Live high - train low altitude camps can enhance endurance power at sea level by 1-2% (Levine & Stray-Gunderson, 1997). More convenient methods to simulate altitude exposure are now available, but their effects on performance are less well characterized. In this study, we investigated intermittent hypoxic training (IHT) using an Hypoxicator, a device that produces oxygen-depleted air that athletes breathe intermittently through masks in a small group at a central venue. Twelve highly-competitive, male cyclists and multi-sport athletes (IHT group) underwent IHT in two, four-week bouts separated by eight weeks. Bout one consisted of 20 one-hour exposures and bout two 18 exposures where normal and low-oxygenated air was breathed in alternating five-minute intervals. The percentage of oxygen inhaled by the subjects was adjusted to produce an oxygen saturation of the blood of 88-92% in the first week of the study, decreasing to 76-80% (equivalent to an altitude of approximately 6000m) in the final week. A control group of 13 similar athletes did not use the Hypoxicator. Performance trials and blood tests were at four-week intervals; there were 3 trials (familiarization and reliability) before use of the Hypoxicator, 3 trials after to determine the effect of simulated altitude, then a second four-week exposure and one more trial. The measures of performance were mean power in a 16-km time trial on a Kingcycle ergometer (IHT group only) and power in a lactate-threshold test at 3 mmol/L above baseline (both groups). The measures from the blood tests were haemoglobin and haematocrit. There was a gradual but erratic improvement in performance in the time trial and lactate threshold tests over the course of the study in both groups, indicating an improvement through training. Relative to the last baseline test (Trial 3), the IHT group showed a 0.6% decrease in mean power over and above the effect of training in the 16-km time trial in Trial 4, nine days after last use of IHT. There was a 0.3% increase in mean power independent of the training effect in Trial 7, after the second round of altitude exposure. Uncertainty in these changes in performance was ±3.5% (95% confidence interval). The changes in lactate threshold in trials 4 and 7 indicate a possible improvement as a result of IHT exposure. Uncertainty in these changes was ±4.0%. There were negligible changes in the haemoglobin and hematocrit of either group at any time. There was small evidence of high responders, who were probably subjects with the DD genotype for the angiotensin converting enzyme gene. The time exposed to IHT had no bearing on performance and there was no evidence "peak" in results at either four or eight weeks after exposure to IHT. In summary, four weeks of IHT exposure probably resulted in a trivial effect on 16-km time-trial performance and the effort-independent measures provided no further clear-cut evidence of a performance improvement.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/1320 |
| Date | January 2004 |
| Creators | Bailey, Christopher Mark |
| Publisher | University of Canterbury. Biological Sciences |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Christopher Mark Bailey, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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