Department of Public Health, Aarhus University, Aarhus, DENMARK.
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, DENMARK.
Med Sci Sports Exerc. 2022 Dec 1;54(12):2073-2086. doi: 10.1249/MSS.0000000000003002. Epub 2022 Jul 15.
We investigated the coupling between muscle glycogen content and localization and high-intensity exercise performance using a randomized, placebo-controlled, parallel-group design with emphasis on single-fiber subcellular glycogen concentrations and sarcoplasmic reticulum Ca 2+ kinetics.
Eighteen well-trained participants performed high-intensity intermittent glycogen-depleting exercise, followed by randomization to a high- (CHO; 1 g CHO·kg -1 ·h -1 ; n = 9) or low-carbohydrate placebo diet (PLA, <0.1 g CHO·kg -1 ·h -1 ; n = 9) for a 5-h recovery period. At baseline, after exercise, and after the carbohydrate manipulation assessments of repeated sprint ability (5 × 6-s maximal cycling sprints with 24 s of rest), neuromuscular function and ratings of perceived exertion during standardized high-intensity cycling (90% Wmax ) were performed, while muscle and blood samples were collected.
The exercise and carbohydrate manipulations led to distinct muscle glycogen concentrations in CHO and PLA at the whole-muscle (291 ± 78 vs 175 ± 100 mmol·kg -1 dry weight (dw), P = 0.020) and subcellular level in each of three local regions ( P = 0.001-0.046). This was coupled with near-depleted glycogen concentrations in single fibers of both main fiber types in PLA, especially in the intramyofibrillar region (within the myofibrils). Furthermore, increased ratings of perceived exertion and impaired repeated sprint ability (~8% loss, P < 0.001) were present in PLA, with the latter correlating moderately to very strongly ( r = 0.47-0.71, P = 0.001-0.049) with whole-muscle glycogen and subcellular glycogen fractions. Finally, sarcoplasmic reticulum Ca 2+ uptake, but not release, was superior in CHO, whereas neuromuscular function, including prolonged low-frequency force depression, was unaffected by dietary manipulation.
Together, these results support an important role of muscle glycogen availability for high-intensity exercise performance, which may be mediated by reductions in single-fiber levels, particularly in distinct subcellular regions, despite only moderately lowered whole-muscle glycogen concentrations.
我们采用随机、安慰剂对照、平行组设计，重点研究肌糖原含量和定位与高强度运动表现之间的关系，使用该设计调查了单纤维亚细胞糖原浓度和肌浆网 Ca 2+ 动力学与高强度间歇耗竭运动性能之间的关系。
18 名训练有素的参与者进行高强度间歇性糖原耗竭运动，然后随机分为高（CHO；约 1 g CHO·kg -1 ·h -1 ；n = 9）或低碳水化合物安慰剂饮食（PLA，<0.1 g CHO·kg -1 ·h -1 ；n = 9）组，进行 5 小时恢复期。在基线、运动后和碳水化合物操作评估重复冲刺能力（5×6 s 最大自行车冲刺，休息 24 s）、标准化高强度自行车运动时的神经肌肉功能和感知用力等级（~90% Wmax ）后，收集肌肉和血液样本。
运动和碳水化合物处理导致 CHO 和 PLA 在整个肌肉（291 ± 78 对 175 ± 100 mmol·kg -1 干重（dw），P = 0.020）和三个局部区域的亚细胞水平上产生不同的肌肉糖原浓度（P = 0.001-0.046）。这与 PLA 中两种主要纤维类型的单纤维中几乎耗尽的糖原浓度有关，尤其是在肌原纤维内区域（在肌原纤维内）。此外，在 PLA 中，感知用力程度增加和重复冲刺能力受损（~8%损失，P < 0.001），后者与整个肌肉糖原和亚细胞糖原分数中度至非常强烈相关（r = 0.47-0.71，P = 0.001-0.049）。最后，CHO 中的肌浆网 Ca 2+ 摄取更好，而不是释放，但神经肌肉功能，包括低频力抑制延长，不受饮食干预的影响。
总之，这些结果支持肌肉糖原可用性对高强度运动表现的重要作用，这可能是通过降低单纤维水平介导的，特别是在不同的亚细胞区域，尽管整个肌肉糖原浓度仅适度降低。
