. Sports Exerc. 18: 658–662, 1986.
 218. Neufer, P. D., A. J. Young, and M. N. Sawka. Gastric emptying during exercise: effects of heat stress and hypohydration. J. Appl. Physiol. 58: 433–439, 1989.
 219. Newsholme, E. A. A possible metabolic basis for the control of body weight. N. Engl. J. Med. 302: 400–405, 1980.
 220. Newsholme, E. A., and B. Crabtree. Substrate cyclesin metabolic regulation and in heat generation. Biochem. Soc. Symp. 41: 61–109, 1976.
 221. Noakes, T. D., E. V. Lambert, M. I. Lambert, P. S. Mc‐Arthur, K. H. Myburgh, and A. J. S. Benade. Carbohydrate ingestion and muscle glycogen depletion during marathon and ultramarathon racing. Eur. J. Appl. Physiol. 57: 482–489, 1988.
 222. Noakes, T. D., N. J. Reher, and R. J. Maughan. The importance of emptying volume in regulating gastric emptying. Med. Sci. Sports Exerc. 23: 307–313, 1991.
 223. Ostman, J., P. Arner, P. Engfeldt, and L. Kager. Regional differences in the control of lipolysis in human adipose tissue. Metabolism 28: 1198–1203, 1979.
 224. Owen, M. D., K. C. Kregel, P. T. Wall, and C. V. Gisolfi. Effects of ingesting carbohydrate beverages during exercise in the heat. Med. Sci. Sports Exerc. 18: 568–575, 1986.
 225. Pallikarakis, N., B. Jandrain, F. Pirnay, F. Mosora, M. Lacroix, A. S. Luycks, and P. J. Lefebvre. Remarkable metabolic availability of oral glucose during long‐duration exercise in humans. J. Appl. Physiol. 60: 1035–1042, 1986.
 226. Peronnet, F., D. Massicotte, G. Brisson, and C. Hillaire‐Marcel. Use of 13C substrates for metabolic studies in exercise: methodological considerations. J. Appl. Physiol. 69: 1047–1052, 1990.
 227. Pirnay, F., J. M. Crielaard, N. Pallikarakis, M. Lacroix, F. Mosora, A. Luyckx, and P. J. Lefebvre. Fate of exogenous glucose during exercise of different intensities in humans. J. Appl. Physiol. 43: 258–261, 1982.
 228. Pirnay, F., M. Lacroix, F. Mosora, A. Luyckx, and P. Lefebvre. Effect of glucose ingestion on energy substrate utilization during prolonged exercise in man. Eur. J. Appl. Physiol. 36: 247–254, 1977.
 229. Pirnay, F., M. Lacroix, F. Mosora, A. Luyckx, and P. J. Lefebvre. Glucose oxidation during prolonged exercise evaluated with naturally labelled 13C glucose. J. Appl. Physiol. 43: 258–261, 1977.
 230. Polonsky, K., J. Jaspan, W. Pugh, J. Dhorajiwala, M. Abraham, P. Blix, and A. R. Moosa. Insulin and glucagon breakthrough of somatostatin suppression. Importance of portal vein hormone measurements. Diabetes 30: 664–669, 1981.
 231. Poortmans, J. R. Protein turnover and amino acid oxidation during and after exercise. Med. Sports Sci. 17: 130–147, 1984.
 232. Porte, D., A. L. Graber, T. Kuzuya, and R. H. Williams. The effects of epinephrine on IRI levels in man. J. Clin. Invest. 45: 228–236, 1966.
 233. Portis, A. J., G. L. Warnock, D. T. Finegood, A. N. Belcastro, and R. V. Rajotte. Glucoregulatory response to moderate exercise in long‐term islet cell autografted dogs. Can. J. Physiol. Pharmacol. 68: 1308–1312, 1990.
 234. Randle, P. J., P. B. Garland, C. N. Hales, and E. A. Newsholme. The glucose‐fatty acid cycle its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. Lancet i: 785–789, 1963.
 235. Reaven, E. P., and G. M. Reaven. Structure and function changes in the endocrine pancreas of aging rats with reference to the modulating effects of exercise and caloric restriction. J. Clin. Invest. 68: 75–84, 1981.
