Few activities beat the calorie burn you get with running. Runners also tend to have toned legs and a healthy heart, which may lead you to believe it's all you need to be fit. Still -- rely solely on any one fitness activity to get you in shape and you set yourself up for injury. Running only fulfills the cardio component of fitness. To have a well-rounded program, the American College of Sports Medicine recommends you include strength training, flexibility and functional, or neuromotor, exercise too.
It May Feel Like Strength
Running is aerobic in nature -- meaning it challenges your cardiovascular and respiratory system. A good run also counts as weight-bearing activity that improves the health of your bones in your legs and spine. All those miles may build muscle endurance in your legs, but it's no substitute for a general strength-training routine. Your arms, chest and back all have muscles that need attention too -- running can't touch them. You may not aspire to be a bodybuilder, but strength training performed twice per week in addition to your runs improves your overall function and offsets the natural loss of muscle mass that occurs with aging. Strength training also improves your running form and helps you prevent injury. When you repetitively use the same muscles over and over, as you do in running, the muscles you don't use repetitively get weaker. This can lead to muscle imbalances that leave you vulnerable to injury.
Running doesn't adequately challenge your range of motion -- that's why you need to stretch regularly two to three days per week, ACSM notes. Static stretching before running -- such as holding a forward bend -- doesn't offer much benefit, found a meta-analysis published in a 2013 issue of the "Scandinavian Journal of Medicine and Science in Sports," and may even lead to diminished performance. Instead, wait until after your run to hold stretches for most of the major groups for 20 to 30 seconds. Alternatively, you can stretch on days you don't run -- just make sure you warm up first or at least wait until after a hot shower so your muscles are pliable.
A Little Coordination
Running makes you super efficient at going forward but doesn't do much to train your body to move laterally or in rotation. Your body is designed to move all around, and you should train it that way. Exercise programs such as yoga and tai chi develop balance and coordination. If you aren't into these Eastern exercises, functional training done with cables, balance devices and kettlebells are other options that complement running.
Variety Is Nice
Cross training makes it more likely that you'll work your whole body every week. Adding in a day of cycling, swimming, kickboxing or interval training helps you target different muscles from those you emphasize during running, or the same muscles in a different way. Cross training also defeats the boredom that can come from doing the same activity every day.