Why was Andy Murray so upset about using a women's ball at Miami Open?
Just a week on from the reopening of the debate around equal pay in tennis, Andy Murray found himself at the centre of another gender-related tennis issue over the weekend.
Murray has been a big advocate of equality in the sport, but on Saturday he was enraged when he was mistakenly given a tennis ball from the women's tour to use during his second-round win against Denis Istomin at the Miami Open.
The world No.2 confronted umpire Mohamed Lahyani and said: "That's one of the women's balls and I could have hit a shot with it."
At the next change of ends, Murray continued: "For me that's not good enough, it's unacceptable. Unacceptable to have one of those balls in there."
Many observers were surprised to hear that the ATP and WTA tours do not use the same balls, so what exactly is the difference between the two, and was Murray justified in being so exasperated?
First of all, the two balls are the same in size and pressure, but in most events, including Miami, men use extra-duty felt, which slows the overall speed, while women use regular-duty felt.
The balls also have a different logo on them, which alerted Murray to the fact that something was up.
Ball manufacturers suggest that club players should use extra duty felt on hard courts and regular felt on clay courts, as the former get too fluffy on clay courts, while the latter quickly become too worn on hard courts.
In practical terms, the women's ball feels lighter and can fly off the racket, especially to the unsuspecting user, as Murray feared he may have been earlier in the match.
As he said after beating Istomin: "I was a bit frustrated because I’d just missed two balls long, and I didn’t know if that was one of the balls that I’d used in the last couple of points.”
Clearly at the top level of tennis, those small margins can be critical, and research suggests that a switch in ball can have huge effects on speed and ball action.
Bob Bryan, who uses both balls on the men's and mixed doubles circuit, believes he can add around six mph to his serve when using the lighter ball.
Bryan's claim was backed up by York University (Canada) tennis coach Michael Mitchell, who has studied the game for more than 25 years.
“They (the men) would probably hit the serve 175 miles per hour if they were using that (women’s) ball, ” Mitchell said in 2012.
The debate around the different balls was ignited four years ago by Andy Roddick finding himself in the same position as Murray. On that occasion, Roddick was about to serve in a match at the US Open when he realised he'd picked up a women's ball. The American said he could instantly notice the difference, and after the match commented: “See, the women use a different ball than we do, and I did what I normally do, get three or four balls and look for the one that looks the lightest to serve.”
Roddick resisted the temptation to serve with the women's ball and see if he could record his quickest ever serve.
Not everyone though is convinced that a lighter ball necessarily equates to greater velocity.
Rick Janes, who is the Technical Consultant at Asics Tennis Racquets, says a lighter ball may actually slow down quicker.
He said: "A lighter ball slows faster. Think of badminton. When they swing at the shuttlecock, it’s going really fast. But, within six feet, it literally stops, like a parachute effect.”
Either way, Murray now has bigger things to worry about, after being eliminated from the Miami Open at the third round stage by Grigor Dimitrov yesterday.
Murray had looked to be in control after winning the first set on a tie-break but eventually lost 6-7, 6-4, 6-3, and the premature exit follows his third-round loss at Indian Wells last week.