Optimal Load for Increasing Muscle Power During Explosive Resistance Training in Older Adults

BACKGROUND: Muscle power (force x velocity) recedes at a faster rate than strength with age and may also be a stronger predictor of fall risk and functional decline. The optimal training paradigm for improving muscle power in older adults is not known, although some literature suggests high velocity, low load training is optimal in young adults. METHODS: One hundred twelve healthy older adults (69 +/- 6 years) were randomly assigned to either explosive resistance training at 20% (G20), 50% (G50), or 80% (G80) one repetition maximum (1RM) for 8-12 weeks or to a nontraining control group (CON). Participants trained twice per week (five exercises; three sets of eight rapidly concentric and slow eccentric repetitions) using pneumatic resistance machines. Repeated-measures analysis of variance and covariance (ANOVA and ANCOVA) were used to determine the effects of training. RESULTS: Average peak power increased significantly and similarly in G80 (14 +/- 8%), G50 (15 +/- 9%), and G20 (14 +/- 6%) compared to CON (3 +/- 6%) (p < .0001). By contrast, a positive dose-response relationship with training intensity was observed for relative changes in average strength (r = .40, p = .0009) and endurance (r = .43, p = .0005). Average strength increased in G80 (20 +/- 7%), G50 (16 +/- 7%), and G20 (13 +/- 7%) compared to CON (4 +/- 4%) (p < .0001). Average muscle endurance increased in G80 (185 +/- 126%, p < .0001), G50 (103 +/- 75%, p = .0004), and G20 (82 +/- 57%, p = .0078) compared to CON (28 +/- 29%). CONCLUSION: Peak muscle power may be improved similarly using light, moderate, or heavy resistances, whereas there is a dose-response relationship between training intensity and muscle strength and endurance changes. Therefore, using heavy loads during explosive resistance training may be the most effective strategy to achieve simultaneous improvements in muscle strength, power, and endurance in older adults.