Résumé
Cardiorespiratory fitness and total haemoglobin mass (Hb mass ) were measured at baseline (BASE), prior to (IMMO pre ) and following (IMMO post ) immobilization and after a 'return-to-sport' (RTS post ) training phase. Compared with IMMO pre , VO 2 at the gas exchange threshold (GET) was reduced (d = -0.53; P < 0.005) at IMMO post , whereas maximal oxygen uptake ( VO 2 max ) did not change significantly (d = 0.14; P = 0.07).
The reduction in GET VO 2 was more pronounced for HEAT than CON (d = -0.77; P = 0.001). At IMMO post , GET and peak power output were lower than IMMO pre (d = -1.4, P < 0.005 and d = 0.43, P = 0.01, respectively), however there was no difference between groups. At RTS post , the VO 2 at GET increased again in both groups yet remained lower than IMMO pre although the reduction in HEAT (d = -0.42; P = 0.43) was less than CON (d = -0.8; P = 0.05). At RTS post , HEAT fully recovered GET power losses compared to IMMO post (d = 1.1; P = 0.001), while CON only showed a trivial change (d = 0.07; P = 0.1). No significant changes were observed in Hb mass , haematocrit or plasma volume throughout the study (P ≥ 0.763). Heat exposure did not attenuate a decline in cardiorespiratory fitness during immobilization-induced de-training, but could potentiate its recovery upon re-commencement of training.