The subjects were prohibited from performing intense exercises 2 days before the study. They had performed no physical activity at all 24 hours before the test. They were also forbidden from consuming caffeine before the test and were instead encouraged to sleep for a minimum of 7 hours and eat their last meal 2 hours before the test. The day before the test, the respiratory capacity of the subjects was measured using a JAEGER Spirometer (Oxycon Delta, Germany)