Training load and heart rate variability in acute exposure to hypobaric hypoxia: A case study

Aim: To analyze the control of training load for an acclimatization strategy employed by two amateur athletes (female and male) prior to a successful ascent to 5460 meters. Methodology: Baseline heart rate variability (HRV) measurements were taken for 195 consecutive days. Four blood samples were taken the week before the main event (Pre), pre-ascent (Pre A), post-ascent (Post A), and one-week post-ascent (Post C). Results: Daily morning HRV recordings were useful for monitoring the state of sympathetic-parasympathetic balance in mountaineers prior to tackling training sessions. Both subjects had increased leukocytes and neutrophil levels, exhibiting variations over 60% between pre-A and post-B conditions. Erythrocytes, hematocrit, and haemoglobin decreased after acute exposure to 5460 m, coinciding with changes in platelet levels between both subjects (-3% and -51%). Conclusions: Daily morning and 5-min HRV recordings are a useful way for monitoring the state of sympatheticparasympathetic balance. Significant changes were observed in some white blood cells.