 236. Refsum, H. E., R. Gjessing, and S. B. Stromme. Changes in plasma amino acid distribution and urine amino acid excretion during prolonged heavy exercise. Scand. J. Clin. Lab. Invest. 39: 407–413, 1979.
 237. Rehrer, N. J., E. Beckers, F. Brouns, W. H. M. Saris, and F. T. Hoor. Effects of dehydration on gastric emptying and gastrointestinal distress while running. Med. Sci. Sports Exerc. 22: 790–795, 1990.
 238. Rehrer, N. J., A. J. M. Wagenmakers, E. J. Beckers, D. Halliday, J. B. Leiper, F. Brouns, R. J. Maughan, K. Westerterp, and W. H. M. Saris. Gastric emptying, absorption, and carbohydrate oxidation during prolonged exercise. J. Appl. Physiol. 72: 468–475, 1992.
 239. Rennie, M. J., R. H. T. Edwards, S. Krywawyck, C. T. M. Davies, D. Halliday, J. C. Waterlow, and D. J. Millward. Effect of exercise on protein turnover in man. Clin. Sci. 61: 627–639, 1981.
 240. Rennie, M. J., W. W. Winder, and J. O. Holloszy. A sparing effect of increased plasma fatty acids on muscle and liver glycogen content in the exercising rat. Biochem. J. 156: 647–655, 1976.
 241. Richter, E. A., H. Galbo, and N. J. Christensen. Control of exercise‐induced muscular glycogenolysis by adrenal medullary hormones in rats. J. Appl. Physiol. 50: 21–26, 1981.
 242. Richter, E. A., H. Galbo, J. J. Hoist, and B. Sonne. Significance of glucagon for insulin secretion and hepatic glycogenolysis during exercise in rats. Horm. Metab. Res. 13: 323–326, 1981.
 243. Richter, E. A., H. Galbo, B. Sonne, J. J. Hoist, and N. J. Christensen. Adrenal medullary control of muscular and hepatic glycogenolysis and of pancreatic hormonal secretion in exercising rats. Acta Physiol. Scand. 108: 1980, 1980.
 244. Riviere, D., F. Crampes, M. Beauville, and M. Garrigues. Lipolytic response of fat cells to catecholamines in sedentary and exercise‐trained women. J. Appl. Physiol. 66: 330–335, 1989.
 245. Rizack, M. A. Activation of an epinephrine‐sensitive lipolytic activity from adipose tissue by adenosine 3′, 5′ phosphate. J. Biol. Chem. 239: 392–395, 1964.
 246. Rodjkmark, S., G. Bloom, M. C. Y. Chou, and J. B. Field. Hepatic extraction of exogenous insulin and glucagon in the dog. Endocrinology 102: 806–813, 1978.
 247. Rodnick, K. J., W. L. Haskell, A. L. M. Swislocki, J. E. Foley, and G. M. Reaven. Improved insulin action in muscle, liver, and adipose tissue in physically trained human subjects. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E489–E495, 1987.
 248. Romijn, J. A., S. Klein, E. F. Coyle, L. S. Sidossis, and R. R. Wolfe. Strenuous endurance training increases lipolysis and triglyceride‐fatty acid cycling at rest. J. Appl. Physiol. 75: 108–113, 1993.
 249. Rosell, S., and E. Belfrage. Blood circulation in adipose tissue. Physiol. Rev. 59: 1078–1104, 1979.
 250. Rowell, L. B., J. R. Blackmon, and R. A. Bruce. Indocy‐anine green clearance and estimated blood flow during mild to maximal exercise in upright man. J. Clin. Invest. 43: 1677–1690, 1964.
 251. Rowell, L. B., E. J. Masoro, and M. J. Spenser. Splanchnic metabolism in exercising man. J. Appl. Physiol. 20: 1032–1037, 1965.
 252. Sacca, L., N. Eigler, P. E. Cryer, and R. S. Sherwin. Insulin antagonistic effects of epinephrine and glucagon in the dog. Am. J. Physiol. 237 (Endocrinol. Metab. Gastrointest. Physiol. 6): E487–E492, 1979.
