Background: The Nordic hamstring exercise is a closed-chain exercise that effectively activates all lower extremity muscles, but there is a lack of consideration of ankle joint which affects exercise effectiveness. One of the major advantages of the Nordic exercise have been known as strengthening lower extremity extensors. This manifests the exercise increases activities of the ankle plantar flexors as well as hip extensors. Objectives: To investigated the impacts of changes in ankle position on the lower extremity musculature and subjective difficulties during the Nordic hip extension exercise. Design: Cross-sectional study. Methods: Twenty the healthy male participants participated in this study. Participants perform three variations of the Nordic exercises including three ankle positions. Each Nordic exercise was defined as ankle position (neutral, dorsiflexion and plantar flexion). During the Nordic exercise, erector spine (ES), gluteus maximus (GM), biceps femoris (BF), gastrocnemius (GCM) activities and subjective difficulties (Borg RPE score) were measured. Results: Muscular activities of the biceps femoris and gastrocnemius were significantly different among the three ankle conditions, which showed controversial results (P<.05). The biceps femoris activity was significantly higher with the dorsiflexion condition, compared to the others (P<.05). On the other hand, activity of the gastrocnemius was significantly higher with the plantarflexion position compared to the others (P<.05). Conclusion: Present study suggests the ankle positional changes could affect lower muscular activities during the Nordic exercise. Although it is difficult to affirm the causes due to limited data, selective activation of the biceps femoris might accomplish with ankle dorsi flexion and that of the gastrocnemius might accomplish with the ankle plantarflexion during the Nordic exercises.

Background: Although several studies have reported functional improvements after forward walking training on a treadmill and after backward walking training on a treadmill, there is a lack of immediate effects data, investigating spatiotemporal parameter, neuromuscular recruitment. Objectives: To compare the immediate effects between forward and backward walking on treadmill training, present study measured muscle activities of the lower extremity, gait parameters, and dynamic balance. Design: Cross-sectional study. Methods: The twenty-four asymptomatic young male subjects were participated in this study. Subjects have performed 15-min of forward and backward walking on treadmill. Before and after treadmill walking, the gait parameters were measured with the GAITRite. The dynamic balance abilities were assessed with the Y-balance test. Muscular activities were collected from the tibialis anterior, gastrocnemius, biceps femoris, and rectus femoris during forward and backward walking. Results: Muscular activities of the biceps femoris and tibialis anterior were significantly different between forward and backward walking conditions, which were higher with the backward walking (P<.05). Compared to the pre-measurement, the normalized dynamic balance composite score of the post-measurement was significantly higher with the backward walking (P<.05). Regardless of the treadmill training method, there were no significant differences between pre and post measurement, both the stride length and step length (P>.05). Conclusion: The performing backward walking training has positive effects for dynamic balance.