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Updated: Jul 16, 2025
11:36
Ex vivo Mechanical Loading of Tendon
Published on: May 28, 2007
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Human muscle-tendon unit mechanobiological responses to consecutive high strain cyclic loading
Gaspar Epro1, Frank Suhr2,3, Kiros Karamanidis1,4
1Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK.
The Journal of Experimental Biology
|September 18, 2023
Summary
Repetitive high-strain exercise can increase Achilles tendon strain and decrease stiffness, especially with frequent loading. Tendon repair may not keep pace with micro-damage, raising injury risk.
Area of Science:
- Sports Medicine
- Biomechanics
- Tendon Physiology
Background:
- Tendons exhibit slower tissue renewal than muscles, increasing vulnerability to repetitive high mechanical strain.
- Insufficient recovery periods following high-strain exercise can exacerbate mechanical demand on tendons.
Purpose of the Study:
- To investigate the adaptive responses of the triceps surae (TS) muscle-tendon unit (MTU) to repetitive high Achilles tendon (AT) strain.
- To analyze extracellular matrix turnover biomarkers in response to cyclic loading.
Main Methods:
- Eleven young males underwent 12 days of progressive resistance exercise with high AT strain (90% MVC).
- One leg (LegT1) was loaded once daily; the alternate leg (LegT3) was loaded thrice daily.
- TS MTU mechanical properties and serum biomarkers were measured.
Main Results:
- Both legs showed a ~10% increase in maximal AT force.
- LegT3 exhibited a ~20% increase in maximal AT strain and decreased AT stiffness after 8 days, persisting after 48h rest.
- LegT1 showed no significant changes in AT mechanical properties.
Conclusions:
- Frequent high-magnitude cyclic loading makes tendons vulnerable to micro-damage accumulation exceeding repair capacity.
- This can lead to increased maximal tendon strain and reduced stiffness, particularly with higher loading frequencies.
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