Q: I know it seems silly, but I often wonder if it makes a difference how I breathe when I'm lifting weights. What do you recommend? - O.R., Seattle, WA

A: Your question's not silly. It's important that you maintain the correct breathing pattern when you lift weights. As you are about to lift, inhale deeply. This will get the needed oxygen into your system. Exhale as you perform the weight movement. Relax briefly, inhale, and repeat the exercise. Don't ever hold your breath when you lift weights. Doing so reduces the flow of blood back to your heart and subsequently affects the blood flow to your brain. The resulting light-headedness and risk of fainting can be dangerous, especially if you are performing an overhead exercise.

Source: fitlinxx.com