Fatigue damage of human tendons

Area of Science:

• Biomechanics
• Tendon Mechanics
• Musculoskeletal Research

Background:

• Human tendons are crucial for transmitting muscle forces to bones.
• Understanding tendon fatigue is vital for preventing injuries in athletes and active individuals.
• Previous research has focused on static loading, but dynamic fatigue effects require further investigation.

Purpose of the Study:

• To investigate the impact of partial mechanical fatigue on the mechanical properties of human tendons in vitro.
• To identify reliable indicators of tendon damage resulting from cyclic loading.
• To explore the potential for in vivo assessment of tendon fatigue damage.

Main Methods:

• Twelve human Extensor digitorum longus tendons were subjected to partial fatigue (25% of median fatigue life) using a cyclic tension-tension stress waveform (4 Hz).
• Maximum stress was set at 20% of ultimate tensile strength (UTS), and minimum stress at 1% of UTS.
• Dynamic mechanical characterization was performed at 10% and 20% UTS before and after fatigue. Quasi-static tests were also conducted.

Main Results:

• Comparative analysis revealed that the damage ratio (DR) for the dynamic tensile modulus is a sensitive indicator of fatigue-induced tendon damage.
• The study quantified changes in mechanical parameters following partial fatigue exposure.
• Specific stress levels and fatigue protocols were established for in vitro tendon testing.

Conclusions:

• The dynamic tensile modulus damage ratio serves as a valuable metric for assessing fatigue damage in tendons.
• This in vitro methodology could potentially be adapted for non-invasive, in vivo evaluation of tendon health and injury risk.
• Further research is warranted to validate this approach in clinical settings.