strengthen

[1]	reinforce , beef up , fortify , renew , bolster , fortify , support , confirm , corroborate , substantiate , buttress , step up , boost
[2]	encourage , hearten , invigorate , fortify , rejuvenate , nourish , energize , vitalize , toughen , brace (up) , steel , innervate , stiffen
[3]	tone , tone up