Comparison of the effects of pre-exercise feeding of glucose, glycerol and placebo on endurance and fuel homeostasis in man

Summary

Six men were studied during exercise to exhaustion on a cycle ergometer at 73% of \(\dot V_{O_{2max} } \) following ingestion of glycerol, glucose or placebo. Five of the subjects exercised for longer on the glucose trial compared to the placebo trial (p<0.1; 108.8 vs 95.9 min). Exercise time to exhaustion on the glucose trial was longer (p<0.01) than on the glycerol trial (86.0 min). No difference in performance was found between the glycerol and placebo trials. The ingestion of glucose (lg · kg−1 body weight) 45 min before exercise produced a 50% rise in blood glucose and a 3-fold rise in plasma insulin at zero min of exercise. Total carbohydrate oxidation was increased by 26% compared to placebo and none of the subjects exhibited a fall in blood glucose below 4 mmol · l−1 during the exercise. The ingestion of glycerol (lg · kg−1 body weight) 45 min before exercise produced a 340-fold increase in blood glycerol concentration at zero min of exercise, but did not affect resting blood glucose or plasma insulin levels; blood glucose levels were up to 14% higher (p<0.05) in the later stages of exercise and at exhaustion compared to the placebo or glucose trials. Both glycerol and glucose feedings lowered the magnitude of the rise in plasma FFA during exercise compared to placebo. Levels of blood lactate and alanine during exercise were not different on the 3 dietary treatments. These data contrast with previous reports that have indicated glucose feeding pre-exercise produces hypoglycaemia during strenuous submaximal exercise and reduces endurance performance. It appears that man cannot use glycerol as a gluconeogenic substrate rapidly enough to serve as a major energy source during this type of exercise.

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References

  1. Ahlborg G, Bergström BJ, Ekelund LG, Hultman E (1967) Muscle glycogen and muscle electrolytes during prolonged physical exercise. Acta Physiol Scand 70:129–142

    Google Scholar 

  2. Ahlborg G, Felig P (1976) Influence of glucose ingestion on fuel-hormone response during prolonged exercise. J Appl Physiol 41:683–688

    Google Scholar 

  3. Bagby GJ, Green HJ, Katsuta S, Gollnick PD (1978) Glycogen depletion in exercising rats infused with glucose, lactate or pyruvate. J Appl Physiol 45:425–429

    Google Scholar 

  4. Bergström J, Hermansen L, Hultman E, Saltin B (1967) Diet, muscle glycogen and physical performance. Acta Physiol Scand 71:140–150

    Google Scholar 

  5. Björkman O, Sahlin K, Hagenfeldt L, Wahren J (1984) Influence of glucose and fructose ingestion on the capacity for long-term exercise in well-trained men. Clin Physiol 4:483–494

    Google Scholar 

  6. Boobis LH, Maughan RJ (1983) A simple one-step enzymatic fluorimetric method for the determination of glycerol in 20 Μl of plasma. Clin Chim Acta 132:173–179

    Google Scholar 

  7. Christensen EH, Hansen O (1939) Hypoglykamie, Arbeitsfahigkeit und Ermudung. Scand Arch Physiol 81:172–179

    Google Scholar 

  8. Costill DL, Saltin B (1974) Factors limiting gastric emptying during rest and exercise. J Appl Physiol 37:679–683

    Google Scholar 

  9. Costill DL, Coyle EF, Dalsky G, Evans W, Fink W, Hoopes D (1977) Effects of elevated plasma FFA and insulin on muscle glycogen usage during exercise. J Appl Physiol 43:695–699

    Google Scholar 

  10. Coyle EF, Hagberg JM, Hurley BF, Martin WH, Ehsani AA, Holloszy JO (1983) Carbohydrate feeding during prolonged strenuous exercise can delay fatigue. J Appl Physiol 55:230–235

    Google Scholar 

  11. Coyle EF, Coggan AR, Hemmert MK, Lowe RC, Walters TJ (1985) Substrate usage during prolonged exercise following a pre-exercise meal. J Appl Physiol 59:429–433

    Google Scholar 

  12. Defronzo RA, Ferrannini E, Sato Y, Felig P, Wahren J (1981) Synergistic interaction between exercise and insulin on peripheral glucose uptake. J Clin Invest 68:1468–1474

    Google Scholar 

  13. Dill DB, Costill DL (1974) Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol 37:47–248

    Google Scholar 

  14. Felig P, Cherif A, Minagawa A, Wahren J (1982) Hypoglycaemia during prolonged exercise in normal men. New Engl J Med 306:895–900

