The effect of knee angle and subject position on plantar flexors isokinetic performance and muscular activity

BACKGROUND: Assessment of the plantar flexion (PF) isokinetic performance has been greatly diverse and based on personal preferences rather than standardized guidelines. OBJECTIVE: To examine the performance of the plantar flexors under different settings including knee joint angle and subject position. METHODS: Thirteen women and 20 men took part in this study. The isokinetic protocol (60 degrees /s) was set to ankle movement between 10 degrees dorsiflexion to 30 degrees PE Participants performed three repetitions of concentric PF in randomly-ordered knee angles; 15 degrees , 45 degrees and 90 degrees , and in seated and supine positions. Surface electromyography (EMG) data were collected from the Soleus (SOL) and Gastrocnemius. RESULTS: Knee angle impacted the PF moment (P <= 0.001-0.026) and work (P <= 0.05) measures in both genders. The moment and work measures were significantly less in the 90 degrees than those in the 45 degrees and 15 degrees positions. The 45 degrees position had the highest values, particularly in sitting in the male participants. Only the GL EMG data was significantly impacted (P = 0.017) by the subject position. However, the difference was trivial (1.6%). The SOL muscle showed a consistent pattern of increased activity when the knee was in flexion. CONCLUSION: The 45 degrees position seems to be optimal for obtaining the highest isokinetic PF scores.