The effects of improved strength on obstacle negotiation in community-living older adults.

Poor mobility has been associated with age-related deterioration in muscle strength. While previous work has examined the effects of improved strength on level walking, we have quantified the effects of a resistance-training program on obstructed gait tasks using biomechanical-dependent measures. Forty-five community-dwelling participants aged 62 years or older were randomised to either a control (n=16) or experimental group (n=29). The experimental subjects exercised for 24 weeks on a progressive resistance-training program designed to improve lower body strength. Dynamic strength was assessed at weeks 0 and 24 as well as specific laboratory gait kinetics and kinematics during stepping over an obstacle and negotiation of a raised surface set at 10, 20 and 30% of each subject's leg length. Significant strength improvements (P<0.05), ranging between 197 and 285%, were recorded in the experimental group. The strength gains in the experimental group were accompanied by significant increases in obstacle-crossing stride velocity (range 5.5-15.5%) due to increases in stride length and decreases in stride duration for both gait tasks. Significant changes in the peak vertical and anterior-posterior ground reaction forces as well as in kinematic variables associated with a safe obstacle traverse such as vertical obstacle heel clearance, limb flexion at obstacle crossing, horizontal foot placement and vertical landing velocity resulted in an improved crossing strategy in the experimental subjects. These findings provide evidence of significant improvements in obstructed gait function of community-living older adults associated with a systematic resistance-training program.