Objectives: This study compared the level of fatigue in vastus medialis obliquus (VMO) and vastus lateralis (VL) and their relative rate of recovery after a lower limb exercise program.Design: Repeated measures design.Setting: Exercise laboratory setting.Participants: Twenty healthy adults without the history of knee problems.Main outcome measures: Median frequency (MMF) of VMO and VL during submaximal isometric knee extension immediately after a fatiguing exercise program of cycling and at hourly intervals of a 7-h recovery period.Results: The normalized MMF of VL had more significant drop (P<0·006) than that of VMO immediately after the cycling exercise. In the 7-h recovery period, the MMF of both muscles rise but the rate was faster in VL than VMO (P<0·01).Conclusion: The VL fatigued relatively more than VMO during cycling exercise. Both muscles recovered from fatigue after exercise, but the rate of recovery was faster in VL than VMO.