Mechanical output and iEMG of single and repeated isokinetic plantar flexions: a study of untrained and endurance-trained women.

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 degrees 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 fatigue 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.