Variability in response to an 8-week low altitude football training camp supplemented with intermittent hypoxic training

Abstract

Introduction: Living and training at altitude is popular among athletes; however, significant individual differences exist in the improvement of sea-level performance. We investigated potential physiological factors that may explain the difference between responders and non-responders. Design: Randomized Controlled Trial. Methods: Twenty male football players completed an 8-week training camp at 825 m above sea-level, supplemented with intermittent hypoxic training three times per week at FIO2 = 0.15. Based on the players 2800 m run performances, players were separated into responders (improved by 10.7 ± 8.1%, mean ± 95% CI, n=14) and non-responders (decreased by 6.1 ± 12.8%, n = 6). Results: Compared to baseline, the responders had a lower resting heart rate (HRrest) at 1 (-4.6 ± 2.7 bpm, Effect Size = 1.2) and 14 days (-6.7 ± 3.3 bpm, ES = 1.7) post-training camp, whereas the non-responders HRrest changed little. Compared to the non-responders, the responders had higher pNN50 at 1 (12.2 ± 11.5, p = 0.04, ES = 1.6) and 14 days (10.1 ± 11.7, p = 0.09, ES = 1.4) post-training camp. In addition, the responders decreased their LF/HF ratio at day 1 (-1.1 ± 0.6, p < 0.01, ES = 1.0) and day 14 post camp (-0.9 ± 0.6, p < 0.01, ES = 0.8), whereas the non-responders LF/HF ratio increased (0.8 ± 0.9 and 0.9 ± 0.9). Conclusions: Reduced HRrest and increased cardiac parasympathetic tone was associated with improved run performance after altitude training and may be used to differentiate altitude responders compared to non-responders.