Holding your breath during strenuous weightlifting, a technique known as the Valsalva maneuver, can stabilize your torso and potentially allow you to lift heavier weights. This method involves bracing your core and building intra-abdominal pressure by holding your breath, commonly used during compound lifts like squats and deadlifts.
While effective for many, the Valsalva maneuver can temporarily increase blood pressure and may lead to dizziness or blackouts. The American Heart Association advises beginners and individuals with cardiovascular disease to avoid holding their breath during lifts. It is also not recommended during pregnancy due to risks to the placenta. If you have concerns, consult a medical provider.
For those who do not use the Valsalva maneuver, the general guideline for breathing during lifts is to exhale during the most difficult part of the exercise (the concentric contraction) and inhale during the easier part (the eccentric contraction). For example, when squatting, inhale as you lower yourself and exhale as you push back up, particularly through the "sticking point." For deadlifts, exhale as you lift the weight and inhale as you lower it.