Tricoli, V. A., Ricard, M. D., Parcell, A. C., & Sawyer, R. D. (2001). Internal vs. external velocity: Effects of strength training protocols on velocity-specific adaptations and human skeletal muscle variables. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 1488.

This study investigated the effects of eight weeks of high velocity isokinetic and isometric ballistic strength training on velocity-specific adaptations. Males (N = 20) were divided into two groups; isokinetic contractions at 300 deg/sec (N = 9) and isometric ballistic at 60 degrees knee angle (N = 11). Ss were tested for peak torque and power at 60, 120, 180, 240, and 300 deg/sec and for maximum isometric peak torque.

There were no changes in most aspects of muscle fiber type in either group. MHC type I and IIa percentage changed from 32.8% to 41.9% and from 52.4% to 42.5% in the isometric ballistic group. Maximum isometric peak torque and rate of force development improved in both groups. Isokinetic function improved only in the isokinetic group.

It was concluded that training involving external velocity (concentric and eccentric contractions) increased isokinetic and isometric properties whereas internal velocity training (isometric contractions) only improved isometric properties.

Implication. Resistance training involving movement improves more strength characteristics than does isometric training.

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