Smith, D. B., Housh, T. J., Johnson, G. O., Evetovich, T. K.,Ebersole, K. T., Rana, S. R., & Bull, A. J. (2003). Mechanomyographic, electromyographic, and peak torque responses to isometric strength training of the vastus lateralis. Medicine and Science in Sports and Exercise, 35(5), Supplement abstract 803.

Adult males (N = 13) were randomly assigned to a training (N = 6) or a control group (N = 7). Maximal isometric peak torque for leg extensions (vastus lateralis) were measured for EMG and MMG amplitude at flexion angles of 30°, 60°, and 90°. Training was on the non-dominant leg at 60° for eight weeks. Training activities were; for the first two weeks two sets at 80% of maximal isometric force; and for the remaining six weeks three sets of muscle actions at 80% of maximal isometric force. Training occurred three times per week.

Peak torque increased with training at the three angles. After four weeks, improvement was 9.8% and in the second four weeks it was 14.8% at 60°. Improvements at 30° and 90° were significant but less than at 60°. There was also a significant increase of 35% in EMG amplitude at 60° over the eight weeks. There was no training effect on the non-trained (dominant) leg or in MMG amplitude.

Implication. Muscle activation is the main isometric training effect. There is no cross-training effect to the untrained limb.

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