# The Effects of Intermittent Hypoxic Training on Anaerobic Performance in Young Men
## 4 Discussion  
The purpose of this study was to evaluate the effects of IHT on anaerobic performance in young men. Our study showed that after interval training in hypoxia (12 workouts for 4 weeks; 12 h of training in hypoxia) only peak power (absolute and relative) was significantly improved in the IHT group. In the control and normoxia training groups a similar effect was not observed. The increase in peak power indicates an improvement in the alactic (phosphagen) energy system's efficiency. On the other hand, after training, no significant changes in parameters informing the efficiency of the lactic (glycolytic) energy system, i.e., mean power, fatigue index or power decrease, were observed in any of the training groups (IHT, NT). The applied intervention also did not significantly affect the participants' speed (dynamics)--peak power was noted in all groups at a similar time from the start of test, both before and after training. However, there was a noticeable tendency for the time to reach peak power to shorten with training. Our results suggest that IHT may have had a significant beneficial effect only on peak power. To our knowledge, this is one of the few studies to comprehensively evaluate the effects of IHT on anaerobic performance in young, untrained men. Previous studies [8; 9; 10] were performed with athletes, which could have significantly influenced the results, due to the high volume training and good physical capacity of the participants. In repeated WAnTs, the practice effect is observed [28]. For this reason, at least one familiarization session with the test is recommended, which, in these studies, was performed a few days before the start of the pivotal test. During a WAnT the fractions of the energy from alactic, lactic and aerobic metabolism, are 31.1%, 50.3% and 18.6%, respectively [29]. This suggests that the improvement in anaerobic performance in a WAnT under hypoxic training may be due to improvements in anaerobic, as well as in aerobic, metabolism. In this study, we focused on evaluating the effects of IHT on anaerobic performance, and we did not investigate the mechanisms underlying the observed effects. Changes in anaerobic performance under hypoxia are primarily attributed to the non-hematological effects of hypoxic training. It is indicated that as an effect of IHT, greater muscle adaptation occurs than during exercise in normoxia [3]. The lower oxygen partial pressure in muscle tissue during IHT may lead to a larger upregulation of hypoxia-inducible factor 1\(\alpha\) (HIF-1\(\alpha\)) [5]. An increased citrate synthase activity, mitochondrial density, fiber cross-sectional area and capillary-to-fiber ratio were noted after IHT. Moreover, the upregulation of factors of mitochondrial biogenesis or enzymes implicated in carbohydrate and mitochondrial metabolism, oxidative stress defense and pH regulation were observed in the participants [3; 5; 30; 31; 32]. Potentially favorable adaptations to anaerobic exercises after IHT were also reported, e.g., improved tissue perfusion, mitochondrial efficiency, better control of muscle O\({}_{2}\) homeostasis and mitochondrial respiration [33; 31], angiogenesis [34] and improved muscle buffering capacity [7]. Unfortunately, the translation of these adaptations into enhanced performance is not always observed, and may be irrelevant for sports [3]. In hypoxia training studies, a decrease in Na\({}^{+}\)-K\({}^{+}\) -ATPase pump activity has been observed [35], and training in hypoxia might be detrimental to muscle contractility [36]. The inclusion of hypoxia in training can also affect PCr re-synthesis [3]. After training in hypoxia a quicker recovery of phosphocreatine was observed [37; 38]. Hypoxia also induces vasodilation [39] to maintain normal pO\({}_{2}\), especially in fast-twitch fibers [40]. An elevated microvascular pO\({}_{2}\) reduces PCr breakdown and speeds up PCr recovery kinetics [41], which can affect the power generated [3]. Our study does not confirm the results presented by [PERSON] et al.