Running requires the same amount of energy to run one mile at any speed; you burn 110 calories per mile. It doesn’t matter if you are a super fit athlete, or an out of shape beginner you will still burn the same number of calories per mile.
However, bike riding is affected by wind resistance so the faster you ride, the more energy you use, and the more calories you burn. You have to compare running and cycling at different cycling speeds.
This is according to fitness expert Dr. Edward Coyle of The University of Texas in Austin, who has worked with Lance Armstrong and other top athletes. He determined average values of oxygen consumption by cyclists to develop a table to estimate the approximate caloric equivalence between running and cycling.
He found that if you ride at 15 mph, you burn 31 calories per mile. This means if you ride 20 miles you burn 20 x 31 = 620 calories. Take the 620 calories and divide by 110 calories per mile for running and you get 5.63 miles of running to burn the same number of calories. Therefore, riding a bicycle 20 miles at an average 15 miles per hour is equal to running 5.6 miles at any speed.
Running will give you a more intense workout in less time. However, a person would need to be at a reasonable fitness level to run 4.8 miles without causing themselves distress. Whereas, it would be easier to ride 20 miles on a bicycle, at 10 mph, to burn the same amount of calories. There would also be far less stress on the body’s joints.
It seems to me that cycling is the best bet for anyone trying to burn calories and loose weight. There is far less stress on knee and hip joints, and the harder you push yourself the greater the reward in calories burned.