Soleus Hoffmann-reflex modulation during walking in healthy elderly and young adults

Area of Science:

• Neuroscience
• Biomechanics
• Gerontology

Background:

• The soleus Hoffmann reflex (H-reflex) is a measure of spinal reflex excitability.
• Age-related changes in motor control and neural mechanisms are common.
• Understanding reflex modulation during locomotion is crucial for assessing functional mobility.

Purpose of the Study:

• To investigate age-related differences in soleus H-reflex modulation during the walking cycle.
• To compare H-reflex size between young and elderly adults across different phases of gait.
• To explore potential implications for ankle stiffness and neural drive in older adults.

Main Methods:

• Measured soleus H-reflex amplitude in 7 young and 13 elderly adults.
• Recorded H-reflex size across 16 discrete time divisions of the walking step cycle.
• Compared H-reflex modulation during walking and while standing.

Main Results:

• Both age groups showed a similar pattern of H-reflex modulation during walking: minimal at heel contact, maximal after midstance, decreasing towards toe-off, and minimal during swing.
• A significant interaction between age and step cycle phase was observed (p < .05).
• Elderly participants displayed significantly smaller H-reflex sizes during two specific midstance phases compared to young adults (p < .05), despite no standing differences.

Conclusions:

• Reduced H-reflex size during the stance phase of walking in elderly individuals suggests altered central reflex mechanisms.
• These changes may contribute to diminished stretch reflex contribution to ankle extensor neural drive.
• Potential implications for reduced ankle stiffness during walking in the elderly population.