Tennis star Iga Swiatek has baffled fans after training with tape over her mouth, leaving fans baffled by the bizarre display.

The 22-year-old World No. 1 had people wondering what was going on after she was spotted preparing for the Canadian Open.

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Pictures released from her training sessions ahead of the event showed the Pole had tape over her mouth as she swung her racket.

Swiatek then took it off at the end of the practice – but it left fans asking online what the benefits of the strange manoeuvre was.

One fan tweeted that they were “very intrigued/confused by this” as another simply replied asking: “What?”

Tennis journalist Kamakshi Tandon wrote: “A lot of coaches are going to be very interested in this new training method.”

And a fellow fan even joked: “How I need to train for every meeting with my extended family.”

However, one apparent expert on the technique revealed on Twitter that Swiatek was “training for nose-breathing”.

They said: “It’s a more efficient and effective method of oxygen delivery to the body’s muscles, whoever has her training this way is smart tbh.

“They’re aiming for maximum endurance and knowing Iga, she’ll get there.”

And Swiatek then provided the explanation herself, although she admitted that she was not fully sure what the full benefits would be.

“It’s harder to breathe when you are only breathing through your nose and it is easier for my heart rate to go up … but I am not going to be able to explain it properly because I am not an expert,” Swiatek confirmed.

Swiatek is hoping to continue an impressive 2023 in Canada following her French Open success in June.

And just last week she lifted the Polish Open on home turf after a 6-0, 6-1 victory over Laura Siegemund.

She has received a first round bye at the Canadian Open and will be in action on Wednesday against an as-yet unknown opponent.