Modulation of the triceps surae H-reflex with training

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• The spinal stretch reflex, like the soleus H-reflex, is crucial for maintaining posture and balance.
• Adaptability of spinal reflexes is essential for motor learning and functional adjustments in the central nervous system.
• Understanding reflex modulation during balance tasks provides insights into sensorimotor integration.

Purpose of the Study:

• To investigate the modulation of the soleus H-reflex during a short-term balance training task in healthy adults.
• To determine if balance training leads to a reduction in H-reflex gain.
• To explore the potential for spinal stretch reflex adaptation with practice.

Main Methods:

• Thirteen neurologically healthy adults performed balance tasks on a single-axis rotating board.
• Soleus H-reflexes were elicited using electrical stimulation and recorded alongside muscle activity (triceps surae, tibialis anterior).
• Maximal M-waves were measured to ensure consistent H-reflex assessment across trials.

Main Results:

• Subjects significantly reduced soleus H-reflex gain during and after balance training (p < .001).
• On average, H-reflex amplitude decreased by 26.2% from initial to final balancing blocks.
• A significant reduction in standing control H-reflex gain was also observed, indicating longer-term reflex adaptability.

Conclusions:

• Short-term balance training induces a progressive reduction in H-reflex gain.
• This H-reflex modulation suggests functional adaptation within the central nervous system.
• The findings support the role of spinal reflex plasticity in motor learning and postural control.