The post-tennis arm-wrestle handshake
The post-match handshake is a traditional part of tennis etiquette. But in recent years, the polite gesture - fitting of a supposed gentleman's game - seems to have undergone a makeover, writes Vanessa Barford.
Something may have grabbed the attention of Wimbledon fans.
The old-school post-match handshake - the kind you would see replicated in polite company or in business meetings - is out.
Instead, when two adversaries signal the end of hostilities, a modern - although curious to some - thumb-gripping clench is very much in.
When two players engage in this manoeuvre across a net, it looks like a cross between a high-five and an arm wrestle. You might call it the "arm-wrestle handshake".
"This handshake is a bit more rock and roll, it's got an edgy masculinity," says sports historian Dr Martin Polley of the University of Southampton.
The trend has been getting more common on the tennis circuit for a while. But now, it's dominant.
Polley says a variety of handshakes are common in sport, with cricketers "biffing gloves" and basket ball players constantly "low-fiving" each other after every shot.
But no-one can identify the moment the change started in tennis. It might be identified as North American in origin and there's even idle speculation about the shake having its roots in African-American youth culture.
Hollywood may also have had an influence. A scene from the 1987 sci-fi film Predator, in which Arnold Schwarzenegger greets Carl Weathers with a handshake that turns into an arm-wrestle, has become a popular online meme.
Both informal and combative, the move is particularly well-suited to sport, says behavioural scientist Kory Floyd of Arizona State University.
"For the winner in a tennis match, it may represent one last expression of dominance over the loser," he says.
However, former British number one tennis player Andrew Castle isn't convinced.
"I love a decent handshake at the end of the game - it's wonderful when you've been through something together to signify the end of the contest," he says.
"But at the age of 49, attempting the hand slap and getting the contact wrong or it turning into a man hug could be mortifying. It's like when men greet each other with a gentle right shoulder-dip to suggest friendship - it's fraught with potential embarrassment."
The move may be ubiquitous in Wimbledon, but its origins remain obscure. If you have your own theory about how and where it started, let us know using the "send us a letter" form on the right of this page.