DISCUSSION
We tested the hypothesis that the contraction mode used during prolonged periods of slow-speed maximal resistance training would affect gains in the contractile rate of force development (RFD) of the quadriceps femoris. The testing of this hypothesis was important given that: (1) there is a substantial body of evidence indicating that both neural and muscular adaptations to concentric and eccentric training are different; and (2) both athletic and clinical/rehabilitation populations often perform extended periods of slow-speed concentric- or eccentric- only training; but (3) there are no data comparing the relative influence of these forms of training on RFD. After 10 weeks of training there was a significant increase in both the total isometric torque production and RFD during knee extension in both groups (i.e., pooled data; see Fig. 1). However, there was no between-group difference in the magnitude of improvement. Perhaps it is more important that given the practical significance of contractile impulse to movement speed potential,changes in contractile impulse measured to timepoints 200 ms from the onset of contraction were also the same. Thus, the effects of concentric- and eccentric-only training on contractile rate of force development and impulse appear to be indistinguishable when training is performed maximally. From a practical point of view, there seems to be no additional benefit or cost in terms of RFD enhancement of performing only a single movement phase, at least when the training is performed with maximum volition as is the case with isokinetic strength training.