The impact of altitude expectation on cyclists performance: A balanced placebo design study

Abstract

Placebo and nocebo effects in sports are understood as an improvement or impairment, respectively, in performance attributed to an intervention-whether mechanical, nutritional, or environmental-that is inert and are primarily induced by positive or negative expectations. Studies using a within-participant balanced placebo design actively manipulate the expectation of the intervention. Despite a large body of evidence examining placebo effects of nutritional interventions, it is not known how much influence they have during altitude. Therefore, this pioneering and innovative study aims to use the balanced placebo design to investigate the impact of altitude expectation on performance during a 16-km time trial conducted on a cycling ergometer under different conditions: normobaric normoxia and normobaric hypoxia. Specifically, we aim to elucidate how sports performance, including power output, heart rate, blood lactate levels, and oxygen saturation, are influenced by expectations regarding the atmospheric conditions they are informed to expect and the actual conditions they experience. A sample size of 20 athletes, including men and women, is expected, with each participant visiting to the laboratory on six occasions: two sessions for familiarization with the hypoxia chamber and the protocol, and four experimental sessions. Upon entering the study, participants will be randomly assigned to one of the predetermined session orders. These orders correspond to various combinations of informing participants about their environment (normobaric normoxia or normobaric hypoxia) and the actual environment they will experience during the session. Prior to each session, participants will be asked to confirm their abstinence from alcohol, caffeine, and strenuous physical activities within the past 24 hours. These sessions will be scheduled at the same time of day to accommodate circadian variation in performance. For sessions corresponding to sea level, the chamber will be set with an FiO2 (%) of 20.9, and when simulating moderate to high altitude (3000 meters above sea level), it will be set at 15.5. Oxygen saturation and heart rate will be continuously monitored, while lactate levels and perceived exertion will be assessed every 4-kilometer. Statistical analysis will include descriptive statistics for participant characteristics, a linear mixed model for mean power output during the 16-km cycling time trial, and correlation analyses of oxygenation and heart rate data during exercise.