Is there a link between exercise and happiness?

If you don't have a big grin on your face from the idea of running on a treadmill, maybe you've never reached that endorphin high. See more staying healthy pictures.

If you've ever been stressed out, you may have attempted to relieve your anxiety in a number of ways: eating, logging hours in front of the television, or increasing your use of tobacco, alcohol or drugs (both legal and illegal). All of these represent attempts to take your mind off your worries, or in some instinctual way to alter your brain chemistry a bit. And sometimes it works.

However, many of our go-to strategies -- like gorging on chocolate ice cream or having an extra glass or two of wine -- also have negative consequences, especially when carried out repeatedly. In the long run, some behaviors undertaken to increase happiness can actually decrease it.

There is another strategy for reducing stress and improving mood that not only seems to make people happier, but also yields positive long-term effects more conducive to long-term happiness: exercise.

When we walk, run, bike or engage in some other form of physical exercise, we generally seem to feel happier and less anxious. People who are in poor physical condition are certainly no strangers to happiness, and one study of Stanford University student-athletes found that happiness for this group was more a result of their personality and temperament than it was of athletic prowess [source: Denny]. However, there are certainly aspects of physical fitness that grease the skids of happiness.

In addition to increased energy, physically active people may feel a sense of accomplishment in meeting personal fitness goals. Also, they may feel proud of the improved physical appearance that those hours in the gym have produced. And getting outdoors on a nice day -- or even working out indoors around a bevy of strangers -- stimulates the mind and shakes up what may be for some people an otherwise monotonous and cubicle-centric daily existence.

But is there a direct link between exercise and happiness? We know that exercise has been shown to improve the sleep patterns of insomniacs, as well as lower their anxiety [source: American Academy of Sleep Medicine]. Studies on rats indicate that exercise mimics the effects of antidepressants on the brain. Exercise is also responsible for the creation of new brain cells in the part of the brain responsible for learning and memory [source: Karolinska Institutet].

Interestingly, happiness and exercise are similar in two notable ways: both are independently associated with a boost to the immune system, and also with the release of endorphins.