Imaging and simulation of Achilles tendon dynamics: Implications for walking performance in the elderly

Area of Science:

• Biomechanics
• Musculoskeletal aging
• Tissue mechanics

Background:

• The Achilles tendon (AT) comprises distinct fascicle bundles from triceps surae muscles, potentially acting independently.
• Understanding AT behavior is crucial for musculoskeletal injury and performance, especially concerning aging effects.
• Tissue imaging and computational modeling advance the study of functional tendon dynamics.

Purpose of the Study:

• To investigate AT behavior during walking in relation to age-related declines in triceps surae mechanical performance.
• To explore the functional implications of reduced inter-fascicle sliding capacity in the aging AT.
• To integrate experimental and computational methods for multi-scale biomechanical insights into aging.

Main Methods:

• Utilized complementary experimental (in vivo imaging) and computational approaches.
• Compared tissue deformations in the AT between young adults and older adults during walking.
• Simulated age-related reductions in inter-fascicle sliding and modulated AT compliance.

Main Results:

• Older adults showed smaller regional AT deformation differences compared to young adults, suggesting reduced inter-fascicle sliding.
• More uniform AT deformations correlated with age-related decreases in ankle moment, power, and positive work during push-off.
• Simulations predicted impaired gastrocnemius muscle-tendon performance and altered fascicle kinematics with reduced sliding capacity.

Conclusions:

• Reduced inter-fascicle sliding in the aging AT may compromise the mechanical independence of triceps surae muscles.
• Age-related changes in AT deformation patterns are linked to elderly gait biomechanics.
• Integrated imaging and modeling provide insights into aging's multi-scale biomechanical effects on the AT.