1. Archive
2. Vol.53, No.5

The Effect of Muscle Contraction Velocity on Cardiorespiratory Responses to Repetitive Isokinetic Exercise in Humans

Abstract: We investigated the effect of muscle contraction velocity on cardiorespiratory responses during exercise. Eight males (23 ± 2 years, 175 ± 5 cm, 64 ± 6 kg, mean ± SD) performed 3-min repetitive one-leg extension exercises at various angular velocities (30, 60, 120, and 240 deg/s) with a controlled relaxation interval, relatively constant (duty cycle = 1:1, A trial) and absolutely constant (relaxation time = 0.75 s, B trial) at a total work of 2,100–2,400 J in an isokinetic mode, using a Cybex II dynamometer. We measured heart rate (HR), mean blood pressure (MAP), minute ventilation (VE), and oxygen uptake (VO₂) during the exercise. The angular velocity significantly affected the increase in HR, MAP, VE, and VO₂ at the end of exercise from resting in both A and B trials (e.g., MAP: 12 ± 2, 10 ± 2, 11 ± 2, and 18 ± 2 mmHg in the A trial). The result suggests that muscle contraction velocity affects cardiorespiratory responses during repetitive isokinetic exercise.

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