Key result
Muscle contraction velocity significantly affected the increase in heart rate, mean blood pressure, minute ventilation, and oxygen uptake during repetitive isokinetic exercise, showing a U-shaped curve.
Why the study?
Does muscle contraction velocity affect cardiorespiratory responses during repetitive isokinetic exercise in healthy males?
Does muscle contraction velocity affect cardiorespiratory responses during repetitive isokinetic exercise in healthy males?
p-value: p=<0.05
Muscle contraction velocity significantly affects cardiorespiratory responses (HR, MAP, VE, VO2) during repetitive isokinetic exercise at a constant work rate, demonstrating a U-shaped relationship.
May inform velocity selection during isokinetic testing in healthy adults; leaves open effects in patients and need for prospective trials.
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 (Vdot;E), and oxygen uptake (Vdot;O(2)) during the exercise. The angular velocity significantly affected the increase in HR, MAP, Vdot;E, and Vdot;O(2) 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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Hayashi et al. (2003) studied Healthy (n=8). Various angular velocities (30, 60, 120, and 240 deg/s) vs. Within-subject comparison across velocities was evaluated on Cardiorespiratory responses (HR, MAP, VE, VO2) (p=<0.05). Muscle contraction velocity significantly affected the increase in heart rate, mean blood pressure, minute ventilation, and oxygen uptake during repetitive isokinetic exercise, showing a U-shaped curve.
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