There’s been a lot of talk and promotion in the fitness industry about high-intensity exercise. If you ask me, most of what is behind this talk is money. If we tell people what they want to hear—“all you need is a few minutes of high-intensity exercise per day”—people are more likely to buy. No one wants to hear that it takes a lot of work to get (and stay) in shape and lose weight. So the fitness industry has extracted a few morsels of truth from scientific research and has run with them, generalizing research findings to whatever suits their needs.
High-intensity anaerobic exercise does indeed have a place in a fitness program for many reasons, not the least of which is to learn how to deal with discomfort. But aerobic exercise is more important. Here’s why:
1) Sustained aerobic exercise alters the metabolic profile of your muscles. It increases the number and size of mitochondria in your muscles, which is where aerobic metabolism and fat burning take place. If you make more mitochondria, your muscles have a greater capacity to burn fat.
2) Usain Bolt notwithstanding, aerobic exercise is more in line with who we are as humans. Humans are aerobic animals. The evolution of our physiology was inherently very dependent on efficient oxygen delivery and on the development of aerobic metabolic pathways, with a relatively minor dependence on anaerobic metabolic systems to sustain whole body performance.
3) Aerobic exercise enlarges your heart. A larger heart increases your stroke volume, improving your cardiovascular system’s ability to pump blood and oxygen.
4) Sustained aerobic exercise causes a constant push of oxygen through your vasculature, which stimulates the growth of new capillaries and a more prolific oxygen delivery system.
5) Aerobic exercise increases blood volume, red blood cells, and hemoglobin, giving you a greater ability to transport oxygen.
6) Aerobic exercise decreases high cholesterol and blood pressure, two of the primary risk factors for heart disease.
7) Aerobic exercise alters your brain chemistry to ameliorate depression and improve mood and creativity.
8) Sustained aerobic exercise, especially exercise that engages many muscles, like running or cross-country skiing, burns more calories. This point can be debated, but calorie burn during workouts is a matter of math: fewer number of minutes at a high intensity vs. more minutes at a lower intensity. If the intensity is so high that the workout is so short, it’s going to burn fewer calories than a longer but lower-intensity workout.
So, there you have it. Anaerobic exercise is a lot of fun—sprinting is a great way to get your aggression out—but never neglect aerobic exercise. It is the single best thing you can do for your health.