Adaptability of elderly human muscles and tendons to increased loading

Area of Science:

• Gerontology
• Muscle Physiology
• Biomechanics

Background:

• Senile sarcopenia, age-related muscle mass loss, causes weakness and reduced mobility.
• Muscle weakness exceeds mass loss, indicating reduced intrinsic force per unit area.
• Factors include neuropathic processes, nutrition, hormones, immunity, and reduced activity.

Purpose of the Study:

• Investigate age-related changes in muscle architecture and tendon properties.
• Determine the impact of these changes on intrinsic muscle force.
• Assess the reversibility of these changes with resistive training.

Main Methods:

• Analysis of human plantarflexors in aging individuals.
• Measurement of muscle volume, fiber fascicle length, pennation angle, tendon stiffness, and Young's modulus.
• Evaluation of changes after 14 weeks of resistive training.

Main Results:

• Sarcopenia associated with reduced muscle volume, fiber fascicle length, and pennation angle.
• Tendon stiffness and Young's modulus decreased, indicating altered material properties.
• Resistive training increased fascicle length and tendon stiffness, but did not alter relative length-tension properties.

Conclusions:

• Age-related muscle weakness involves changes in muscle architecture and tendon mechanics.
• Resistive training can reverse some of these detrimental changes.
• The body may possess mechanisms to maintain the muscle's operating range despite physical activity changes in old age.