Here is a very different leg exercise that you can incorporate with your squats to help you achieve your goals. This type of exercise will help you get "out of the hole", meaning you'll be able to blast through that sticking point at the bottom when you have difficulty getting the weight up with heavy weight. This will build up your core and actually build up your abs tremendously in addition to your legs, because of the emphasis it places on stabilizing the weight and the energy that's transferred into your midsection.