Isokinetic cross-training effect in foot drop following common peroneal nerve injury

BACKGROUND: To our knowledge, no studies on foot drop (FD) caused by peripheral nerve lesion investigated whether unilateral training of the unaffected ankle dorsiflexors induced a clinically meaningful strength improvement in the affected untrained leg, namely a cross-training (CT) effect. METHOD: A 59-year-old man, who suffered since childhood from surgically-induced damage of the common peroneal nerve, performed an 8-week maximal-intensity isokinetic training of the healthy leg. Before and after training, patient underwent bilateral isokinetic testing, functional and mobility tests including 6-minute walking test, 10-meter walking test, timed-up-and go test, ankle ROM and neurophysiological recordings including motor thresholds, cortical silent period of the hemisphere innervating the affected tibialis anterior and mean EMG recruitment. RESULTS: After cross-training, the affected-untrained dorsiflexors showed notable increases in all dynamometric parameters. Similarly, all functional tests improved considerably. The cortical silent period was reduced and the maximal EMG recruitment increased. CONCLUSIONS: Improvements in muscle performance and neurophysiological drive in the affected non-trained limb due to training of the unaffected side indicate that cross-training may be a viable rehabilitative approach to foot drop.