Flexibility of the use of residual tibial anterior motor units during walking in neuromuscular diseases

Abstract

The use of tibial anterior (TA) motor units in lower motoneurone disorders was studied during comfortable walking that was the main function of TA. The findings were compared to those in normal subjects. The loss of TA power was compensated either by increases of recruitment and firing rate of residual TA units or by a change from the normal plantigrade gait pattern to the infantile digitigrade pattern putting less strain on TA. Moderately paralysed subjects usually maintained plantigrade gait by excessive use of residual TA units but tended to change to digitigrade gait on fatigue thus economizing with remaining TA power. Severely paralysed subjects used digitigrade gait but plantigrade gait could be restored by application of a toe using string, i.e. the string might increase the strain on TA instead of decreasing it.