Peripheral joint cooling increases spinal reflex excitability and serum norepinephrine

Area of Science:

• Physiology
• Neuroscience
• Sports Medicine

Background:

• Peripheral joint cooling is used to alter reflex excitability.
• The physiological mechanisms underlying these alterations are not fully understood.

Purpose of the Study:

• To investigate the effect of ankle cryotherapy on plasma norepinephrine levels.
• To determine if cryotherapy influences the H:M ratio, a measure of reflex excitability.

Main Methods:

• Twenty-two adults underwent two experimental sessions: one with ankle ice application and one with a control (room temperature marbles).
• Measurements included soleus Hmax, Mmax, H:M ratio, and plasma norepinephrine at various time points before, during, and after application.
• Statistical analysis was performed to compare measurements between conditions.

Main Results:

• Plasma norepinephrine levels were significantly higher immediately and 10 minutes after ice application compared to the control.
• The H:M ratio, Hmax, and Mmax were significantly elevated 10 and 20 minutes post-application and post-removal of ice.
• These changes indicate increased reflex excitability following cryotherapy.

Conclusions:

• Ankle cryotherapy increases plasma norepinephrine, suggesting a central nervous system response involving neurotransmitter release.
• Joint cooling affects both peripheral and central nervous system mechanisms.
• Cryotherapy enhances reflex excitability, with sustained effects even after cold removal.