Want a free workout to treat your holiday hangover?

WeTrain, a Philly start-up, is offering one free workout session - if you send the company a message using social media. And you have to mention that the company just won Philly's version of the hit television show Shark Tank.

A 30-minute session regularly costs $17 or $25, if you split it with another person.

Philly's version of the television show is called Veteran Shark Tank. And the winners were Zachary Hertzel and Jon Sockol, co-founders of the start-up WeTrain, at the Dec. 7 competition at the Cira Centre next to Amtrak's 30th Street Station.

WeTrain supplies on-demand personal trainers who will come to your house or local park for 30- to 60-minute sessions. "All the money goes to the trainer, instead of to a gym," Hertzel said.

Philly is a hotbed of start-ups. Hertzel, a former Army flight medic, is a graduate student at Thomas Jefferson University, while Sockol is a Wharton School M.B.A. candidate.

Hertzel grew frustrated with the fitness-gym business model after working as a certified master trainer for eight years, but missing out on the profits.

"In the gym industry, the national average fee is $60 for an hour. They only pay $10 or less an hour to the trainer, and it's expensive for the client," he said.

Hertzel was part of a team inventing the Stair Angel at Jefferson JAZ Tank incubator competition. (Stair Angel helps the elderly or disabled navigate stairs.)

"WeTrain's model is on-demand. You hit the app on your iPhone, and a nationally certified and vetted trainer shows up in 15 minutes," Hertzel said. "All the money goes straight to the trainer, and we do high-intensity workouts."

So far, 45 trainers have signed up with WeTrain in Philadelphia, and it says it expects to expand to the suburbs in 2016.

This year's third annual Veteran Shark Tank attracted such vets as Hertzel, who was deployed twice, for a year in Iraq and another year in Afghanistan.

The brainchild of Alex Archawski, founder and director of the Greater Philadelphia Veterans Network, Veteran Shark Tank helps seed start-ups founded by veterans.

"The WeTrain app had only been out two weeks when they pitched at the Shark Tank," Archawski said.

WeTrain also allows trainers to earn equity in the business.

"WeTrain trainers are all independent contractors and set their own hours. But we have a sweat-equity program in which a chunk of the company is set aside for trainers who earn points. When the company IPOs or sells they get a monetary reward," Hertzel said.

"Trainers have been abused for so long that this is really revolutionary. If you were an Uber driver for a $68 billion company [Uber Technologies], and you were allowed to earn equity, why wouldn't you? That doesn't exist anywhere. We figured it out."

Sockol expects to earn his M.B.A. this spring. Mitch Burdy is WeTrain's marketing director.

Hertzel is the only veteran on the founders team, but there are also five veterans among the trainers, and that makes for a hard-core workout.

"We work high-intensity interval training - that's our business - and military individuals are highly qualified. That's how they get all their exercise. We call them 'smoke sessions,' " Hertzel said.

"Interval training is the best way to lose weight, and not in the gym. We do it anywhere, in your living room or out in the park."

A one-hour session is a hard workout, but "you can sit down during rest breaks, and trainers provide education. You'll go home sweaty and burn calories."

Meanwhile, the judges for recent 2015 Veteran Shark Tank were Robert Moore, co-founder and CEO of RJ Metrics; Danielle Cohn, director of entrepreneurial engagement at Comcast; Mike Maher, co-founder and CEO of the real estate brokerage Houwzer (a previous Veteran Shark Tank winner); and Margaret Bradley Berger, executive director of the Goldman Sachs 10,000 Small Businesses Initiative.

Maher said Veteran Shark Tank helped put his start-up company Houwzer on the Philadelphia business map. He previously founded Benjamin's Desk, the Center City co-working space.

Houwzer is on track for $75 million in sales in its first year and saved consumers more than $500,000 in listing commissions in its last six months, he said. Houwzer bypasses the traditional real estate brokerage and allows homeowners to list their own houses.

"We turned down early stage capital from several angel investors and a small venture capital firm out of San Francisco to bootstrap Houwzer, which is now doing $50,000 a month," Maher said.