Over the same distance, running requires more work, uses more energy and burns more calories than cycling. Running and cycling at approximately the same level of intensity for the same period of time, however, may help you to burn about the same amount of calories. As each exercise targets different muscles, you may wish to include both in your training.
Distance and Time
Maintaining the equivalent of a 10- to 12-minute mile over the course of your run, you can run five miles in 50 to 60 minutes. As 13 mph is an approximately equivalent pace for cycling over this distance, it should take you 23 minutes to cover five miles on your bike. While cycling helps you to cover five miles more quickly, you may wish to extend your bike trip to 10 to 13 miles for a workout that approximates a five-mile run.
The amount of calories that you burn while running and cycling depends on your weight, the intensity of the workout, your current fitness level and your metabolism. As the last two are difficult to estimate, most online calculators rely on your body weight and workout intensity to determine how many calories you burn while performing a given exercise. For a 155-lb. person, running 5 to 6 mph burns between 563 and 704 calories in an hour, while cycling at a pace of 12 to 13.9 mph burns approximately 563 calories in an hour.
While an hour of moderate intensity cycling and an hour-long, five-mile run can help you to burn the same amount of calories, cycling and running target different muscles. Assuming that your ride or run includes some inclines and declines, both exercises work most major muscles from your hips down, including those on both sides of your thighs, your hamstrings, calves, shins and buttocks. But running engages your gluteal muscles more because you do not fully extend your hips while cycling. Both activities require the use of your abdominals and lower back for stability. Cycling relies more on your chest and arms to support your weight on the handlebars, while running uses your chest and arm muscles to provide counter-balance and momentum.
Impact and Intensity
Cycling involves fluid, circular leg motions, and is relatively low-impact. Running places a great deal of stress on the joints of your lower body and your spine. Whether or not you run on soft surfaces and use supportive shoes, the joints of your lower body absorb most of the impact of the ground. As your bike bears the majority of this impact, cycling may be a better option than regular five-mile runs if you wish to avoid or are recovering from joint problems. However, an increase in running speed can help you to burn more calories than an equivalent increase in cycling speed, so running may be your best option if you wish to lose weight.