Effects of Short- and Long-Term Detraining on Maximal Oxygen Uptake in Athletes: A Systematic Review and Meta-Analysis

V̇O(2)max, a gold standard for evaluating cardiorespiratory fitness, can be enhanced by training and will gradually decrease when training stops. This study, which followed the Cochrane Collaboration guidelines, is aimed at assessing the effect of short- and long-term detraining on trained individuals' V̇O(2)max through a systematic review and meta-analysis and performed a subgroup analysis to evaluate the effects of different ages, detraining formats, and training statuses on V̇O(2)max variation between short- and long-term training cessation. Web of Science, SPORTDiscus, PubMed, and Scopus, four databases, were searched, from which 21 of 3315 potential studies met the inclusion criteria. Significant decreases in V̇O(2)max were identified after short-term training cessation (ES = −0.62 [95% CI -0.94; -0.31], p < 0.01; within-group I(2) = 35.3%, Egger′s test = −1.22, p = 0.335) and long-term training cessation (ES = −1.42 [95% CI -1.99; -0.84], p < 0.01; within-group I(2) = 76.3%, Egger′s test = −3.369, p < 0.01), which shows that the detraining effect was found to be larger on V̇O(2)max in long-term training cessation than in short-term training cessation (Q = 6.5, p = 0.01). However, there was no significant difference regarding V̇O(2)max change between 30-90 days detraining and larger than 90 days detraining (Q = 0.54, p = 0.46) when conducting subgroup analysis. In addition, younger (<20) individuals showed a greater reduction in V̇O(2)max after long-term detraining than adult individuals (Q = 5.9, p = 0.05), and athletes with higher trained-state V̇O(2)max showed a significant decline in V̇O(2)max after long-term detraining compared with the lower trained-state group (Q = 4.24, p = 0.03). In conclusion, both short- and long-term training cessation have a detrimental effect on V̇O(2)max, and a greater impact on V̇O(2)max was found in long-term training cessation compared to short-term training cessation; however, there was no significant change in V̇O(2)max when the duration of training cessation was more than 30 days. To buffer the detrimental effects of detraining, especially long-term training cessation, performing some physical exercise during training cessation can effectively weaken detraining effects. Thus, to prevent athlete's V̇O(2)max from decreasing dramatically from detraining, athletes should continue performing some physical exercise during the cessation of training.