You can't see all of your leg muscles, but that doesn't mean you can neglect them. Men's Health provides this workout video about the "clean pull" exercise. This move will work all of those muscles you can't see! Great legs workout.
Load a bar-bell and roll it to your shins. Grab the bar with an overhand grip, palms facing you, and place your feet shoulder-width apart. Keeping your back flat and arms straight, squeeze your glutes as you straighten your legs. Rise onto your toes and shrug your shoulders, then lower the bar to the floor.
This explosive exercise targets the muscles of the posterior chain - basically the muscles you can't see in the mirror such as your lower back, glutes and hamstrings. The trapezius muscles of the upper back and neck area will also be worked as you shrug the bar at the top of the lift. This advanced move should only be attempted by those who are already highly proficient at the standard deadlift.
We do not recommend this exercise for beginners but as a variation for the more advanced lifter. Also make sure you have enough space to execute the "clean pull" safely in your own gym environment.