Destiny's Child's gruelling stage and exercise combination was encouraged by Beyonce's dad, Mathew Knowles. Photo / Getty Images

Beyoncé sang while running on a treadmill as part of her Olympics-style training with Destiny's Child.

Her former bandmate Michelle Williams, 43, said the gruelling stage and exercise combination was encouraged by Beyoncé's dad Mathew Knowles, 70, who used to manage the R&B group.

Williams told Australia's KIIS FM: "That was training for all the girls in Destiny's Child.

"He [Mathew] was a great coach. I would liken him to a coach who wanted to make sure his team gets the championship."

Destiny's Child, which also featured Kelly Rowland, were formed in Houston, Texas, and debuted in 1997 with the single No No No before disbanding in 2006 after racking up 60 million in global record sales.

They have reformed for several life performances, including the Superbowl in 2013.

Williams talked about her past in the band after she was unmasked on the Australian version of The Masked Singer on Tuesday night.

Former Spice Girl Mel B was left speechless after she managed to guess the singer's identity, exclaiming: "I knew I knew that voice. I knew it. I knew it. You are amazing."

Williams replied: "From one girl group to another girl group who is the blueprint who paved the way.

"The times when we were in London, all those times in the early 2000s, we would be meeting everybody, but not the Spice Girls!"

Williams also said the significance behind her performance of 'Say Something' by A Great Big World and Christina Aguilera was down to her break-up last year with fiancé Chad Johnson.

She said: "It's no secret I was engaged and it did not work out. I just remember those words. It kind of articulated this is what I've been wanting to say.

"It's until you really emote it in full voice, it was almost like therapy. And so it just came out in that way. That's what music can do to you when you just let it go."