the mechanisms of exercise-induced fatigue have not been investigated using proteomic techniques, an approach that could improve our understanding and generate novel information regarding the effects of exercise. in this study, the proteom alterations of rat skeletal muscle were investigated during exercise-induced fatigue. the proteins were extracted from the skeletal muscle of sd rat thigh, and then analyzed by two-dimensional electrophoresis and pdquest software. compared to control samples, 10 significantly altered proteins were found in exercise samples, two of them were upregulated and eight of them were downregulated. these proteins were identified by maldi tof-ms. the two upregulated proteins were identified as mlc1 and myosin l2 (dtnb) regulatory light-chain precursors. the eight decreased proteins are glyceraldehyde-3-phosphate dehydrogenas (gapdh); beta enolase; creatine kinase m chain (m-ck); atp-amp transphosphorylase (ak1); myosin heavy chain (mhc); actin; troponin i, fast-skeletal muscle (troponin i fast-twitch isoform), fstni; troponin t, fast-skeletal muscle isoforms (tntf). in these proteins, four of the eight decreased proteins are related directly or indirectly to exercise induced fatigue. the other proteins represent diverse sets of proteins including enzymyes related to energy metabolism, skeletal muscle fabric protein and protein with unknown functions. they did not exhibit evident relationship with exercise-induced fatigue. whereas the two identified increased proteins exhibit evident relationship with fatigue. these findings will help in understanding the mechanisms involved in exercise-induced fatigue.