<P> Similarly to complex training, contrast loading relies on the intense nervous system activation and enhanced muscle fibre recruitment from the heavy lift to help improve the power with which the subsequent exercise can be performed . This physiological effect is commonly referred to as post-activation potentiation, or the PAP effect . By way of explanation, if a light weight is lifted, and then a heavy weight is lifted, and then the same light weight is lifted again, then the light weight will feel lighter the second time it is lifted . This is due to the increased PAP effect from the heavy lift allowing for greater power to be applied and thus making the subsequent lighter lift feel even lighter than before . Explosive power training programmes are frequently designed to specifically utilise the PAP effect . </P> <Table> <Tr> <Td> </Td> <Td> This section contains instructions, advice, or how - to content . The purpose of Wikipedia is to present facts, not to train . Please help improve this article either by rewriting the how - to content or by moving it to Wikiversity, Wikibooks or Wikivoyage . (July 2009) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section contains instructions, advice, or how - to content . The purpose of Wikipedia is to present facts, not to train . Please help improve this article either by rewriting the how - to content or by moving it to Wikiversity, Wikibooks or Wikivoyage . (July 2009) </Td> </Tr> <P> Strength training is a safe form of exercise when the movements are controlled, and carefully defined . Or some safety measures can also be taken before the training . However, as with any form of exercise, improper execution and the failure to take appropriate precautions can result in injury . A helmet, boots, gloves, and back belt can aide in injury prevention . Principles of weight training safety apply to strength training . </P>

The most important principle of strength development is