 253. Sacca, L. C., C. Vigorito, M. Cicala, G. Corso, and R. S. Sherwin. Role of gluconeogenesis in epinephrine‐stimulated hepatic glucose production in humans. Am. J. Physiol. 245 (Endocrinol. Metab. 8): E294–E302, 1983.
 254. Salans, L. B., and J. W. Doherty. The effect of insulin upon glucose metabolism by adipose cells of different size. J. Clin. Invest. 50: 1399–1410, 1971.
 255. Samols, F., and G. C. Weir. Adrenergic modulation of pancreatic A, B, and D cells. J. Clin. Invest. 63: 230–238, 1979.
 256. Saris, W. H. M., B. H. Goodpaster, A. E. Jeukendrup, F. Brouns, D. Halliday, and A. J. M. Wagenmakers. Exogenous carbohydrate oxidation from different carbohydrate sources during exercise. J. Appl. Physiol. 75: 2168–2172, 1993.
 257. Savard, R., J. P. Despres, M. Marcotte, and C. Bouchard. Endurance training and glucose conversion into triglycerides in human fat cells. J. Appl. Physiol. 58: 230–235, 1985.
 258. Sawchenko, P. E., and M. I. Friedman. Sensory functions of the livera review. Am. J. Physiol. 236 (Regulatory Integrative Comp. Physiol. 5): R5–R20, 1979.
 259. Seftoft, L., J. Trap‐Jensen, J. Lyngsoe, J. P. Clausen, J. J. Hoist, S. L. Nielsen, J. F. Rehfeld, and O. S. D. Muckadell. Regulation of gluconeogenesis and ketogenesis during rest and exercise in diabetic subjects and normal men. Clin. Sci. Mol. Med. 53: 411–418, 1977.
 260. Sellers, T. L., A. W. Jaussi, H. T. Yang, R. W. Heninger, and W. W. Winder. Effect of the exercise‐induced increase in glucocorticoids on endurance in the rat. J. Appl. Physiol. 65: 173–178, 1988.
 261. Sembrowich, W. L., C. D. Lanuzzo, C. W. Saubert, R. E. Shepherd, and P. D. Gollnick. Substrate mobilization during prolonged exercise in 6‐hydroxydopamine treated rats. Pflugers Arch. 349: 57–62, 1974.
 262. Shapiro, B., I. Chowers, and G. Rose. Fatty acid uptake and esterification in adipose tissue. Biochim. Biophys. Acta 23: 115–120, 1957.
 263. Shepherd, R. E., E. G. Noble, G. A. Klug, and P. D. Gollnick. Lipolysis and cAMP accumulation in adipocytes in response to physical training. J. Appl. Physiol. 50: 143–148, 1981.
 264. Shepherd, R. F., W. L. Sembrowich, H. E. Green, and P. D. Gollnick. Effect of physical training on control mechanisms of lipolysis in rat fat cell ghosts. J. Appl. Physiol. 42: 884–888, 1977.
 265. Shimazu, T., and M. Usami. Further studies on the mechanism of phosphorylase activation in rabbit liver in response to splanchnic nerve stimulation. J. Physiol. (Lond.) 329: 231–242, 1982.
 266. Sigal, R. J., C. Purdon, D. Bilinski, M. Vranic, J. B. Halter, and E. B. Marliss. Glucoregulation during and after intense exercise: effects of beta‐blockade. J. Clin. Endocrinol. Metab. 78: 359–366, 1994.
 267. Simonson, D. C., V. A. Koivisto, R. S. Sherwin, E. Ferrannini, R. Hendler, and R. A. Defronzo. Adrenergic blockade alters glucose kinetics during exercise in insulin‐dependent diabetics. J. Clin. Invest. 73: 1648–1658, 1984.
 268. Sirek, A., M. Vranic, O. V. Sirek, M. Vigas, and Z. Policova. Effect of growth hormone on acute glucagon and insulin release. Am. J. Physiol. 237 (Endocrinol. Metab. Gastrointest. Physiol. 6): E107–E112, 1979.
 269. Smith, U., J. Hammarsten, P. Bjorntorp, and J. Kral. Regional differences and effect of weight reduction on human fat cell metabolism. Eur. J. Clin. Invest. 9: 327–333, 1979.
 270. Sole, C. C., and T. D. Noakes. Faster gastric emptying for glucose‐polymer and fructose solutions than for glucose in humans. Eur. J. Appl. Physiol. 58: 605–612, 1989.
