Sir Rod Stewart has shared how one health trick has helped him maintain a long and successful career, which is set to continue with his upcoming performance at the Glastonbury festival. For decades, Sir Rod has been a household name thanks to sell-out tours around the world as well as regularly shooting to the top of the charts during the peak of his stardom. Rising to fame in the early 1970s, it wasn't until the release of his third album, Every Picture Tells A Story, that he surged to world-wide acclaim, with the record reaching the number one spot in the UK, USA, Canada, and Australia. Now, aged 80, the Da Ya Think I'm Sexy singer still has fans clamouring for his every word as he travels from country to country during his sell-out tours. But with many wondering how he still has the stamina to perform at such a high level despite his age, he recently shared a potential clue while speaking at the US retirees' organisation AARP. Sharing how one conversation with the beloved American singer, Frank Sinatra, led to him adopting a health trick, he said: "Frank Sinatra once said to me, 'Rod, the secret to being a great singer is having powerful lungs. Do lots of underwater swimming, where you hold your breath.'" And, sharing how he has followed the singer's advice over the years, Sir Rod added: "I have an indoor pool, gym, golf course. The trainer throws a brick into the pool, I have to dive in, push the brick to the end, and come up." While holding your breath underwater for too long can be dangerous, there are some benefits to our lungs when doing so in short bursts. According to Medical News Today, it can help the lungs to send oxygen to the body’s organs efficiently. However, despite recently sharing how he practices one health hack, his health has taken somewhat of a hit in recent weeks with the star reportedly suffering from a bout of flu. As a result, fans were left disappointed after a number of his US shows were postponed at short notice, with Sir Rod informing his Instagram followers that he was cancelling four dates and postponing a further two, writing: "So sorry my friends," and added: "I'm devastated and sincerely apologise for any inconvenience to my fans. I'll be back on stage and will see you soon." But, he is set to return to the stage later this month at the Glastonbury festival, the first time that he will have played there since 2002.