The Principle of Progression states that there is an optimal period of time and overload that progression can occur in the body without inducing injury. If the workload increases too quickly muscle or ligament damage may occur. On the other hand increasing a workload too slowly may not create much improvement at all. The Progression Principle also addresses rest. Not enough rest results in poor gains, injury and a possible reversal in fitness gains. This is considered over- training. Too much rest may yield a lack of results, as would increasing a workload too quickly. This principle is very similar to the Adaptation Principle and both require new stimulus and/intensity for continued gains.