68-year-old fitness instructor makes for popular sweat sessions

HOUSTON (KTRK) -- When 68-year-old Ellen Goren took over teaching fitness classes at the Evelyn Rubenstein Jewish Community Center of Houston, it was quite the surprise.

"I said, 'There's no way this lady's going to be a teacher,"" recalls Daniel Levin.

"I walk in the class, and they take one look at this tiny little old lady, and they say, 'Oh this is going to be easy,'" said Goren.

Clients like Levin got a rude awakening.

"We started, and oh my god, I can't do anything she can do. She is intense," said Levin.

"By the time they're 10 minutes into the class, I usually say something like, 'Don't go home and tell your significant other that your grandma was lifting more weights and more reps than you.' And they laugh," said Goren.

But no matter how much Goren kicks their butts, they still keep coming back for more.

"I was sore. I had a hard time sitting down to use the restroom," said Pamela Bercutt.

"It's a surprise that somebody my age, my size is slamming it to them. And I like that," she added.

Goren's toughness comes from 35 years in a tough profession as a corporate attorney. She only started her fitness journey a decade ago.

"I was diagnosed with osteopenia, which is low bone density in my spine, so I said to my doctor, I don't want you to give me drugs, I want you to send me to a physical therapist," explained Goren.

Her physical therapy sessions soon turned into aerobic classes.

"I did a little Zumba, and then body pump, and before I knew it, I was lifting like a champ. I couldn't stop," remembered Goren.

Now, she spends each day personal training and pushing people to reach their fitness goals.

"I center my career around having people exceed their perceived limitations, so if they come in and say 'I can't do this. I can't lift heavy,' my goal is to help them to see how they can do it," she said.

She's known for her calorie-burning bootcamps and body-burning pilates classes.

And her best advice when it comes to finding the motivation to get in shape--a simple two words.

"Don't wait. Don't wait," said Goren.