The next breakthrough in exercise could be the work of some young inventors from New Jersey.

They are about to showcase their creation on a national stage.

77-year-old Evelyn Guantanino lives with her granddaughter Melissa Phalen, one of the co-creators of this new machine, Tred-Med.

"Her health hasn't been so good lately so we really wanted to help her because we wanted to have her around longer," says Melissa.

So she enlisted three fellow 7th graders at Saddle Brook Middle School to create an exercise machine to help Evelyn regain mobility after a hip replacement.

The girls retrofitted an old treadmill they found on Craig's List with resistance bands for the upper body, a pedometer and timed music intervals.

Most importantly, they removed the motor so that seniors power the machine completely on their own giving them full control either sitting or standing without having the fear of falling. 

"We want them to experience a fairly light to somewhat hard exercise because that really shows that they're really working out their body, their upper and lower extremities," says Christine Rocchio, co-creator of Tred-Med.

The creators, Melissa, Julianna, Sarah and Christine researched at the library, conducted interviews with seniors and doctors, and worked with their teacher, Marilyn Ryan to perfect the Tred-Med and entered it into the Christopher Columbus National Science Awards Competition. 

The girls were chosen as one of 30 semi-finalists out of 400 entries.

"I've seen that prizes are a good motivator, but the real prize was getting out into the community and finding out that they can make a difference," says Marilyn Hamot.

According to their mentor, sports therapist Dr. Robert DeStefano, the Tred-Med could truly help seniors avoid some of the problems that can arise from inactivity.

Evelyn Guantanino says she'd buy the machine because it's fun and because she'll do whatever it takes.

"There's no price tag on being able to walk better, you know. It makes you feel good," says Evelyn. 

A professional treadmill like can cost up to $6,000, but Dr. DeStefano says that the girls should probably charge about a sixth of that for theirs, so it's accessible to everybody. 

He also believes the girls should patent their idea as soon as possible.

"I think there's some competitive pieces of equipment for it, but nothing that combines everything that this is offering, so I think it's a viable product," says Dr. DeStefano.

The girls compete in the national finals next week at Disney World for the grand prize of $25,000 for product development.