By Gabe Mirkin, M.D.
Have you wondered whether you burn more calories when you run or when you ride a bicycle? The standard comparison is that one mile of running equals a little more than three miles of cycling, but that’s lousy science.
It all depends on how intensely you exercise. Running requires the same amount of energy per mile at any speed (generally 110 calories per mile), but cycling is slowed so much by wind resistance that the faster you ride, the harder you have to pedal and more energy you use. This means that you have to compare your running and cycling at different cycling speeds.
If you hate math and don’t want to crunch the numbers yourself, you can use this handy online calculator
If you want to understand the math, Dr. Edward Coyle of the University of Texas in Austin has made the calculations easy by providing conversion factors for different riding speeds. First he determined average values of oxygen consumption by cyclists to estimate the approximate caloric equivalence between running and cycling.
For example, riding 20 miles at 15 mph causes you to burn 620 calories (20 miles X 31 calories per mile = 620 calories). To find the same value for runners, take the 620 calories and divide them by 110 calories per mile for running and you get 5.6 miles to burn the same number of calories. So riding a bicycle 20 miles at 15 miles per hour is equal to running 5.6 miles at any speed.
Dr. Coyle’s conversion factors for different cycling speeds are:
• 10 MPH (26 calories per mile) = 4.2
• 15 MPH (31 calories per mile) = 3.5
• 20 MPH (38 calories per mile) = 2.9
• 25 MPH (47 calories per mile) = 2.3
• 30 MPH (59 calories per mile) = 1.9
Divide the number of miles ridden by the conversion factor for your riding speed to tell you the equivalent miles of running at any speed. Thus, for 20 miles ridden at 10MPH, divide 20 miles by 4.2, which tells you that your ride is equivalent to 4.8 miles of running.
This formula is for an average-size adult who weighs approximately 155 pounds. A larger cyclist would divide by a slightly higher number; a smaller cyclist, by a slightly lower one. Wind and hills are not accounted for, nor is drafting (riding behind another cyclist), which can reduce your energy expenditure by up to one-third.
Other Factors to Consider When Comparing Running and Cycling
• Running causes more wear-and-tear injuries: If you exclude getting hit by a car, it is safer to cycle than to run. Cycling is done in a smooth rotary motion with almost no impact force. On the other hand, runners are far more likely to become injured than cyclists because of the high impact of their feet hitting the ground. When you run at a six-minute-per-mile pace, your foot hits the ground with a force equal to three times your body weight. This force is transmitted up your legs to your hips and back, and done repetitively, it can shatter bones and tear muscles and tendons (Br J Sports Med, Apr 2016;50(8):450-7). Runners who are injured frequently are likely to benefit most by shortening their strides, which then coincidentally increases likelihood of their landing on the front part of their feet, rather than on their heels
• Cycling does not strengthen your bones: The high impact force of running strengthens bones and helps to prevent osteoporosis. Cycling has not been shown to prevent osteoporosis because it has little or no impact force. Cyclists need to add a resistance training program (weight lifting) to gain the bone-strengthening benefits of exercise.
All aerobic exercise makes your heart stronger and helps to prevent heart attacks, and exercising intensely is more effective than just casual exercise. Everyone should try to exercise every day to help prolong life and prevent disease. Choose running, cycling, or any other aerobic exercise that you enjoy and will do on a regular basis. If you exercise with a partner or make other friends who share your love of your sport, you will be more likely to continue to exercise faithfully as you age.