The interaction between leading and trailing limbs during stopping in humans.

While the initiation of gait has been well studied, the mechanisms of stopping the forward progression of the center of mass have received less attention. The purpose of this current experiment was to examine the effects of constraining cadence on how the body is brought to a stop. Lower limb electromyogram (gluteus medius, hamstrings and soleus (SOL)) and force plate data were compared between two gait conditions, walking and planned stopping, at three different cadences (100, 125 and 150% of normal cadence). As cadence increased, the onset of muscle activity prior to heel-strike decreased for all muscles except SOL. SOL activity was evident prior to heel-strike during stopping and after heel-strike during walking. As cadence increased, onset times before heel-strike were shorter in stopping and SOL became active more rapidly after heel-strike in walking. The normalized duration of muscle activity remained invariant as cadence increased. This activity was always longer under the lead limb during stopping at each cadence. This was reflected by increases in the braking forces produced by the leading limb. The rate at which force was generated was not different between gait conditions but increased with increasing cadence. Thus, subjects relied less on the trailing limb and more on the leading limb as cadence increased.