Hamstring Muscle-Tendon Adaptations to Resistance Training: Insights and Applications for Practitioners

Introduction

Hamstring injuries are one of the most common issues encountered in sports, particularly those involving sprinting or explosive movements. Preventing hamstring strains, especially in high-performance athletes, requires an in-depth understanding of how targeted resistance training can influence muscle and tendon health. A recent study by Lazarczuk et al. (2024) explored the effects of two popular hamstring exercises—Nordic Hamstring and Hip Extension—on muscle-tendon geometry. The findings have significant implications for injury prevention and rehabilitation practices.

Key Findings from the Research

This study looked at how 10 weeks of either Nordic Hamstring or Hip Extension exercises could influence muscle hypertrophy and tendon adaptation in the hamstrings of 30 recreationally active males. Using MRI scans to track changes, the researchers uncovered the following:

Hamstring muscle anatomy

• Muscle Hypertrophy: Both exercises significantly increased the cross-sectional area (CSA) of hamstring muscles, particularly the semitendinosus (Nordic Hamstring) and biceps femoris long head (BFlh) (Hip Extension).

• Tendon Adaptation: Despite muscle hypertrophy, there was limited evidence of tendon or aponeurosis growth. This suggests that the intervention period may have been too short or the intensity insufficient to stimulate tendon changes.

• Specific Muscle-Tendon Interactions: The Hip Extension exercise caused an increase in the BFlh muscle volume-to-interface area ratio, indicating a potential increase in localized tissue strain at the muscle-tendon junction. This imbalance could lead to higher injury risk if not carefully managed.

Gareth Bale

Clinical Applications for Practitioners

1. Tailoring Strength Training for Injury Prevention

The finding that different exercises target specific hamstring muscles more effectively can help practitioners design better rehabilitation and injury prevention programs. For example:

• Nordic Hamstring exercises should be favored for developing the semitendinosus and biceps femoris short head, both of which are crucial for knee stability.

• Hip Extension exercises should be prioritized to strengthen the biceps femoris long head, which plays a vital role during high-speed running.

2. Tendon Health and the Importance of Longer Interventions

While this study demonstrated robust muscle growth, tendon adaptations were limited. Practitioners should consider extending the training duration or adjusting exercise intensity to stimulate tendon growth. This is important because disproportionate muscle hypertrophy without corresponding tendon adaptation can increase strain on the musculotendinous junction, raising injury risk.

Clinically, this finding supports the need for longer-term loading programs to not only increase muscle size but also enhance tendon resilience, particularly for athletes returning from hamstring strain injuries.

3. Exercise Selection Based on Functional Goals

Hip extension and Nordic Exercises

For practitioners working with athletes in sports that involve sprinting and sudden changes in direction, exercise selection should be based on sport-specific demands:

• Nordic Hamstrings are beneficial for eccentric strength, which is crucial for deceleration and preventing overstretch injuries.

• Hip Extensions are more effective for increasing muscle mass in the BFlh, making them useful for athletes requiring power and high-speed running performance.

4. Managing Musculotendinous Junction Strain

One concern raised by this research is the potential for localized strain at the musculotendinous junction, especially in the BFlh, after hypertrophy from the Hip Extension exercise. Monitoring athlete readiness using assessments such as muscle-tendon ultrasound or strength testing could help practitioners identify athletes at risk of injury due to muscle-tendon imbalances.

This also suggests that rehabilitation programs should include exercise variety to ensure balanced muscle and tendon development. Isometric exercises, in particular, may be beneficial in managing tendon stress while still allowing for muscle hypertrophy.

Conclusion

The research by Lazarczuk et al. (2024) highlights how specific hamstring exercises affect muscle and tendon growth. For sports medicine practitioners and physical therapists, this offers valuable insights into designing targeted injury prevention and rehabilitation programs. Muscle hypertrophy is crucial for performance and injury prevention, but tendon adaptation must not be overlooked. Tailoring training protocols with longer durations and a balance of exercises will ensure both muscles and tendons are prepared for the demands of high-performance sports.

Reference: Shon, C. (2023). Hamstring Injury Rehabilitation and Prevention in the Female Athlete. International Journal of Sports Physical Therapy. Retrieved from https://ijspt.scholasticahq.com/article/38254-hamstring-injury-rehabilitation-and-prevention-in-the-female-athlete

Lazarczuk, S. L., Collings, T. J., Hams, A. H., Timmins, R. G., Shield, A. J., Barrett, R. S., & Bourne, M. N. (2024). Hamstring Muscle-Tendon Geometric Adaptations to Resistance Training Using the Hip Extension and Nordic Hamstring Exercises. Scandinavian Journal of Medicine & Science in Sports, 34(9), e14728.