Exercise training in normobaric hypoxia in endurance runners. I. Improvement in aerobic performance capacity

Abstract

This study investigates whether a 6-wk intermittent hypoxia training (IHT), designed to avoid reductions in training loads and intensities, improves the endurance performance capacity of competitive distance runners. Eighteen athletes were randomly assigned to train in normoxia [Nor group; n = 9; maximal oxygen uptake (VO2 max) = 61.5 +/- 1.1 ml x kg(-1) x min(-1)] or intermittently in hypoxia (Hyp group; n = 9; VO2 max = 64.2 +/- 1.2 ml x kg(-1) x min(-1)). Into their usual normoxic training schedule, athletes included two weekly high-intensity (second ventilatory threshold) and moderate-duration (24-40 min) training sessions, performed either in normoxia [inspired O2 fraction (FiO2) = 20.9%] or in normobaric hypoxia (FiO2) = 14.5%). Before and after training, all athletes realized 1) a normoxic and hypoxic incremental test to determine VO2 max and ventilatory thresholds (first and second ventilatory threshold), and 2) an all-out test at the pretraining minimal velocity eliciting VO2 max to determine their time to exhaustion (T(lim)) and the parameters of O2 uptake (VO2) kinetics. Only the Hyp group significantly improved VO2 max (+5% at both FiO2, P < 0.05), without changes in blood O2-carrying capacity. Moreover, T(lim) lengthened in the Hyp group only (+35%, P < 0.001), without significant modifications of VO2 kinetics. Despite similar training load, the Nor group displayed no such improvements, with unchanged VO2 max (+1%, nonsignificant), T(lim) (+10%, nonsignificant), and VO2 kinetics. In addition, T(lim) improvements in the Hyp group were not correlated with concomitant modifications of other parameters, including VO2 max or VO2 kinetics. The present IHT model, involving specific high-intensity and moderate-duration hypoxic sessions, may potentialize the metabolic stimuli of training in already trained athletes and elicit peripheral muscle adaptations, resulting in increased endurance performance capacity.

The effects of intermittent hypoxia training on hematological and aerobic performance in triathletes

“…Indeed, Czuba et al (5) affirmed that an intensity of 60-70% of the heart rate reserve is not a sufficient training stimulus and will not lead to improvements in aerobic capacity. Regarding the test time, we measured an increase of 6% in the IHTG, a result in consonance with previous studies (7,17,30) and that disagrees with another study that did not find an increase in this parameter (23). These differences in performance might be influenced by the initial athletic performance level of participants, as well as by the session duration, simulated altitude and intensity of hypoxia training (15).…”

“…Theoretically, IHT can improve aerobic capacity and endurance performance at sea level through a series of adaptive changes, however, studies in the field of IHT are inconclusive (7,31). The results of the present research showed no changes in physiological and performance variables in the experimental groups after the 7 weeks of training.…”

Entrenamiento en hipoxia intermitente y rendimiento ciclista en triatletas / Intermittent hypoxic training and cycling performance in triathletes

“…Los trabajos previos que comprueban los efectos en el umbral anaeróbico producidos por los programas de IHT aprecian una clara mejora del rendimiento asociado a esta variable y por lo tanto, están en consonancia con los resultados obtenidos en nuestra investigación. Así, Dufour et al(2006) observaron una mejora del 4 % en el umbral anaeróbico en atletas de resistencia de alto nivel después de 12 sesiones de 1 hora de duración al 14.5 % de FIO2. Estos resultados también coinciden con Czuba et al (2011) que observaron mejoras en el umbral anaeróbico de ciclistas élite después de 3 semanas realizando 3 sesiones de 1 hora de duración al 15.2 % del FiO2.…”

Effect of normobaric hypoxia on cardiorespiratory and metabolic risk markers in healthy subjects

“…Meanwhile, new alternatives for traditional altitude training regimes have been proposed, known as "living low and training high", and the effects on endurance performance have been demonstrated extensively in athletes [10][11][12]. Recently, several studies have reported the effects of hypoxia training on physical fitness not only in athletes but also in nonathletes [13][14][15][16][17].…”