0256 Disorders of fatty acid oxidation can be dangerous, even life threatening. Little is known about how these deficiencies alter normal physiological responses to stress. Previously, we have studied the responses of male and female very-long-chain acyl- CoA dehydrogenase (VLCAD) deficient mice to high intensity exercise and have observed that males experience a delay in recovery while females apparently do not. This conclusion was based on measurement of muscle function 24 h post-exercise. PURPOSE: In the present study, we investigated the hypothesis that VLCAD deficiency in female mice as in the previous study would not affect recovery from exercise during the 24 h immediately post-exercise. METHODS: VLCAD deficient and non-deficient 129Sv/C57BL6 mice were divided into two groups, exercised and non-exercised. Exercising mice intitially ran at a speed of 16 m-min−1 and 0% grade. The speed and grade were increased at 6-min intervals to 24 m-min−1 and 0% grade, 30 m-min−1 at 2% grade, 35.5 m-min−1 at 4% grade, 41 m-min−1 at 6% grade, and 47 m-min−1 at 8% grade. Just prior to exercise (0) and at 6, 12, and 24 hours following exercise, skeletal muscle function of the gastrocnemius muscle was determined in exercised mice and non-exercised controls. Measures included peak twitch tension (Pt), the force-frequency response at 40, 60, 80, 100, 120, and 140 Hz, maximum tetanic tension (Po), the contraction time (CT), and the fatigue index (FI). The effects of the disorder on the responses of glucose, lactic acid, and run time to exhaustion were also examined. Final data were analyzed using a 2 (disorder) × 4 (time post-exercise) ANOVA. RESULTS: Similar to previous observations, the female VLCAD deficient mice were not affected by either the enzyme deficiency or exercise. However, both run time to exhaustion and blood glucose were significantly (p<0.05) reduced in VLCAD Deficient mice. Blood lactate was not different. CONCLUSIONS: These data indicate that acute exercise in female VLCAD deficient mice does not affect recovery of muscle function after exercise despite an effect on performance.