Kinetic and kinematic characteristics of plyometric exercise on the impulse machine for elbow flexors

Abstract

Since plyometric exercise typically involves an unknown force, safety considerations prompt a kinetic analysis prior to utilizing the exercise for patients. A recently developed device, the Impulse machine, provides a means of plyometric exercise with fine adjustment of the force. The force applied to the subject during the Impulse exercise, however, partly depends on the subject's effort, so kinetic and kinematic characteristics of the exercise need to be examined. Twelve college-aged women performed elbow flexion for the experiment. The participants performed two types of exercise, tonic and phasic, at five randomly assigned inertial loads (1.47, 3.74, 6.01, 8.28, and 10.55 kg). Tonic exercise involves continuous contraction of the elbow flexors, albeit with variation in intensity and type of contraction during the exercise, whereas phasic exercise consists of alternate contraction and relaxation of the elbow flexors. A WATSMART three-dimensional motion analysis system was used to determine kinetic and kinematic characteristics of the exercise. Differences in force, angular velocity, and power between tonic and phasic exercise, and among five loads, were tested using a two-way analysis of variance. For angular velocity and power, concentric and eccentric activities were analyzed separately. With the inertial load at 10.55 kg, the mean (± standard deviation) maximal tension on the Impulse machine was 145 (± 34.3) N for tonic exercise and 177 (± 34.0) N for phasic exercise. Maximal angular velocity was 383 (± 116.7) deg/sec for eccentric activity and 349 (± 92.9) deg/sec for concentric activity during tonic exercise, and 493 (± 172.8) deg/sec for eccentric activity and 414 (± 126.1) deg/sec for concentric activity during phasic exercise. As the load was raised, maximal force significantly increased (p <.05).