Intermittent hypoxia enhances voluntary activation and reduces performance fatigability during repeated lower limb...

Area of Science:

• Neuroscience
• Exercise Physiology
• Rehabilitation Science

Background:

• Acute intermittent hypoxia (AIH) shows therapeutic potential for motor deficits post-spinal cord injury.
• The precise link between AIH-induced excitability changes and functional performance needs clarification.
• Discrepancies in AIH effects on excitability in able-bodied individuals warrant further study.

Purpose of the Study:

• To investigate the impact of repetitive AIH on voluntary activation and spinal reflex excitability.
• To determine if AIH mitigates performance decrements during fatiguing contractions.
• To clarify the functional implications of AIH for muscle force production.

Main Methods:

• Four consecutive days of AIH intervention were administered.
• Voluntary activation was assessed using the central activation ratio during repeated maximal plantar flexion contractions.
• Changes in torque generation, spinal reflex excitability, and antagonist coactivation were measured.

Main Results:

• Repetitive AIH significantly increased voluntary activation and peak torque during fatiguing contractions.
• No significant changes were observed in resting spinal reflex excitability.
• Antagonist muscle coactivation during fatiguing contractions remained unchanged post-AIH.

Conclusions:

• Repetitive AIH reduces performance fatigability by enhancing descending neural drive.
• AIH may be a valuable therapeutic strategy for promoting motor recovery after neurological injury.
• Optimizing voluntary activation is key for functional recovery, particularly in walking.