Impact of Muscle Glycogen Availability on the Capacity for Repeated Exercise in Man.

• Autores: James L.J. Bilzon, Abdullah F. Alghannam, Dawid Jedrzejewski, Mark G. Tweddle, Hannah Gribble, Dylan Thompson, Kostas Tsintzas, James A. Betts
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 48, Nº. 1, 2016, págs. 123-131
• Idioma: inglés
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• Resumen

  • AB Purpose: This study aims to examine whether muscle glycogen availability is associated with fatigue in a repeated exercise bout following short-term recovery. Methods: Ten endurance-trained individuals underwent two trials in a repeated-measures experimental design, each involving an initial run to exhaustion at 70% of V[spacing dot above]O2max (Run 1) followed by a 4-h recovery and a subsequent run to exhaustion at 70% of V[spacing dot above]O2max (Run 2). A low-carbohydrate (L-CHO; 0.3 g[middle dot]kg body mass-1[middle dot]h-1) or high-carbohydrate (H-CHO; 1.2 g[middle dot]kg body mass-1[middle dot]h-1) beverage was ingested at 30-min intervals during recovery. Muscle biopsies were taken upon cessation of Run 1, after recovery, and at exhaustion during Run 2 in L-CHO (F2). In H-CHO, muscle biopsies were obtained after recovery, at the time point coincident with fatigue in L-CHO (F2), and at the point of fatigue during the subsequent exercise bout (F3). Results: Run 2 was more prolonged for participants on H-CHO (80 +/- 16 min) than for participants on L-CHO (48 +/- 11 min; P < 0.001). Muscle glycogen concentrations were higher at the end of recovery for participants on H-CHO (269 +/- 84 mmol[middle dot]kg dry mass-1) than for participants on L-CHO (157 +/- 37 mmol[middle dot]kg dry mass-1; P = 0.001). The rate of muscle glycogen degradation during Run 2 was higher with H-CHO (3.1 +/- 1.5 mmol[middle dot]kg dry mass-1[middle dot]min-1) than with L-CHO (1.6 +/- 1.3 mmol[middle dot]kg dry mass-1[middle dot]min-1; P = 0.05). The concentration of muscle glycogen was higher with H-CHO than with L-CHO at F2 (123 +/- 28 mmol[middle dot]kg dry mass-1; P < 0.01), but no differences were observed between treatments at the respective points of exhaustion (78 +/- 22 mmol[middle dot]kg dry mass-1[middle dot]min-1 for H-CHO vs 72 +/- 21 mmol[middle dot]kg dry mass-1[middle dot]min-1 for L-CHO). Conclusion: Increasing carbohydrate intake during short-term recovery accelerates glycogen repletion in previously exercised muscles and thus improves the capacity for repeated exercise. The availability of skeletal muscle glycogen is therefore an important factor in the restoration of endurance capacity because fatigue during repeated exercise is associated with a critically low absolute muscle glycogen concentration