Scalp muscle contractions can reduce blood flow to the scalp, potentially leading to lower transcutaneous oxygen levels in balding regions.

“well when these scalp muscles contract they reduce blood flow to the top of the scalp because they pinch off the carotid arterial the subarterial artery bands that then indirectly supply the top of the blood to the scalp there was a study by goldman in 1996 that demonstrated that uh transcutaneous oxygen levels to balding regions were 40 percent lower than non-balding controls and his presumption is that this effect couldn't be explained by general hair follicle miniaturization itself it had to be a physiological roadblock and the only thing that would explain this is the contraction of these scalp perimeter muscles that pinch off these carotid arterial branches and then the lower blood supply to the top of the scalp”