Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, CANADA.
Med Sci Sports Exerc. 2020 Jan;52(1):205-213. doi: 10.1249/MSS.0000000000002091.
Blood flow-restricted or occlusion exercise enhances muscle hypertrophy and strength during resistance training. The acute effects on voluntary and electrically evoked muscle contractile characteristics with impaired blood flow at low- and high-contraction forces have not been explored.
On separate days, nine males completed two different protocols of concentric elbow flexor contractions. A repetitive low-force (25% of isometric maximum voluntary contraction [MVC]) with blood flow occlusion (BFO) (300 mm Hg) protocol was compared with a high-force (80% MVC) free blood flow protocol (HF), until range of motion (0°-90°) was impaired. Torque, velocity, and power were compared with baseline and between protocols. Maximum voluntary contraction and voluntary activation were assessed during and after each protocol. Muscle twitch, low (20 Hz) and high (50 Hz) tetanus, and compound muscle action potential (Mmax) area were measured at 0, 2, 5, 10, and 20 min of recovery.
Repetitions to failure (FP) were lower for HF (16) versus BFO (21), and MVC at FP was reduced more during BFO (77%) compared with HF (23%), with no difference in voluntary activation (10% loss) between protocols. At FP, velocities for BFO and HF were similarly reduced by approximately 63% and 56%, respectively; however, peak power decreased more during BFO (90%) compared with HF (67%). Total work for BFO was approximately 40% lower than for HF. Peak power for HF was recovered by 2 min, whereas BFO required 20 min. Low-frequency fatigue (20 Hz/50 Hz) was greater after BFO (70% decrease vs ~29% decrease after HF), whereas Mmax area was unaffected.
Concentric elbow flexions at low-force with BFO cause greater impairments in strength and power than HF and, therefore, may be a replacement for high-force exercise used in chronic training.
血流限制或闭塞运动在抗阻训练中增强肌肉肥大和力量。在低收缩力和高收缩力下血流受损时，自愿和电诱发肌肉收缩特性的急性影响尚未被探索。
在不同的日子里，九名男性完成了两种不同的向心肘屈肌收缩方案。一个重复的低力（25%的等长最大自主收缩[MVC]）与血流闭塞（BFO）（300mmHg）方案相比，一个高力（80% MVC）自由血流方案（HF），直到运动范围（0°-90°）受损。比较力矩、速度和功率与基线和方案之间的关系。在每个方案期间和之后评估最大自主收缩和自愿激活。在 0、2、5、10 和 20 分钟恢复时测量肌肉抽搐、低（20Hz）和高（50Hz）强直和复合肌肉动作电位（Mmax）面积。
HF（16）的重复次数低于 BFO（21），并且 BFO 时的 MVC 降低更多（77%），而 BFO（10%）和 HF（23%）之间的自愿激活没有差异。在 FP 时，BFO 和 HF 的速度分别降低了约 63%和 56%；然而，BFO 时的峰值功率降低更多（90%），HF（67%）时的峰值功率降低更多。BFO 的总工作量比 HF 低约 40%。HF 的峰值功率在 2 分钟内恢复，而 BFO 需要 20 分钟。BFO 后的低频疲劳（20Hz/50Hz）更高（70%的降低与 HF 后的~29%的降低相比），而 Mmax 区域不受影响。
低力下的向心肘屈肌 BFO 比 HF 引起更大的力量和功率下降，因此可能替代慢性训练中使用的高力运动。
