Weighted clothing are garments that have heavy materials incorporated into them, to add weight to various parts of the body, usually as part of resistance training. The effect is achieved through attaching weighted pieces to the body (or to other garments) which leave the hands free to grasp objects. Unlike with held weights or machines, weighted clothing can leave users more able to do a variety of movements and manual labour. In some cases certain weighted clothing can be worn under normal clothing, to disguise its use to allow exercise in casual environments. 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. It is normally done in the form of small weights, attached to increase endurance when performed in long repetitive events, such as running, swimming, punching, kicking or jumping. Heavier weighted clothing can also be used for slow, controlled movements, and as a way to add resistance to body-weight exercises. Core Neck Sometimes, weights are draped over or tied to the neck. As weighted vests often have weight placed here, they effectively have the same benefits. Advantages to neck weights and more upper-body-centric weighted vests is that they allow easier spinal flexion (contracting abdominals or stretching extensor spinae) and extension (contracting extensor spinae, stretching abdominals). This makes them prime for adding resistance to these movements, and takes out the requirement of using the arms to anchor weight to the upper body to add resistance. Torso Vests The purpose of using a weight vest is to add extra weight for body-weight exercises and to create an overload effect for walking, distance running or speed, agility and quickness (SAQ) drills. Research demonstrates that using an overload during sprinting or speed drills requires lower-body muscles to generate more force against the ground which could lead to gains in strength and power and ultimately faster acceleration during running. Weight vests are used by athletes to increase strength and efficiency