Buffering with exercise?

Hi there,

I am not sure I am using exercise as a buffer. I have insomnia and often I feel really tired and sleepy during the day. I could choose to allow that tiredness and nap. What I do instead is exercise. Of course I do not need to force myself out of the state I am in, but I do it to wake me up, to be able to feel productive during the rest of the day. Thanks in advance for the advice.