Neuromuscular Changes and Damage after Isoload versus Isokinetic Eccentric Exercise

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PurposeThis study compared the effects of isoload (IL) and isokinetic (IK) knee extensor eccentric exercises on changes in muscle damage and neuromuscular parameters to test the hypothesis that the changes would be different after IL and IK exercises.MethodsTwenty-two young men were paired based on their strength and placed in the IL (N = 11) or the IK (N = 11) group. The IL group performed 15 sets of 10 eccentric contractions with a 150% of predetermined one-repetition maximum load. The IK group performed 15 sets of several maximal eccentric contractions matched set by set for the total amount of work and mean angular velocity with the IL group. Muscle damage markers (voluntary isometric peak torque, muscle soreness, and creatine kinase activity) and neuromuscular variables (e.g., voluntary activation, H-reflex, M-wave, and evoked torque) were measured before, immediately after, and 24, 48, 72, and 96 h postexercise.ResultsVoluntary isometric peak torque decreased to the same extent (P = 0.94) in both groups immediately after (IL = −40.6% ± 13.8% vs IK = −42.4% ± 10.2%) to 96 h after the exercise (IL = −21.8% ± 28.5% vs IK = −26.7% ± 23.5%). Neither peak muscle soreness (IL = 48.1 ± 28.2 mm vs IK = 54.7 ± 28.9 mm, P = 0.57) nor creatine kinase activity (IL = 12,811 ± 22,654 U·L−1 vs IK = 15,304 ± 24,739 U·L−1, P = 0.59) significantly differed between groups. H-reflex (IL = −23% vs IK = −35%) and M-wave (IL = −10% vs IK = −17%) significantly decreased immediately postexercise similarly between groups.ConclusionThe changes in muscle damage and neuromuscular function after the exercise are similar between IL and IK, suggesting that resistance modality has little effects on acute muscle responses.

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