Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UNITED KINGDOM.
Centro de Investigación en Fisiología del Ejercicio-CIFE, Facultad de Ciencias, Universidad Mayor, Santiago, CHILE.
Med Sci Sports Exerc. 2018 Nov;50(11):2339-2350. doi: 10.1249/MSS.0000000000001705.
Moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) are associated with different adjustments in motor output. Changes in motor unit (MU) peripheral properties may contribute to these adjustments, but this is yet to be elucidated. This study evaluated early changes in MU conduction velocity (MUCV) and MU action potential amplitude after 2 wk of either HIIT or MICT.
Sixteen men were assigned to either an MICT group or HIIT group (n = 8 each), and participated in six training sessions over 14 d. HIIT: 8 to 12 × 60-s intervals at 100% peak power output. Moderate-intensity continuous training: 90 to 120 min continuous cycling at ~65% V˙O2peak. Preintervention and postintervention, participants performed maximal voluntary contractions (MVC) and submaximal (10%, 30%, 50%, and 70% of MVC) isometric knee extensions while high-density EMG was recorded from the vastus medialis (VM) and vastus lateralis (VL) muscles. The high-density EMG was decomposed into individual MU by convolutive blind-source separation and tracked preintervention and postintervention.
Both training interventions induced changes in MUCV, but these changes depended on the type of training (P < 0.001). The HIIT group showed higher values of MUCV after training at all torque levels (P < 0.05), MICT only displayed changes in MUCV at low torque levels (10%-30% MVC, P < 0.002). There were no changes in MU action potential amplitude for either group (P = 0.2).
Two weeks of HIIT or MICT elicit differential changes in MUCV, likely due to the contrasting load and volume used in such training regimes. This new knowledge on the neuromuscular adaptations to training has implications for exercise prescription.
中等强度连续训练（MICT）和高强度间歇训练（HIIT）与运动输出的不同调整有关。运动单位（MU）外周特性的变化可能导致这些调整，但这尚未阐明。本研究评估了 HIIT 或 MICT 后 2 周 MU 传导速度（MUCV）和 MU 动作电位幅度的早期变化。
16 名男性被分配到 MICT 组或 HIIT 组（每组 n = 8），并在 14 天内参加了 6 次训练。HIIT：8 至 12 次，每次 60 秒，强度为 100%最大功率输出。中等强度连续训练：90 至 120 分钟连续自行车运动，强度约为 65%最大摄氧量峰值。干预前和干预后，参与者进行最大自主收缩（MVC）和亚最大（10%、30%、50%和 70%的 MVC）等长膝关节伸展运动，同时从股直肌（VM）和股外侧肌（VL）记录高密度肌电图。高密度肌电图通过卷积盲源分离分解为单个 MU，并在干预前和干预后进行跟踪。
两种训练干预都引起了 MUCV 的变化，但这些变化取决于训练类型（P < 0.001）。HIIT 组在所有扭矩水平下的 MUCV 值均高于训练后（P < 0.05），而 MICT 仅在低扭矩水平（10%-30%MVC，P < 0.002）下显示 MUCV 变化。两组的 MU 动作电位幅度均无变化（P = 0.2）。
2 周的 HIIT 或 MICT 引起 MUCV 的不同变化，这可能是由于两种训练方案使用的负荷和量不同所致。关于训练对神经肌肉适应性的新知识对运动处方具有重要意义。
