Intense leg workouts have shown to increase the release of growth and testosterone hormones more than any other exercise. These are natural muscle building hormones that will help improve your overall athletic performance. You might not believe it but your legs produce the majority of your power during heavy lifting.
Yes, even when you are bench pressing, it is your legs that are engaged to help provide a stable platform to pump from. Performing functional exercises like deadlifts, squats will strengthen your legs, glutes and lower body while developing all round muscle and mobility.