Effects of short-term training combining strength and balance exercises on maximal strength and upright standing steadiness in elderly adults

This study investigated the effects of two training programmes of 6 weeks combining strength and balance exercises in different proportions. One training programme [n=10; 71.4 (6.3) years] consisted mainly of strength exercises (ST) and the other programme [n=8; 71.4 (6.4) years] included a majority of balance exercises (BT). Maximal strength of lower leg muscles and centre of pressure (CoP) steadiness during upright stance in various sensory conditions were measured before and after training. The input-output relation of motor evoked potential (MEP) induced by transcranial magnetic stimulation and H reflex was also assessed in soleus during upright standing. The maximal strength of the ankle plantar flexor muscles increased after training programmes (p<0.001) with a trend for greater gain in ST (+35.7%) compared with BT (+20.8%, p=0.055). The gain in strength was positively correlated with the increase in voluntary activation (p<0.001). Both training programmes decreased maximal amplitude and mean fluctuations of CoP displacements recorded in the backward-forward direction when standing on a foam mat (p<0.05) but not on a rigid surface. The electromyographic activity of the ankle plantar flexor muscles during upright standing decreased (p<0.05) after training but not for the tibialis anterior. Results obtained for H reflex and MEP input-output relations suggest an increased efficacy of Ia afferents to activate low-threshold motor neurones and a decrease in corticospinal excitability after training. This study indicates that short-term training combining strength and balance exercises increases maximal strength and induces change in the neural control of lower leg muscles during upright standing.