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The work of walking: a calorimetric study.
P Webb1, W H Saris, P F Schoffelen
1Department of Human Biology, University of Limburg, Maastricht, The Netherlands.
Medicine and Science in Sports and Exercise
|August 1, 1988
Summary
This study demonstrates that level walking generates mechanical work, contrary to previous assumptions. Energy expenditure during walking exceeds heat production, indicating work is performed, primarily through foot-ground interactions.
Area of Science:
- Human Physiology
- Biomechanics
- Energy Metabolism
Background:
- Traditional assumptions posit that all metabolic energy during level walking is converted to heat, with no external work performed.
- This study challenges the established view by investigating energy expenditure during locomotion.
Purpose of the Study:
- To quantify the mechanical work done during level walking.
- To determine if energy expenditure during walking aligns with heat production alone.
Main Methods:
- Human participants (5 women, 5 men) underwent calorimetry while walking on a treadmill at varying speeds (2.5-6.7 km/h) and cycling on an ergometer.
- Measurements included fuel oxidation, heat loss, and mechanical power output.
- Additional trials involved walking with weighted backpacks and horizontal loads.
Main Results:
- During cycling, energy from fuel oxidation equaled heat loss plus ergometer power output.
- During level walking, energy from fuel oxidation exceeded heat loss, indicating mechanical work was performed.
- Work output increased with walking speed (14-63 W), representing 11-13% of the incremental fuel cost.
Conclusions:
- Level walking involves the performance of mechanical work, challenging the traditional assumption of heat production only.
- The work done is likely attributed to foot-ground interactions, such as shoe deformation.
- This work energy does not reappear as thermal energy during recovery.