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Biomechanical Testing of Murine Tendons
Published on: October 15, 2019
Sex comparison of hamstring structural and material properties.
J Troy Blackburn1, David R Bell, Marc F Norcross
1Neuromuscular Research Laboratory, University of North Carolina at Chapel Hill, 124 Fetzer, CB # 8700, Chapel Hill, NC 27599-8700, USA. troyb@email.unc.edu
Clinical Biomechanics (Bristol, Avon)
|November 26, 2008
Summary
Males have stiffer hamstrings than females, largely due to larger muscle size, not material differences. This finding may explain why females have a higher risk of anterior cruciate ligament injuries.
Area of Science:
- Biomechanics
- Orthopedics
- Sports Medicine
Background:
- Musculotendinous stiffness resists joint perturbation, enhancing joint stability.
- Females exhibit lower hamstring stiffness than males, potentially contributing to sex-based differences in anterior cruciate ligament (ACL) injury risk.
- The underlying reasons for sex differences in hamstring stiffness (muscle size vs. material properties) remain unclear.
Purpose of the Study:
- To investigate whether sex differences in hamstring stiffness are attributed to muscle size or inherent material properties.
- To test the hypothesis that males exhibit greater hamstring stiffness, stress, strain, and elastic modulus than females.
- To examine the correlation between hamstring stiffness and muscle size.
Main Methods:
- Assessed hamstring stiffness in 20 males and 20 females using knee flexion/extension following joint perturbation.
- Estimated hamstring length and changes in length via motion capture.
- Measured hamstring cross-sectional area using ultrasound to calculate material properties (stress, strain, elastic modulus).
Main Results:
- Males demonstrated significantly greater hamstring stiffness than females (P<0.001).
- No significant differences in hamstring stress, strain, or elastic modulus were observed between sexes (P>0.05).
- Hamstring stiffness correlated significantly with cross-sectional area and a combination of cross-sectional area and resting length.
Conclusions:
- Male hamstrings offer greater structural resistance to changes in length during joint perturbation.
- Material properties of the hamstring musculotendinous unit do not differ significantly between sexes.
- The observed sex difference in hamstring stiffness is primarily attributed to differences in muscle size, potentially impacting joint stability and ACL injury risk in females.
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