The importance of personalization in high altitude protocols for hematologic and metabolic benefits in sports: A multi-dimensional N-of-1 case study.

The hematologic and metabolic benefits of high altitude exposure have been extensively studied in athletes due to their promising performance enhancing effects. However, despite the increased research and development of various high altitude protocols for achieving peak performance, the reproducibility of the results at the individual level remains sparse. To systematically address this limitation and establish a more effective method to achieve consistent results at the individual level, we conducted a multi-dimensional study of one elite endurance athlete in two Phases. In Phase 1, we applied the standard protocol of LHTH (Live-High-Train-High) using a commercially available, at-home, normobaric, high altitude simulation tent under the SHTL (Sleep-High-Train-Low) model. Then, we developed the athlete's personalized protocol for peak hematologic parameters during their off-season. This protocol determined the exact total high altitude exposure time required to achieve peak hematologic parameters, which in the case of this athlete, amounted to 45 nights with approximately 8hrs per night. In Phase 2, we replicated the Phase 1 protocol during the athlete's in-season and observed the same or even higher hematologic and metabolic benefits compared to Phase 1. During both phases, we collected thousands of multi-dimensional data points to ensure that the athlete's lifestyle and environmental factors remained stable, and to increase the likelihood that physiological changes resulted primarily from the high altitude exposure. The data trends in both Phases validated that, for this athlete, hematologic measures such as red blood cell count, hematocrit, and hemoglobin, as well as electrolyte content, body weight and gut microbiome composition improved to their personal best values after a total of approximately 15 days of high altitude exposure (45 nights with roughly 8hrs per night totaling 360hrs or 15days). These improvements did not occur after the 21 days recommended by the LHTH protocol highlighting the significance of personalization in high altitude protocols that are designed for peak performance parameters. Therefore, to maximize the benefits in hematologic and other metabolic values and thus increase muscle oxygen supply and peak aerobic capacity through high altitude exposure, each athlete may require a unique total duration of high altitude exposure tailored to their individual physiology. This duration must be determined by their specific response in hematologic peaking. Therefore, initially establishing a personalized protocol for an athlete by determining their required total duration of high altitude exposure for peak hematologic values during their off-season and applying this protocol during their in-season phase may lead to more successful and reproducible benefits compared to following a generalized protocol alone.