Effects of concentric andeccentric training on muscle strength, cross-sectional area,and neural activation. J. Appl. Physiol. 81(5): 2173–2181,1996.—We compared the effects of concentric (Con) andeccentric (Ecc) isokinetic training on quadriceps musclestrength, cross-sectional area, and neural activation. Women(age 20.0 6 0.5 yr) randomly assigned to Con training (CTG;n 5 16), Ecc training (ETG; n 5 19), and control (CG; n 5 19)groups were tested before and after 10 wk of unilateral Con orEcc knee-extension training. Average torque measured duringCon and Ecc maximal voluntary knee extensions increased18.4 and 12.8% for CTG, 6.8 and 36.2% for ETG, and4.7 and 21.7% for CG, respectively. Increases by CTG andETG were greater than for CG (P , 0.05). For CTG, theincrease was greater when measured with Con than with Ecctesting. For ETG, the increase was greater when measuredwith Ecc than with Con testing. The increase by ETG withEcc testing was greater than the increase by CTG with Contesting. Corresponding changes in the integrated voltagefrom an electromyogram measured during strength testingwere 21.7 and 20.0% for CTG, 7.1 and 16.7% for ETG, and28.0 and 29.1% for CG. Quadriceps cross-sectional areameasured by magnetic resonance imaging (sum of 7 slices)increased more in ETG (6.6%) than in CTG (5.0%) (P , 0.05).We conclude that Ecc is more effective than Con isokinetictraining for developing strength in Ecc isokinetic muscleactions and that Con is more effective than Ecc isokinetictraining for developing strength in Con isokinetic muscleactions. Gains in strength consequent to Con and Ecc trainingare highly dependent on the muscle action used for trainingand testing. Muscle hypertrophy and neural adaptationscontribute to strength increases consequent to both Con andEcc training