Impaired Hyperemic Response to Exercise Post Stroke.

Area of Science:

• Neurology
• Physiology
• Rehabilitation Medicine

Background:

• Individuals with chronic stroke often exhibit reduced resting blood flow in the paretic lower limb.
• The hyperemic response (increased blood flow) to muscle contractions in stroke survivors has not been thoroughly investigated.

Purpose of the Study:

• To quantify and compare the blood flow response to graded knee extensor muscle contractions in the paretic and non-paretic lower limbs of chronic stroke survivors and healthy controls.
• To correlate these blood flow measures with lower limb function and physical activity levels in stroke survivors.

Main Methods:

• Superficial femoral artery blood flow was measured using ultrasonography in 10 chronic stroke survivors and 10 controls.
• Blood flow was assessed before and after 10-second knee extensor contractions at 20%, 40%, 60%, and 80% of maximal voluntary contraction (MVC).
• Measurements were normalized to lean muscle mass and correlated with limb strength, coordination, and physical activity.

Main Results:

• Stroke survivors showed significantly reduced blood flow in both paretic and non-paretic limbs across all contraction intensities compared to controls, even after normalization.
• Increased blood flow following an 80% MVC contraction was the strongest predictor of paretic limb strength, inter-limb strength symmetry, paretic limb coordination, and physical activity.
• The impaired hemodynamic response to high-intensity exercise was a more significant predictor of lower limb function than resting perfusion.

Conclusions:

• The reduced hyperemic response to muscle contraction in chronic stroke is not solely explained by limb-specific weakness or atrophy, as the non-paretic limb also shows impairment.
• These findings highlight a potential role for therapies targeting vascular perfusion to improve lower limb function and rehabilitation outcomes post-stroke.