Alteration of proton diffusivity associated with passive muscle extension and contraction

Purpose: To determine whether passive muscle extension and contraction affect the proton diffusivity of the muscle.

Materials and methods: Five male subjects were examined. The fractional anisotropy (FA), and primary (lambda(1)), secondary (lambda(2)), and tertiary eigenvalues (lambda(3)) of the right tibialis anterior and medial gastrocnemius muscles were compared between conditions of passive plantar flexion and passive dorsiflexion of the ankle joint.

Results: In the tibialis anterior, FA, and lambda(1) at dorsiflexion decreased significantly (P < 0.01 and P < 0.01, respectively) compared to those at plantar flexion, but lambda(3) at dorsiflexion increased significantly (P = 0.02). In the gastrocnemius, FA and lambda(1) at dorsiflexion increased significantly (P < 0.01 and P < 0.01, respectively) compared to those at plantar flexion, but lambda(3) at dorsiflexion decreased significantly (P < 0.01). The lambda(2) value showed no significant change in either the tibialis anterior or medial gastrocnemius.

Conclusion: The results indicate that passive muscle extension and contraction associated with passive joint movement would affect the proton diffusivity of the muscle. This alteration of proton diffusivity is probably associated with microscopic structural changes of the muscle.