Overreaching is the correct, scientific term for what most of the fitness industry refers to as “overtraining,” which is a reduction in workout performance despite continued efforts to the contrary (scientists reserve the term “overtraining” for a medical diagnosis that has been provided after extensive investigation).
Traditionally, strength coaches have assumed that overreaching involves the accumulation of a great deal of fatigue at the same time as adaptations continue to occur under the surface.
Thus, when a taper or a deload is taken, the fatigue disappears and the beneficial adaptations are revealed.
This causes an apparent, sudden increase in strength that is sometimes called “supercompensation.”
However, new research suggests that the mechanisms that cause reductions in workout performance despite continued efforts may actually be quite undesirable, involving losses in muscle mass, possibly because of the effects of systemic stress.