Deteriorations in physical qualities during a 10-week unsupervised off-season period in academy rugby union players.

To determine the changes in physical qualities of academy rugby union players over a 10-week unsupervised off-season period. Body mass, jump height, sprint performance, and intermittent running (30:15 IFT) of 64 academy rugby union players (age = 17.2 ± 0.4 y) were recorded before and after the off-season. Changes in body mass (+1.4 ± 1.3 kg), countermovement jump (-2.2 ± 1.2 cm), squat jump (-1.5 ± 1.8 cm), 10 m sprint (+0.06 ± 0.05 s), 40 m sprint (+0.13 ± 0.11 s) and 30:15 IFT (-0.8 ± 0.8 kmŸh Understanding the individuality of the changes in physical qualities of academy rugby union players during the off-season is important to ensure players return safely to pre-season training loads.