Fujimoto Masahiro, Uchida Eri, Nagano Akinori, Rogers Mark W, Isaka Tadao
Human Augmentation Research Center, National Institute of Advanced Industrial Science and Technology, Kashiwa, Japan.
College of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan.
Front Sports Act Living. 2021 May 17;3:670649. doi: 10.3389/fspor.2021.670649. eCollection 2021.
Lower-limb weight-bearing load distribution in stationary standing influences the timing of rapid first step initiation of importance for functional movement activities and agility performance in sports. This study investigated the effect of pre-step lower-limb loading and unloading with preparatory knee flexion-extension movements on sidestepping performance in fifteen male collegiate basketball players. Participants performed two-choice (step limb) reaction time sidestepping under two conditions: without preparatory movements before the go cue (no-prep-NP) and with continuous alternating knee extension and flexion movements (prep-P). The reaction signal was provided at the beginning of knee extension and flexion and during these movements which corresponded with the largest and smallest loading instants and the transition states between those instants. Sidestepping performance was assessed with three-dimensional kinematic data and ground reaction forces. Step initiation onset time was significantly faster by 13-15% than the NP condition when initiated in the knee flexion phase ( ≤ 0.028, ≥ 0.70), whereas step-limb unloading interval from step initiation to step lift-off was significantly faster by 12-15% in the knee extension phase ( ≤ 0.01, ≥ 0.74). The preparatory movements significantly shortened step lift-off by 10-12% ( ≤ 0.013, ≥ 0.73) and step duration by 17-21% ( < 0.001, ≥ 0.85) with 19-22% faster step velocity ( < 0.001, ≥ 0.84), which resulted in 14-15% shorter overall time to step landing ( < 0.001, ≥ 0.84), irrespective of the loading phases. These results indicated that lower-limb loading with pre-step knee flexion facilitated faster step initiation, while lower-limb unloading with knee extension facilitated faster step-limb unloading, both resulting in faster step lift-off. Bilateral knee flexion-extension movements as a preparatory action could be utilized by invasion sports players to facilitate reactive stepping performance for more effective movement initiation.
静止站立时下肢的负重负荷分布会影响快速迈出第一步的时机，这对功能性运动活动和运动中的敏捷表现至关重要。本研究调查了在15名男性大学篮球运动员中，通过准备性的膝关节屈伸动作进行步前下肢加载和卸载对侧步性能的影响。参与者在两种条件下进行二选一（选择步幅侧肢）反应时侧步：在出发信号前无准备动作（无准备-NP）和进行持续交替的膝关节伸展和屈曲动作（准备-P）。反应信号在膝关节伸展和屈曲开始时以及这些动作期间提供，这些动作对应于最大和最小加载瞬间以及这些瞬间之间的过渡状态。用三维运动学数据和地面反作用力评估侧步性能。当在膝关节屈曲阶段开始时（≤0.028，≥0.70），步起始时间比NP条件下显著快13-15%，而在膝关节伸展阶段，从步起始到步离地的步幅侧肢卸载间隔显著快12-15%（≤0.01，≥0.74）。准备动作显著缩短步离地时间10-12%（≤0.013，≥0.73）和步持续时间17-21%（<0.001，≥0.85），步速快19-22%（<0.001，≥0.84），这导致步落地总时间缩短14-15%（<0.001，≥0.84），与加载阶段无关。这些结果表明，步前膝关节屈曲进行下肢加载有助于更快的步起始，而膝关节伸展进行下肢卸载有助于更快的步幅侧肢卸载，两者都导致更快的步离地。侵入性运动运动员可以利用双侧膝关节屈伸动作作为准备动作，以促进反应性侧步性能，实现更有效的运动起始。
