Soft tissues store and return mechanical energy in human running.

Area of Science:

• Biomechanics
• Human Physiology
• Sports Science

Background:

• Soft body tissues deform during running, dissipating mechanical energy.
• Individual tissue contributions (e.g., heel pad) are known, but aggregate soft tissue work is not.

Purpose of the Study:

• To estimate the total mechanical work performed by all soft tissues during human running.
• To quantify the energy dissipation and rebound associated with soft tissue deformation across various running speeds.

Main Methods:

• Calculated soft tissue work by comparing joint work on rigid segments to whole-body work on the center of mass (COM).
• Measured work in 8 healthy adults running at speeds from 2 to 5 m/s.
• Analyzed fluctuations in soft tissue mechanical power over the stance phase.

Main Results:

• Soft tissues performed significant aggregate negative work (energy dissipation), increasing linearly with running speed.
• At 3 m/s, soft tissues dissipated approximately -19 J per stance, over 25% of total body negative work.
• Peak negative soft tissue power was comparable to the knee joint's power (~ -500 W).
• Soft tissue rebound contributed significant positive work (~13 J per stance, ~17% of total body positive work).

Conclusions:

• Soft tissue deformation is a major contributor to energy dissipation during running.
• This dissipation necessitates compensatory muscle work, representing a substantial metabolic cost.
• Estimated soft tissue energy dissipation could account for up to 29% of net metabolic expenditure at 5 m/s.