A proposed model for load carriage on sloped terrain

Area of Science:

• Biomechanics
• Human Physiology
• Ergonomics

Background:

• Load carriage energy expenditure differs significantly between uphill and downhill locomotion.
• Accurate modeling of complex terrain requires estimating downhill movement costs, which may not follow linear relationships.
• Downhill movement may necessitate increased work for stability, impacting net energy costs.

Purpose of the Study:

• To develop a predictive model for estimating energy expenditure during uphill and downhill load carriage.
• To investigate the relationship between walking grade, load, and oxygen uptake.
• To create a model that accounts for the non-linear costs associated with downhill movement.

Main Methods:

• Measured oxygen uptake (VO2) in 16 subjects walking at 1.34 m/s on various grades (-12% to +12%) with different loads (0, 9.1, 18.1 kg).
• Collected data across a range of inclines to capture varying energy demands.
• Pooled data due to lack of significant gender differences.

Main Results:

• No significant gender differences in energy expenditure were observed.
• Minimum oxygen uptake (VO2) during walking occurred at a -8% grade.
• Data indicated a non-linear relationship between grade and energy cost, particularly for downhill movement.

Conclusions:

• A predictive model was developed, considering level walking costs and vertical displacement costs for the total mass (body + load).
• Uphill work cost was calculated using an efficiency factor, while downhill work utilized an exponential function of slope angle.
• The model's downhill component was partially validated by comparing predictions with existing studies on level and negative slope walking.