Changes in autonomic response and resistance to acute graded hypoxia during intermittent hypoxic training

Vagal activity and oxygen saturation response to hypoxia: Effects of aerobic fitness and rating of hypoxia tolerance

“…Regarding HRV, we found insignificant and small changes in the sympathovagal balance (LF/HF ratio) across the three experimental phases in RG. Similar results for LF/HF were published previously (Bobyleva & Glazachev, 2007;Botek et al, 2015). A significant reduction in vagal activity (Ln HF) occurred during the hypoxia period compared with the preliminary phase in both RG (moderate effect) and SG (very large effect).…”

“…Based on this result, it is tenable that differences in autonomic cardiac disturbances during acute normobaric hypoxia could be partly attributed to VO 2 max level. Bobyleva and Glazachev (2007) demonstrated that hypoxia-sensitive subjects undergoing intermittent hypoxic training (IHT) (20 sessions of 60 minutes) had a blunted sympathetic response and a slower decline in SpO 2 during hypoxia. Therefore, future research is needed to clarify the effect of IHT on SpO 2 and ANS response in aerobic well trained subjects that in our study exhibit both autonomic cardiac impairment and a greater SpO 2 change during acute hypoxia.…”

“…Skewed probability distributions of LF, HF, LF/HF, and rMSSD variables were corrected applying a natural logarithm (Ln). According to previously published studies (Bobyleva & Glazachev, 2007;Botek et al, 2015) subjects were divided into two groups based on the median SpO 2 value during the hypoxic phase (70.9%). The subjects with SpO 2 ≥ 70.9% were assigned to the Resistant group (RG, range 70.9-86.7%, n = 14).…”

“…Some studies have revealed that a similar level of short-term acute normobaric hypoxia induces individual differences in the magnitude of SpO 2 response that consequently are related to variable changes in autonomic cardiac regulation (Bobyleva & Glazachev, 2007;Botek, Krejčí, De Smet, Gába, & McKune, 2015). Importantly, the SpO 2 response to hypoxia at rest (Burtscher, Flatz, & Faulhaber, 2004) and the combination of rest and exercise (Karinen, Peltonen, Kähönen, & Tikkanen, 2010;Rathat, Richalet, Herry, & Larmignat, 1992) has been suggested by some authors to be a promising marker of susceptibility to acute mountain sickness (AMS) development, while others have reported opposite findings (Wille et al, 2012;O'Connor, Dubowitz, & Bickler, 2004).…”

“…The normobaric hypoxic environment (FiO 2 = 9.6%, simulated altitude of 6 200 m) was created using the MAG-10 system (Higher Peak, Boston, MA, USA). The given normobaric hypoxia level has been widely used in previous studies for intermittent hypoxia exposure (Millet, Roels, Schmitt, Woorons, & Richalet, 2010), and/or to determine effect of intermittent hypoxia training to autonomic cardiac regulation (Bobyleva & Glazachev, 2007). Figure 1.…”