LAUSR

PURPOSE This study compared the concentric and eccentric training effects on fatigue induced by eccentric and concentric protocols. METHODS Twenty-two men and women (22 ± 3.6 years) were assigned to concentric (GCON, n=11) or eccentric training (GECC, n=11). The concentric (CON) and eccentric (ECC) protocols were composed of 4 sets of 20 knee extension/flexion repetitions. Force losses were analysed by comparing 10 repetitions' mean torques during the protocols and verifying the maximal voluntary contraction (MVC) and rate of torque development (RTD) before and after the protocols. Muscle damage was assessed using echo intensity (EI) of the vastus lateralis 48 hours after the protocols. Training consisted of 6 weeks of isokinetic exercise at 60°.s-1 (concentric or eccentric) twice weekly. RESULTS Before training, both protocols resulted in dynamic and isometric force losses in GCON and GECC (P<0.01), but the magnitude was greater after the CON protocol than after the ECC protocol (P<0.001). After training, both GCON and GECC showed similar force decreases during the CON and ECC protocols (P<0.01), and these changes were not different from the pre-training decreases. Regarding MVC after training, GECC showed lower force decreases than GCON after ECC exercise (-13.7 vs. -22.3%, respectively, P<0.05), whereas GCON showed lower MVC decreases after CON exercise compared with pre-training (-29.2%, P<0.05). RTD losses were similar after the protocols before and after the training regimens. No changes in EI were observed after the protocols before and after training. CONCLUSIONS Both interventions resulted in similar force decreases during fatigue protocols when compared with those associated with pre-training.