The effects of intermittent hypoxic training on aerobic capacity and endurance performance in cyclists

For this journal club we looked at the following journal article:

Czuba M, Waskiewicz Z, Zajac A, et al. The effects of intermittent hypoxic training on aerobic capacity and endurance performance in cyclists. Journal of Sports Science and Medicine 2011; 10: 175-183

What was the aim of the paper?

The aim of the paper was to look at the efficacy of intermittent hypoxic training at 95% of lactate threshold on endurance performance and aerobic capacity in cyclists. The authors did not include a hypothesis. The research was carried out by scientists at the Jerzy Kukuczka Academy of Physical Eduction in Poland.

What did the study involve?

The researchers recruited 20 male elite cyclists and randomly divided them into a hypoxia (H) group (who trained in a normobaric hypoxic environment, O2= 15.2%) and a control group (normoxia environment). The experiment consisted of baseline testing, followed by three weeks of progressive training and one week recovery in which the training load was significantly reduced, and then post-testing. The testing involved taking resting blood samples, body mass and body composition. This was then followed by a progressive cycle ergometer test to determine VO2max and lactate threshold and the researchers measured heart rate, minute ventilation, oxygen uptake and expired carbon dioxide. After 24 hour rest, the participants performed a 30km time trial and heart rate, blood lactate, speed, cadence and power were measured. The training programme was the same for both groups and involved three sessions per week with a 15 minute warm-up, 30-40 minutes of core training (30 min at 95% lactate threshold workload in 1st week, 35 min in second week and 40 min in third week) and a 15 minute cool down. Intensity for the control group was 100% of lactate threshold workload.

What were the main results?

The researchers results showed that after the three week training period, there was a significant increase in VO2max, maximum workload and lactate threshold workload during the incremental test in the hypoxia group compared to the control group. The results also indicated a significant reduction in the time of the trial and a significant increase in average generated power and speed during the time trial in the hypoxia group. However, there was no difference in red blood cell count, haemoglobin concentration and haematocrit value. The authors conclude that intermittent hypoxic training at lactate threshold intensity improves aerobic capacity and endurance performance at sea level.

What can we take from it?

I enjoyed reading this paper and agree with Ben that it had some very interesting points. The research question was focussed and the study design was suitable for the research question, but it was unfortunate that they did not include a hypothesis.

The main point that I want to highlight is that the researchers did not use a repeated measures, crossover design and therefore the participants did not serve as their own control, which means that the groups could have been unbalanced and it may have introduced bias to the results. The training period of three weeks was fairly short, but the training sessions were quite long (around an hour) and at a high intensity, which may not be suitable for the general population. However, as Carla mentions, a three week training programme that improves sea level performance could be appealing to athletes to gain a competitive edge.

I’ve picked out the following comments about the research.

  • The paper fails to find any changes to haematological parameters, suggesting that this intervention was not harsh enough to bring about significant erythropoiesis.
  • Future research should use the same intervention, but have more follow-up analysis and include muscle biopsies to measure for changes in skeletal muscle.
  • The only problem I can see with the present study is that the training only went for 3 weeks, it does not state what type of program the athletes come off, as a supercompensation effect could have accounted for the increases in power, lactate threshold and such.
  • This paper highlights that hypoxia is a complimentary tool to training and not the primary stimulus.

 

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6 Comments

Filed under Altitude training, Sport Science Journal Club

6 responses to “The effects of intermittent hypoxic training on aerobic capacity and endurance performance in cyclists

  1. Ben Macklin

    I found the paper very interesting, some (potentially) very exciting findings suggesting that as a result of the hypoxic stimulus, improvements in endurance performance were caused by muscular adaptations that either do not occur when training in normoxia, or do but to a lesser extent. Links in nicely with previous research by Katayama et al. (2004) and Gore et al. (2001), who observed marked improvements to buffering capacity and oxidative enzymes. These could have been prevalent in the Czuba paper, explaining the decrease in average heart rate during the post 30km TT, leading to the suggestion that 3 weeks of intermittent hypoxic training at moderate altitude (~2,500m) and with a moderate intensity (around lactate threshold) results in improved economy.

