What are the best exercises to increase leg strength for sports?

To increase leg strength to improve sports performance, you are going to have to develop "functional" leg strength. That means you will need to develop more than just strong legs. You'll also need to train for balance, agility and power. Try starting out by doing squats, single leg squats and lunges on wobble boards, balance pads and beams. Then get strong on basic squats and lunges. Finally build off your squatting pattern by performing plyometric box and hurdle jumps and start lunging with speed. Then perform these explosive jumps and lunges in all different directions.

To develop your leg strength for sports it is critical to perform exercises that also include a challenge to your core. Leg strength on its own may not transfer to athletics without the body’s ability to use that strength in a functional manner. That being said, total body or integrated movements like squat to row and multi-planar lunge to reach to curl to overhead press will give you a tremendous amount of bang for your buck. These exercises can build the strength of the muscles around the ankles, knees and hips as well as integrate the core and upper body simultaneously. In sports, the legs don’t just run on their own. The have the trunk stacked on top of the with the arms and head moving to some degree. Total body, or integrated-style exercises will give you the best results when trying to improve leg strength for sport. 

Personally, I think squats and lunges are the two most important leg exercises and there are a variety of ways of doing them. Working in all planes of movement is very important. You want to work in the frontal, the sagittal, and the transverse planes and it is very, very important to work in all of these, particularly in the transverse plane which is often neglected. Doing a front lunge, a side lunge, and a transverse lunge, as well as a front squat, side squat, and a transverse plane squat all are important in increasing leg strength for sports. Once we move into the power training phase, we will also include box jumps, which will also help increase your leg strength and power.