Early adaptations of eccentric training show several advantages over concentric training. The purpose of this study was to quantify the effects of 4-weeks of multi-joint eccentric versus traditional leg press (TLP) training on muscle strength, rate of torque development (RTD) and jump and sprint performance adaptations. Twenty-six resistance trained adults performed either an eccentric or a TLP resistance training program twice per week for 4-weeks. Single-joint isometric maximum and rapid strength (peak torque and RTD, respectively) and isokinetic strength of the knee extensors and flexors, multi-joint eccentric strength, leg press strength (1-RM), 40-m sprint, and vertical and long jump were measured before (Pre), at the midpoint (Mid), and after (Post) a 4-week training period. Four weeks of isokinetic multi-joint eccentric training elicited greater test-specific strength gains (ES=1.06) compared to TLP (ES=0.11). The eccentric group (ES=0.51 and 0.54) also yielded moderate improvements in the early-middle phase RTD (RTD100-200) whereas the TLP group showed small-moderate improvements (ES=0.37). The majority of the single-joint strength variables showed negligible improvements. Performance tests showed no (broad jump) to small (vertical jump; sprint for the leg press) improvements. Eccentric multi-joint training induced significant improvements for lower body strength in a short amount of time in a trained population. These accelerated adaptations and also the lowered energy requirements of eccentric exercise may be useful for clinicians or practitioners when prescribing training programs for those who are injured, sedentary, or elderly, who are in need of time efficient muscle function improvements.