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

作者：Gejl Kasper Degn; Hvid Lars Grondahl; Frandsen Ulrik; Jensen Kurt; Sahlin Kent; Ortenblad Niels^*

来源：Medicine and Science in Sports and Exercise, 2014, 46(3): 496-505.

DOI：10.1249/MSS.0000000000000132

• FATIGUE
• RECOVERY
• CALCIUM REGULATION
• ELITE ATHLETES
• MUSCLE FUNCTION

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 (W-peak) in elite endurance athletes. Methods Fourteen highly trained male triathletes (VO2max = 66.5 +/- 1.3 mL O-2 center dot kg(-1)center 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 center 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, r(2) = 0.30). The 4 h of cycling exercise reduced W-peak by 5.5%-8.9% at different cadences (P < 0.05), and W-peak was normalized after 4 h of recovery with CHO, whereas W-peak remained depressed (P < 0.05) after water provision. W-peak 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 W-peak 4 h postexercise.

• 出版日期2014-3