Gait initiation and impairments of ground reaction forces as illustrated in old age by 'La marche à petits pas'.

Ground reaction forces during gait initiation and kinematics of the first step were recorded in 11 elderly patients with idiopathic 'marche à petits pas' and 18 age-matched normal adults. Smaller values of vertical forces, and impaired amplitudes and directions of anteroposterior forces might explain start difficulties of the patients. Higher vertical displacement of the foot, and laborious establishment of the rhythm in the patients could also be related to the perturbations observed in the reaction forces. These perturbations are likely to reflect impairments of muscular synergies of the lower limbs and the lack of limb co-ordination.