range of motion, and muscle swelling. It has been shown, however, that these changes develop independently in time from one another and that the soreness is therefore not the cause of the reduction in muscle function. Possible function as a warning sign Soreness might conceivably serve as a warning to reduce muscle activity to prevent injury or further injury. With delayed onset muscle soreness (DOMS) caused by eccentric exercise (muscle lengthening), it was observed that light concentric exercise (muscle shortening) during DOMS can cause initially more pain but was followed by a temporary alleviation of soreness with no adverse effects on muscle function or recovery being observed. Furthermore, eccentric exercise during DOMS was found to not exacerbate muscle damage, nor did it have an adverse effect on recovery, indicating that soreness is not necessarily a warning sign to reduce the usage of the affected muscle. However, it was also observed that a second bout of eccentric exercise within one week of the initial exercise did lead to decreased muscle function immediately afterwards. Repeated-bout effect After performing an unaccustomed eccentric exercise and exhibiting severe soreness, the muscle rapidly adapts to reduce further damage from the same exercise. This is called the "repeated-bout effect". As a result of this effect, not only is the soreness reduced the next time the exercise is performed, but other indicators of muscle damage, such as swelling, reduced strength and reduced range of motion, are also more quickly recovered from. The effect is mostly, but not wholly, specific to the exercised muscle; experiments have shown that some of the protective effect is also conferred on other muscles. The magnitude of the effect is subject to many variations, depending for instance on the time between bouts, the number and length of eccentric contractions and the exercise mode. It also varies between people and between indicators of muscle damage. Generally, though, the protective effect lasts for at least several weeks. It seems to gradually decrease as time between bouts increases, and is undetectable after about one year. The first bout does not need to be as intense as the subsequent bouts in order to confer at least some protection against soreness. For instance, eccentric exercise performed at 40% of maximal strength has been shown to confer a protection of 20 to 60% from muscle damage incurred by a 100% strength exercise two to three weeks later. Also, the repeated-bout