While running and cycling mostly use the same muscles, the mechanics of running and cycling are different and use the muscles in different ways. During running, the muscles of the lower body help to move the body through four stages -- heel strike, single limb support, push-off and leg swing.

When you run or perform any other aerobic activity, staying in your target heart rate range can help ensure that you are working hard enough to see results, but not working so hard that you are at risk for injury or illness. Your optimal target heart rate depends on your age and how fit you are.

When you are running -- whether it is for training purposes, enjoyment or exercise -- obstacles can get in the way. For example, weight issues, arthritis and other orthopedic concerns can make running more difficult. Hemorrhoids are another example of a condition that may be irritated by a physical activity.

If you lack a treadmill and the weather is lousy, you can run in place. All that running, with no movement forward may be too reminiscent of work for some, but you'll still burn calories and get in shape.

Jogging two miles per day might have you huffing and puffing, but it won't lead to fast weight loss. Exercise doesn't burn as many calories as you might think; the combination of diet and exercise will do more for you than exercise alone.

All things being equal -- body mass, flexibility, proportionality and stride rate -- then taller people can run faster than shorter people. However, the mechanics of running depends upon more than runner height.

When the needle on the thermometer drops below freezing, your enthusiasm for outdoor weather might wane too. To keep your exercise momentum moving, bring your exercise indoors and start running in place at home instead.

Pronation happens when your foot rolls toward the inside and flattens while walking or running. Some pronation is normal, but too much pronation can bring about foot, knee, ankle and hip injuries.

Biology and exercise performance is quite individual. While generally doing cardio on an empty stomach is not a good idea, it certain cases, it can offer some advantages.

Even if you have no equipment, you can get a cardio workout at home just by using your own bodyweight.

Building muscle at home takes consistency and a proper workout and diet plan. Weightlifting equipment helps but isn't necessary.

No access to bands, bars, bells, balls, benches or boxes? No biggie (and no need to skip leg day). All you need is your body weight, 10 minutes (or 10 one-minute exercise breaks throughout your day) and a willingness to work hard.