competition. Track shoes are exceptionally light, some shoes weighing less than five ounces (142 grams) each, half the weight of many standard running shoes. In most track shoes, the toe region bends up to allow space for protruding spikes and to encourage athletes to run on their toes. This upward angle, known as "taper," varies widely depending on the intended use of the shoe, and the taper angle can be rigid or flexible. Shoes with a large taper are said to be "aggressive." This shoe design may cause harm to the athlete if worn for extended periods of time outside of competition. Injury may occur when walking in a leisurely fashion, as the athlete is not on his or her toes, which is the manner in which the shoes were meant to be worn. Types of shoes There is considerable variation among track shoes depending on their intended use within the sport of track and field. Sprint spikes generally have a very stiff spike plate with the greatest number of spike wells. The taper is highest and most rigid in sprint spikes, maximizing the efficiency of energy transfer with each stride. Very little heel support is needed because sprinters spend most or all of their time on their toes. Sprint spikes may have a zip-up cover instead of or in addition to laces to improve aerodynamics. Sprint spikes should fit tightly but they should not be too tight to the point that the runners toes are cramping and they should not be too loose that will result in the runner losing power and speed. They should fit tighter than regular athletic shoes yet still comfortable enough to perform in. Distance shoes have a more flexible spike plate with less taper and fewer spikes. Because of the longer race distances, support through the mid-foot and heel is as important as efficiency with distance spikes. This means that distance spikes generally have a softer, more durable sole, particularly through the heel region. Although still "glove-like," the fit for distance spikes is generally slightly looser than for sprint spikes, given the longer race duration. Middle distance spikes are a hybrid of a sprint shoe and a distance shoe, featuring an intermediate level of taper, spike plate rigidity, cushioning and support. Certain middle distance spikes are also popular among hurdlers because they have a relatively steep taper for sprinting and a cushioned heel for