Green, MS, Martin, TD, and Corona, BT. Effect of caffeine supplementation on quadriceps performance after eccentric exercise. J Strength Cond Res 32(10): 2863-2871, 2018-Caffeine use is common among athletes seeking to capitalize on its potential ergogenic effects. Limited research has examined caffeine's effects when used after activities that resulted in exercise-induced muscle damage (EIMD). This study examined the effect of caffeine supplementation on uninjured and injured muscle. Eight men and women (N = 16) who were physically active individuals participated in this study (age: 24.3 ± 4.3 years; height: 173.0 ± 7.0 cm, mass: 75.2 ± 11.5 kg; body fat: 18.2 ± 15.9%). One leg was assessed under uninjured and injured (100 eccentric quadriceps contractions) conditions after caffeine supplementation (6 mg·kg), with the other leg assessed under both conditions after placebo supplementation. Compared with the placebo, caffeine increased peak isokinetic torque by 6.8 ± 2.3 and 9.4 ± 2.5% in uninjured and injured muscle, respectively, but had no effect on maximal voluntary isometric torque or fatigue index in uninjured or injured muscle, with treatments exhibiting similar (p > 0.05) alterations in isometric torque (-11.9 ± 2.2%), fatigue index (-13.9 ± 3.4%), and soreness (+44.0 ± 4.7) after eccentric contractions. The results of this study suggest that caffeine possesses a similar ergogenic effect on isokinetic torque in both uninjured and injured states, but no effect on the production of isometric torque, perception of soreness, or degree of relative fatigue. Athletes should consider the potential caffeine supplementation possesses during recovery from activities that resulted in EIMD.