Day-to-day variability in cardiorespiratory responses to hypoxic cycle exercise

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Sports Science

Background:

• Repeated exercise in hypoxia may induce unintended training effects.
• Understanding hypoxic exercise response variability is crucial for accurate research.

Purpose of the Study:

• To determine if hypoxic exercise responses change with repeated testing.
• To assess the day-to-day variability of cardiorespiratory and metabolic responses to hypoxic exercise.

Main Methods:

• Healthy young males completed 5 hypoxic exercise trials over 2 weeks.
• Exercise involved incremental stages of peak power in hypoxia (FiO2 = 0.13).
• Measured responses included ventilation, gas exchange, heart rate, blood lactate, and perceived exertion.

Main Results:

• Exercise intensity increased cardiorespiratory and metabolic demands, and reduced oxyhaemoglobin saturation.
• No systematic changes in responses were observed across the 5 trials.
• Most measures demonstrated high repeatability (coefficient of variation ≤10%), except O2 consumption, CO2 production, and blood lactate.

Conclusions:

• The tested hypoxic exercise protocol does not elicit a training response with repeated exposure over 2 weeks.
• The protocol exhibits low day-to-day variability, enabling sensitive detection of minor cardiorespiratory changes during hypoxia.