Hip Muscle Power, Lateral Balance Function, and Falls in Aging

Falls and their consequences are among the major problems in the medical care of older individuals. The long-term goal of this research is to develop a mechanistically based therapeutic intervention to enhance muscle power, weight-shifting capability, and lateral balance function through protective stepping to prevent falls. When human balance is challenged, protective stepping is a vital strategy for preventing a fall during activities of daily life. Many older people at risk for falls have particular difficulties with successfully stepping sideways as a protective response to loss of balance in the lateral direction. The investigators propose that age-related declines in lateral balance function through impaired weight transfer and protective stepping linked with falls, result from neuromuscular and biomechanical limitations in hip abductor-adductor (AB-AD) muscle power generation. Moreover, the investigators hypothesize that these balance and neuromotor impairments can be improved with high-velocity muscle resistance power training that will be more effective than conventional muscle resistance strength training. The specific aims are, Aim 1: To conduct a single blind, randomized, and controlled trial comparing the effects of 12 weeks of hip AB-AD muscle power training against strength training, and the rate of retention after 3 months of no training in community living older adults by determining a) the changes in neuromotor performance (kinetics, kinematics, muscle activation patterns) of pre-step weight transfer during waist-pull induced side stepping, and rapid voluntary reaction time (RT) sidestepping; and by b) the changes in isolated hip AB-AD muscle neuromotor performance. Weight shifting and stepping ability will be tested with different initial induced stepping limb load conditions, and by varying voluntary stepping limb selection certainty with simple and choice RT tasks; Aim 2: To compare the effectiveness of hip AB-AD muscle power and strength training in reducing the rate of prospective falls over a one-year monitoring period post-training. Secondary analyses will assess the number of in-task falls, and the effect of muscle power versus strength training on changes in functional balance and mobility. Overall, the studies are expected to establish support for the superiority of velocity dependent power training over strength training on enhancing muscle performance, protective balance control and functional mobility outcomes, and for the prevention of falls among older adults.