He's limited. Page 133 of the World of Darkness rulebook states that only 1 willpower point can be spent per turn, regardless of how it's used. So, if your hypothetical strongman spent willpower to attack his opponent, he cannot then spend more willpower to bolster his defense against an incoming attack.

The reason for this, from a narrative perspective, is that, by spending a willpower point, you are throwing all of your effort into that action. Once you have done that, you cannot then throw the same level of effort into other actions.