If your a runner, especially if your a runner you should consider adding to your winter training program eccentric movements in the gym. When we land while running we are landing at 2 to 4 times our body weight and our primary protection system is our muscles acting as shock absorbers or contracting eccentrically. The sudden jolt of landing is offset by the sudden contraction of the muscle bracing the landing. The opposite of an eccentric contraction is a concentric contraction in which the muscles propel the body foward or when the foot pushes off from the ground. Concentric movements are used heavily in the sport of cycling where there is no landing phase of movement just propelling. In running both are used though in cycling the concentric contractions are generally longer and deeper. Eccentric training can best be described as the lowering phase of a weight training movement. An example of a preventive injury movement for running is slowly doing heel drops for your calfs. Eccentric weakness in the calf muscles can contribute to Achilles tendinitis, an injury that can sideline your running for months. By simply performing eccentic movements in the off season your reinforcing your "shock absorbing" system. Your muscluar system will become more reactive to impact also creating more stabilty thus improving your running performance as well.