 271. Sonne, B., K. J. Mikines, E. A. Richter, N. J. Christensen, and H. Galbo. Role of liver nerves and adrenal medulla in glucose turnover of running rats. J. Appl. Physiol. 59: 1650–1656, 1985.
 272. Sotsky, M., S. Shilo, and H. Shamoon. Regulation of coun‐terregulatory hormone secretion in man during exercise and hypoglycemia. J. Clin. Endocrinol. Metab. 68: 9–16, 1989.
 273. Souba, W. W., R. J. Smith, and D. W. Wilmore. Glutamine metabolism by the intestinal tract. J. Parenter. Enter. Nutr. 9: 608–617, 1985.
 274. Stallknecht, B., J. Vinten, T. Ploug, and H. Galbo. Increased activities of mitochondrial enzymes in white adipose tissue in trained rats. Am. J. Physiol. 261 (Endocrinol. Metab. 24): E410–E414, 1991.
 275. Stralfors, P., H. Olsson, and P. Belfrage. Hormone sensitive lipase. Enzymes 18: 147–177, 1987.
 276. Sumida, K. D., J. H. Urdiales, and C. M. Donovan. Enhanced gluconeogenesis from lactate in perfused livers after endurance training. J. Appl. Physiol. 74: 782–787, 1993.
 277. Sutton, J. R. Hormonal and metabolic responses to exercise in subjects of high and low work capacities. Med. Sci. Sports Exerc. 10: 1–6, 1978.
 278. Tate, C. A., P. E. Wolkowicz, and J. McMillin‐Wood. Exercise‐induced alterations of hepatic mitochondrial function. Btochem. J. 208: 695–701, 1982.
 279. Terjung, R. L., L. Budohoski, K. Nazar, A. Kobryn, and H. Kaciuba‐Uscilko. Chylomicron triglyceride metabolism in resting and exercising dogs. J. Appl. Physiol. 52: 815–820, 1982.
 280. Terjung, R. L., and H. Kaciuba‐Uscilko. Lipid metabolism during exercise: influence of training. Diabetes Metab. Rev. 2: 35–51, 1986.
 281. Turcotte, L. P., A. S. Rovner, R. R. Roark, and G. A. Brooks. Glucose kinetics in gluconeogenesis‐inhibited rats during rest and exercise. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E203–E211, 1990.
 282. Valverde, I., M. Ghiglione, R. Matesanz, and S. Casado. Chromatographic pattern of gut glucagon‐like immunoreactivity (GLI) in plasma before and during glucose absorption. Horm. Metab. Res. 11: 343–346, 1979.
 283. Vanhandel, P. J., W. J. Fink, G. Branam, and D. Costill. Fate of 14C gluocse ingested during prolonged exercise. Int. J. Sports Med. 1: 127–131, 1980.
 284. Varro, G. E., J. A. Harris, and J. E. Geenen. Effect of decreased local circulation on the absorptive capacity of a small intestine loop in the dog. Am. J. Dig. Dis. 10: 170–177, 1965.
 285. Vaughan, M., and D. Steinberg. Effect of hormones on lipolysis and re‐esterification of free fatty acids during incubation of adipose tissue in vitro. J. Lipid Res. 4: 193–199, 1963.
 286. Victor, R. G., D. R. Seals, and A. L. Mark. Differential control of heart rate and sympathetic nerve activity during dynamic exercise. Insight from intraneural recordings in humans. J. Clin. Invest. 79: 508–516, 1987.
 287. Vinten, J., and H. Galbo. Effect of physical training on transport and metabolism of glucose in adipocytes. Am. J. Physiol. 244 (Endocrinol. Metab. 7): E129–E134, 1983.
 288. Vinten, J., and H. Galbo. Effect of physical training on transport and metabolism of glucose in adipocytes. Biochim. Biophys. Acta 841: 223–227, 1985.
 289. Vissing, J., G. A. Iwamoto, K. J. Rybicki, H. Galbo, and J. H. Mitchell. Mobilization of glucoregulatory hormones and glucose by hypothalamic locomotor centers. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E722–E728, 1989.
