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°/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.Relevance to industryStability of the knee extensors and flexors is essential for lower limb balance and stability and the ability to improve not only strength, but muscular function is useful to avoid injuries that occur due to lower limb weakness such as slips and falls. Muscle coactivation is related to joint stability and muscle efficiency and is affected by several factors, including the magnitude of the forces exerted, the position, displacement and the velocity of the joint [Kellis et al., 2003; Miller et al., 2000] as well as fatigue [Psek and Caffarelli, 1993. Behavior of coactive muscles during fatigue. Journal of Applied Physiology 74(1), 170–175]. By reducing antagonist muscle coactivation, one can improve the efficiency of movement.