Breathing during exercise is an important component to getting the most out of your workout. Holding your breath, breathing too fast or too slow, too deep or too shallow can affect heart rate and perceived intensity of an exercise. Follow these basic tips:
When doing cardio (aerobic) exercise, take slightly deeper and longer breaths than normal, maintaining a regular rate and breathing more through the stomach rather than your chest.
When stretching, take deep and long breaths, inhaling through the nose and exhaling through the mouth to help your body get into a relaxed state.