Work

Impact of heat exposure during immobilization‐induced de‐training and re‐training on aerobic capacity and haemoglobin mass

Year: 2026

Type: article

Abstract: The aim of this work was to assess the effect of heat exposure on cardiorespiratory and haematological responses during de‐training and re‐training. Nineteen men (33.8 ± 2.7 years; 182 ± 5.7 cm, 84.4 ± 9.3 kg) completed 4 weeks of pre‐training followed by heat exposure (HEAT; n = 9) or control (CON; n = 10). Both groups then de‐trained for 2 weeks with lower‐limb immobilization followed by 2 weeks of re‐training. 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 , at the gas exchange threshold (GET) was reduced ( d = −0.53; P < 0.005) at IMMO post , whereas maximal oxygen uptake () did not change significantly ( d = 0.14; P = 0.07). The reduction in GET 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 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.

Source: Experimental Physiology

DOI: 10.1113/ep092931