Range of motion physiotherapy reduces the force deficit in antagonists to denervated rat muscles

We used a rat hindlimb model of tibial nerve transection to determine if a loss of mechanical function exists in innervated antagonists compared with denervated muscles. We tested two hypotheses: (1) denervation of the rat ankle plantar flexors results in decreased force production of the ankle dorsiflexors, and (2) daily passive ankle range of motion (ROM) physiotherapy prevents or reduces the force deficit.

Adult Lewis rats were assigned to one of three groups: (1) a sham (S) group, in which the tibial nerve was exposed but not transected; (2) a no rehabilitation (NR) group, in which a 2-cm segment of tibial nerve was excised at midthigh to denervate the ankle plantar flexors; or (3) a rehabilitation (R) group, in which a 2-cm segment of tibial nerve was excised and the animals were subjected to ankle passive ROM physiotherapy for two 5-min sessions each day. After 14 days, maximum isometric tetanic force (F(0)) and specific force (sF(0)) were measured in the extensor digitorum longus (EDL) muscle, an ankle dorsiflexor.

Compared with those from animals in the S group, EDL muscles from animals in the NR group demonstrated a 22% decrease in both F(0) and sF(0). In the EDL from animals in the R group, daily passive ROM physiotherapy diminished the deficit in F(0) but not in sF(0).

These data support the hypotheses that nerve injuries result in impaired mechanical function in the innervated antagonists to denervated muscles and that passive ROM physiotherapy can improve force production in these muscles.