Active Research Areas

Muscle-tendon injuries, such as hamstring strains, are some of the most frequently occurring sport-related injuries and result in a high burden for athletes and teams as a result of time away from sport and costs associated with treatment and rehabilitation. Additionally, muscle-tendon injuries have some of the highest recurrence rates, with 30% or more of athletes sustaining a repeat injury. Despite their frequent occurrence, our ability to accurately identify athletes who are most at risk for these injuries is limited. Generally agreed-upon risk factors include history of injury and age; however, both of these are non-modifiable. Subsequently, the primary goal of this area of research is to identify modifiable risk factors for injury and re-injury by studying the following areas:

Muscle strength

Eccentric strength has been the primary focus of much prior work on modifiable risk factors for hamstring strain injuries (HSI). Our research has found, however, that the association between eccentric hamstring strength and future HSI is, at best, small. Ultimately, hamstring strength is one portion of a much larger injury prediction puzzle and assessing strength in conjunction with other metrics of muscle performance and structure may provide the best chance of identifying risk factors and implementing injury-reduction strategies.

On-field sprinting mechanics

During sprinting, the hamstrings are active, rapidly lengthening, and absorbing energy to decelerate the limb prior to foot contact. Our research has revealed that during high-speed running the hamstring muscle force increases ~1.3-fold as running velocity increases from 80% to 100% of maximum and that the greatest muscle-tendon unit stretch is incurred by the biceps femoris long head. As such, “poor” running mechanics that increase muscle-tendon strain have long been considered a causative factor for HSI; however, there is limited empirical data to indicate if running mechanics influence HSI risk.

Muscle and tendon structure

Variations in hamstring muscle and tendon morphology have been associated with an increase in tissue (mechanical) strain. A larger ratio of hamstring muscle width to aponeurosis width (i.e., a larger muscle relative to a smaller aponeurosis) results in higher levels of tissue strain at the muscle-tendon junction (the most common site of HSI) during running. Moreover, biceps femoris long head architecture has been shown to be a key risk factor for HSI, with short fascicle lengths associated with a ~4-fold increase in HSI risk.

Musculoskeletal injuries requiring surgical intervention to restore joint stability, rectify structural pathology, and reestablish musculotendon function (such as anterior cruciate ligament reconstruction and hip arthroscopy) are an unfortunate, but common, occurrence in competitive sports. Rehabilitation following such injuries and surgeries is a long and challenging process, typically measured in months or years. To facilitate a successful return to sport and maximize long term athlete health, our lab performs detailed, longitudinal assessments throughout the pre- and post-surgical process to monitor the following:

Neuromuscular function

Peak athletic performance requires athletes to be strong, fast, and stable. Lower extremity injury and surgical intervention results in neuromuscular dysfunction and muscle atrophy that can make athletes weak, slow, and unstable. Our comprehensive assessments of muscle strength, power, and activation help guide post-operative interventions to restore all aspects of muscle performance. Our research shows that incomplete recovery of neuromuscular function is a barrier to normalizing lower extremity movement patterns, both limiting sports performance and increasing risk for future injury.

Lower extremity biomechanics

Our normative databases of running and jumping mechanics provide specific comparisons for athletes recovering from lower extremity injury and surgery. Our research has shown that abnormal movement mechanics during athletic tasks such as running and jumping can persist for months to years following surgery. Impaired biomechanics are specific to each injury; for example, an athlete post-anterior cruciate ligament (ACL) reconstruction may land with reduced knee flexion angles and generate less knee extensor torque, while an athlete post-Achilles tendon repair may produce less plantarflexor power when hopping. Individualized assessment of each athlete’s biomechanical profile allows us to evaluate an athlete’s performance impairments, subsequent injury risk, and develop targeted rehabilitation strategies to rectify the observed abnormalities.

Bone health

An underestimated consequence of musculoskeletal injury and surgery is the potential impact on bone health. Our research has identified persistent deficits in bone mineral density of the distal femur over the initial 2-years after ACL reconstruction. Bone loss may be an important metric to consider as a precursor to the development of post-traumatic knee osteoarthritis. We continue to expand this line of research with a focus on: 1) methodological considerations for assessing bone mineral density after injury, 2) exploring relationships between bone health, neuromuscular function, and knee biomechanics, and 3) long-term bone health outcomes.

Long term outcomes

ACL injury and surgical reconstruction is associated with an increased risk of post-traumatic knee osteoarthritis. However, the factors contributing to this risk are poorly understood. Future investigations will quantify muscle performance, movement biomechanics, and cartilage health in former athletes who underwent ACL reconstruction 2-20 years prior. This research will identify potential modifiable factors in attempt to reduce the burden of osteoarthritis in this population. Further, we aim to better understand the impact of sustaining a significant lower extremity injury during collegiate athletics on future health outcomes.

Taking care of athletes means more than just helping when they are sick or injured. Our research spans several areas that evaluate mental health and well-being in athletes, as well as the ways in which they interact with injuries and illnesses.  The overarching goals of this work is to promote athlete health and performance by reducing injury and illness risk, as well as identifying actionable ways to promote mental health and well-being.  We currently work in multiple overlapping but distinguishable areas outlined below:

Sleep, well-being and injury

Based on our work and others’, we now recognize that psychosocial factors play a large role in the risk of injury in athletes. Impairments in sleep and well-being appear to have sport-specific and independent impacts on short-term injury risk.  Our current work seeks to use this information to generate actionable, real-time injury risk predictions that can be used to intervene and prevent injury on an individual level.

Athlete mental health

Mental illness is unfortunately common among adolescents and young adults and has been exacerbated by the COVID-19 pandemic. Our work continues to explore the unique factors that influence mental illness in athletes and how this has changed during COVID-19. Through increased recognition of the factors that impact mental heath in athletes, we can better identify individuals at risk and intervene on their behalf.

Psychosocial impacts of injuries

Within sports medicine, we are increasingly recognizing that injuries do not just have physical consequences, but can result in significant psychosocial impacts on athletes. These represent not only a threat to athlete health, but can significantly impede return to sport and performance, independent of physical recovery. We are working to identify those individuals at greatest risk, in order to intervene in a timely and impactful way to improve mental health and well-being after injuries.

Mindfulness in athletes

Mindfulness represents an efficacious, low-risk, and low-cost intervention to improve mental health and well-being within a broad range of patient populations. Early research suggests that it may also reduce injury risk, aid performance, and improve well-being among athletes. Our work is exploring how mindfulness impacts mental health and well-being in athletes, particularly during the COVID-19 pandemic.

Sport-related concussion has been a continually growing topic of interest in the sports medicine world as researchers, clinicians, and athletes have recognized the severity, longevity, and multitude of health-related problems associated with concussions. Thus, reducing the risk of sport-related concussions is a priority for athletes, coaches, and health care providers. The more we learn about sport-related concussions, the better job we can do of protecting young athletes from these injuries and maintain an appropriate balance between the benefits of sport participation and the risk of injury.

Biomechanics of Head Impacts

Our lab is using custom-fit, instrumented mouthpieces to quantify the head impacts sustained by University of Wisconsin football players, as current understanding of the directions and magnitudes of accelerations experienced by football players during on-field play is limited. The mouthpieces combine standard mouthguard material with embedded sensors capable of accurately measuring head and neck accelerations. The findings of this study will help us better understand the frequency and severity of head impacts sustained by University of Wisconsin football players during practices and games, and the circumstances (equipment, training, or individual actions) surrounding these impacts. The ultimate goal of this study is to improve player safety and reduce the risk of sport-related concussions through adaptations in training practices and design and implementation of protective equipment.