To understand how, when, and why you use oxygen during exercise, you must first understand the types of exercise you perform. Exercise is broken down into two categories: aerobic activity and anaerobic activity. Depending upon the activity you perform, your body decides whether you do or do not need more oxygen to sustain energy.
Aerobic Activity and Oxygen Use
Aerobic literally translates to “with oxygen,” meaning your body uses oxygen production to generate energy. Aerobic exercises include brisk walking, jogging, paced running, cycling, and many other forms of activity that keep your heart rate maintained at a steady state. During these activities, your body needs longer sustained energy.
When you first begin aerobic exercise, your body converts glycogen stores into glucose to make a chemical called adenosine triphosphate, or ATP. ATP is the energy transporter for all cells. Once this initial energy boost of glycogen burns up, your body begins using oxygen as fuel. This energy switch gives you what is commonly known as the “runner’s high.” At this point, oxygen begins converting fat stores into energy to push you through your activity.
Anaerobic Activity and Energy Stores
Anaerobic translates to “without oxygen.” This doesn’t mean that anaerobic exercise requires you to stop breathing. It simply means that the intensity of your workout requires more oxygen than your body is able to take in, forcing you to use stored energy within your muscle cells. As we learned previously, stored energy in the form of glycogen converts to glucose to produce ATP. This is a process that happens during all exercise.
However, unlike aerobic activity where your body switches to oxygen as an energy source, anaerobic activity causes your body to go into oxygen debt. Without oxygen to fuel your body, you begin building lactic acid in your blood stream. This is what gives you that “burn” when you lift weights or perform rigorous activities.
Anaerobic activities include sprinting, weight lifting, interval training, circuit training, hill climbing, and any other form of high intensity exercise that provides short burst of energy followed by periods of rest. Your body is able to restore some of its oxygen debt through short periods of rest after high intensity activity. You do not need to fully recover your oxygen levels before returning to exercises because lactic acid actually provides you with a source of fuel to push through your workout.
Improving Your VO2 Max
The volume of oxygen you readily consume during intense activity measures your fitness level. The definition of VO2 max is the maximum amount of oxygen, measured in milliliters, you can use in 1 minute per kilogram of body weight. To put it simply, the more fit you are, the more readily you use oxygen when working out.
Performing high intensity exercise greatly improves your VO2 max. That is why your workouts should include both aerobic and anaerobic exercise. Your anaerobic workouts actually improve your ability to use oxygen efficiently during aerobic activity.
To maximize your ability to use oxygen during exercise, design a workout program that incorporates at least three days of weight lifting and two days of aerobic activity. Each session should last 30 to 60 minutes.