Physiological and Performance Effects of Altitude Training for Elite Athletes: A Systematic Review and Meta-Analysis

Abstract

<p><b>Background:</b> At the elite level, minute variances in performance can be the difference between a podium finish and competing in a final. As such, coaches are continuously looking at developing ways to improve performance. One strategy used by athletes in order to facilitate physiologic and exercise performance improvement is through hypoxic exposure. Two models appear to dominate the discussion: live high, train low (LHTL) and live high, train high (LHTH). The former proposes living at altitude (2000m – 3000m) but training at or near sea level (600m – 1200m). Whilst the LHTH model requires athletes to live and train at altitude ranges beyond (1250 to 3000m)</p> <p><b>Objectives:</b> To identify the physiological and performance adaptations associated with LHTL or LHTH for elite endurance athletes.</p> <p><b>Methods:</b> 1) A narrative review of the literature was carried out to address and explore current literature within altitude training. 2) A systematic review and meta-analysis were performed to determine how altitude training (both LHTL and LHTH) influences the physiological and performance effects in elite and high performing athletes, contrasting different models of altitude exposure.</p> <p><b>Results:</b> 1) Narrative review: key results for physiological and performance adaptations for the narrative review seem to indicate that an optimal height of 2000 – 2500m for 3 – 4 weeks for LHTH, while under models adopting a train low component (LHTL), optimal adaptation height should range between 2500 – 3000m for 3 – 4 weeks (>12 h·day-1). </p> <p>2) Systematic review and meta-analysis: 24 studies were included in the final analysis. Improvements in tHb_mass, HCT and lactate were found. For hemoglobin mass, a small increase was found following altitude training (g = 0.23; 95% CI = 0.09 to 0.36; <i>P</i> < 0.01). Regarding HCT, a small moderate increase was noted, however, this was not significant (g = 0.35; 95% CI = -0.03 to 0.72; <i>P</i> = 0.07). Finally, in relation to lactate, following altitude training, athletes produced moderately more favourable lactate responses to exercise than control (g = 0.55; 95% CI = -0.01 to 1.10; <i>P</i> = 0.05). Despite moderate improvements in some physiological markers (tHbmass, HCT and lactate), results did not demonstrate enhanced exercise performance improvements (TT: g = 0.12; 95% CI = -0.13 to 0.37; <i>P</i> = 0.35; Oxygen consumption: g = 0.13; 95% CI = -0.08 to 0.35; <i>P</i> = 0.22; PPO: g = 0.09; 95% CI = -0.13 to 0.32; <i>P</i> = 0.42). </p> <p><b>Conclusion</b></p> <p>Improvements in tHb_mass, HCT and lactate were found. Altitude training modalities (LHTL and LHTH) should be used by well-trained and elite athletes to enhance physiological adaptations. However, the degree to which these physiological markers improve performance outcomes needs further investigation. The moderate number of studies examined within the current meta-analysis limits the confidence of these findings, and it is likely this training modality has a broader effect on physiology and hence performance than this.</p>