The Claim
The efficiency of converting mechanical work into metabolic energy during load carriage is approximately 16%, which is lower than the typical 25% efficiency of muscle work, indicating that mechanical work measures underestimate actual muscle energy expenditure due to co-contraction and passive tissue dynamics.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
When carrying a load, the body converts only about 16% of mechanical work into metabolic energy, compared to 25% during normal muscle work. This means measuring only mechanical work underestimates the total energy the muscles actually use because of additional forces like simultaneous muscle contractions and tissue resistance.
See the scientific wording
The efficiency of converting mechanical work into metabolic energy during load carriage is approximately 16%, which is lower than the typical 25% efficiency of muscle work, suggesting that mechanical work measures may underestimate actual muscle energy expenditure due to factors like co-contraction or passive tissue dynamics.
When carrying a heavy load, the body must move more mass with each step, forcing muscles in the ankle and knee to work harder to redirect the body's center of mass. These muscles generate force through chemical reactions that burn more energy than the movement they produce, and they also activate simultaneously with opposing muscles to stabilize joints, wasting additional energy. As a result, the total energy used by the body is much higher than what can be measured by just tracking movement.
What the research says
1 studyStudy: Mechanics and energetics of load carriage during human walking
When people walk with a heavy backpack, their bodies use more energy than just the work their muscles do to move their body — like how a car uses more gas than just what’s needed to move forward, because of friction and engine strain. This study found that only about 16% of the energy used shows up as visible movement, meaning muscles are working harder behind the scenes.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.