Carbohydrate Dependence During Hard-Intensity Exercise in Trained Cyclists in the Competitive Season: Importance of Training Status

Abstract

To test the hypothesis that intensive endurance training increases CHO utilisation during hard-intensity exercise, seven competitive road cyclists (Cy) performed three 50-min steady-state exercise tests on a cycle ergometer above their ventilatory threshold (+ 15 %) over the course of a cycling season (January [ET1], May [ET2] and September [ET3]). We compared the data with the baseline values of seven sedentary controls (Sed). CHO oxidation in Cy was higher in ET2 and ET3 than in ET1 (p < 0.05), was lower in ET3 than in ET2 (p < 0.05) and was higher in Cy than in Sed only in ET2 (p < 0.05). Lactate kinematics were lower in Cy than in Sed in all conditions (p < 0.05), but in Cy they were lower in ET2 than in ET1 and higher in ET3 than in ET2 (p < 0.05). Race performance was impaired and the overtraining score was increased at ET3 in comparison with ET2 (p < 0.05). We conclude that competitive cyclists increase CHO oxidation during hard-intensity exercise over the course of a season, but show a decline by the end of the season in association with the appearance of an overtraining state. Thus, well-trained cyclists develop a CHO dependence, which is modified with training status.

Key words

Indirect calorimetry - performance - overtraining - substrate oxidation

References

• 1 Aïssa Benhaddad A, Bouix D, Khaled S, Michallef J P, Mercier J, Bringer I, Brun J F. Early hemorheology aspects of overtraining in elite athletes.  Clinical Hemorheology. 1999;  20 117-125
• 2 Barstow T J. Characterization of VO₂ kinetics during heavy exercise.  Med Sci Sports Exerc. 1994;  26 1327-1334
• 3 Borg G AV. Perceived exertion: a note on “history” and methods.  Med Sci Sports Exerci. 1973;  5 90-93
• 4 Bosquet L, Leger L, Legros P. Blood lactate response to overtraining in male endurance athletes.  Eur J Appl Physiol. 2001;  84 107-114
• 5 Beaver W L, Wassermann K, Whipp B J. A new method for detecting anaerobic threshold by gas exchange.  J Appl Physiol. 1986;  60 217-225
• 6 Brooks G A, Mercier J. Balance of carbohydrate and lipid utilization during exercise: the “crossover” concept.  J Appl Physiol. 1994;  76 2253-2261
• 7 Brooks G A. Importance of the “crossover” concept in exercise metabolism.  Clin Exp Pharmacol Physiol. 1997;  24 889-895
• 8 Brooks G A, Dubouchaud H, Brown M, Sicurello J P, Butz C E. Role of mitochondrial lactate dehydrogenase and lactate oxidation in the intracellular lactate shuttle.  Proc Natl Acad Sci USA. 1999;  96 1129-1134
• 9 Coggan A R, Kohrt W M, Spina R J, Bier D M, Holloszy J O. Endurance training decreases plasma glucose turnover and oxidation during moderate-intensity exercise.  J Appl Physiol. 1990;  68 990-996
• 10 Coggan A R, Kohrt W M, Spina R J, Kirwan J P, Bier D M, Holloszy J O. Plasma glucose kinetics during exercise in subjects with high and low lactate thresholds.  J Appl Physiol. 1992;  73 1873-1880
• 11 Costill D L, Flynn M G, Kirwan J P, Houmard J A, Mitchell J B, Thomas R, Park S H. Effects of repeated days of intensified training on muscle glycogen and swimming performance.  Med Sci Sports Exerc. 1988;  27 249-254
• 12 Donovan C M, Brooks G A. Endurance training affects lactate clearance, not lactate production.  Am J Physiol. 1983;  244 E83-E92
• 13 Durnin J VGA, Rahaman M N. The assessment of fat in the human body from measurement of skinfold thickness.  Br J Nut. 1967;  21 681-689
• 14 Febbraio M A, Lambert D L, Starkie R L, Proietto J, Hargreaves M. Effect of epinephrine on muscle glycogenolysis during exercise in trained men.  J Appl Physiol. 1998;  84 465-470
• 15 Fry R W, Morton A R, Keast D. Overtraining in athletes. An update.  Sports Med. 1991;  12 32-65
• 16 Gaesser G A. Influence of endurance training and catecholamines on exercise VO₂ response.  Med Sci Sports Exerc. 1994;  26 1341-1346
• 17 Gollnick P D. Metabolism of substrates: energy substrate metabolism during exercise and as modified by training.  Federation Proc. 1985;  44 353-357
• 18 Holloszy J O, Coyle E F. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences.  J Appl Physiol. 1984;  56 831-838
• 19 Holloszy J O, Kohrt W D. Regulation of carbohydrate and fat metabolism during and after exercise.  Annu Rev Nutr. 1996;  16 121-138
