Physiological strain associated with high-intensity hypoxic intervals in highly trained young runners

Area of Science:

• Exercise Physiology
• Sports Science
• Altitude Training

Background:

• High-intensity interval training (HIIT) is effective for improving athletic performance.
• Hypoxic training, simulating high altitudes, is increasingly used to enhance endurance.
• The physiological strain of combining HIIT with hypoxia (HHIT) requires further investigation.

Purpose of the Study:

• To compare the physiological strain of hypoxic high-intensity interval training (HHIT) versus normoxic HIIT.
• To assess the impact of HHIT on cardiorespiratory, metabolic, hormonal, and performance variables in elite runners.

Main Methods:

• Eight highly trained young runners completed 5x3-minute intervals at 90% vVO2max in normoxia (N) and simulated 2,400m altitude (H).
• Measurements included cardiorespiratory responses (VE, VO2, HR, SpO2), perceived exertion (RPEc), blood lactate, bicarbonate, EPO, neutrophils, and performance tests (sprint, jump).

Main Results:

• HHIT elicited similar ventilation but lower oxygen consumption, heart rate, and oxygen saturation compared to normoxic HIIT.
• Perceived exertion was significantly higher during HHIT.
• Changes in lactate, bicarbonate, and EPO were possibly greater with HHIT, while neutrophils were likely lower. Sprint performance may have slightly improved with HHIT, but jump performance and heart rate variability showed no clear differences.

Conclusions:

• HHIT is perceived as more strenuous but does not impose an exaggerated physiological load compared to normoxic HIIT in highly trained athletes.
• HHIT may not be the optimal training strategy for concurrently enhancing both the cardiorespiratory and neuromuscular systems influencing running performance in this population.