Breathing is something the body does so automatically that under certain circumstances, it is very easy to forget to do. This is one of the most common cues I will be telling clients, “breath.” Why? During a workout, you’re sending neuromuscular signals to cause muscular contraction to perform each exercise, as the intensity level of the exercise increases slightly, more thought and focus is placed into the muscle contraction, so much so that we literally forget to breath. Obviously, this becomes a problem as our muscles need oxygen in order to breakdown the necessary energy sources used for muscle contraction. When we stop breathing, we starve our muscles of much need oxygen and prevent the removal of carbon monoxide by-products.
Another side-effect that is typically produced when an individual stops breathing is in increase in internal thoracic pressure, called the Val Salva maneuver. This increase in pressure involves a huge increase in total muscle tension (not just in the muscles needed for the current exercise) and causes a rapid increase in heart rate. Because breathing is typically so second nature to us, it takes time and practice to learn how to consciously focus on breathing. While performing each exercise, focus on creating an even, and controlled rhythm of breathing. This allows air to continuously move in and out of your lungs, ensuring that oxygen is being delivered to the working muscles, and prevent excess tension from developing in the none-exercising muscles.
Check out a related blog: Breathing During Strength Training and the Valsalva Maneuver