Sweat–flow synchrony predicts skin cooling

A proposed mechanism asks why ageing skin may cool poorly even when average sweating and blood flow appear intact. It proposes that heat loss depends on timing: sweat arrives as blood vessels carry heat to the skin. Under a constant, moderate heat load, the proposed test would measure sweat pulses, skin blood flow, temperature and actual heat flux, the heat leaving the body. It would compare matched blood-flow pulses timed with sweat secretion against pulses shifted half a cycle away. The prediction is greater heat loss over minutes only with synchrony, despite equal average sweat and flow. The test must change timing without directly altering sweat glands and account for heat added by the apparatus. It could identify a hidden heat-loss deficit in middle-aged skin.