The loss of the ability of skeletal muscle to generate force is one of the most appropriate and valid means by which to quantify muscle damage. However, measurements of maximal muscle force may include many potential sources of error, the most common of which is the lack of central drive to the muscles. The aim of the present study was to therefore determine the reliability of maximal isometric quadriceps muscle force and voluntary activation over a time-scale that is typically employed to examine the aetiology of exercise-induced muscle damage. We also characterised the reliability of several twitch interpolation variables and determined the effects of different calculation methods on estimates of voluntary activation, specifically the central activation ratio (CAR) and interpolated twitch ratio as calculated from both unpotentiated (ITTUNPOT) and potentiated twitches (ITTPOT). Eight healthy active males, mean (SD): age 21.4 (0.9) years; mass 83.6 (8.2) kg; height 179.8 (2.4) cm performed repeated maximal voluntary isometric contractions (MVC) of the quadriceps over a 7 day period (baseline and 2h, 6h, 24h, 48h, 72h, 7 days post). Differences across the 7 sessions were assessed using repeated measurements ANOVA. Ninety-five percent repeatability coefficients were also calculated according to Bland and Altman (1999). There was a significant difference (P0.05) where 95% repeatability coefficients of 76.03 N, 4.42%, 8.44 N, 25.92 N and 43.58 N were observed, respectively. These data indicate that young healthy well-familiarised subjects can reproduce their perceived maximal efforts both within and between days where activation levels of >90% are routinely achieved. Providing activation remains within these limits in the 7-days following an acute bout of exercise, the researcher may be 95% certain that exercise-induced muscle damage is present in individual subjects (taken from similar subject populations) if MVC force falls outside these limits.