The dreaded leg day is the stuff of legends. A great leg workout may have you prepared to apply for handicapped parking, but with the right training, your results can be phenomenal. But above all, it is important that you do train your legs. With the number of major arteries running through your legs, and their major role in your body support and mobility, skipping leg training can be the one thing stopping you from true fitness.
Your legs are your body's biggest muscles. Training your legs means that your metabolism increases and your endurance grows. Overall muscle growth occurs when your central nervous system is taxed and releases growth hormone to improve your strength, Naturally, training your body's biggest muscle will increase your overall muscle growth and strength. You are literally standing on a gold mine of metabolic, muscular, and strength potential. Leg training will also increase your heart health.
Building muscles increases overall oxidation of the body. Furthermore, your have some major arteries goring through your legs (femoral, popliteal, peroneal, etc.) that will improve your overall blood flow as your leg strength and size increases. This means more vitality and renewed energy throughout your day. Moving around becomes more difficult as your legs grow weaker. With most professional sports, combative and otherwise, demand great leg strength. Capitalize on that strength to improve your mobility, and your body's stability.
How do you go about doing this? Squats are a great way to work not just the legs but the whole body. The leg press, personal preference, is a great way to make your legs super strong by adding a great amount of weight for a relatively short range. You can train a leg press upwards of 1000 pounds, which is much riskier to attempt with squats. Training mabu (the horse stance, a classic martial arts stance with many variations) will give your legs a great level of endurance while also strengthening your lower back. (Below is an example of a deep horse stance, courtesy of a younger Jackie Chan! I wouldn't recommend you try putting china bowls on you to test your balance though.)