Effects of High-Intensity Interval Training Under Normobaric Hypoxia on Cardiometabolic Risk Markers in Overweight/Obese Women.

Promising benefits on cardiometabolic risk factors have been reported with prolonged programs of cyclic hypoxia. The aim of this study was to examine whether cyclic hypoxia exposure while exercising through two protocols of high-intensity interval training in overweight/obese women is more effective to improve cardiometabolic risk markers than exercising in normoxia. Participants included 86 overweight/obese women, who started a 12-week program of 36 sessions, and were randomly divided into four groups: (1) interval training in hypoxia (IHT; FIO = 17.2%; n = 13), (2) interval training in normoxia (INT; n = 15), which included 3-minute high-intensity exercise (90% Wmax) followed by 3 minutes of active recovery (55%-65% Wmax), (3) repeated-sprint training in hypoxia (RSH; FIO = 17.2%; n = 15), and (4) repeated-sprint training in normoxia (RSN; n = 18), which included 30 seconds of all-out effort (130% Wmax) followed by 3 minutes of active recovery (55%-65% Wmax). Body composition, anthropometric, biochemical, and clinical parameters were assessed at baseline (A), after 18 training sessions (B), and during the 7 days after the last session (C). IHT and RSH showed a significant (p < 0.001 and p = 0.016, respectively) decrease in the waist circumference at both B and C assessments compared with A. Hypoxia groups presented a significant reduction in the percentage of trunk fat with a moderate effect size (IHT: d = 0.56; RSH: d = 0.93). In the normoxia groups, total cholesterol (CHOL) tended to decrease (INT: -4.21% and RSN: -5.18%), whereas it tended to increase in the hypoxia groups (IHT: +2.91% and RSH +4.07%). An interaction effect between conditions (through pooled data) on waist circumference (p = 0.01), percentage of trunk fat mass (p < 0.001), and CHOL (p = 0.019) was observed. Both training regimens under normobaric cyclic hypoxia were more effective at causing decreased abdominal fat in overweight/obese women than the same protocols in normoxia.