ALLEN PARK, Mich. -- He finished his workout, got in his car and drove 1.8 miles from the Detroit Lions' practice facility to a Starbucks inside a Barnes & Noble. Zach Zenner sat down, opened up his laptop and began his second job: trying to save the lives of children.

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For at least two hours each day this spring, inside the bookstore he has gone to since his rookie year, Zenner logged on to a microscope almost 1,000 miles away at Sanford Research. There, he read images of the stained brains of mice studied in a lab. He recorded the results and analyzed the data.

This was Zenner’s latest offseason, medical-research project, joining Dr. Jill Weimer’s team at Sanford searching for effective drug treatments and, hopefully, eventually, a cure for Batten Disease. This was different than Zenner's past two years studying hypertension and diabetes in Detroit-based labs, earning him a medical-journal publication. This time, he was working remotely instead of having his hands in everything. His responsibilities changed, forcing him to use different brain muscles.

And he was working to find a way to keep children alive from a rare, debilitating disease.

All 13 types of Batten Disease -- a group of lysosomal storage genetic disorders -- affect children. The National Institutes of Health estimates that between two and four of every 100,000 children in the United States will be diagnosed with a form of Batten. Almost all are fatal, most by the time the child reaches age 12. There is no cure. Only one form -- CLN2 -- has a potentially effective treatment.

When Zenner started working on Batten, he didn’t know much about it. Assigned to write an introduction for a couple of papers, he began to dive deep into the disease. Children with Batten, according to the NIH, appear healthy at birth and can start showing symptoms anywhere from infancy to age 4 or 5, depending on the form.

For the second consecutive offseason, Zach Zenner devoted time to medical research. Michael Rothstein

Eventually, the children can become blind, unable to communicate and are sometimes confined to a wheelchair.

“It just puts it in perspective what you’re doing,” Zenner said. “It might seem like all you’re doing is crunching numbers and looking at image slides, but then you always have to have in the back of your mind what the overall picture is, which is trying to help those kids out that have it.”

Zenner ended up on the project because it fit his schedule demands. He knew he would have to work remotely due to a combination of his hectic life, lab location, football training and the birth of his first child.

Sanford invited him to work there, in part, because he already is accepted to the University of South Dakota's Sanford School of Medicine. A good opportunity to do quality research along with making connections for his future, he accepted.

He met Weimer, who was skeptical of the arrangement at first. She figured she might hear from him once or twice and that he’d work when he could. She didn’t expect him to become a fully immersed part of the group, including participating in the group WhatsApp chat and twice-weekly lab meetings via Skype.

“I was pleasantly surprised,” Weimer said. “Even the week after they had the baby, he logged into lab meetings. He’s holding the baby in his arms while his wife was getting some rest. It was so impressive.”

Zenner became one of two “Weimer Lab Ghosts” along with Katherine White, whom he worked with almost daily -- communicating what they were seeing and the data they were tracking.

Zenner’s past two years placed him in labs studying mice under microscopes, participating in different tests, feeding them, recording data and sometimes doing postmortem surgery to help with results. This project, over the span of six months, featured his critical thinking and a more intensive scientific-writing regimen.

“To go back and write again is such a good exercise and so important in science,” Zenner said. “To do that was really good. A good exercise. It was just different skills. The image analysis is something that is a part of any lab work and ended up just being more of my focus this time around, and it’s good.

“It’s a good skill to have, and although it is different, it is still very important for a lot of labs that you work in.”

Weimer had Zenner record the results he read on the microscope blindly -- meaning he didn’t know which slides were the disease with drug treatment and which were without -- so he could make unbiased decisions about whether or not the treatment was working.

Much of Zenner’s work focused specifically on CLN6, with which symptoms begin within a child’s first few years. It leads to children losing the ability to walk, speak and, eventually, see. Kids with CLN6 usually die by their early teenage years. There is also an adult-onset version of CLN6 that has a slower rate of decline.

CLN6 is trickier, Weimer said; from her observations, if a family’s first child has it, somehow the second child often does, as well -- even though it should be only a 1-in-4 possibility.

For any type of Batten to occur, the child has to receive a bad gene from both parents, both of whom have to be carriers for the disease. A lot of recent Batten disease research funding came from the Charlotte and Gwenyth Gray Foundation, a nonprofit started by Gordon Gray -- a producer on the films "Miracle," "The Rookie" and "Million Dollar Arm" -- and his wife, Kristen. Their two daughters have Batten. Money raised by their research helped create a gene therapy clinical trial in less than a year.

Zach Zenner wants to play football as long as he can, but his future lies in medicine. Mike DiNovo/USA TODAY Sports

“Part of what Zach was involved in was helping us with the analysis of screening gene therapy in other forms of Batten disease and just knowing that sometimes it could take a long time for kids to get the cue to receive the gene therapy,” Weimer said. “Or some of them aren’t eligible for the gene therapy trial, so what other drugs or treatments are there out on the market that we can actually be treating these kids with?

“Also, gene therapy is so new, we have no clue how long it is going to last, so we’ll always want to have an arsenal of treatments ready to go. So the drugs Zach was involved in screening were really those next-generation treatments that we kind of have cued up after the gene therapy.”

Zenner, standing in the Lions' locker room earlier this month, shook his head when he was asked what he learned about Batten. He could have been there for hours and not covered all of it. Working on a rare disease parents and children have no control over left him with a greater appreciation of the wonder of the human body.

“I’m always struck by how easy it is for things to go wrong, like you have one genetic mutation and you’re missing this protein and now you have an autosomal storage disorder and you have progressive nerve degeneration and you die when you’re 8 years old,” Zenner said. “You know, it’s horrible. But it’s such a small thing that turns into such a large consequence.

“I’m always struck by how the human body is put together and how so many things can go wrong. But when you look at the general population, how often it doesn’t go wrong and the miracle of human life, I guess.”

Studying humans -- and helping them -- has always been Zenner’s goal. He applied to medical school before he knew professional football would be a reality.

He has deferred Sanford’s acceptance yearly as he stayed with the Lions. While Sanford still has an agreement to accept him, because his NFL career has been an actual career -- something unknown when he was an undrafted free agent out of South Dakota State in 2015 -- he likely has to retake the MCAT.

It would seem like it could have been a decision point for Zenner between football and medicine, but he insisted it isn’t. Football, with which he’s on the roster bubble with the Lions, is still the priority. Zenner is committed to football for as long as it will have him. But he also knows what’s waiting for him after.

“What we’ve discussed a little bit of is a conditional acceptance -- like if I retake my MCAT and I get a certain score, then I will maintain my acceptance to the school,” Zenner said. “It’s more a 'take it to stay at USD.' It’s not like they revoked it.

“It’s not a decision point for me. Having to retake it -- at this point in my career, I’m going to have to retake it either way.”

As long as the Sanford acceptance remains, and there’s no reason to think it won’t, he’ll eventually start classes there. When he does, he already has been offered a job in Weimer’s lab. She told Zenner he can return to do research in offseasons. When he does eventually start med school, she has a medical-student training grant ready for him so he can work for her while receiving a stipend as part of an internship program.

Zenner and Weimer hope that is still far off. After this spring, there’s little question about Zenner’s long-term future. It’ll be in medicine. In the short-term, he has an offseason working home.

“The way that it’s set up it is really easy for them to cut out little chunks for people to work on,” Zenner said. “With the way, how kind they are and how it is set up that way, it’s really easy for me to keep going back.”

When he does, there will be more lives to try to save while working from South Dakota, his home or a coffee shop somewhere.