Different hypoxic training modalities have become a common addition to endurance athletes` training during the last few decades. Recently, technological advancements allowing for the simple simulation of altitude exposure by employing normobaric hypoxia have led to an even greater increase in their utilisation. It has been suggested that, besides classical hypoxic protocols employing longer exposures (> 12 h·day-1), performance can also be enhanced by intermittent protocols utilising shorter daily exposures (< 6 h·day-1) either at rest or combined with exercise. Even though the latest study findings regarding their influence on improved performance are ambiguous, they are habitually used in elite and recreational sport, chiefly due to their convenience and simple application. This short review will focus on currently used hypoxic training modalities with special reference to the effects of protocols utilising short exposures on performance at sea level and altitude. Moreover, the main underlying physiological mechanisms that can lead to improved performance following protocols utilising short hypoxic exposures will be reviewed. We will also examine the individual variability in response to hypoxic stimuli and possible combinations of hypoxic modalities for enhancing performance following hypoxia manipulations. The cumulative body of knowledge, as reviewed in this paper, does not indicate a robust improvement in performance as a consequence of short intermittent exposures in normobaric hypoxia. However, beneficial adaptations can be anticipated in some athletes and an individualised approach is thus warranted.
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