Original investigation

Journal of Strength and Conditioning Research

Alejandro Muñoz-López, Moisés de Hoyo, F. Javier Nuñez & Borja Sañudo

2020 · Published Ahead of Print

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The purposes of this study were to analyze the effects of different types of muscle contraction (concentric and eccentric) on the passive muscular contraction properties of knee muscles and how muscle contraction can affect the muscles in different knee functions. In total, 23 active healthy men (age: 24.65 ± 1.95 years, height: 1.78 ± 0.05 m, mass: 75.33 ± 8.37 kg) participated in this study. Muscle soreness, muscle contractile properties assessed with tensiomyography (TMG) (vastus lateralis [VL] and biceps femoris [BF]), and isometric peak torque were tested before and immediately after 32 maximal repetitions of an isokinetic leg extension and flexion exercise at 180° per second. Muscle contractions were randomized to each subject’s leg. From the TMG variables, only contraction velocity showed significant interactions in time × muscle × contraction (p = 0.046; partial ηp = 0.19). A greater reduction was observed in the BF (-29.03%) than in the VL (-21.25%). There was a significant decrease in contraction velocity after concentric p < 0.001, d = 1.18) and eccentric (p = 0.007, d = 0.51) exercise for the BF, while for VL, a decrease was only observed after concentric exercise (p = 0.007, d = 0.66). The leg extension exercise showed reductions in the isokinetic peak torque (p < 0.001; partial ηp = 0.83). Isometric peak torque (p < 0.001; partial ηp = 0.80) and muscle soreness (p < 0.001; partial ηp = 0.70) decreased after exercise. In conclusion, muscle mechanical properties were differently affected in relation to the muscle contraction and knee muscles involved, after a fatiguing leg extension isokinetic exercise. Isometric peak torque and muscle soreness were also reduced immediately after exercise. These results are particularly important to understand how TMG parameters are modified depending on the type of contraction.

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