So I realize I just resurrected a zombie thread (dead for 4 years), but I'll post this anyway. If you want to manipulate leg size I think the force/velocity curve holds your answer. The principle of the force/velocity curve is that heavy weights lifted at maximum velocity will be moved slower than light weights lifted at maximum velocity. Bench pressing 200 lbs at max speed may result in movement at half a mile per hour while bench pressing just the weight of a broom handle at max speed would result in movement closer to 15mph (or 60mph if you're Bruce Lee). Regardless of the weight being lifted, the muscle is still contracting its maximum potential velocity. Look up a picture of the force velocity curve to follow along with this idea. Exercises that exist on the upper left side of the curve will result in gains in muscle size and strength and decrease in speed while exercises that exist on the lower right side of the curve will result in decreases in muscle size and strength and increase in speed. Sprinters don't have big legs because they sprint. They have big legs because they accelerate. Their leg size is developed in the first 30 meters out of the starting blocks (not to mention the weight room). The reason is that acceleration is a much lower velocity/higher force phase of the run (upper left of the F/V curve). Soccer players spend 90% of their running time on the field either accelerating or decelerating and very little time at top speed. This is why soccer players are notorious for big legs. Baseball pitchers, on the other hand, have the skinniest arms compared to their teammates because they spend most of their time at the lower right end of the F/V curve. High velocity with only the weight of the baseball. To get small legs do exercises that involve very low force output at very high speeds; running down-hill, cycling in the lowest gear, martial arts, etc. Definitely don't neglect maximum effort in your muscles (like sitting on the couch for a week) but when you do exert yourself maximally, do it with nearly zero resistence so that your velocity will be high. Your body will adapt to that by reducing its muscle mass in order to make your limbs lighter and easier to move at those speeds.