Positive Effect of Low-Intensity Physical Exercise Combined with Motor Imagery Training on Voluntary Strength and Brain of Elderly People

The purpose of this study was to explore the effect of Low-intensity physical exercise combined with motor imagery training(MIT) on increasing voluntary muscle strength and related central nervous system adaptations in elderly people.Twenty-seven healthy elderly(age:75±7.9 yrs,8 women) volunteers were randomly assigned into 3 groups:Low-intensity physical exercise combined with MIT group,CST group(trained with high-intensity muscle contractions),or a no-practice control(CTL) group.MIT and CST lasted for 12 weeks(5sessions/week).The participants' right-elbow flexor muscle strength,electromyography(EMG),and motor activity-related cortical potential(MRCP) directly related to the strength production were measured before and after training.The CST group had the highest strength gain(17.6%,P<0.001),the MIT group also had significant strength gains(13.8%,P<0.001),which was not statistically different from that of the CST group even though the exercise intensity for the MIT group was only 30% MVC level.The no-practice CTL group did not have significant strength changes.Surprisingly,only the MIT group demonstrated a significant enhancement in the MRCP(28.6%,P<0.001).These results suggest that MIT combined with low-intensity physical exercise is an effective method for voluntary muscle strengthening.Training of the cortical motor control centers might translate to greater descending command to the target muscle,leading to strength gains in elderly people.