Department of Sport Science and Physical Education, Faculty of Health and Sport Sciences, University of Agder, Kristiansand, Norway.
Norwegian Olympic Federation, Oslo, Norway.
Scand J Med Sci Sports. 2021 Jul;31(7):1420-1439. doi: 10.1111/sms.13952. Epub 2021 May 7.
The purpose of the present study was to compare the effects of short-term high-frequency failure vs non-failure blood flow-restricted resistance exercise (BFRRE) on changes in satellite cells (SCs), myonuclei, muscle size, and strength. Seventeen untrained men performed four sets of BFRRE to failure (Failure) with one leg and not to failure (Non-failure; 30-15-15-15 repetitions) with the other leg using knee-extensions at 20% of one repetition maximum (1RM). Fourteen sessions were distributed over two 5-day blocks, separated by a 10-day rest period. Muscle samples obtained before, at mid-training, and 10-day post-intervention (Post10) were analyzed for muscle fiber area (MFA), myonuclei, and SC. Muscle size and echo intensity of m.rectus femoris (RF) and m.vastus lateralis (VL) were measured by ultrasonography, and knee extension strength with 1RM and maximal isometric contraction (MVC) up until Post24. Both protocols increased myonuclear numbers in type-1 (12%-17%) and type-2 fibers (20%-23%), and SC in type-1 (92%-134%) and type-2 fibers (23%-48%) at Post10 (p < 0.05). RF and VL size increased by 5%-10% in both legs at Post10 to Post24, whereas the MFA of type-1 fibers in Failure was decreased at Post10 (-10 ± 16%; p = 0.02). Echo intensity increased by ~20% in both legs during Block1 (p < 0.001) and was ~8 to 11% below baseline at Post24 (p = 0.001-0.002). MVC and 1RM decreased by 5%-10% after Block1, but increased in both legs by 6%-11% at Post24 (p < 0.05). In conclusion, both short-term high-frequency failure and non-failure BFRRE induced increases in SCs, in myonuclei content, muscle size, and strength, concomitant with decreased echo intensity. Intriguingly, the responses were delayed and peaked 10-24 days after the training intervention. Our findings may shed light on the mechanisms involved in resistance exercise-induced overreaching and supercompensation.
本研究旨在比较短期高频力竭与非力竭血流限制阻力训练（BFRRE）对卫星细胞（SCs）、肌核、肌肉大小和力量变化的影响。17 名未经训练的男性使用膝关节伸展器以 20%的 1 次最大重复（1RM）进行 BFRRE，一组力竭（Failure），一组非力竭（Non-failure；30-15-15-15 次），分别用一条腿完成。共进行 14 次训练，分布在两个 5 天的训练块中，中间间隔 10 天的恢复期。在干预前、训练中期和 10 天干预后（Post10）采集肌肉样本，分析肌肉纤维面积（MFA）、肌核和 SC。通过超声测量股直肌（RF）和股外侧肌（VL）的肌肉大小和回声强度，通过 1RM 和最大等长收缩（MVC）测量膝关节伸展强度，直至 Post24。两种方案均能增加 1 型（12%-17%）和 2 型纤维（20%-23%）的肌核数量，以及 1 型（92%-134%）和 2 型纤维（23%-48%）的 SC 数量，在 Post10 时达到统计学意义（p<0.05）。RF 和 VL 的大小在两条腿中均增加了 5%-10%，在 Post10 到 Post24 之间，而 Failure 组的 1 型纤维 MFA 在 Post10 时减少了（-10±16%；p=0.02）。在 Block1 期间，两条腿的回声强度增加了约 20%（p<0.001），在 Post24 时降至基线以下约 8-11%（p=0.001-0.002）。Block1 后，MVC 和 1RM 减少了 5%-10%，但在 Post24 时，两条腿的 MVC 和 1RM 均增加了 6%-11%（p<0.05）。总之，短期高频力竭和非力竭 BFRRE 均能增加 SC、肌核含量、肌肉大小和力量，同时降低回声强度。有趣的是，这些反应延迟，在训练干预后 10-24 天达到峰值。我们的研究结果可能为阻力训练引起的过度训练和超补偿的机制提供了一些启示。
