A repeated bout of eccentric exercise after 2 weeks resulted in no significant changes in muscle force or soreness, despite persistent myofibrillar disruption in 23% of pixels.
Does repeated eccentric exercise induce rapid force recovery independently of cell disruption?
Rapid force recovery following repeated eccentric exercise appears to be mediated at least in part by neural factors and may occur independently of cell disruption.
To investigate the "rapid-adaptation" phenomenon, we examined force, neural, and morphological adaptations in 12 subjects who performed 100 eccentric contractions with the quadriceps muscle (bout 1) and repeated the same exercise after a 2-wk hiatus (bout 2). Two days after bout 1, quadriceps muscle strength and surface electromyographic (EMG) activity declined approximately 37 and 28%, respectively, in the control group (n = 6). At day 2 after bout 1, significant increases occurred in patellar tendon reflex amplitude (approximately 25%), muscle soreness (fivefold), and serum creatine kinase (220%), and 65 +/- 12% of the total number of pixels in the EMG indicated myofibrillar disruption. At day 7 after bout 1, all variables returned to normal. At day 2 after bout 2, no significant changes occurred in force, EMG, creatine kinase, or soreness, but reflex amplitude increased, and 23 +/- 4% of the total number of pixels in the EMG still indicated myofibrillar disruption. The results suggest that the rapid force recovery following eccentric exercise is mediated at least in part by neural factors and that this recovery may occur independently of cell disruption.
Hortobágyi et al. (Sun,) conducted a other in Healthy subjects (implied) (n=12). Repeated eccentric exercise (bout 2) vs. Initial bout of eccentric exercise (bout 1) was evaluated on Force, neural, and morphological adaptations (including muscle strength, EMG activity, and myofibrillar disruption). A repeated bout of eccentric exercise after 2 weeks resulted in no significant changes in muscle force or soreness, despite persistent myofibrillar disruption in 23% of pixels.
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