When you've had a hard day and want to unwind, few things feel as good as a nice, warm bath. Ever wondered why a warm bath feels so good? Here are some of the scientifically-proven benefits:

Relief for achy muscles and joints: Because water is buoyant, it reduces gravity's pull on joints. When submerged, the body weighs about 90 percent less, diminishing weight and compression of the joints. Warm water also raises body temperature and increases circulation, which encourages better movement. Heat also gets your blood moving, which can help sore or tight muscles to relax.

A healthy heart: Taking a warm bath can help reduce blood pressure, according to some research. Reduced blood pressure can help in preventing more serious heart conditions. Be sure to consult your doctor if you have a heart condition, because a hot bath will also raise the rate of your heartbeat.

Better sleep: A theory that a colder core body temperature can help to induce sleep is why some scientists recommend sleeping in a cold room. A warm bath before bed can yield similar results. At night, our body temperatures naturally drop, which signals the production of melatonin. Soaking in a warm bath will raise your body temperature, then exiting to a cool room will more rapidly cool it down. This may instigate the production of melatonin and better prepare you for a good night's sleep.

Decreased anxiety and improved mood: Dr. Bruce Becker of Washington State University says that 20 minutes of sitting in a 102°F tub changes the autonomic nervous system similarly to stress and anxiety-reducing activities like exercise. Dr. Becker also says that regular bath or hot tub sessions even have a positive effect on problem-solving.

Burn calories: A Loughborough University study has shown that an hour-long soak in a bath in 100°F water burns the same amount of calories as a 30-minute walk. The study also showed a reduction in blood sugar levels and a reduction in inflammation, both beneficial for long-term sufferers of diseases like type-2 diabetes.