From Precision Fitness: "Don’t forget to breath! . Inhale through your nose and exhale through your mouth at the point of maximum exertion during the exercise. Failure to breathe correctly during heavy weight lifting may cause potentially harmful increases in blood pressure."
From Miami Valley Fitness: "Breathe. Holding your breath while performing heavy loads leads to dizziness, fatigue, and possibly nausea. Just as breathing is vital to life, breathing is vital to the life of your strength-training program. Think of oxygen as your muscle’s fuel. Holding your breath starves the muscles of oxygen-rich blood and can impede your workout. Exhale (through the mouth, 1-2 seconds) when you exert the muscle (positive phase), and inhale through the nose when you release (negative phase, 3-4 seconds). "
From Physician's Fitness Coach:
"Breath Control
Breathing is important during your workout because you need to supply a good deal of oxygen to your muscles and brain.
During Strength Training
It is very important that you breathe correctly when doing your weight lifting exercises, so keep these basic rules of breathing in mind:
1) DO NOT hold your breath!
2) Inhale during the lowering phase
3) Exhale during the lifting phase.
During Cardio Training
Without giving it much conscious thought, most runners breathe in a 2/2 rhythmic ratio. They take two steps as they inhale; they take two more steps as they exhale. While running very slowly, they often breathe in a 3/3 ratio. While running very fast, they might breathe 2/1 or 1/1, but 2/2 is much more common.
Your jaw should be relaxed, your mouth slightly open. The oxygen will come through your nose and mouth to your lungs, to your blood and to your muscles without you needing to give it a lot of thought."
