Enhanced agonist intermuscular coherence supports improvements in force steadiness driven by motor imagery training...

Despite advances in understanding of motor-related cortical network contributions to improvements in motor performance following motor imagery, few studies have considered older adults and how long-term motor imagery training (MIT) may benefit motor performance. Here, we aimed to understand the short and longer-term changes in common neural drive and force steadiness driven by MIT in younger and older adults. Two groups of participants (Younger: n =12, 22.1 ± 4.7 years; Older: n =13, 64.2 ± 9.3 years) completed five MIT sessions of an upper-limb movement involved in an everyday task (elbow flexion). Before and after the first and last session of MIT, participants performed a sustained 15% maximal elbow flexion contraction, where force steadiness and intermuscular coherence between agonist (biceps brachii short-long head) and agonist-antagonist (biceps brachii (averaged short and long head)-triceps brachii) muscle pairs were assessed. Participants also performed an untrained elbow extension task to evaluate transfer of force steadiness. In line with previous literature, one session of MIT improved force steadiness but did not modify intermuscular coherence. After five sessions of MIT, force steadiness improved in both groups; however, increased agonist intermuscular coherence was only observed for the older adults. Overall, findings indicate increased agonist coherence may be preferentially enhanced to support improved force control driven by repeated MIT sessions during aging. Force steadiness also improved in the untrained elbow extension task in both groups, indicating transfer. Together, these results demonstrate that MIT may help mitigate age-related declines in motor control.