Mechanical Output and iEMG of Single and Repeated Isokinetic Plantar Flexions: A Study of Untrained and Endurance-Trained Women

Abstract

Isokinetic plantar flexion peak torque (PT), contractional work (CW), and integrated electromyographic activity (iEMG) were analyzed in a group of untrained females and a group of female elite orienteers.

Similar levels of PT, CW, and iEMG were observed in both groups during single maximum maneuvers (30-180 ° s¹). During repetitive (200) maximum plantar flexions, the untrained females showed a steeper and more pronounced decline in CW during the first 50 contractions than the orienteers. After this fatique phase, all subjects could maintain a steady-state level of CW throughout the test. This level of CW was significantly (20%) higher in the orienteers than in the untrained females. The iEMGs of the gastrocnemii and soleus muscles decreased to significantly (10%) lower levels in the untrained women than in the orienteers. For both groups, the soleus muscle showed a significantly higher steady-state level of iEMG (10%) than mm. gastrocnemii. In the untrained group, CW/iEMG of m. triceps surae decreased to a plateau level significantly lower than in the orienteerers who could virtually maintain the initial CW/iEMG throughout the test. The differences observed could be explained by adaptations to performed endurance training in the orienteers.

Key words

human - muscle contraction - isokinetic - electromyography - endurance - fatigue - female