SPECIFICITY OF STRENGTH TRAINING
Behm, D. G., & Sale, D. G. (1993). Intended rather than actual movement velocity determines velocity-specific training response. Journal of Applied Physiology, 74(1), 359-368.
"Strength training increases strength most at the specific velocity of movement at which the training exercises are performed. Strength increases are progressively smaller at velocities farther removed from the training velocity. This velocity-specific training response has been observed in isokinetic training at different velocities, in a comparison of isometric exercise and ballistic weight lifting (movements performed as rapidly as possible), and in a comparison of conventional heavy resistance weight training and explosive jump training." (p. 359)
Ss (M = 8; F = 8) trained 3 days per week for 16 weeks by doing attempted ballistic unilateral ankle dorsiflexions against resistance that either permitted the isometric contractions (one limb no movement) or a relatively high-velocity (5.23 rad/s on an isokinetic dynamometer) movement (other limb). Training sessions consisted of 5 x 10 contractions of each type. Training produced the same high-velocity-specific training response in both limbs (p < 0.001).
Peak torque increased most at the highest velocity (5.23 rad/s = 38% improvement) in comparison to lower velocities (0, 0.26, 0.52, 1.04, 1.55, 3.02, and 4.19 rad/s). Both limbs showed similar increases in voluntary isometric rate of torque development (26%) and relaxation (47%) and in evoked tetanus rate of torque development (14%). Similar decreases in evoked twitch time to peak torque (6%) and half-relaxation time (11%) were also observed.
These training adaptations, previously associated specifically with high-velocity resistance training, were produced by a training regimen that prevented an actual rapid movement occurring. This suggests that the principal stimuli for the high-velocity training response are the repeated attempts to perform ballistic contractions and the high rate of force development of the ensuing contraction. The type of muscle action (isometric or concentric) that is intended (imagined in the preparatory phase of the task) appears to be of lesser importance.
Implications. The training of speed movements is determined by preparatory imagery and thought content. Whether or not the movement occurs does not seem to be crucial for a performance change to occur. Since this study positioned the body segment to be moved in a stretched position, that could be a requirement for a training effect to occur. For example, to throw a baseball faster, a practice activity would be to have the athlete lean back with the arm fully extended behind at a position of maximum stretch. Then the movement is attempted but prevented.
"The mechanisms responsible for the velocity-specific response to training are unknown. Adaptations could occur in the nervous system or in the muscles. At the highest speeds of movements, it is thought that adaptations are neural, that is, movements with the greatest speed and effort are developed as a learned response. Their training is neural and does not involve physiological changes in the muscles." (p. 359)
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