The next time you go for a run, pay attention to how hard you’re working. Is your breathing controlled or labored? Are you clicking along at a moderate pace or do you have steep hills to climb every 10 minutes?
If you’ve been working out for any length of time, there’s a good chance you’ve heard people talk about aerobic training, such as jogging at a moderate pace, and anaerobic training, such as a run that takes you up and down hills.
What determines whether or not the activity you’re doing is aerobic or anaerobic comes down to oxygen levels. Exercise can be aerobic (with oxygen), anaerobic (without oxygen) or a combination of both.
Aerobic Energy System
Activities are considered aerobic or “with oxygen,” if they stimulate your heart rate and cause your breathing to increase and they can be performed at a level that can be maintained for an extended period of time.
Benefits of aerobic exercise include:
- Reducing the risk of developing heart disease, hypertension, obesity and type 2 diabetes
- Managing chronic health condition such as high blood pressure and high blood sugar
- Strengthening your heart and keeps your arteries clear—aerobic exercise helps lower LDL cholesterol and increase HDL cholesterol
- Warding off cognitive decline
- Increasing stamina
- Improving mood and manage certain mental health conditions such as depression and anxiety
Examples of aerobic exercise include walking, jogging, swimming, cycling, cardio equipment (elliptical, stairclimber, stationary bike), aerobic classes and hiking.
Activities that are considered aerobic use fat, with the help of oxygen and carbohydrates, to provide a steady supply of energy for activity. Unlike anaerobic exercises, the intensity of aerobic exercise is lower and doesn't require fast and powerful contractions to produce force.
However, aerobic exercises can become anaerobic if performed at a level of intensity that is too high. For example, if you’re cycling on a spin bike and increase the tension or get out of the saddle too much, your heart rate may not have a chance to go back down to the aerobic range. That’s why longer workouts need to have built-in recovery breaks that allow your heart rate to return to your aerobic training zone.
Anaerobic exercise is considered short-lasting, high-intensity activity, where your body’s demand for oxygen exceeds the oxygen supply available.
Let’s say your workout consists of heavy squats, deadlifts and bench. Typically, when you finish a set of heavy squats, you’re out of breath and you know there’s not much gas left in the tank to squeeze out a few more reps. So, you take a step back from the squat rack and rest for a few minutes before climbing back under the bar to rep out another set.
Unlike the nice, easy jog you took the day before that relied primarily on the aerobic system, lifting weights—which is an anaerobic exercise—requires a huge amount of energy to produce large amounts of force.
However, this force only lasts between a few seconds to less than 3 minutes because anaerobic respiration doesn't produce energy fast enough to meet the demands of your body. That’s why you need to take a break in between sets.
Other examples of anaerobic exercise include sprinting, high-intensity interval training, powerlifting and most athletic sports.
The benefits of regularly performing anaerobic exercise include:
- Building strength and lean muscle mass
- Strengthening your bones
- Reversing the effects of bone loss and reducing the risk of broken bones and osteoporosis
- Increasing fat loss
- Improving cardiovascular health
- Helping to improve mood and manage certain mental health conditions such as depression and anxiety
The Best of Both Worlds
Lots of athletic activities and certain exercises rely on both energy systems. Soccer, for example, requires an athlete to alternate between quick bursts of sprinting, which is anaerobic, and longer stints of jogging, which is aerobic.
Someone training for a marathon will rely primarily on the aerobic system while exercising. However, if they incorporate other methods of training during their workouts such as sprints or hill repeats, they will activate the anaerobic system (while going full force), before transitioning back to the aerobic system as soon as steady-state running resumes.