 290. Vissing, J., J. L. Wallace, A. J. W. Scheurink, H. Galbo, and A. B. Steffens. Ventromedial hypothalamic regulation of hormonal and metabolic responses to exercise. Am. J. Physiol. 256 (Regulatory Integrative Comp. Physiol. 25): R1019–R1026, 1989.
 291. Vranic, M., R. Kawamori, S. Pek, N. Kovacevic, and G. Wrenshall. The essentiality of insulin and the role of glucagon in regulating glucose utilization and production during strenuous exercise in dogs. J. Clin. Invest. 57: 245–255, 1976.
 292. Wahren, J., P. Felig, G. Ahlborg, and L. Jorfeldt. Glucose metabolism during leg exercise in man. J. Clin. Invest. 50: 2715–2725, 1971.
 293. Wahren, J., L. Hagenfeldt, and P. Felig. Splanchnic and leg exchange of glucose, amino acids, and free fatty acids during exercise in diabetes mellitus. J. Clin. Invest. 55: 1303–1314, 1975.
 294. Wahren, J., Y. Sato, J. Ostman, L. Hagenfeldt, and P. Felig. Turnover and splanchnic metabolism of free fatty acids and ketones in insulin‐dependent diabetics during exercise. J. Clin. Invest. 73: 1367–1376, 1984.
 295. Wahrenberg, H., P. Engfeldt, J. Bolinder, and P. Arner. Acute adaptation in adrenergic control of lipolysis during physical exercise in humans. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E383–E390, 1987.
 296. Wardzala, L. J., M. Crettaz, E. D. Horton, B. Jeanrenaud, and E. S. Horton. Physical training of lean and genetically obese Zucker rats: effect of fat cell metabolism. Am. J. Physiol. 243 (Endocrinol. Metab. 6): E418–E426, 1982.
 297. Wasserman, D. H., J. L. Bupp, J. L. Johnson, D. Bracy, and D. B. Lacy. Glucoregulation during rest and exercise in depancreatized dogs: role of the acute presence of insulin. Am. J. Physiol. 262 (Endocrinol. Metab. 25): E574–E582, 1992.
 298. Wasserman, D. H., and A. D. Cherrington. Hepatic fuel metabolism during exercise: role and regulation. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E811–E824, 1991.
 299. Wasserman, D. H., R. J. Geer, D. E. Rice, D. Bracy, P. J. Flakoll, L. L. Brown, J. O. Hill, and N. N. Abumrad. Interaction of exercise and insulin action in man. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E37–E45, 1991.
 300. Wasserman, D. H., R. J. Geer, P. E. Williams, D. B. Lacy, and N. N. Abumrad. Interaction of gut and liver in nitrogen metabolism during exercise. Metabolism 40: 307–314, 1991.
 301. Wasserman, D. H., D. B. Lacy, D. Bracy, and P. E. Williams. Metabolic regulation in peripheral tissues and transition to increased gluconeogenic mode during prolonged exercise. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E345–E354, 1992.
 302. Wasserman, D. H., D. B. Lacy, and D. P. Bracy. Relationship between arterial and portal vein immunoreactive glucagon during exercise. J. Appl. Physiol. 75: 724–729, 1993.
 303. Wasserman, D. H., D. B. Lacy, C. A. Colburn, D. P. Bracy, and A. D. Cherrington. Efficiency of compensation for the absence of the fall in insulin during exercise. Am. J. Physiol. 261 (Endocrinol. Metab. 24): E587–E597, 1991.
 304. Wasserman, D. H., D. B. Lacy, R. E. Goldstein, P. E. Williams, and A. D. Cherrington. Exercise‐induced fall in insulin and hepatic carbohydrate metabolism during exercise. Am.J. Physiol. 256 (Endocrinol. Metab. 19): E500–E508, 1989.
 305. Wasserman, D. H., D. B. Lacy, R. E. Goldstein, P. E. Williams, and A. D. Cherrington. Exercise‐induced fall in insulin and the increase in fat metabolism during prolonged exercise. Diabetes 38: 484–490, 1989.
 306. Wasserman, D. H., D. B. Lacy, D. R. Green, P. E. Williams, and A. D. Cherrington. Dynamics of hepatic lactate and glucose balances during prolonged exercise and recovery. J. Appl. Physiol. 63: 2411–2417, 1987.
