Exercise-induced Fatigue in Severe Hypoxia after an Intermittent Hypoxic Protocol

Area of Science:

• Exercise Physiology
• Altitude Training
• Neuromuscular Fatigue

Background:

• High altitude acclimatization alleviates exercise-induced central fatigue.
• Adaptations to high altitude may be induced by intermittent hypoxic (IH) exposures.
• Investigating IH as a method to improve exercise performance in hypoxia.

Purpose of the Study:

• To determine if exercise tolerance in severe hypoxia improves after an IH protocol.
• To assess if IH alleviates exercise-induced central fatigue.

Main Methods:

• Nineteen men underwent ten 2-h exposures in severe hypoxia (IH) or normoxia (control).
• Seven sessions included 30-min cycling at 25% peak power in IH or matched heart rate in normoxia.
• Neuromuscular fatigue was assessed using transcranial magnetic and femoral nerve stimulation before and after cycling to task failure.

Main Results:

• Intermittent hypoxic exposure significantly improved time to task failure in severe hypoxia.
• The reduction in maximal voluntary contraction and cortical voluntary activation was attenuated after IH.
• No significant improvements were observed in the control group.

Conclusions:

• Whole-body exercise tolerance in severe hypoxia is prolonged following an IH protocol.
• The observed improvement is likely linked to an alleviation of the central component of neuromuscular fatigue.
• Intermittent hypoxia may be an effective strategy to enhance exercise capacity in hypoxic conditions.