• 20 Hohorst H. L-(+)-Lactate: determination with lactic dehydrogenase and DPN. In: Bergmeyer HU (ed) Methods of Enzymatic Analysis. New York; Academic 1963: 266-270
• 21 Jeukendrup A E, Mensink M, Saris W HM, Wagenmarkers A MJ. Exogenous glucose oxidation during exercise in endurance-trained and untrained subjects.  J Appl Physiol. 1997;  82 835-840
• 22 Kanaley J A, Mottram C D, Scanlon P D, Jensen M D. Fatty acid kinetic responses to running above or below lactate threshold.  J Appl Physiol. 1995;  79 439-447
• 23 Karlsson J, Jacobs I. Muscle glycogen utilization during exercise and after training.  Acta Physiol Scand. 1974;  90 210-217
• 24 Kiens B, Essen-Gustavsson B, Christensen N J, Saltin B. Skeletal muscle substrate utilization during submaximal exercise in man: effect of endurance training.  J Appl Lon. 1993;  469 459-478
• 25 Knopfli B, Calvert , Bar-Or O, Villiger B, von Duvillard S P. Competition performance and basal nocturnal catecholamine excretion in cross-country skiers.  Med Sci Sports Exerc. 2001;  33 1228-1232
• 26 Legros P. Le groupe de surentraînement. Le surentraînement: diagnostic des manifestations psychocomportementales précoses.  Science Sports. 1993;  8 71-77
• 27 Lehman M J, Lormes W, Opitz-Gess A, Steinacker J M, Netzer N, Foster C, Gastmann U. Training and overtraining: an overview and experimental results in endurance sports.  J Sports Med Phys Fitness. 1997;  37 7-17
• 28 Manetta J, Khaled S, Bouix D, Krechiem K, Brun J F, Orsetti A. Evaluation d’un questionnaire alimentaire court par comparaison avec un entretien diététique chez des sujets sportifs et sédentaires.  Science Sport. 1997;  12 210-213
• 29 Manetta J, Brun J F, Mercier J, Préfaut C. The effects of exercise training intensification on glucose disposal in elite cyclists.  Int J Sports Med. 2000;  21 338-343
• 30 Manetta J, Brun J F, Mercier J, Préfaut C. Insulin and non-insulin-dependent glucose disposal in middle-aged and young athletes versus sedentary men.  Metabolism. 2001;  50 349-354
• 31 Manetta J, Brun J F, Pérez-Martin A, Callis A, Préfaut P, Mercier J. Fuel oxidation during exercise in middle-aged men: Effect of training and glucose disposal.  Med Sci Sports Exerc. 2002;  34 423-429
• 32 Mazzeo R S, Marshall P. Influence of plasma catecholamines on the lactate threshold during graded exercise.  J Appl Physiol. 1989;  67 1319-1322
• 33 McGilvery R W, Goldstein G W. Biochemistry. A Functional Approach. Philadelphia; PA: Saunders 1983: 810-976
• 34 Millet G P, Millet G Y, Hofmann M D, Candeau R B. Alterations in running economy and mechanics after maximal cycling in triathletes: influence of performance level.  Int J Sports Med. 2000;  21 127-132
• 35 Molé P A, Oscia L B, Holloszy J O. Adaptation of muscle to exercise. Increase in level of palmityl CoA synthetase, carnitine palmityltransferase, and palmityl CoA deshydrogenase, and in the capacity to oxidize fatty acids.  J Clin Invest. 1971;  50 2323-2330
• 36 O'Brien M J, Viguie A, Mazzeo R S, Brooks G A. Carbohydrate dependence during marathon running.  Med Sci Sports Exerc. 1993;  25 1009-1017
• 37 Peronnet F, Massicote D. Table of nonprotein respiratory quotient: an uptake.  Can J Sport. 1991;  16 23-29
• 38 Petibois C, Cazorla G, Deleris G. FT-IR spectroscopy utilization to sportsmen fatigability evaluation and control.  Med Sci Sports Exerc. 2000;  33 1228-1232
• 39 Romijn J A, Coyle E F, Sidossis L S, Hibbert J, Wolfe R R. Comparison of indirect calorimetry and a new 13C/12C ratio method during strenuous exercise.  Am J Physiol. 1992;  263 E64-E71
• 40 Romijn J A, Coyle E F, Sidossis L S, Gastaldelli A G, Horowitz J F, Endert E, Wolfe R R. Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration.  Am J Physiol. 1993;  265 E380-E391
• 41 Sidossis L S, Wolfe R R, Coggan A R. Regulation of fatty acid oxidation in untrained vs. trained men during exercise.  Am J Physiol. 1998;  274 E510-E515
• 42 Snyder A C, Kuipers H, Cheng B, Servais R, Fransen E. Overtraining following intensified training with normal muscle glycogen.  Med Sci Sports Exerc. 1995;  27 1063-1070
• 43 Urhausen A, Gabriel H HW, Weiler B, Kinderman W. Ergometric and psychological findings during overtraining: A long term follow-up study in endurance athletes.  Int J Sports Med. 1997;  19 114-120
• 44 Whipp B J. The slow component of O₂ uptake kinetics during heavy exercise.  Med Sci Sports Exerc. 1994;  26 1319-1326