 307. Wasserman, D. H., H. L. A. Lickley, and M. Vranic. Interactions between glucagon and other counterregulatory hormones during normoglycemic and hypoglycemic exercise in dogs. J. Clin. Invest. 74: 1404–1413, 1984.
 308. Wasserman, D. H., H. L. A. Lickley, and M. Vranic. Effect of hematocrit reduction on hormonal and metabolic responses to exercise. J. Appl. Physiol. 58: 1257–1262, 1985.
 309. Wasserman, D. H., J. S. Spalding, D. P. Bracy, D. B. Lacy, and A. D. Cherrington. Exercise‐induced rise in glucagon and the increase in ketogenesis during prolonged muscular work. Diabetes 38: 799–807, 1989.
 310. Wasserman, D. H., J. S. Spalding, D. B. Lacy, C. A. Colburn, R. E. Goldstein, and A. D. Cherrington. Glucagon is a primary controller of the increments in hepatic glycogen‐olysis and gluconeogenesis during exercise. Am. J. Physiol. 257 (Endocrinol. Metab. 20): E108–E117, 1989.
 311. Wasserman, D. H., P. E. Williams, D. B. Lacy, D. Bracy, and A. D. Cherrington. Hepatic nerves are not essential to the increase in hepatic glucose production during muscular work. Am. J. Physiol. 259 (Endocrinol. Metab. 22): E195–E203, 1990.
 312. Wasserman, D. H., P. E. Williams, D. B. Lacy, D. R. Green, and A. D. Cherrington. Importance of intrahepatic mechanisms to gluconeogenesis from alanine during prolonged exercise and recovery. Am. J. Physiol. 254 (Endocrinol. Metab. 17): E518–E525, 1988.
 313. Weber, J. M., S. Klein, and R. R. Wolfe. Role of the glucose cycle in control of net glucose flux in exercising humans. J. Appl. Physiol. 68: 1815–1819, 1990.
 314. Welbourne, T. C. Interorgan glutamine flow in metabolic acidosis. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E1069–E1076, 1987.
 315. Wheeler, K. B., and J. G. Banwell. Intestinal water and electrolyte flux of glucose polymer electrolyte solutions. Med. Sci. Sports Exerc. 18: 436–439, 1986.
 316. White, T. P., and G. A. Brooks. [u‐14c]‐glucose, ‐alanine, and ‐leucine oxidation in rats at rest and two intensities of running. Am. J. Physiol. 240 (Endocrinol. Metab. 3): E155–E165, 1981.
 317. Williams, B. D., R. R. Wolfe, D. P. Bracy, and D. H. Wasserman. Gut proteolysis contributes essential amino acids during exercise. Med. Sci. Sports Exerc. 24: 1062, 1992.
 318. Williams, J. H., M. Mager, and E. D. Jacobson. Relationship of mesenteric blood flow to intestinal absorption of carbohdyrates. J. Lab. Clin. Med. 63: 853–862, 1964.
 319. Williams, R. S., and T. Bishop. Enhanced receptor‐cyclase coupling and augmented catecholamine‐stimulated lipolysis in exercising rats. Am. J. Physiol. 243 (Endocrinol. Metab. 6): E345–E351, 1982.
 320. Winder, W. W., J. Arogyasami, H. T. Yang, K. G. Thompson, L. A. Nelson, K. P. Kelly, and D. H. Han. Effects of glucose infusion in exercising rats. J. Appl. Physiol. 64: 2300–2305, 1988.
 321. Winder, W. W., M. A. Beattie, C. Piquette, and R. T. Holman. Decrease in liver norepinephrine in response to exercise and hypoglycemia. Am. J. Physiol. 244 (Regulatory Integrative Comp. Physiol. 13): R147–R152, 1983.
 322. Winder, W. W., J. M. Hagberg, R. C. Hickson, A. A. Ehsani, and J. O. Holloszy. Time course of sympathoadrenal adaptation to endurance training in man. J. Appl. Physiol. 45: 370–374, 1978.
 323. Winder, W. W., R. C. Hickson, J. M. Hagberg, A. A. Ehsani, and J. McLane. Training‐induced changes in the hormonal and metabolic response to submaximal exercise. J. Appl. Physiol. 46: 766–771, 1979.
