Phase contrast motor unit MRI (PC-MUMRI) to investigate changes to muscle twitch dynamics in a healthy ageing cohort

Functional changes to the muscle’s contractile and relaxation properties occur with age. Current techniques which measure twitch dynamics provide limited information about individual muscles. We used phase contrast motor unit MRI (PC-MUMRI) to non-invasively measure the contraction and relaxation times of lower leg muscles in a healthy ageing cohort, relating this to isometric maximum voluntary contraction (MVC). Contraction and relaxation times increased with ageing and were negatively correlated with MVC. PC-MUMRI offers a sensitive method to measure muscle twitch dynamics and could be combined with other MR techniques to characterise functional changes to muscle with ageing.