Muscle Glycogen Content Modifies SR Ca2+ Release Rate in Elite Endurance Athletes.

• Autores: Kasper D. Gejl, Niels Ortenblad, Lars Grondahl Hvid, Kent Sahlin, Ulrik Frandsen, Kurt Jensen
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 46, Nº. 3, 2014, págs. 496-505
• Idioma: inglés
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• Resumen

  • AB Purpose: The aim of the present study was to investigate the influence of muscle glycogen content on sarcoplasmic reticulum (SR) function and peak power output (Wpeak) in elite endurance athletes. Methods: Fourteen highly trained male triathletes (V[spacing dot above]O2max = 66.5 +/- 1.3 mL O2[middle dot]kg-1[middle dot]min-1), performed 4 h of glycogen-depleting cycling exercise (HRmean = 73% +/- 1% of maximum). During the first 4 h of recovery, athletes received either water (H2O) or carbohydrate (CHO), separating alterations in muscle glycogen content from acute changes affecting SR function and performance. Thereafter, all subjects received CHO-enriched food for the remaining 20-h recovery period. Results: Immediately after exercise, muscle glycogen content and SR Ca2+ release rate was reduced to 32% +/- 4% (225 +/- 28 mmol[middle dot]kg-1 dw) and 86% +/- 2% of initial levels, respectively (P < 0.01). Glycogen markedly recovered after 4 h of recovery with CHO (61% +/- 2% of preexercise) and SR Ca2+ release rate returned to preexercise level. However, in the absence of CHO during the first 4 h of recovery, glycogen and SR Ca2+ release rate remained depressed, with the normalization of both parameters at the end of the 24 h of recovery after receiving a CHO-enriched diet. Linear regression demonstrated a significant correlation between SR Ca2+ release rate and muscle glycogen content (P < 0.01, r2 = 0.30). The 4 h of cycling exercise reduced Wpeak by 5.5%-8.9% at different cadences (P < 0.05), and Wpeak was normalized after 4 h of recovery with CHO, whereas Wpeak remained depressed (P < 0.05) after water provision. Wpeak was fully recovered after 24 h in both the H2O and the CHO group. Conclusion: In conclusion, the present results suggest that low muscle glycogen depresses muscle SR Ca2+ release rate, which may contribute to fatigue and delayed recovery of Wpeak 4 h postexercise