The effect of intermittent simulated altitude exposure via re-breathing on cycling performance

by Babcock, Carmen J.

Increased participation of competitive athletes in new methods of simulated altitude warrants research on changes in performances. PURPOSE: To ascertain the effects of intermittent simulated altitude exposure via re-breathing on cycling performance. METHODS: Eighteen, well-trained male cyclists engaged in the use of a re-breathing simulated altitude device for 15 days. Subjects were randomly assigned to 1 of 2 simulated altitude groups; a low constant exposure group (CON) or progressively increased exposure group (TRT). Each exposure consisted of alternating between a rebreathing device and atmospheric air for 6 min and 4 min, respectively over 1 hour. Oxygen saturation was monitored with a pulse oximeter; and either held constant (98% over 15 days; equivalent altitude equal 150 m) or progressively reduced (90% on the 1 ii st day to 77% on the 15th day; equivalent altitudes equal 3600-6300 m). An exercise performance test was performed to familiarize subjects to the protocol (FAM), prior to simulated altitude exposure (PRE) and following simulated altitude exposure (POST). The critical power protocol was used to examine power output in a highly aerobic event (15 minute time trial) and a highly anaerobic event (3 minute time trial). Performance was also investigated through measurements of lactate, oxygen consumption, and heart rate. Blood characteristics examined include hematocrit, reticulocyte and serum Ferritin values, prior to and following simulated altitude exposure. RESULTS: There was a significant improvement (p=.004) for the TRT group at POST in the 15 minute time trial (PRE = 325.0 ± 12.2 watts, POST = 335.0 ± 11.9 watts) and estimated 60 minute time trial (PRE = 300.1 ± 28.4; POST = 322.4 ± 36.1) compared to no improvement in the CON group. The TRT group improvement was 3-4.5% in average power output. There were no significant differences in the power outputs of the 3 minute time trial at POST for either group. There were no significant differences in haematological measures at POST for either group. A decreased VO2 Index (PRE = 0.165 ± 0.016; POST = 0.152 ± 0.023), p=.075 and a significant decrease (p = .026) in heart rate (HR) Index (HRavg/wattavg) was revealed for the TRT group (PRE = 0.564 ± 0.044; POST = 0.544 ± 0.053). CONCLUSIONS: In competitive cyclists, the use of a re-breathing device resulted in improved performance for events which rely heavily on aerobic power but none for anaerobic power. These findings are similar in regard to performance adaptations found in other acclimatization investigations, terrestrial or simulated. It is suggested that the re-breathing form of simulated altitude may be utilized as an alternative to terrestrial or other forms of simulated altitude, in efforts to mediate performance gains in endurance type events. iii To my parents, Patricia L. Babcock & Ronald W. Babcock iv