This study's objective was to determine whether 14 days of dietary creatine supplementation preceding an injurious bout of eccentric contractions affect the in vivo strength loss of mouse anterior crural muscles. Three groups of nine mice each were fed a meal diet for 14 days, one group at each of three levels of creatine supplementation (i.e., 0, 0.5, and 1% creatine). Electrically stimulated concentric, isometric, and eccentric contraction torques produced about the ankle were measured both before and after a bout of 150 eccentric contractions. Tibialis anterior muscle creatine concentration was significantly increased by the supplementation, being 12% higher in the mice fed the 1% creatine diet compared with control mice. After the bout of eccentric contractions, the reductions in torque (i.e., 46-58%) were similar for the isometric contraction, all eccentric contractions, and the slow (i.e., 200 ^o/s) concentric contractions; above 200 ^o/s, the percent reduction in concentric torque increased progressively to 85-88% at 1,000-1,200 ^o/s. However, there was no effect of creatine supplementation on the isometric torque loss or on the torque loss at any eccentric or concentric angular velocity (P  0.62). In conclusion, a moderate increase in muscle creatine concentration induced by dietary supplementation in mice does not affect the strength loss after eccentric contractions.