The specific aims of this research are delineated as the following: Aim 1: To investigate the neuromuscular and biomechanical mechanisms of the emerging processes of proactive and reactive balance control during sitting and standing in patients with stroke at different stages of the recovery course. Aim 2: To determine the relationships between brain lesion sites and the recovery patterns of reactive and proactive balance control mechanisms in patients with stroke. Aim 3: To determine the relationships between the impairments in reactive and proactive balance control mechanisms and functional outcome as well as fall incidence in patients following stroke. Aim 4: To investigate the efficacy of different training regimens in improving reactive and proactive balance control strategies and in preventing falls in stroke patients with different brain lesion sites. Principally, three hypotheses are to be tested: Hypothesis 1:The emerging processes and recovery patternes of proactive and reactive balance control may be different among stroke patients with different brain lesion locations. Hypothesis 2:There are positive correlations between the level of impairments in reactive and proactive balance control mechanisms and functional outcome as well as fall incidence in patients following stroke. Hypothesis 3:Training regimens that could best facilitate the emergence or improvement in reactive and proactive balance control strategies are different.