Leg curl machines are one of the most effective pieces of exercise equipment used for leg training. Leg curl exercises target the hamstrings and can be performed lying or standing. There are lying leg curl machines and seated leg curl machines in both home use and commercial grade varieties. Several of the models offer dual functionality as they can also be used for training the quads also by doing leg extensions. These dual use machines are great for gyms or individuals that are short on space or running on a tight budget.