The use of weighted clothing is a form of resistance training, generally a kind of weight training. In addition to the greater effect of gravity on the person, it also adds resistance during ballistic movements, due to more force needed to overcome the inertia of heavier masses, as well as a greater momentum that needs deceleration at the end of the movement to avoid injury. The method may increase muscle mass or lose weight; however, there have been concerns about the safety of some uses of weights, such as wrist and ankle weights.