Hokken Rune, Laugesen Simon, Aagaard Per, Suetta Charlotte, Frandsen Ulrik, Ørtenblad Niels, Nielsen Joachim
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark.
Geriatric Research Unit, Department of Geriatrics, Bispebjerg-Frederiksberg and Herlev-Gentofte Hospitals, University of Copenhagen, Kobenhavn, Denmark.
Acta Physiol (Oxf). 2021 Feb;231(2):e13561. doi: 10.1111/apha.13561. Epub 2020 Oct 4.
Glycogen particles are found in different subcellular localizations, which are utilized heterogeneously in different fibre types during endurance exercise. Although resistance exercise typically involves only a moderate use of mixed muscle glycogen, the hypothesis of the present study was that high-volume heavy-load resistance exercise would mediate a pattern of substantial glycogen depletion in specific subcellular localizations and fibre types.
10 male elite weightlifters performed resistance exercise consisting of four sets of five (4 × 5) repetitions at 75% of 1RM back squats, 4 × 5 at 75% of 1RM deadlifts and 4 × 12 at 65% of 1RM rear foot elevated split squats. Muscle biopsies (vastus lateralis) were obtained before and after the exercise session. The volumetric content of intermyofibrillar (between myofibrils), intramyofibrillar (within myofibrils) and subsarcolemmal glycogen was assessed by transmission electron microscopy.
After exercise, biochemically determined muscle glycogen decreased by 38 (31:45)%. Location-specific glycogen analyses revealed in type 1 fibres a large decrement in intermyofibrillar glycogen, but no or only minor changes in intramyofibrillar or subsarcolemmal glycogen. In type 2 fibres, large decrements in glycogen were observed in all subcellular localizations. Notably, a substantial fraction of the type 2 fibres demonstrated near-depleted levels of intramyofibrillar glycogen after the exercise session.
Heavy resistance exercise mediates a substantial utilization of glycogen from all three subcellular localization in type 2 fibres, while mostly taxing intermyofibrillar glycogen stores in type 1 fibres. Thus, a better understanding of the impact of resistance training on myocellular metabolism and performance requires a focus on compartmentalized glycogen utilization.
糖原颗粒存在于不同的亚细胞定位中，在耐力运动期间，不同纤维类型对其利用存在异质性。尽管抗阻运动通常仅适度消耗混合肌糖原，但本研究的假设是，高强度大负荷抗阻运动会导致特定亚细胞定位和纤维类型中糖原大量消耗。
10名男性精英举重运动员进行抗阻运动，包括四组五次（4×5）重复的1RM后深蹲，负荷为1RM的75%；四组五次（4×5）重复的1RM硬拉，负荷为1RM的75%；四组十二次（4×12）重复的1RM后足抬高分腿蹲，负荷为1RM的65%。在运动前后获取肌肉活检样本（股外侧肌）。通过透射电子显微镜评估肌原纤维间（肌原纤维之间）、肌原纤维内（肌原纤维内）和肌膜下糖原的体积含量。
运动后，生化测定的肌肉糖原减少了38（31:45）%。特定位置的糖原分析显示，在1型纤维中，肌原纤维间糖原大幅减少，但肌原纤维内或肌膜下糖原无变化或仅有微小变化。在2型纤维中，所有亚细胞定位的糖原均大幅减少。值得注意的是，相当一部分2型纤维在运动后肌原纤维内糖原水平接近耗尽。
大负荷抗阻运动导致2型纤维中所有三个亚细胞定位的糖原大量消耗，而1型纤维主要消耗肌原纤维间的糖原储备。因此，要更好地理解抗阻训练对肌细胞代谢和性能的影响，需要关注糖原的分区利用。
