Objective: To determinate the content or activity changes of the nitric oxide-nitric oxide synthase (NO-NOS) system in the vastus lateral muscle of rat under different exercise loads

and to explore the impact of exercise training on vastus lateral muscle. Method: Sixty male rats were divided randomly into quiet control group (n=20)

moderate exercise intensity group (n=20)

exercise fatigue group (n=20). The rats in the quiet control were feeded regularly

and without any intervention

the rats in the moderate exercise intensity group were trained with swimming moderately

the rats in the exercise fatigue group were established to be fatigue model.The content or activity changes of the NO-NOS system in the vastus lateral muscle were determinated by biochemical kits. Result: Comared with the quiet control group

the content or activity of NO

total nitric oxide synthase (tNOS)

endothelial nitric oxide synthase (eNOS)

neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) were significantly increased after moderate intensity. Compared with the moderate-intensity group

the activity of iNOS in the exercise fatigue group was significantly decreased. Conclusion: The NO-NOS system in the vastus lateral muscle will have varying degrees of change under different exercise loads

moderate-intensity exercise can increase the content or activity of NO

NOS

eNOS

nNOS and iNOS

and high fatigue movement can decrease the activity of iNOS and eNOS.