A celebrity personal trainer has tragically died in the gym.

Mexican-based trainer Einar Méndez was aged 48 at the time of his sudden death.

The announcement was made on his official Instagram account with a video featuring his wife, Yan.

Sitting on a lounge in dark clothes, a cap, and large sunglasses, she told his 46,700 followers in Spanish that her husband had died of a “sudden heart attack” on September 4 after a gym workout, People reported.

“He was strong, resilient, kind,” she said in a translated quote.

“Everyone who knew him knows exactly who Einar Méndez was.”

Ms Méndez said that he was “fiercely dedicated to his work”.

“He wanted to help many people who didn’t have the means to learn training technique,” she continued.

“He wanted to start a foundation, to help everyone without resources.”

She went on to slam those “speculating” about his shock death.

“Let him rest in peace,” she said.

“We’re in deep pain with a void that will never, ever be filled.”

A translated caption of the post read, “Rest In Peace Love Of My Life. Fly high and I promise we will meet again”, followed by emojis of a dove, shell, and white love heart.

Among his celebrity clients was Mexican TV host Martha Debayle, who worked with Méndez for nine years.

In a lengthy tribute on her Instagram, the television personality wrote that she was “deeply saddened” by his death.

“Before he was a coach, Einar was Yan’s husband, his wife for 30 years, and a father to his three daughters,” she wrote.

“And that’s where today it becomes impossible to measure this loss.”

Debayle said he “died doing what he loved most: working out”.

“I’m going to miss you so much,” she added.

“And I know there won’t be a day I train and don’t think about you.”

Méndez will be farewelled on September 13.