Effects of normobaric intermittent hypoxic training on hypobaric performance

The purpose of the present study was to examine the effects of a normobaric intermittent hypoxic training (NIHT) intervention protocol, when compared to normobaric normoxia (NN) training, on maximal aerobic endurance performance in both (NN) and hypobaric hypoxia (HH). Eleven male Reserve Officers' Training Corps (ROTC) cadets (age 19.55 + or - 1.44 y, mass 75.80 + or - 8.82 kg, stature 177.45 plus or minus 6.67 cm) completed the 6 week training intervention in either the NIHT (EXP, n = 6) or NN (CON, n = 5) conditions. Pre- and post-testing included assessments of peak oxygen uptake (VO2peak) in both NN and HH conditions with the NIHT group also completing a follow-up VO2peak assessment after a 1 week detraining period. Participants also completed blood draws to assess any changes to the blood's O2-carrying capacity. Mixed ANOVA was performed to analyze differences between the within-subjects factor (time) and between-subjects factor (EXP and CON). Repeated measures ANOVA were also performed to analyze differences for all variables between the pre-, post-, and follow-up results of the EXP group. The present study revealed that NIHT failed to elicit greater aerobic endurance performance in either NN or HH conditions when compared to NN endurance training. Further, NIHT did not induce significant adaptations of the blood's O2-carrying capacity compared to endurance training in normoxia. However, there was a significant main effect of time (P < .05) on endurance performance in the NN condition as demonstrated by a 5.44% increase in VO2peak. There was also a significant main effect of time (P < .01) on endurance performance in the HH condition as demonstrated by an 11.48% increase in VO2peak. Further, there was also a significant interaction of time x training group (P < .05) for resting arterial O2 saturation as measured via pulse oximetry (SpO2) as a result of a 2.39% increase in SpO2 values for the EXP group and a simultaneous decrease of 2.72% in SpO2 values for the CON group from the pre- to post-testing measurements conducted in the HH chamber. These findings may have critical relevance for military personnel conducting operations in high altitude locations