Just like your not supposed to puff your cheeks when playing an instrument, but that never stopped Dizzy Gillespie. More of a suggestion than a rule

Gillespie also exemplified why the rule against puffing your cheeks is more than just a suggestion.

Jokes aside, you absolutely are. Bracing properly is a critical skill in both olympic weightlifting and traditional strength training.

Ah, shows how much I know about lifting... in general I've always been reminded to keep breathing when exercising.