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A signalling role for muscle glycogen in the regulation of pace during prolonged exercise.
Br J Sports Med. 2005 Jan; 39(1):34-8.BJ

Abstract

INTRODUCTION

In this study we examined the pacing strategy and the end muscle glycogen contents in eight cyclists, once when they were carbohydrate loaded and once when they were non-loaded.

METHODS

Cyclists completed 2 hours of cycling at approximately 73% of maximum oxygen consumption, which included five sprints at 100% of peak sustained power output every 20 minutes, followed immediately by a 1 hour time trial. Muscle biopsies were performed before and immediately after exercise, while blood samples were taken during the 2 hour steady state rides and immediately after exercise.

RESULTS

Carbohydrate loading improved mean power output during the 1 hour time trial (mean (SEM) 219 (17) v 233 (15) W; p<0.05) and enabled subjects to use significantly more muscle glycogen than during the trial following their normal diet. Significantly, the subjects, kept blind to all feedback except for time, started both time trials at similar workloads (approximately 30 W), but after 1 minute of cycling, the workload average 14 W higher throughout the loaded compared with the non-loaded time trial. There were no differences in subjects' plasma glucose and lactate concentrations and heart rates in the carbohydrate loaded versus the non-loaded trial. Of the eight subjects, seven improved their time trial performance after carbohydrate loading. Finishing muscle glycogen concentrations in these seven subjects were remarkably similar in both trials (18 (3) v 20 (3) mmol/kg w/w), despite significantly different starting values and time trial performances (36.55 (1.47) v 38.14 (1.27) km/h; p<0.05). The intra-subject coefficient of variation (CV) for end glycogen content in these seven subjects was 10%, compared with an inter-subject CV of 43%.

CONCLUSIONS

As seven subjects completed the time trials with the same end exercise muscle glycogen concentrations, diet induced changes in pacing strategies during the time trials in these subjects may have resulted from integrated feedback from the periphery, perhaps from glycogen content in exercising muscles.

Authors+Show Affiliations

UCT/MRC Research Unit for Exercise Science and Sports Medicine, Sports Science Institute, Boundary Road, Newlands, Cape Town 7700, South Africa. lrauch@sports.uct.ac.zaNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Journal Article
Randomized Controlled Trial

Language

eng

PubMed ID

15618337

Citation

Rauch, H G L., et al. "A Signalling Role for Muscle Glycogen in the Regulation of Pace During Prolonged Exercise." British Journal of Sports Medicine, vol. 39, no. 1, 2005, pp. 34-8.
Rauch HG, St Clair Gibson A, Lambert EV, et al. A signalling role for muscle glycogen in the regulation of pace during prolonged exercise. Br J Sports Med. 2005;39(1):34-8.
Rauch, H. G., St Clair Gibson, A., Lambert, E. V., & Noakes, T. D. (2005). A signalling role for muscle glycogen in the regulation of pace during prolonged exercise. British Journal of Sports Medicine, 39(1), 34-8.
Rauch HG, et al. A Signalling Role for Muscle Glycogen in the Regulation of Pace During Prolonged Exercise. Br J Sports Med. 2005;39(1):34-8. PubMed PMID: 15618337.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A signalling role for muscle glycogen in the regulation of pace during prolonged exercise. AU - Rauch,H G L, AU - St Clair Gibson,A, AU - Lambert,E V, AU - Noakes,T D, PY - 2004/12/25/pubmed PY - 2005/2/19/medline PY - 2004/12/25/entrez SP - 34 EP - 8 JF - British journal of sports medicine JO - Br J Sports Med VL - 39 IS - 1 N2 - INTRODUCTION: In this study we examined the pacing strategy and the end muscle glycogen contents in eight cyclists, once when they were carbohydrate loaded and once when they were non-loaded. METHODS: Cyclists completed 2 hours of cycling at approximately 73% of maximum oxygen consumption, which included five sprints at 100% of peak sustained power output every 20 minutes, followed immediately by a 1 hour time trial. Muscle biopsies were performed before and immediately after exercise, while blood samples were taken during the 2 hour steady state rides and immediately after exercise. RESULTS: Carbohydrate loading improved mean power output during the 1 hour time trial (mean (SEM) 219 (17) v 233 (15) W; p<0.05) and enabled subjects to use significantly more muscle glycogen than during the trial following their normal diet. Significantly, the subjects, kept blind to all feedback except for time, started both time trials at similar workloads (approximately 30 W), but after 1 minute of cycling, the workload average 14 W higher throughout the loaded compared with the non-loaded time trial. There were no differences in subjects' plasma glucose and lactate concentrations and heart rates in the carbohydrate loaded versus the non-loaded trial. Of the eight subjects, seven improved their time trial performance after carbohydrate loading. Finishing muscle glycogen concentrations in these seven subjects were remarkably similar in both trials (18 (3) v 20 (3) mmol/kg w/w), despite significantly different starting values and time trial performances (36.55 (1.47) v 38.14 (1.27) km/h; p<0.05). The intra-subject coefficient of variation (CV) for end glycogen content in these seven subjects was 10%, compared with an inter-subject CV of 43%. CONCLUSIONS: As seven subjects completed the time trials with the same end exercise muscle glycogen concentrations, diet induced changes in pacing strategies during the time trials in these subjects may have resulted from integrated feedback from the periphery, perhaps from glycogen content in exercising muscles. SN - 1473-0480 UR - https://www.unboundmedicine.com/medline/citation/15618337/A_signalling_role_for_muscle_glycogen_in_the_regulation_of_pace_during_prolonged_exercise_ L2 - http://bjsm.bmj.com/cgi/pmidlookup?view=long&amp;pmid=15618337 DB - PRIME DP - Unbound Medicine ER -