Key result
Increasing isometric contraction intensity from 20% to 50% maximal force increased heart rate by a mean of 15.1 beats/min for handgrip and 20.7 beats/min for wheel-turn exercises.
Why the study?
Does the muscle mass and intensity of isometric contraction affect the contraction-induced rise in heart rate in healthy men?
Does the muscle mass and intensity of isometric contraction affect the contraction-induced rise in heart rate in healthy men?
The magnitude of heart rate increase during isometric exercise is directly related to both the intensity of the contraction and the mass of the contracted muscle.
Isometric exercise prescriptions should factor in intensity and muscle mass to anticipate heart rate responses; confirms direct dependence in healthy men.
The purpose of this study was to determine the effect of muscle mass and the level of force on the contraction-induced rise in heart rate. We conducted an experimental study in a sample of 28 healthy men between 20 and 30 yr of age (power: 95%, alpha: 5%). Smokers, obese subjects, and those who performed regular physical activity over a certain amount of energetic expenditure were excluded from the study. The participants exerted two types of isometric contractions: handgrip and turning a 40-cm-diameter wheel. Both were sustained to exhaustion at 20 and 50% of maximal force. Twenty-five subjects finished the experiment. Heart rate increased a mean of 15.1 beats/min [95% confidence interval (CI): 5.5-24.6] from 20 to 50% handgrip contractions, and 20.7 beats/min (95% CI: 11.9-29.5) from 20 to 50% wheel-turn contractions. Heart rate also increased a mean of 13.3 beats/min (95% CI: 10.4-16.1) from handgrip to wheel-turn contractions at 20% maximal force, and 18.9 beats/min (95% CI: 9. 8-28.0) from handgrip to wheel-turn contractions at 50% maximal force. We conclude that the magnitude of the heart rate increase during isometric exercise is related to the intensity of the contraction and the mass of the contracted muscle.
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Gálvez et al. (2000) studied Healthy (n=28). Isometric contractions (handgrip and wheel-turn) vs. Different intensities and muscle masses was evaluated on Contraction-induced rise in heart rate. Increasing isometric contraction intensity from 20% to 50% maximal force increased heart rate by a mean of 15.1 beats/min for handgrip and 20.7 beats/min for wheel-turn exercises.