Relationship between changes in haemoglobin mass and maximal oxygen uptake after hypoxic exposure

Abstract

Background: Endurance athletes have been using altitude training for decades to improve near sea-level performance. The predominant mechanism is thought to be accelerated erythropoiesis increasing haemoglobin mass (Hb(mass)) resulting in a greater maximal oxygen uptake (VO₂(max)). Not all studies have shown a proportionate increase in VO₂(max) as a result of increased Hb(mass). The aim of this study was to determine the relationship between the two parameters in a large group of endurance athletes after altitude training.

Methods: 145 elite endurance athletes (94 male and 51 female) who participated in various altitude studies as altitude or control participants were used for the analysis. Participants performed Hb(mass) and VO₂(max) testing before and after intervention.

Results: For the pooled data, the correlation between per cent change in Hb(mass) and per cent change in VO₂(max) was significant (p<0.0001, r(2)=0.15), with a slope (95% CI) of 0.48 (0.30 to 0.67) intercept free to vary and 0.62 (0.46 to 0.77) when constrained through the origin. When separated, the correlations were significant for the altitude and control groups, with the correlation being stronger for the altitude group (slope of 0.57 to 0.72).

Conclusions: With high statistical power, we conclude that altitude training of endurance athletes will result in an increase in VO₂(max) of more than half the magnitude of the increase in Hb(mass), which supports the use of altitude training by athletes. But race performance is not perfectly related to relative VO₂(max), and other non-haematological factors altered from altitude training, such as running economy and lactate threshold, may also be beneficial to performance.

Keywords: Aerobic fitness/Vo2 Max; Altitude; Elite performance; Endurance; Exercise.

Figure 1

Linear regression (and 95% CI) for changes between preintervention and postintervention for Hb_mass and , n=145. Regression slope (solid line) and 95% CIs (dashed line) are shown. Top panel is for intercept free to vary, and bottom panel intercept constrained through the origin. Open circles are control participants and filled circles are altitude participants.

Figure 2

Linear regression (and 95% CI) for changes between preintervention and postintervention for Hb_mass and , control (n=62), altitude (n=83). Regression slope (solid line) and 95% CIs (dashed line) are shown. Top panels are for intercept free to vary, and bottom panels for intercept constrained through the origin. Left-side graphs are control groups (including IHE and IHT alone) and right-side graphs are altitude groups.

Figure 3

Linear regression between Hb_mass and in raw units. Regression slope (solid line) and 95% CIs (dashed line) are shown. Data are cumulative for pre-exposure and postexposure to altitude, n = 290. Top panel is for intercept free to vary, and bottom panel intercept constrained through the origin.