    However, the paper fails to find any changes to haematological parameters, suggesting that this intervention was not harsh enough to bring about significant erythropoiesis. But, this finding should be reconsidered, as Hamlin et al. (2009) observed the highest erythropoietic response 2 days post exposure, meaning that by the time the follow up tests were performed by Czuba et al. (6 days post exposure), any changes to blood parameters may have been missed. Furthermore, the paper failed to supplement its participants with iron, which could have limited erythropoiesis (Stray-Gundersen et al. 1992). And finally, I believe that a more realistic placebo should have been utilised (maybe change the humidity of the inspired air) to make the placebo more believable.

    Future research should use the same intervention, but have more follow up analysis and include muscle biopsies to measure for changes in skeletal muscle.

  2. Interesting findings, the haematological changes are usually seen after 12 hours sleep in a hypoxic chamber for 10 days in a live high train low environment. (Piehl Aulin et al, 2007)
    The only problem I can see with the present study is that the training only went for 3 weeks, it does not state what type of program the athletes come off, as a supercompensation effect could of accounted for the increases in power, lactate threshold and such. As when training in a hypoxic environment your performance is blunted until the adaption takes place, long term training in such an environment would not be ideal. Maybe a combination of live high train low, and train high schedule might yield more beneficial results.

  3. Carla Gallagher

    A well controlled study with some interesting findings given that the ‘live low – train high’ protocol is often not promoted within the elite arena due to altitude induced decrements in training intensity often observed and reported within the literature.

    Nevertheless a three week training programme that enhances sea level performance and VO2 max would appear appealing to many athletes incorporating periods of IHT into their training regime hoping to gain a competitive edge. The paper highlights the advantages of IHT well.

    I do agree with Ben that haematological parameters could have been missed by the authors due to the relatively prolonged time frame between training and testing parameters. Aditionally the literature reported within the discussion would suggest that the hypoxic insult was not great enough for an erythropoetic response, the study by Rodriguez and colleagues exposed participants to a simulated altitude equivalent to 5000m, maybe suggesting that the 2500m used in the present study was not great enough to elicit a significant response. The authors also fail to report on their findings of a decrease in CK within the discussion despite reporting it within the results section?? It is therefore difficult to observe why they measured this parameter and no other oxidative markers following the suggestion in the introduction that glycolytic enxyme activity may be altered.

    • Creating a simulated altitude equivalent to 5000m would mean that the hypoxic group would not be able to complete training at the same intensity. It’s a trade off that the larger dose may create haematological adaptation but if the training has decreased will it lead to improved performance? Probably not. And then of course there is individual responders vs non-responders as 5000m is considered pretty high!

  4. This paper highlights that hypoxia is a complimentary tool to training and not the primary stimulus. If you don’t train hard enough and expect hypoxia to give you benefits it is unlikely! Earlier papers (Hoppeler and Vogt 2001) looking at muscular adaptation showed that if the exercise was not of a sufficient intensity (which a lot of endurance papers have been) then adaptation did not occur. Perhaps these studies would have seen results but it would take a lot longer than 4 weeks to see.

    Although the comments above mention ‘missing’ the blood parameters I think that the rest week used is much more applied to real life training and highlights that muscular adaptation (increase mitochondrial density, cappilary length density) and gene expressions (upregulation of glycolytic pathway) could play more important roles when using IHT than haematological adaptations.

    Another interesting point would be that the hypoxic group actually worked at a slightly lower workload (in terms of Wattage on the bike). While this was necessary due to lactate threshold altering acutely in hypoxia, it could mean that their legs would be fresher following 3 weeks training while they have actually had an improved cardiovascular response. Buchheit et al 2012 shows that while perceived exertion may increase in hypoxia, physiological stress did not differ from normoxia (in high intensity interval work). In terms of elite sport could this provide an edge psychologically as well as physically?

    Combining three sessions a week training in hypoxia alongside sleeping in it to ensure a significant dose (12-14 hours/day) is accumulated could lead to larger improvements. However training load must be carefully monitored to ensure adequate recovery occurs, merely jumping in a tent without structure could lead to increased fatigue.

  5. Mark E.

    Interesting discussion.

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