Effectiveness Of An 8-week Progressive Resistance Training Protocol On Muscle Activation And Recovery Time During Slipping In Older Adults

The age-related loss of muscle mass, strength, and power are thought to play a critical role in recovering from a slip or trip and avoiding fall-related injuries. Evidence suggests that resistance training can mitigate physical function decreases. PURPOSE: To examine the effects of an 8-week individualized resistance training protocol on slipping recovery time and muscle activation in older adults. METHODS: Eight older adults (5 F and 3 M; age = 69.4 ± 7 yr; weight = 68.6 ± 8 kg; height = 168.7 ± 5 cm) participated in the study. The participants were tested at baseline and after the 8-wk resistance training protocol. Participants walked for 30-sec at their self-selected pace (SSP) while wearing a safety harness. A forward perturbation was presented randomly on a split-belt instrumented treadmill, in which the belt speed accelerated to double the SSP value during the support phase of the dominant leg instantaneously and then returned to SSP. Recovery time is the time from the presentation of a stimulus to recovery of the ground reaction force profiles. Vertical Ground Reaction Forces (vGRF) and EMG activity of vastus lateralis, rectus femoris, hamstrings, tibialis anterior and gastrocnemius were recorded for both dominant and non-dominant leg before during and after the perturbation. Dependent variables include peak vGRF, rate of force development, recovery time (RT) and peak EMG activity (pEMG). RESULTS: A two way repeated ANOVA (time x recovery steps) showed a main effect of steps (p < 0.001) for all dependent variables. Post hoc analysis revealed that the step immediately after the perturbation was significantly higher for vGRF(p < 0.001) and all pEMG values (p = 0.002) compared to all other steps, as well as faster for RT (p < 0.001). There was a significant interaction for pEMG of the vastus lateralis (p = 0.002) with the step after the perturbation at baseline had the highest value overall. RT was similar at baseline and after the 8-wk resistance training protocol. CONCLUSION: The step immediately after the perturbation is important, highlighting its paramount role in sustaining balance. Notably, quadriceps activation exhibits heightened efficiency following an 8-week resistance training protocol. National Strength and Conditioning Association's Young Investigator Grant