Strength and muscle coactivation in older adults after lower limb strength training

This study assessed quantitatively knee extension and flexion muscle coactivation and strength before and after a 6-week strength-training program in older adults. Fifteen older adults between the ages of 55 and 75 years participated in this study. The knee extensors and flexors were trained using an isokinetic dynamometer (Cybex) at a slow speed (45 degrees/s) and it was found that both bilateral and unilateral leg strength improved after 6 weeks. Muscle coactivation was estimated using electromyography (EMG) from the quadriceps and hamstrings. It was found that there was a significant negative correlation (p < 0.05) between the amount of strength produced and the amount of antagonist coactivation and that as the amount of antagonist coactivation was reduced, there was an increase in the strength produced.