The Hoffmann reflex is different in men and women

Area of Science:

• Neuroscience
• Human Physiology
• Endocrinology

Background:

• The Hoffmann reflex (H-reflex) is a measure of spinal cord excitability.
• Sex hormones, such as estradiol and progesterone, are known to influence neuromuscular function.
• Previous research has not directly compared H-reflex responses between sexes under controlled hormonal conditions.

Purpose of the Study:

• To investigate potential sex differences in the H-reflex response.
• To compare the maximum H-reflex to M-wave (H:M) ratio between men and women.
• To control for the influence of estradiol and progesterone levels during testing.

Main Methods:

• Cohort study design with healthy male and female participants (mean age 22.4±3.4 years).
• Assessment of the maximum H:M ratio of the H-reflex.
• Saliva samples were analyzed to ensure similar estradiol and progesterone levels in all participants at the time of testing.

Main Results:

• Female participants demonstrated a significantly higher H:M ratio compared to male participants.
• No significant differences were found in saliva levels of estradiol and progesterone between sexes.
• This study is the first to report sex differences in the H:M ratio under similar hormonal conditions.

Conclusions:

• Women exhibit greater spinal cord excitability, as indicated by a higher H:M ratio, compared to men.
• These differences persist even when estradiol and progesterone levels are comparable.
• Findings suggest intrinsic sex-based variations in neuromuscular control that warrant further investigation.