Repeat-sprint training in hypoxia for team sport athletes

There are well documented athletic performance benefits for endurance athletes living at natural or simulated altitude. Furthermore, recent evidence has suggested that team sport athletes can gain similar levels of physiological benefit and performance enhancement when living at altitude. However, much less is known about the responses to training in a reduced oxygen environment (hypoxia), and in particular, research investigating repeat-sprint training in hypoxia (RSH), a recently developed team sport specific method of altitude training, is limited. Therefore, the primary aim of this thesis was to explore the physiological and performance responses of team sport athletes performing RSH, and to subsequently develop recommendations for optimal team sport training practices that encompass RSH.

Study one compared the acute physiological and performance responses to a 3 x 9 x 4 s repeat-sprint training session performed on a non-motorised treadmill at sea-level, and at three different levels of simulated altitude (2000 m, 3000 m and 4000 m). Here, it was demonstrated that blood oxygen saturation declined significantly with each increase in simulated altitude, which corresponded with a decline in total work performed throughout the session. However, it was found that the only significant reductions in mean power output during the first set of repeated sprints was in the 4000 m condition, and peak power output was also only significantly impaired during the 4000 m trial throughout the third set. These results suggest that moderate simulated altitudes (2000-3000 m) may be more suitable for RSH than higher altitudes (i.e., 4000 m).

Study two then assessed whether there were any acute physiological responses to RSH which might impact on post-exercise recovery. The inflammatory and reactive oxygen species (ROS) response to a repeat-sprint training session performed on a cycle ergometer in either sea-level or hypoxic (3000 m) conditions were assessed in 10 team sport athletes using a single blind, crossover design. This investigation showed that the ROS response (assessed via F2-Isoprostane) to sea-level and hypoxic repeat-sprint training was similar, with a ~10% reduction noted at 1 h post-exercise. Furthermore, the inflammatory response (assessed via interleukin-6) to RSH was modest, with only a ~2-fold increase in the sea-level group, and a ~3.5-fold increase in the RSH group at 1 h post-exercise. These results indicate that, while it is possible that RSH may slightly increase the acute inflammatory response to training, this response is modest when compared to other longer duration training methodologies, and therefore there appears little concern that RSH training may negatively impact the post-exercise inflammatory or ROS response.

Finally, having determined that RSH did not unduly increase the post-exercise inflammatory or ROS response, study three implemented a training intervention utilising the simulated altitude deemed most appropriate from study one. Here, 30 team sport athletes from the same semi-elite football club performed 5 weeks of regular team sport pre-season training with an additional 15 repeat-sprint cycling sessions added at either sea-level (n=10) or in a hypoxic environment (3000 m, n=10). A control group (n=10) performed no additional training. It was found that the additional repeat-sprint training (regardless of condition) improved cycle repeat-sprint ability (RSA); however, there was no impact of hypoxia on cycle RSA performance, and no additional improvements to running RSA or intermittent endurance performance were found for either training group compared to the control. Cycle RSA was improved to a greater extent in the sea-level training group compared to the hypoxic group, which highlights the uncertainty in whether RSH may provide any additional performance benefits to repeat-sprint training in sea-level conditions. These findings suggest that any performance enhancement attributable to RSH remain equivocal, and further evidence for the benefits of RSH to team sport athletes is required prior to recommending that team sport programs invest in hypoxic training facilities.

Overall, these three investigations have provided team sport athletes and coaches with practical information for how best to implement a RSH program. Training should be performed in a sport-specific manner with a moderate simulated altitude (2000-3000 m) selected as the training environment. It should be noted though, that due to the lack of evidence for improved sea-level performance found here (and in other investigations), it remains questionable whether a hypoxic training facility represents a worthwhile investment. However, given that no negative physiological or performance outcomes were found, it is suggested that teams with ready access to hypoxia could administer RSH (within the recommendations presented above) as a training strategy to vary the physiological stimulus, and also assess the individual response of their athletes.