To maximize force during strength exercises, grip the implement tightly and contract the core, potentially filling the body with air.

“If you want to generate force, right, you want to move a heavy barbell or dumbbell, you want to do a chin up with the maximal force, that's when you can employ the opposite, which would be to grip the bar or dumbbell, et cetera, very tightly. And you want to contract your core or even fill your body with air as a, say, plug all the leaks, et cetera.”