• altitude
• elite performance
• haematology

Since 2012, Lundby and Robach1–3 have consistently stated that ‘altitude training does not convincingly increase exercise performance and should not be recommended to elite (endurance) athletes’.2 This research group suggests3 that altitude training and particularly ‘live high–train low (LHTL) may only increase total haemoglobin mass (Hb_mass) [and possibly maximal oxygen consumption (VO_2max)] in athletes with an initial low Hb_mass value’. This statement comes from the analysis of nine selected studies4–12 on the relationship between group mean pre-LHTL value of Hb_mass and increase in Hb_mass after LHTL.3 The inverse correlation (r=−0.86; P<0.01) between initial Hb_mass value and percentage increase in Hb_mass would suggest that athletes starting an intervention with high relative Hb_mass levels have smaller chances to further increase their relative Hb_mass following altitude training. The rationale behind was that those athletes had already maximised their Hb_mass level by training at sea level.3

We have concerns that this statement does not seem to be supported by several other studies,13–21 done by well-respected research groups, using what are widely considered to be best-practice techniques and protocols. These studies with outcomes conflicting with works of Lundby and Robach1–3 include those with shorter time course13 14 or lower hypoxic exposures15 16 to moderate altitude (2500–3000 m), which showed Hb_mass increases ranging between 2.1% and 3.7%. In fact, Lundby and Robach’s own work has shown a +5% Hb_mass improvement after 17 days of altitude training in five male cross-country skiing Olympic medallists with already high initial value of 13.5 g/kg.1

However, the most problematic issue of this flawed analysis3 is that conclusions appear to rely on Hb_mass measures that may be inaccurate. Indeed, three4 8 11 out of nine studies used for …