Changes in the activities of lower limb muscles during standing broad jumps with incremental intensity
Yuichi HIRANO and Hidenori AOKI
This study investigated changes in the activities of lower limb muscles during standing broad jumps with incremental intensity. The subjects were asked to increase the intensity of standing broad jump gradually and then perform 5 jumps with maximal effort after these trials. During these jumps, the activities of 4 muscles were recorded : Rectus Femoris (RF) , Biceps Femoris (BF) , Tibialis Anterior (TA) and Gastrocnemius (GA). Additionally, subjects were asked to perform 5 plantar-flexions at low, moderate and high intensity using an isokinetic dynamometer and the activities of TA and GA were recorded. Muscle activities during jumps increased as the intensity increased. Though TA is considered to be an antagonist during the push-off phase of a jump, it also showed gradually increased activity along with the other agonist muscles. Furthermore, TA activity was analyzed in two separate phases : before and during GA activity. As a result, in most subjects, TA activity during GA activity increased as the intensity increased. However, TA activity before GA activity showed no specific trend. The incremental activity of TA was also observed during mono-articular movement. It would seem that co-activation played a role in braking the movement of the ankle joint during the countermovement of the jump.
