Komi P V, Norman R W
Int J Sports Med. 1987 Mar;8 Suppl 1:48-54. doi: 10.1055/s-2008-1025703.
Based on the assumption that the stretch-shortening cycle is a natural way of muscle function, the occurrence of such a cycle was investigated in a diagonal technique of cross-country skiing. Cinematographic, special force platform, and telemetered EMG techniques were employed. The four subjects studied were all elite international level cross-country skiers, and the measurements were taken either under world championship conditions (cinematography) or during special test situations outdoors (EMG, force platform, and cinematography). The skiing was performed on the fixed uphill course (competition) and on the variable uphill tracks (2.5 degrees-11 degrees). The latter condition allowed mounting of a special long force platform system under the track. The results indicated that the leg kick phase is preceded by a typical unweighting phase, which is followed by braking and propulsion phases. Angular velocity curves of the hip, knee, and ankle joints revealed indirectly the segmental occurrence of the stretch-shortening cycle. Similar phenomena could be identified for the elbow joint during the pole plant and thrust phases. On a steep uphill track, the muscle activation pattern and the ground reaction forces resembled in many instances those of slow level running. Based on the results, a model was suggested to describe how the preloading of the leg thrust phase takes place as a sequential flow from one joint to another.
基于拉长-缩短周期是肌肉功能的一种自然方式这一假设，在越野滑雪的对角技术中对这种周期的发生情况进行了研究。采用了电影摄影、特殊测力平台和遥测肌电图技术。所研究的四名受试者均为国际顶尖水平的越野滑雪运动员，测量是在世界锦标赛条件下（电影摄影）或在户外特殊测试情况下（肌电图、测力平台和电影摄影）进行的。滑雪在固定的上坡赛道（比赛）和可变的上坡雪道（2.5度-11度）上进行。后一种情况允许在雪道下方安装特殊的长测力平台系统。结果表明，腿部蹬地阶段之前有一个典型的失重阶段，随后是制动和推进阶段。髋、膝和踝关节的角速度曲线间接揭示了拉长-缩短周期在各节段的发生情况。在撑杆和推撑阶段，肘关节也能发现类似现象。在陡峭的上坡雪道上，肌肉激活模式和地面反作用力在许多情况下类似于慢速平地跑步。基于这些结果，提出了一个模型来描述腿部蹬地阶段的预加载是如何作为一种从一个关节到另一个关节的连续流程发生的。
