Changes with age in monosynaptic reflexes elicited by mechanical and electrical stimulation

Area of Science:

• Neurology
• Gerontology
• Physiology

Background:

• The Achilles tendon reflex (T) shows inconsistent age-related changes in scientific literature.
• Age-related alterations in the Hoffmann reflex (H) are not well-documented.

Purpose of the Study:

• To compare Achilles tendon reflex (T) and Hoffmann reflex (H) in healthy young and old adults.
• To investigate potential fusimotor involvement in age-related changes of monosynaptic reflexes.

Main Methods:

• Stimulus-response data collection for both T and H reflexes.
• Comparison of mechanically and electrically elicited reflexes between young and old cohorts (n=20 each).

Main Results:

• No significant age-related difference was observed in the response:stimulus ratio for the T reflex.
• H reflex amplitude was 32.7% smaller (P<0.04) and M waves were 24% smaller (P<0.025) in older adults.
• No significant age differences were found between mechanically and electrically elicited reflexes.

Conclusions:

• Age does not significantly affect the Achilles tendon reflex (T).
• Monosynaptic reflex changes in aging are characterized by reduced H reflex and M wave amplitudes.
• The findings do not support fusimotor system involvement in age-related monosynaptic reflex alterations.