The problem: Cut-and-pivot sports like soccer tend to boost the likelihood of tearing or rupturing the dreaded anterior cruciate ligament (ACL). The same danger exists with agility training, which incorporates ever more lateral movement as you progress in difficulty. But you can help prevent injury by honing your body's proprioception the ability to sense where its parts are and stabilize itself to avoid putting too much strain on the knee. One method: the weighted decelerating lunge. It increases the strength of the ACL itself and may also increase the nerve sensitivity and feedback to the muscles.
Start by taking a giant step forward and dropping into a standard lunge, slowing your momentum with your forward leg. Lean into it a bit. Got it? Tie a bungee cord to the base of a pole in front of you and keep it taut as you drop into the lunge; the cord will pull you forward, increasing the load your knee is trained to stabilize. Do 2 3 sets of 15 reps, twice a week.