It's not often the Duchess of Cambridge opts for a sleeveless dress, generally preferring to cover up in coat dresses while home in the UK. But when carrying out engagements in warmer climes, her sculpted arms occasionally put in an appearance.
The royal - along with Prince William - arrived in Trench Town in Jamaica on day four of their Caribbean tour, with Kate wearing a sleeveless dress as her third outfit of the day.
During their visit to the birthplace of reggae music, Kate, 40, stood out in an altered Willow Hilson Vintage dress.
While the 1950s stripped coral and turquoise dress previously sported spaghetti straps, the bodice appears to have been amended to create thicker straps for the royal.
The dress revealed the duchess' toned arms and prompted us to dig into her workout regime.
The duchess is a well-known fan of cardio - in particular, running. Appearing on House of Rugby, Mike Tindall was asked which royals he'd like on his rugby team, to which he said, "I've got the Duchess of Cambridge on one wing because she loves running, she can run all day. Engine!"
It seems her sporty nature runs in the family. "Kate is an exercise junkie. Pippa and Kate take their toned physiques extremely seriously. And mother Carole, in her 60s, is in extremely good shape," a royal insider previously told the Daily Mail.
The source revealed Kate's secret is the plank. "It tightens her muscles," they said. "There are three elements, the basic plank, the side plank and the prone sky dive, all of which are positions Kate can hold for 45 seconds or longer and repeat at least 10 times each."
Watch: Prince William and Kate meet Jamaican governor-general
Kate was an advocate for CrossFit in its earlier days, which involves a combination of resistance training, weights, running and squats, and can improve health, performance or aid weight loss. The insider said she had reached "almost army fitness level" - all without a personal trainer.
She also reportedly has a membership at Harbour Club in Chelsea, a luxurious gym space in West London, where her mother-in-law, Princess Diana, went, as well as access to one conveniently in Kensington Palace.
Away from the gym, Kate has a keen interest in tennis, as a regular at Wimbledon and a patron of the Lawn Tennis Association. She's even played on the court with US Open champion and first British woman to win a Grand Slam singles title since the 1977 Wimbledon Championships, Emma Raducanu.
Raducanu even said Kate's "forehand is incredible" and that she was "very, very impressed", to ITV News reporters after the match.
The duchess is able to practice on her own court at Anmer Hall, her country house in Norfolk.
In terms of overall fitness, it's thought the duchess used the so-called Louise Parker method to increase her strength after giving birth.
The Four Pillars of the method, according to the company's website, are 'eat beautifully', 'move intelligently' 'think successfully' and 'live well'.
This includes a range of balanced food tailored to you with 'no shakes, no supplements, no points', moving everyday with exercises you enjoy, rewiring your behaviour patterns to 'support your motivation' and incorporating lifestyle hacks that 'save time, simplify your lifestyle, and create space for you to prioritise your wellbeing'.
Other activities Kate has been known to enjoy include yoga, walking, skiing, skipping, indoor rowing and intense interval training, with her Swiss gym ball once a favourite to maintain toned abs.
The Duke and Duchess of Cambridge even made their public debut as a couple on a ski trip in Switzerland in 2004.