Strategies associated with altered segment parameters during voluntary gait modifications

The coordination of movement results from complex interactions between neur al and mechanical systems. To investigate the influence of limb mechanics o n the control strategies used during gait modifications, participants were instructed to walk and step over various obstacles (2,10 & 30cm) with and w ithout an external mass (4.5kg) attached around the centre of mass of each leg segment. Overall, with the attached mass there was an increase in the a mount of pull-off energy applied at the hip, while the contribution of the knee to limb flexion decreased particularly for the higher obstacles. It wa s further found that knee action during weighted conditions served more to slow the backward motion of the leg following toe off than to flex the knee . The modifications employed to accommodate the change in limb dynamics ill ustrate both the flexibility of the locomotor control system and its sensit ivity to the mechanical properties of the limb.