Bryan Heidersheit - Hamstring Strain Risk, Profiling & Return-to-Play

Episode 158: In this Research Unpacked Episode from Inform Performance, Dylan Carmody chats to Bryan Heiderscheit. Bryan is a Physical Therapist, Biomechanist and Professor/Vice Chair of research in the Department of Orthopedics and Rehabilitation at the University of Wisconsin School of Medicine and Public Health, he is also the director of UW Badger Athletic Performance.

Topics Discussed 

• Hamstring Injury Risk Factors
• Methods of Profiling and Monitoring Hamstring Performance
• Guiding Principles for Hamstring Rehabilitation
• Screening and Assessment of Hamstring Strength
• The Impact of Detraining on Hamstring Health
• Nuances in Nordic Hamstring Curl Analysis

Key Points

• Known risk factors for hamstring strains include: 
  • Increasing age: As athletes get older, their risk of hamstring injury tends to increase. This may be due to age-related changes in muscle composition, reduced elasticity, and slower recovery times.
  • Prior hamstring injury: A history of hamstring strain significantly increases the likelihood of future injuries. This emphasizes the importance of thorough rehabilitation and ongoing preventive measures for athletes who have previously experienced hamstring strains.
• Factors such as strength, flexibility, hydration, and training load have not been conclusively established as risk factors. While these elements are often considered in injury prevention programs, current research has not provided strong evidence for their direct role in hamstring strain risk. This highlights the complex nature of injury prediction and the need for individualized approaches to prevention.
• Eccentric hamstring strength has received significant attention in research and clinical practice. However, it may only require a minimum threshold for injury prevention rather than continuous improvement. This suggests that once an athlete achieves a certain level of eccentric strength, further increases may not provide additional protective benefits against hamstring strains.
• The acute injury mechanism involves separation of muscle attachments under high tensile load, differing from artificially induced injuries in early studies. This understanding has evolved from previous research that used laceration or contusion models, which do not accurately represent the strain injuries seen in sports. The current model emphasizes the importance of tensile forces in hamstring injury mechanisms.
• "Popping sarcomeres" may contribute to the injury process, with rapid lengthening and subsequent remodeling of sarcomere units. This microscopic phenomenon involves the disruption of myosin-actin connections within muscle fibers, leading to rapid elongation of sarcomeres. The subsequent remodeling process is thought to play a role in both the injury mechanism and the recovery process.
• Longer muscle fascicles may potentially reduce injury risk, an area of active investigation. Research suggests that increased fascicle length could provide a protective effect against hamstring strains. This has led to interest in training methods that may promote fascicle lengthening as part of injury prevention programs.
• Exercise interventions can potentially alter muscle architecture: 
  • Fascicle length may increase by 0.5-1.5 cm after 3-4 weeks of training
  • High-load eccentric exercises are most effective for promoting these changes
  • Positioning muscles at longer lengths during exercise may be beneficial for maximizing architectural adaptations
• Detraining effects on hamstring muscles: 
  • Strength and cross-sectional area remain relatively stable for 1-2 weeks following cessation of training
  • Architectural changes (e.g., fascicle length) can reverse within 7-10 days of detraining
  • Weekly high-load eccentric exercise is recommended to maintain adaptations, particularly during off-season periods or when regular training is interrupted 

Where you can find Bryan

• Linkedin
• Research Gate

Sponsors

VALD Performance, makers of the Nordbord, Forceframe, ForeDecks and HumanTrak. VALD Performance systems are built with the high-performance practitioner in mind, translating traditionally lab-based technologies into engaging, quick, easy-to-use tools for daily testing, monitoring and training.

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