 324. Winder, W. W., M. L. Terry, and V. M. Mitchell. Role of plasma epinephrine in fasted exercising rats. Am. J. Physiol. 248 (Regulatory Integrative Comp. Physiol. 17): R302–R307, 1985.
 325. Winder, W. W., H. T. Yang, A. W. Jaussi, and C. R. Hopkins. Epinephrine, glucose, and lactate infusion in exercising adrenomedullated rats. J. Appl. Physiol. 62: 1442–1447, 1987.
 326. Wirth, A., C. Diehm, H. Mayer, H. Morl, I. Vogel, P. Bjorntorp, and G. Schlierf. Plasma C‐peptide and insulin in trained and untrained subjects. J. Appl. Physiol. 50: 71–77, 1981.
 327. Wirth, A., G. Holm, B. Nilsson, U. Smith, and P. Bjorntorp. Insulin kinetics and insulin binding in physically trained and food‐restricted rats. Am. J. Physiol. 238 (Endocrinol. Metab. 1): E108–E115, 1980.
 328. Wolf, P. D., E. H. Fischer, and E. G. Krebs. Amino acid sequence of the phosphorylated site in rabbit liver glycogen phosphorylase. Biochemistry 9: 1923–1929, 1970.
 329. Wolfe, R. R., and S. George. Stable isotope methods for studying metabolism. Exerc. Sports Sci. Rev. 21: 3–23, 1993.
 330. Wolfe, R. R., R. D. Goodenough, M. H. Wolfe, G. T. Royle, and E. R. Nadel. Isotopic analysis of leucine and urea metabolism in exercising humans. J. Appl. Physiol. 52: 458–466, 1982.
 331. Wolfe, R. R., S. Klein, F. Carraro, and J. M. Weber. Role of triglyceride‐fatry acid cycle in controlling fat metabolism in humans during and after exercise. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E382–E389, 1990.
 332. Wolfe, R. R., E. R. Nadel, J. H. F. Shaw, L. A. Stephenson, and M. Wolfe. Role of changes in insulin and glucagon in glucose homeostasis in exercise. J. Clin. Invest. 77: 900–907, 1986.
 333. Wolfe, R. R., M. H. Wolfe, E. R. Nadel, and J. H. F. Shaw. Isotopic determination of amino acid urea interactions in exercise in humans. J. Appl. Physiol. 56: 221–229, 1984.
 334. Yamatani, K., Z. Shi, A. Giacca, R. Gupta, S. Fisher, H. L. A. Lickley, and M. Vranic. Role of FFA‐glucose cycle in glucoregulation during exercise in total absence of insulin. Am. J. Physiol. 263 (Endocrinol. Metab. 32): E646–E653, 1992.
 335. Yaspelkis, B. B., J. G. Patterson, P. A. Anderla, Z. Ding, and J. L. Ivy. Carbohydrate supplementation spares muscle glycogen during variable‐intensity exercise. J. Appl. Physiol. 75: 1477–1485, 1993.
 336. Young, D. R., J. Shapira, R. Forrest, R. R. Adachi, R. Lim, and R. Pelligra. Model for evaluation of fatty acid metabolism in man during prolonged exercise. J. Appl. Physiol. 23: 716–725, 1967.
 337. Young, J. C., J. L. Treadway, E. I. Fader, and R. Caslin. Effects of oral hypoglycemic agent methylpalmoxirate on exercise capacity of streptozotocin diabetic rats. Diabetes 35: 744–748, 1986.
 338. Zinker, B. A., T. Mohr, P. Kelly, K. Namdaran, D. P. Bracy, and D. H. Wasserman. Exercise‐induced fall in insulin: mechanism of action at the liver and effect on skeletal muscle glucose metabolism. Am. J. Physiol. 266 (Endocrinol. Metab. 29): E683–689, 1994.

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David H. Wasserman, Alan D. Cherrington. Regulation of Extramuscular Fuel Sources During Exercise. Compr Physiol 2011, Supplement 29: Handbook of Physiology, Exercise: Regulation and Integration of Multiple Systems: 1036-1074. First published in print 1996. doi: 10.1002/cphy.cp120123