Savelberg H H C M, Fastenau A, Willems P J B, Meijer K
Department of Human Movement Science, Nutrition and Toxicology Research Institute, Faculty of Health, Medicine and Life Sciences, Universiteit Maastricht, Maastricht, The Netherlands.
Clin Biomech (Bristol). 2007 Aug;22(7):805-12. doi: 10.1016/j.clinbiomech.2007.05.002. Epub 2007 Jun 15.
In this study the effect of a changed load/capacity ratio on sit-to-stand performance and on the underlying net joint moments was investigated. In subjects with muscle weakness the load/capacity ratio is increased due to reduced muscle capacity. In the current study this ratio was manipulated by changing the load. This approach allowed studying the isolated effect of an increased load/capacity ratio on sit-to-stand strategy.
Ten healthy women performed sit-to-stand movements under four load conditions. The load/capacity ratio was manipulated by adding 0%, 15%, 30% and 45% of the body mass to a weight vest. To determine changes in sit-to-stand strategy flexion of the trunk and temporal characteristics were assessed. Joint moments at ankle, knee and hip joints and activation patterns of major leg muscles were determined from the kinematics and kinetics.
Increasing the extra load from 30% to 45% changed the sit-to-stand performance. In the 45% condition maximal trunk flexion was increased and movement time significantly elongated. The strategy change was associated with a disproportionate increase of the net hip extension moment and a delayed peak of the net knee extension moment.
This study shows that experimentally observed changes in sit-to-stand strategy can be attributed to an increase in the load/capacity ratio. For treatment purposes this implies that increasing muscle strength, reducing body mass or a combination of these could be a suitable approach to improve sit-to-stand performance. The experimental model applied will be useful to study the isolated effect of the load/capacity ratio.
在本研究中，研究了负荷/能力比的变化对从坐到站动作表现以及潜在的净关节力矩的影响。在肌肉无力的受试者中，由于肌肉能力下降，负荷/能力比会增加。在本研究中，通过改变负荷来控制这一比例。这种方法有助于研究负荷/能力比增加对从坐到站策略的单独影响。
10名健康女性在四种负荷条件下进行从坐到站动作。通过在重量背心增加0%、15%、30%和45%的体重来控制负荷/能力比。为了确定从坐到站策略的变化，评估了躯干的屈曲和时间特征。根据运动学和动力学确定踝关节、膝关节和髋关节的关节力矩以及主要腿部肌肉的激活模式。
额外负荷从30%增加到45%时，从坐到站的动作表现发生了变化。在45%负荷条件下，最大躯干屈曲增加，动作时间显著延长。策略的改变与净髋关节伸展力矩的不成比例增加以及净膝关节伸展力矩的峰值延迟有关。
本研究表明，实验观察到的从坐到站策略的变化可归因于负荷/能力比的增加。从治疗角度来看，这意味着增加肌肉力量、减轻体重或两者结合可能是改善从坐到站动作表现的合适方法。所应用的实验模型将有助于研究负荷/能力比的单独影响。
