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Mechanical determinants of gradient walking energetics in man
A E Minetti1, L P Ardigò, F Saibene
1Istituto Tecnologie Biomediche Avanzate, C.N.R., Milano, Italy.
The Journal of Physiology
|December 1, 1993
Summary
The most energy-efficient walking gradient is approximately -10.2%, determined by the balance between positive and negative external work and muscle efficiencies. This finding explains the optimal metabolic cost during locomotion.
Area of Science:
- Biomechanics
- Human Locomotion
- Exercise Physiology
Background:
- Understanding the metabolic cost of walking on different gradients is crucial for optimizing human movement.
- Mechanical work during locomotion can be divided into internal work (body segment movement) and external work (center of mass movement).
Purpose of the Study:
- To determine the most metabolically economical gradient for walking.
- To partition mechanical work into internal and external components and analyze their relationship with metabolic cost.
- To investigate the efficiencies of positive and negative external work at varying speeds and gradients.
Main Methods:
- Measured metabolic cost and mechanical work (internal and external) during walking on uphill, level, and downhill gradients at different speeds in four subjects.
- Partitioned external work into positive (W+ext) and negative (W-ext) components.
- Utilized linear multiple regression to analyze the relationship between work components, efficiencies, and metabolic cost.
Main Results:
- The most economical walking gradient was found to be -10.2%.
- External work was partitioned into positive and negative components, with a unique ratio regardless of speed at each gradient.
- Internal work remained constant across gradients at a given speed, indicating no role in determining the optimal gradient.
- Muscle efficiencies for negative and positive work decreased with increasing speed, while their ratio remained constant.
Conclusions:
- The interplay between external work partitioning (W+ext/W-ext ratio) and differential muscle efficiencies (eff-/eff+) explains the observed metabolic optimum gradient of approximately -10%.
- The findings highlight the importance of considering both positive and negative work efficiencies in understanding the energetics of human locomotion on inclines.