    Google Scholar 

  15. Foster C, Costill DL, Fink WJ (1979) Effects of pre-exercise feedings on endurance performance. Med Sci Sports 11:1–5

    Google Scholar 

  16. Hagenfeldt L, Wahren J (1969) Human forearm muscle metabolism during exercise II. Uptake, release and oxidation of FFA and glycerol. Scand J Clin Lab Invest 21:263–276

    Google Scholar 

  17. Hermansen L, Hultman E, Saltin B (1967) Muscle glycogen during prolonged severe exercise. Acta Physiol Scand 71:129–139

    Google Scholar 

  18. Karlsson J, Saltin B (1971) Diet, muscle glycogen, and endurance performance. J Appl Physiol 31:203–206

    Google Scholar 

  19. Keller K, Schwarzkopf R (1984) Pre-exercise snacks may decrease exercise performance. Physic Sports Med 12:89–91

    Google Scholar 

  20. Koivisto VA, Karonen S-L, Nikkila EA (1981) Carbohydrate ingestion before exercise: comparison of glucose, fructose and sweet placebo. J Appl Physiol 51:783–787

    Google Scholar 

  21. Lin ECC (1977) Glycerol utilisation and its regulation in mammals. Annu Rev Biochem 46:765–795

    Google Scholar 

  22. Luyckx AS, Pirnay F, Lefebvre PJ (1978) Effect of glucose on plasma glucagon and free fatty acids during prolonged exercise. Eur J Appl Physiol 39:53–61

    Google Scholar 

  23. Masoro EJ (1977) Lipids and lipid metabolism. Annu Rev Physiol 39:301–321

    Google Scholar 

  24. Maughan RJ (1982) A simple, rapid method for the determination of glucose, lactate, pyruvate, alanine, 3-hydroxybutyrate and actetoacetate on a single 20 Μl blood sample. Clin Chim Acta 122:231–240

    Google Scholar 

  25. McMurray RG, Wilson JR, Kitchell BS (1983) The effects of fructose and glucose on high intensity endurance performance. Res Quart Exer Sport 54:156–162

    Google Scholar 

  26. Miller JM, Coyle EF, Sherman WM, Hagberg JM, Costill DL, Fink WJ, Terblanche SE, Holloszy JO (1983) Effect of glycerol feeding on endurance and metabolism during prolonged exercise in man. Med Sci Sports Exerc 15:237–242

    Google Scholar 

  27. Nelson JD, Poussier P, Marliss EB, Albisser AM, Zinman B (1982) Metabolic response of normal man and insulin-infused diabetics to postprandial exercise. Am J Physiol (Endocrin Metab) 242:E309-E316

    Google Scholar 

  28. Newsholme EA (1978) Substrate cycles: their metabolic, energetic and thermic consequences in man. In: Substrate mobilisation and energy provision in man (PB Garland, CN Hales, eds), Biochem Soc Symp 43:183–205

  29. Noma A, Okabe H, Kita M (1973) A new colorimetric micro-determination of free fatty acids in serum. Clin Chim Acta 43:317–320

    Google Scholar 

  30. Pruett EDR (1970) Glucose and insulin during prolonged work stress in men living on different diets. J Appl Physiol 28:199–208

    Google Scholar 

  31. Terblanche SE, Fell RD, Juhlin-Dannfelt AC, Craig BW, Holloszy JO (1981) Effects of glycerol feeding before and after exhausting exercise in rats. J Appl Physiol 50:94–101

    Google Scholar 

  32. Ville CA, White VK, Hastings AB (1982) Metabolism of 14 C-labelled glucose and pyruvate by rat diaphragm muscle in vitro. J Biol Chem 195:287–297

    Google Scholar 

  33. Wilmore JH, Costill DL (1974) Semiautomated systems approach to the assessment of oxygen uptake during exercise. J Appl Physiol 36:618–620

    Google Scholar 

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Correspondence to M. Gleeson.

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Gleeson, M., Maughan, R.J. & Greenhaff, P.L. Comparison of the effects of pre-exercise feeding of glucose, glycerol and placebo on endurance and fuel homeostasis in man. Europ. J. Appl. Physiol. 55, 645–653 (1986). https://doi.org/10.1007/BF00423211

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Key words

  • Exercise
  • Glucose ingestion
  • Glycerol ingestion
  • Endurance
  • Metabolism