Hodges Gregory Neil, Kriellaars Dean Johannes
Department of Physiotherapy, Health Sciences Centre, Winnipeg, Manitoba, Canada.
J Appl Biomech. 2013 Dec;29(6):712-20. doi: 10.1123/jab.29.6.712. Epub 2013 Feb 20.
Despite the common use of elastic resistance in training, only the static loading characteristics have been studied, whereas the dynamic components remain undetermined. The purpose was to determine the effect of two movement strategies on the shoulder resultant joint moment (RJM) during internal/external rotation exercise with elastic load. Ten healthy subjects performed sweep and step movement strategies over a constant range of motion and cadence (1:1). Shoulder RJM was determined using a Newtonian model with elastic force measured by force transducer, joint angle by electrogoniometer, and limb acceleration by accelerometer. Relative to the sweep strategy, the step strategy revealed a 49% increase in angle-specific RJM during the initial phase, RJM was reduced to 67-69% during midrange, and increased to over 110% at the end of the repetition. These RJM differences were wholly attributable to strategy-dependent changes in limb acceleration. Shoulder RJM in the sweep strategy was almost entirely explained by moment of elastic force. Movement strategy can substantially alter shoulder loading despite constant range of motion and cadence, impacting the magnitude and nature of the stimulus for neuromuscular adaptation. These acceleration-dependent changes in shoulder RJM may be important to consider for exercise efficacy and safety.
尽管在训练中弹性阻力的使用很普遍，但仅对其静态负荷特征进行了研究，而动态成分仍未确定。目的是确定两种运动策略对弹性负荷下内/外旋转运动期间肩部合成关节力矩（RJM）的影响。十名健康受试者在恒定的运动范围和节奏（1:1）下执行扫掠和步进运动策略。使用牛顿模型确定肩部RJM，其中弹性力由力传感器测量，关节角度由电子测角仪测量，肢体加速度由加速度计测量。相对于扫掠策略，步进策略在初始阶段特定角度的RJM增加了49%，在运动范围中部RJM降低到67-69%，在重复结束时增加到超过110%。这些RJM差异完全归因于肢体加速度的策略依赖性变化。扫掠策略中的肩部RJM几乎完全由弹力矩解释。尽管运动范围和节奏恒定，但运动策略可显著改变肩部负荷，影响神经肌肉适应刺激的大小和性质。这些肩部RJM中依赖于加速度的变化对于运动效果和安全性而言可能是重要的考虑因素。
