Muscle acts in one of three ways: overcoming an imposed load (concentric), yielding to a load (eccentric) or holding a load (isometric). Conditioning coaches and athletes are familiar with overcoming or holding loads, but are less familiar with yielding eccentric muscle actions. The relationship between force and velocity in eccentric actions is such that as the velocity of eccentric actions increase so too does the maximal force production, this is in stark contrast to concentric actions where force production is inversely related to velocity i.e. heavy loads are moved slowly. In addition, eccentric muscle actions are different to concentric or isometric actions in that they rely on sensory feedback to achieve a desired trajectory utilising alternative processes both neural and mechanical. Eccentric exercise has been shown to improve: hypertrophy of muscle, muscular strength, adaptation to eccentric activity, neural cross-over, and assist those with low levels of cardiovascular fitness. The main disadvantages of utilising eccentric exercise are: delayed onset muscle soreness, damaged muscle cells, reduced neural reflexes, acute strength loss and an altered resting state. Eccentric movements are however inherent to athletic activity. Eccentric training therefore needs to be part of an athlete`s preparation for competition. It is worth noting that not all eccentric actions are the same, clumping eccentric movements into one group may cause specificity of training errors and confusion when talking between professions. The movement purpose determines the mode of eccentric movement. Eccentric rehabilitation utilises low loads with low velocity; heavy eccentric training utilises high (heavy) loads, and the subsequent action is not necessarily a high velocity contraction; stretch-shortening cycle training involves extensive use of elastic energy generated in the musculotendinous unit and quickly initiated into a rapid concentric action. Each of these modes are used to varying degrees in sporting movements, it is important to differentiate which mode or combination of modes is appropriate for the athlete. The drop jump may be a useful tool in determining an athlete`s ability to utilise the stretch-shortening cycle or to attenuate force. It is possible to apply appropriate training principles to heavy eccentric training and stretch-shorten cycle training. In doing so eccentric training will prepare athletes for competition and improve sporting performance.