Laboratory of Biomechanics and Motor Behavior, State University of Rio de Janeiro, Rio de Janeiro, Brazil.
J Strength Cond Res. 2010 Oct;24(10):2749-54. doi: 10.1519/JSC.0b013e3181c6a139.
This study sought to compare the myoelectric activity of the hip adductors (HAs) and rectus femoris (RF) when the hip was in a neutral position or externally rotated by 30° or 50° (H0, H30, and H50, respectively) during a parallel squat. Ten healthy subjects performed 10 repetitions of squats in each of the 3 hip positions and the myoelectric activities of the HAs and RF were recorded. The signal was then divided into categories representing concentric (C) and eccentric (E) contractions in the following ranges of motion: 0-30° (C1 and E1), 30-60° (C2 and E2), and 60-90° (C3 and E3) of knee flexion. From those signals, an root mean square (RMS) value for each range of motion in each hip position was obtained. All values were normalized to those obtained during maximum voluntary isometric contraction. We found that HAs showed a significant increase in myoelectric activity during C3 and E3 in the H30 and H50 positions, as compared with H0. Meanwhile, RF activity did not significantly differ between hip positions. Both muscles showed higher activation during 60-90° (C3 and E3) of knee flexion, as compared with 0-30° (C1 and E1) and 30-60° (C2 and E2). The results suggest that if the aim is to increase HA activity despite the low percentage of muscle activation, squats should be performed with 30° of external rotation and at least 90° of knee flexion.
本研究旨在比较髋关节处于中立位（H0）或外旋 30°（H30）或 50°（H50）时，在平行深蹲中髋关节内收肌（HAs）和股直肌（RF）的肌电活动。10 名健康受试者分别在 3 种髋关节位置下完成 10 次深蹲，记录 HAs 和 RF 的肌电活动。然后，将信号分为代表屈髋 0-30°（C1 和 E1）、30-60°（C2 和 E2）和 60-90°（C3 和 E3）的同心（C）和偏心（E）收缩的类别。从这些信号中，获得每个髋关节位置在每个运动范围内的均方根（RMS）值。所有值均归一化为最大随意等长收缩时的值。我们发现，与 H0 相比，HAs 在 H30 和 H50 位置的 C3 和 E3 时肌电活动明显增加。同时，RF 活动在髋关节位置之间没有显著差异。与 0-30°（C1 和 E1）和 30-60°（C2 和 E2）相比，在 60-90°（C3 和 E3）时，两个肌肉的激活度都更高。结果表明，尽管肌肉激活百分比较低，如果目的是增加 HA 活动，则应进行外旋 30°和至少 90°的膝关节屈曲的深蹲。
