I am not sure how to express this. I want to say that, when I am rested my body works at the top of its strenght/ability/effectivness. Now all this sounds a little odd to me, so maybe you have something better to suggest.
You have misspelt "strength" and "effectiveness". Check your spelling before you post.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.