New research aims to link repeat hamstring injuries with altered brain activity in athletes

By Laurel White

Scott Crawford has had his fair share of hamstring injuries.

As a former collegiate soccer player, Crawford knows all too well about the pain, the frustration, and — perhaps worst of all — the reality that once you’ve injured your hamstring, it’s very likely to happen again. 


“Reinjury rates are high,” says Crawford, an assistant professor in the School of Education’s Department of Kinesiology. “There’s been a lot of ink spilled on injury mechanisms and injury rates and rehab practices and progressions, and yet our reinjury rates flatline.”

Crawford says it’s very likely experts in rehabilitation therapy are missing a key insight or a crucial tool when it comes to helping patients fully recover from hamstring injuries — and he has an idea about what that missing link may be: communication between hamstring muscles and the brain. 

“The thought is that something may be going on in the central nervous system,” he explains. 

Next month, Crawford will begin a multi-year research project exploring this possibility. The research will be funded by a two-year grant through UW–Madison’s Institute for Clinical and Translational Research’s KL2 Scholar Program. The program, funded by the National Institutes of Health, is aimed at providing promising early-career researchers with training, mentoring, and protected time to pursue research projects. 

“There’s a good foundation of research for us to build off of,” Crawford says of his KL2 project. “We can use that foundation as a springboard to do creative, innovative, and impactful work.”

In 2021, researchers in Australia used transcranial magnetic stimulation (a noninvasive treatment that uses magnetic fields to stimulate nerve cells in the brain) to compare the brain function of previously-injured and healthy athletes while they flexed their hamstrings. The study showed there were differences in brain activity between participants who had experienced a hamstring injury in the past few years and those who hadn’t.

Crawford found this work to be important — and inspiring. He says the differences in brain signals between healthy and previously injured athletes could be chalked up to the brain attempting to protect the body from injuring itself again.

“The muscle is subservient to the brain,” he says. “Whatever the brain tells the muscle to do, the muscle is going to do.”

Crawford says it’s also possible the communication between the previously injured muscles and the brain has been clouded by the effects of injury, like swelling. He likens this potential phenomenon to a “bad game of telephone.”

In his new study, Crawford will attempt to flesh out this complicated relationship by taking ultrasound images of muscle function and functional MRI images of brain activity in athletes who have experienced hamstring injuries and those who haven’t. 

“We’re going to be using ultrasound to assess local tissue mechanics — how the muscle changes as it goes through its contraction — and using functional MRI to assess brain activity based on blood oxygenation in the brain,” he explains. 

Ultimately, Crawford hopes to develop a new, more effective treatment that would allow athletes with hamstring injuries to move on from the malady for good. 

“This research has potential to transform the current rehabilitation paradigm,” he says. 


Crawford’s mentors on the project include Dane Cook, professor in the Department of Kinesiology and director of the Marsh Center for Research in Exercise and Movement. Cook says the project is a promising step toward a more complete model for injury rehabilitation, including a return to full participation in sport or exercise for athletes. 

“The value, impact, and exciting features of Scott’s research proposal and longer-term plan is that it is intended to provide practitioners with a more holistic model of injury recovery — one that considers both peripheral and central nervous system factors,” he says. 

Crawford will also continue to receive support on the project from faculty in UW–Madison’s orthopedics and mechanical engineering programs — areas he has had extensive academic experience with. Crawford earned his bachelor’s degree in mechanical engineering from Cedarville University and master’s and PhD in biomedical engineering from The Ohio State University. He completed his postdoctoral training in the University of Nebraska Athletic Performance Lab before an additional postdoctoral training in the UW–Madison Department of Orthopedics & Rehabilitation and Badger Athletic Performance lab.

Crawford says an interdisciplinary approach informed by his unique background energizes and motivates his work. 

“There are a lot of really complex and interrelated disciplines and concepts that I really enjoy trying to tease out,” he says. “If we can make strides in one particular area, tease something out for the next generation of researchers to take and run with, that’s the fun thing about science and research.”

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