Coyle et al. (1984) suggested that the reduction in VO2max following a period of detraining takes place in two stages. The first stage is likely to occur within 2-3 weeks and may result in a reduction of VO2max by 5-7% (Coyle et al. 1984; Houmard et al. 1992). This initial decrease is thought to result from a decrease in maximal cardiac output brought about by a reduction in stroke volume (Coyle et al. 1984; Martin III et al, 1986). These changes occur at a ‘central’ level (i.e. at the heart rather than in the skeletal muscle) and so alternative exercises can be introduced to prevent detraining and the reduction in VO2max (Mujika & Padilla, 2001).
The second stage takes place over a longer period of time (8-10 weeks) and may result in VO2max returning to pre-training levels (Davidson & McNaughton, 2000; St-Amand et al, 2012). The rate of decline and the level at which VO2max subsequently stabilises depends on the training status of the individual (Mujika & Padilla, 2000). The changes occurring during this second stage are more specific to the trained skeletal muscle. Consideration should be given to the introduction of alternative sport specific exercises that involve the same muscle groups without placing additional stress on the muscle/joint. If this is not possible, VO2max can be maintained by using alternative exercises but if these are not sport specific then the athlete will quickly lose aerobic endurance (Mujika & Padilla, 2001). Read More http://www.running-physio.com/cross-training/