The stronger a man's handshake, the more functioning of his penis according to science.
Researchers have found every 5kg increase in hand grip strength relates to an 18 per cent decrease in the likelihood of erectile dysfunction.
The study, by Chonnam National University in South Korea, suggests that a loss of muscle can lead to problems in the bedroom. Apparently declining testosterone affects the strength and performance of the penis.
"The principal finding of the present study was that men with lower hand grip strength had a higher risk of moderate to severe erectile dysfunction," wrote the authors of the study.
"Also our study demonstrated that erectile dysfunction was significantly associated with age, haemoglobin, self-related health and physical activity in ageing men."
For years, vigorous handshakes from men were deemed only a display of supposed power and dominance. They were usually linked to strength, but not necessarily down below.
There are numerous accounts of businessmen and politicians affirming their ambitions to gain the upper hand by greeting peers and counterparts with fierce grips.
Political analysts have long been interested in the likes of Donald Trump, who appears to 'grab' the hand of another person before yanking it firmly towards him. Could it be a sign of insecurity too?
The research charted 1,771 men over the age of 50 and gauged the strength of their grip. Measurements of their erectile capabilities ranged from mild, mild to moderate, severe, to non-existent.
Handshakes were analyzed using a mechanical dynomometer, which measures how much mass someone can compress incrementally by 5kg.
Men tend to weaken as they age. This brings with it a number of health problems, including erectile dysfunction.
The research, which was published in science journal The Ageing Male, found: "Handgrip strength measured in a sitting position represent the muscle strength of forearm and upper extremities, and measured in a standing position can include lower extremities and core muscle strength."
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