Fig 4. In vivo recording of muscle isometric contractile forces to determine numbers of reinnervated motor units.

A. In the second set of experiments (Repair, Table 1), bipolar electrodes placed on the regenerated common peroneal (CP) nerve were used to electrically stimulate the CP nerve supramaximally to evoke extensor digitorum longus (EDL) muscle twitch (B) and tetanic isometric contractions or to stimulate the CP nerve incrementally in order to evoke all-or-none increments in twitch force. Motor unit (MU) number was calculated as the ratio of the muscle and average MU twitch forces—motor unit number estimation (MUNE).