88 Journal of Strength and Conditioning Research, 2003, 17(1), 88–94  2003 National Strength & Conditioning Association The Effect of Short-Term Isokinetic Training on Force and Rate of Velocity Development LEE E. BROWN 1 AND MICHAEL WHITEHURST 2 1 Human Performance Laboratory, Arkansas State University, State University, Arkansas 72467; 2 Florida Atlantic University, Boca Raton, Florida 33431. ABSTRACT This study determines the effects of short-term isokinetic training on rate of velocity development (RVD) and force. Three groups were pre- and posttested for knee extension RVD and force at 1.04 (slow) and 4.18 rad·s -1 (fast) on a Kin- Com dynamometer. The slow and fast groups completed 2 days of velocity-specific training, whereas the control group did not train. Four-way analysis of variance results demon- strated significant (p  0.05) decreases in RVD between pre- and posttests for the slow group at the slow velocity (RVD— 1.25  0.04° vs. 1.08  0.03°) and for the fast group at the fast velocity (RVD—14.24  0.33° vs. 13.59  0.29°). Force exhibited no significant differences between testing days for any group. These results demonstrate that short-term isoki- netic training results in velocity-specific RVD improvements. These acute RVD improvements may serve to offset strength deficits in power environments on the basis of the mutable relationship between force and velocity. Key Words: strength, resistance training, acceleration Reference Data: Brown, L.E., and M. Whitehurst. The effect of short-term isokinetic training on force and rate of velocity development. J. Strength Cond. Res. 17(1):88–94. 2003. Introduction A pproximately 8 weeks of heavy resistance training can produce significant gains in strength. The con- sensus position supported by experimental studies is that gains in strength are the primary result of muscle tissue changes collectively called hypertrophy (12). What is less well known is the phenomenon that re- sults in the manifestation of increased strength after only a few strength-training sessions. The suggestion is that initial changes in strength after training occur at a rate too fast to be accounted for by morphological changes. Therefore, neurological changes must play a role in acute strength expression. Moritani and deVries (20) investigated the relative contributions of neural and hypertrophic factors to muscle strength gains. Af- ter 8 weeks of training, all subjects had increased their maximal strength and the electromyographic changes clearly illustrated that changes in electrical activity at the elbow flexor were primarily responsible for early strength increases, whereas hypertrophic responses gradually increased as a contributory factor over time. Therefore, the short-term acute strength gains in un- trained subjects appeared to be due to neural adap- tations. Much of the previous strength research has focused on slow-velocity, high-resistance movements. Howev- er, the effect of high-velocity, low-resistance training has not been thoroughly investigated. Additionally, re- search has focused almost exclusively on torque pro- duction as the outcome, with little consideration given to the possible training adaptations related to a sub- ject’s ability to produce greater limb acceleration. Pre- vious studies have not emphasized acceleration adap- tations accompanying short-term training. Such short- term acceleration gains could affect human perfor- mance by the mutable nature of force and velocity. A decline or deficit in force production of a limb may be balanced by an increase in the velocity of that limb (25). However, proper measurement of this phenome- non can prove to be problematic. Prevost et al. (24) had volunteers train for 2 days in either a slow group (0.52 rad·s -1 ) or a fast group, (5.22 rad·s -1 ) performing 3 sets of 10 repetitions be- tween pre- and posttests. Mean peak torque did not change at the slow-test limb velocity for either group, whereas the fast group exhibited approximately 22% increase in mean peak torque between pre- and post- tests. They attributed this to neural facilitation, and it is well established that performance gains after short- term training are primarily a function of neural factors (1, 2, 14, 17, 21). However, a 22% increase in forcepro- duction after low-load, high-velocity exercise appears excessive. Because isokinetic training involves an acceleration phase of movement (8) and the failure to control for this phase will artificially increase force production, (26) a neurally mediated increase in acceleration or the rate of velocity development (RVD) may be responsible