Longitudinal haematological responses to training load and heat acclimation preceding a male team pursuit cycling world record

Abstract

This study evaluated relationships between changes in training load, haematological responses, and endurance exercise performance during temperate and heat acclimation (HA) training preceding a male team cycling pursuit world record (WR). Haemoglobin mass (Hb_mass) and concentration ([Hb]), plasma volume (PV) and blood volume (BV) were assessed in nine male track endurance cyclists (∼3 occasions per month) training in temperate conditions (247–142 days prior to the WR) to establish responses to differing acute (ATL) and chronic (CTL) training loads. Testing was performed again pre- and post-HA (22–28 days prior to the WR). Endurance performance (V̇O₂_max, 4MMP, lactate threshold 1 and 2) was assessed on three occasions (238–231, 189–182 and 133–126 days prior to the WR). In temperate conditions, CTL was associated with Hb_mass (B = 0.62, P = 0.02), PV (B = 4.49, P = 0.01) and BV (B = 6.51, P = 0.04) but not [Hb] (B = −0.01, P = 0.17). ATL was associated with PV (B = 2.28, P < 0.01), BV (B = 2.63, P = 0.04) and [Hb] (B = −0.01, P = 0.04) but not Hb_mass (B = 0.10, P = 0.41). During HA, PV increased 8.2% (P < 0.01), while Hb_mass, CTL and ATL were unchanged. Hb_mass and [Hb] were associated with all performance outcomes (P < 0.05), except V̇O_2max. PV and BV were not associated with performance outcomes. During temperate training, changes in Hb_mass were most strongly associated with changes in CTL. Both CTL and ATL were associated with changes in PV, but HA was associated with increased PV and maintenance of Hb_mass without increasing ATL or CTL. In practical terms, maintaining high CTL and high Hb_mass might be beneficial for improving endurance performance.