Torque Curves and Heart Rate Responses to Isometric, Eccentric and Concentric Isokinetic Exercises of the Knee and Elbow Joints

Yoon, Tae Sik

Abstract

OBJECTIVE
To investigate the torque curves and heart rate responses to isometric, eccentric and concentric isokinetic exercises with a maximal voluntary contraction of the right knee and elbow joints in 30 healthy men(26.6+/-2.2 years). METHOD: Subjected performed the eccentric and concentric isokinetic exercises with 10 repetitions at 60o/sec, while performing the isometric exercises at a joint angle of 60 degrees for the same period of time with Cybex 6000. Peak torque, angle of peak torque, and total work were measured and the flexor-to-extensor ratios of peak torque were calculated. Heart rates were recorded simultaneously at rest and immediately after the exercise, and the time required to return to the resting heart rate level was also recorded for each exercise session.
RESULTS
Peak torque and total work for the eccentric exercise were significantly higher than those for the concentric exercise(p<0.01) of the knee and elbow joints. Eccentric peak torques for flexors and extensors of the knee joint occurred at a significantly longer muscle length than the concentric peak torques(p<0.01). Flexor-to-extensor ratios of a peak torque of the knee joint between the eccentric and concentric isokinetic exercises did not show a significant difference. Torques at a joint angle of 60 degrees were highest in the eccentric isokinetic exercise, followed in the order by isometric, and then concentric isokinetic exercises of the knee joint(p<0.01), and concentric torque at a joint angle of 60 degrees was significantly lower than those of the eccentric and isometric exercises of the elbow joint. The increase in heart rate and the time of returning to the resting heart rate level were independent of the size of the contracting muscle mass and the types of exercise. The increment ratio for the heart rate was 70.4+/-23.6%.
CONCLUSION
In conclusion, the response of heart rate to the exercise is not influenced by the contracting muscle mass or the types of exercise in a short duration of maximal voluntary contraction, implying that special precautionary measures are not required for the isometric, eccentric and concentric isokinetic exercises.