There are only a few papers to date showing the “overshoot phenomenon” (Andersen et al. 2000 & 2005) and only one paper done using professional athletes within a season (de Lacey et al. 2014). Explained very simply, an “overshoot” occurs when a taper or detraining from resistance training takes place. Or in other words, time off is taken from resistance (weight) training. Anecdotally I have heard the Great Britain cycling team used this leading into the 2008 Beijing Olympics for the track cycling and cleaned up the gold medals. For now, let’s go into a little more detail.
There are 3 types of pure muscle fibres (to keep it very simple). Type I, Type IIA and Type IIX. Muscle fibres can also posses more than one type, e.g. Type IIA/IIX, but for now, we’ll stick to just 3 fibre types. Type I are your slow twitch fibres contributing more to the endurance aspect of muscle contraction. Type IIA and IIX are your fast twitch fibres and contract much more rapidly than Type I. Type IIX contract approximately twice as fast as Type IIA and about 5-10 times faster than Type I but fatigue very quickly.
As resistance training is undertaken for an extended period of time, (e.g. in Andersen et al. 2000 & 2005 it was 3 months for a total of 38 sessions) an adaptation occurs where the number of Type IIA muscle fibres increase while the number of Type IIX decrease compared to pre training. As shown in Andersen et al. (2000), a significant increase in Type IIA and a significant decrease in Type IIX were found post training. So we have a decrease in the bodies most powerful muscle fibres and an increase in more efficient fast twitch fibres.