Hypoxic Exposure at Rest or During Light to Moderate-Intensity Exercise Improved Blood Pressure and Heart Rate Variability in Cardiovascular Risk Individuals

Saengjan W, Hamlin MJ, Muangritdech N, Namboonlue C, Tong-un T, Manimmanakorn N, Manimmanakorn A. Hypoxic Exposure at Rest or During Light to Moderate-Intensity Exercise Improved Blood Pressure and Heart Rate Variability in Cardiovascular Risk Individuals, JEPonline 2023;26(3):28-44. This study evaluated the effects of 6 weeks of intermittent hypoxic at rest or plus exercise and long-lasting effects on blood pressure and heart rate variability (HRV) in cardiovascular risk individuals. Thirty combinations of several CVD risks participants: hypertension, hyperlipidemia, and obesity were randomly allocated into 3 groups: (a) the Control Group (CON, n = 11) received no intervention; (b) the intermittent hypoxic exposure during rest (IHR, n = 9), and the intermittent hypoxic training (IHT, n = 10) combined with walking on a motorized treadmill at a light to moderate-intensity. Both IHR and IHT performed 8 sessions of 3 minutes of hypoxic breathing alternated with 3 minutes of normoxic breathing for 6 weeks. All participants blood pressure and HRV were measured at baseline, at week 6 (POST1), and at week 10 (POST2). The IHR and IHT Groups showed significantly lower SBP (P < 0.05) compared to the CON Group, but not DBP and MAP after the IH training program. Compared to CON, the low-frequency band (VLF) and the low-frequency band and the high-frequency band (LF/HF ratio) showed a significant decrease only in IHT (P < 0.05) at POST1 and VLF remained significantly decreased at POST2. VLF in the IHT Group remained significantly lower than in the IHR Group at POST2. After the IH training program, IHT revealed a significant increase in HF (P < 0.05) compared to the CON Group. HF (n.u.) was a significantly stronger negative correlation with changes in SBP (P < 0.05). The IHT Group showed more effectiveness than the IHR Group. The study suggested this IH training program improved SBP and HRV at POST1. An increase in parasympathetic activity may have played an important role in the SBP reduction seen in this study. Key Words: Exercise, Hyperlipidemia, Hypertension, Intermittent Hypoxic Training, Obesity, Sympathetic Activity