This study investigated the acute responses to volume-load-matched heavy-load (80% 1RM) versus light-load (40% 1RM) power-oriented resistance training sessions in well-functioning older adults. Using a randomized cross-over design, 15 volunteers completed each condition on a leg press. Neuromuscular (maximal isometric force and rate of force development) and functional performance (power during sit-to-stand test), lactate, and muscle damage biochemistry (creatine kinase, lactate dehydrogenase and C-reactive protein serum concentration) were assessed pre- and post-exercise. Performance declines were found after heavy-load (Cohen's d effect size (d); maximal isometric force 0.95 d; rate of force development 1.17 d; sit-to-stand power 0.38 d, all p < 0.05) and light-load (maximal isometric force 0.45 d; rate of force development 0.9 d; sit-to-stand power 1.17 d, all p < 0.05), while lactate concentration increased only after light-load (1.7 d, p = 0.001). However, no differences were found between conditions (all p > 0.05). Both conditions increased creatine kinase the day after exercise (marginal effect 0.75 d, p < 0.001), but no other blood markers increased (all, p > 0.05). Irrespective of the load used, power training induced non-clinically significant decreases in sit-to-stand performance, moderate declines in maximal isometric force, but pronounced decreases in the rate of force development. Furthermore, the metabolic stress and muscle damage were minor; both sessions were generally well tolerated by well-functioning older adults without previous experience in resistance training.

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