Triceps surae muscle-subtendon interaction differs between young and older adults

Area of Science:

• Biomechanics
• Gerontology
• Musculoskeletal Physiology

Background:

• Triceps surae muscle-tendon interaction is vital for walking.
• Aging may reduce subtendon sliding within the Achilles tendon.
• The effect of aging on subtendon interaction and muscle contractile behavior is unclear.

Purpose of the Study:

• To investigate aging effects on triceps surae muscle-subtendon interaction.
• To compare subtendon tissue displacement and muscle length changes between young and older adults.
• To test the hypothesis that older adults exhibit more uniform subtendon displacements and altered muscle length changes.

Main Methods:

• Dual-probe ultrasound imaging during isolated muscle contractions.
• Simultaneous recording of gastrocnemius (GAS) and soleus (SOL) fascicle kinematics and tendon displacements.
• Ramped maximum isometric voluntary contractions across a range of ankle plantarflexion angles.

Main Results:

• Older adults demonstrated more uniform subtendon tissue displacements.
• These displacements were linked to anatomically consistent, potentially unfavorable changes in muscle contractile behavior.
• A smaller difference in peak shortening between GAS and SOL muscles was observed in older adults during force generation.

Conclusions:

• Aging alters triceps surae muscle-subtendon interaction, leading to more uniform tissue displacements.
• These biomechanical changes may explain reduced ankle moment generation during walking in older adults.
• Findings provide a basis for understanding age-related declines in walking performance.