Exactly! Also Boyd and Ike had that whole rival thing going on so they probably trained and got buff together.
I'll admit I was initially surprised at how big Ike got but then I remembered that he had his father's legacy to live up to. The Greil Mercenaries could not be led by some weak sauce.
Thus hunky, muscle toned, Ike was born. And pfft I am not complaining one bit.