Wang Aiwen, Li Xiaohan, Huang Huiming
Faculty of Sport Science, Research Academy of Grand Health, Ningbo University, Ningbo 315211, China.
Brain Sci. 2021 Apr 25;11(5):541. doi: 10.3390/brainsci11050541.
Poor knee biomechanics in a volleyball spike jump generally result in a higher knee injury risk, which can be altered by an internal focus of attention (FOA). The constrained action hypothesis (CAH) purports that the FOA inhibits sports performance whereas no ecologically valid evidence has been found in previous studies. The purpose of this research is to explore the effect of video feedback on knee biomechanics in a volleyball spike jump including landing and take-off phases. The video feedback was performed in a natural way. Fourteen volleyball male players were recruited in this study. A paired t-test was used to detect the effect of the feedback; meanwhile, statistical parameter mapping (SPM) statistics were used for the continuum differences during movement. After biofeedback, the initial contact flexion angle of the knee ( = 2.179, = 0.049), the maximal flexion angle of the knee ( = 3.242, = 0.006) and the maximal internal rotation angular velocity of the knee ( = 5.209, = 0.003) increased significantly; the maximal extension moment of the knee ( = 3.962, < 0.001) and the maximal flexion moment of the knee ( = -3.711, = 0.002) significantly decreased; the maximal abduction moment significantly decreased ( = 3.069, = 0.037) but the maximal internal rotation moment significantly increased ( = 2.813, = 0.018); the first peak of the vertical ground reaction force (vGRF) ( = 7.618, < 0.001) and the average loading rate to the first peak ( = 4.205, = 0.004) significantly decreased; the other peaks of the vGRF were not found to have differences; a larger knee flexion was found during the phase from 31.17 to 73.19% ( = 2.611, = 0.012); a larger adduction angular velocity was found during the phase from 49.07 to 62.46% ( = 3.148, = 0.004); a smaller external rotational angular velocity was found during the phase from 45.85 to 49.96% ( = 5.011 = 0.017); there was an increased flexion moment of the knee during the phase from 19.72 to 21.38% ( = 0.029, = 0.029) and an external moment of the knee during the phase from 85.55 to 95.06% ( = 4.214, < 0.001); the vGRF significantly decreased during the phase from 3.13 to 5.94% ( = 4.096, = 0.014) and 19.83-21.97% ( = 4.096, = 0.024) but significantly increased in the phase of 91.43-100% ( = 4.096, < 0.001). The impulse of the vGRF and knee power were not found to be different compared with before biofeedback. Therefore, our study suggests video feedback in a natural practice has the potential to improve knee movement whilst not altering the performance in a volleyball spike jump. This indicates that the CAH theory is possibly not suitable in a real competition. Due to the complexity of human movements and the limitations of this study, muscle activities must be considered in the future.
排球扣球跳中膝关节生物力学不佳通常会导致更高的膝关节受伤风险，而注意力内部焦点（FOA）可以改变这种情况。受限行动假说（CAH）声称，注意力内部焦点会抑制运动表现，然而在以往研究中尚未发现具有生态学效度的证据。本研究的目的是探讨视频反馈对排球扣球跳（包括落地和起跳阶段）中膝关节生物力学的影响。视频反馈以自然的方式进行。本研究招募了14名男性排球运动员。采用配对t检验来检测反馈的效果；同时，使用统计参数映射（SPM）统计方法来分析运动过程中的连续差异。生物反馈后，膝关节的初始接触屈曲角度（t = 2.179，p = 0.049）、最大屈曲角度（t = 3.242，p = 0.006）和最大内旋角速度（t = 5.209，p = 0.003）显著增加；膝关节的最大伸展力矩（t = 3.962，p < 0.001）和最大屈曲力矩（t = -3.711，p = 0.002）显著降低；最大外展力矩显著降低（t = 3.069，p = 0.037），但最大内旋力矩显著增加（t = 2.813，p = 0.018）；垂直地面反作用力（vGRF）的第一个峰值（t = 7.618，p < 0.001）和到第一个峰值的平均加载率（t = 4.205，p = 0.004）显著降低；未发现vGRF的其他峰值有差异；在31.17%至73.19%阶段发现膝关节有更大的屈曲（t = 2.611，p = 0.012）；在49.07%至62.46%阶段发现有更大的内收角速度（t = 3.148，p = 0.004）；在45.85%至49.96%阶段发现有更小的外旋角速度（t = 5.011，p = 0.017）；在19.72%至21.38%阶段膝关节的屈曲力矩增加（t = 0.029，p = 0.029），在85.55%至95.06%阶段膝关节有一个外展力矩（t = 4.214，p < 0.001）；在3.13%至5.94%阶段（t = 4.096，p = 0.014）和19.83 - 21.97%阶段（t = 4.096，p = 0.024）vGRF显著降低，但在91.43%至100%阶段显著增加（t = 4.096，p < 0.001）。与生物反馈前相比，未发现vGRF的冲量和膝关节功率有差异。因此，我们的研究表明，在自然练习中的视频反馈有改善膝关节运动的潜力，同时不会改变排球扣球跳的表现。这表明受限行动假说理论可能不适用于实际比赛。由于人类运动的复杂性以及本研究的局限性，未来必须考虑肌肉活动。
