The Effect of Natural or Simulated Altitude Training on High-Intensity Intermittent Running Performance in Team-Sport Athletes: A Meta-Analysis
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While adaptation to hypoxia at natural or simulated altitude has long been used with endurance athletes, it has only recently gained popularity for team-sport athletes.
To analyse the effect of hypoxic interventions on high-intensity intermittent running performance in team-sport athletes.
A systematic literature search of five journal databases was performed. Percent change in performance (distance covered) in the Yo-Yo intermittent recovery test (level 1 and level 2 were used without differentiation) in hypoxic (natural or simulated altitude) and control (sea level or normoxic placebo) groups was meta-analyzed with a mixed model. The modifying effects of study characteristics (type and dose of hypoxic exposure, training duration, post-altitude duration) were estimated with fixed effects, random effects allowed for repeated measurement within studies and residual real differences between studies, and the standard-error weighting factors were derived or imputed via standard deviations of change scores. Effects and their uncertainty were assessed with magnitude-based inference, with a smallest important improvement of 4% estimated via between-athlete standard deviations of performance at baseline.
Ten studies qualified for inclusion, but two were excluded owing to small sample size and risk of publication bias. Hypoxic interventions occurred over a period of 7–28 days, and the range of total hypoxic exposure (in effective altitude-hours) was 4.5–33 km h in the intermittent-hypoxia studies and 180–710 km h in the live-high studies. There were 11 control and 15 experimental study-estimates in the final meta-analysis. Training effects were moderate and very likely beneficial in the control groups at 1 week (20 ± 14%, percent estimate, ± 90% confidence limits) and 4-week post-intervention (25 ± 23%). The intermittent and live-high hypoxic groups experienced additional likely beneficial gains at 1 week (13 ± 16%; 13 ± 15%) and 4-week post-intervention (19 ± 20%; 18 ± 19%). The difference in performance between intermittent and live-high interventions was unclear, as were the dose of hypoxia and inclusion of training in hypoxia.
Hypoxic intervention appears to be a worthwhile training strategy for improvement in high-intensity running performance in team-sport athletes, with enhanced performance over control groups persisting for at least 4 weeks post-intervention. Pending further research on the type of hypoxia, dose of hypoxia and training in hypoxia, coaches have considerable scope for customising hypoxic training methods to best suit their team’s training schedule.
The authors gratefully acknowledge the support of the authors of the selected studies in providing further information when requested.
MH supported and overviewed the literature search and selection of relevant articles and was the primary advisor regarding data interpretation and review of the manuscript. CL conducted the literature search, reviewed articles, selected relevant articles, interpreted analysed data and constructed the first draft of manuscript. WH was the primary advisor regarding data synthesis and inclusion of studies for meta-analysis, performed the meta-analysis and advised on interpretation of results.
Compliance with Ethical Standards
Preparation of this article was supported by the Lincoln University Research Fund. However, the funder did not contribute in any way to the development of the protocol or the interpretation of results.
Conflict of interest
Michael Hamlin, Catherine Lizamore and Will Hopkins declare that they have no conflicts of interest relevant to the content of this analysis.
This article was a meta-analysis and therefore did not require separate human ethics approval.
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