Are early and late rate of force development differently influenced by fast-velocity resistance training?

This study examined the effect of fast-velocity concentric isokinetic resistance training (FV) on the rate of force development (RFD) at early (<100ms) and late phases (>100ms) of rising muscle force. Nine men participated in a 6-week resistance training intervention for the lower body, and nine matched subjects participated as controls (CON). During concentric isokinetic (180 degrees s1) knee extension training, subjects were instructed to do each contraction as fast and forcefully as possible'. Maximal muscle strength (MVC) and RFD (010, 020, ..., 0250ms from the onset of contraction) were measured during maximal voluntary isometric contraction of the knee extensors (KE). There were no significant changes in MVC of KE in both groups after intervention (FV=314 center dot 2 +/- 101 center dot 1 versus 338 center dot 7 +/- 88 center dot 0N.m, 0 center dot 05; CON=293 center dot 3 +/- 94 center dot 8 versus 280 center dot 0 +/- 72 center dot 2N.m, 0 center dot 05). The RFD increased 3971% at time intervals up to 90ms from the onset of the contraction (P<0 center dot 05), whereas no change occurred at later time intervals. Similarly, relative RFD (i.e.%MVC.s1) (RFDr) increased 3356% at time intervals up to 70ms from the onset of the contraction (P<0 center dot 05). It can be concluded that a short period of resistance training performed with concentric fast-velocity isokinetic muscle contractions is able to enhance RFD and RFDr obtained at the early phase of rising muscle force.