Skeletal muscle repair is vital for the maintenance of muscle mass & function, both of which decline with ageing. Research suggests a greater susceptibility to muscle injury & prolonged recovery with advancing age (1), which may contribute to sarcopenia & dynapenia. We investigated the effects of ageing on functional responses to a single bout of eccentric (ECC) or concentric (CON) exercise. We hypothesized: 1) ECC would cause greater functional decline & slower recovery in old (O) vs. young (Y) men, & 2) CON would minimally impact function. We recruited 8 Y (22±1 y, mean±S.E.M) & 8 O (70±1 y) healthy, exercise naïve volunteers. Participants performed a single bout of unilateral ECC & CON (legs randomized to ECC or CON): 7×10 repetitions at 80% of ECC/CON one-repetition maximum (1-RM). We assessed muscle soreness, sensitivity to pain, peak torque, power & lower body function at baseline (BL), immediately after (0c h) & 5, 24, 72 & 168 h following ECC & CON. Y had a higher ECC & CON 1-RM than O (ECC Y: 265±18 vs. O: 190±13; CON Y: 152±14 vs. O: 95±6 kg, t-test P<0.005). At BL, Y exhibited greater peak torque than O (Y: 253±21 vs. O: 166±15 Nm; two-way ANOVA P<0.05). ECC resulted in peak torque declines (compared to BL) in both Y & O at 0 h (Y: 171±15.3, P<0.0001; O: 128.5±11, P<0.05) which persisted up to 24 h post-ECC in the O (113±13, P<0.0005) & 72 h in the Y (201±24, P<0.0005). Peak torque had returned to BL in both groups by 168 h. CON produced peak torque declines in the Y at 0 h (207.5±20.3, P<0.05), which remained at 72 h (210±29, P<0.05) & returned to BL by 168 h. CON had no effect on peak torque in the O. No BL age-related differences were observed for power (Y: 228±32 vs. 179±26 W). Immediately after ECC, power declined in the Y at 0 h (169±16, P<0.05) & persisted until 24 h (150±24, P<0.0005). Power did not decline in the Y following CON or in the O following ECC or CON. No changes in lower body function, measured by a short physical performance battery test (SPPBT), were seen in the Y or O. Sensitivity to pain was heightened in both Y & O at 5 h (Y: 11±2; O: 7±1 lbs, P<0.05) post-ECC compared to BL (Y: 13±1; O: 10±1) & remained until 72 h (11±1, P<0.05) in the Y only. Sensitivity to pain did not change post CON. Following ECC, muscle soreness was elevated at 0 h (6±1 cm, one-way ANOVA P<0.005) & continued until 72 h (4.9±0.8, P<0.005) in the Y, & was elevated at 24 h in O (6±1, P<0.0001). Soreness was elevated at 24 h post CON in both Y & O (Y: 5±1; O: 4±1, P<0.005). We find no evidence to support an age-related increase in ECC injury susceptibility or delayed functional repair. These findings may be explained by differences in absolute loads lifted with O being exposed to markedly lower loads during the study, perhaps due to reduced cross sectional area. Furthermore, the data suggests ECC is safe to perform in the O.