Beyoncé used to run and sing her album at the same time.

According to her former trainer, Mark Jenkins, this helped build up her stamina.

Beyoncé also used to use this technique when her father was her manager.

Jenkins suggested aerobic exercises and interval circuits for people who don't want to get winded.

Mark Jenkins has trained celebrities for more than 25 years — and he's never met anyone as focused as Beyoncé.

"No quit," Jenkins said of the singer at the Burner fitness app launch event. "[Beyoncé] would look and then she would do [the exercise], she was very very focused."

One thing that Jenkins, and Beyoncé's father and former manager, Mathew Knowles, had the singer do was run and sing at the same time. Jenkins noted that he didn't just make Beyoncé sing, but sing her entire album as it sounds on the album.

"It was a long time ago, but I had her run through her album [...] in the Georgia heat," Jenkins told INSIDER. "That'll do it because then you can sing and dance if you were running and [you] could make it sound good."

A post shared by Beyoncé (@beyonce) Sep 12, 2016 at 9:08pm PDT

Jenkins has his other clients, including singer D'Angelo and Raphael Saadiq, do the same thing.

"I just finished 60 days with Raphael Saadiq, and he's 5-foot-1," Jenkins said. "We used the [altitude] mask, and we ran through the California hills."

The altitude mask is a popular fitness accessory used to make your lungs stronger and increase your "ventilatory threshold," according to one study. Essentially, it lowers the amount of air you can breathe and is marketed as a way to make your lungs stronger, as Tonic reports. The verdict, however, is still out on the effectiveness of the product.

Although the mask wasn't available when Jenkins was working with Beyoncé, he said he would have "absolutely" had her use it. One product he did have her use was a parachute: not to jump out of planes but to add resistance to her running which, according to The Runners Guide, helps to improve strength and speed.

Jenkins had Beyoncé perform aerobic exercise — with or without accessories — so she could sing and dance without getting winded. And that same trick can work for mere mortals. He suggested doing interval circuits to build stamina and make the most of your time — both of which busy mom, singer, and designer Beyoncé needs.

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