Energy Expenditure Algorithms in Physics
Energy expenditure links biology and mechanics. It estimates how much chemical energy the body uses during rest and motion. A useful calculator should not depend on one equation only. Human movement changes with mass, speed, slope, efficiency, and body composition. This tool compares several models, then reports a selected output.
Basal Models
Basal metabolic rate is the resting energy base. It represents energy used for breathing, circulation, temperature control, and cell work. Mifflin-St Jeor uses weight, height, age, and sex. Revised Harris-Benedict uses similar variables with different coefficients. Katch-McArdle uses lean mass, so body fat data improves it. Averaging these values can reduce dependence on one model.
Activity Models
MET calculations are common in exercise science. One MET describes resting oxygen demand. A gross MET estimate includes rest and movement together. A net MET estimate subtracts one resting MET, then adds session rest separately. This helps when comparing active work against resting cost.
Mechanical Work
Physics adds another view. Climbing requires work against gravity. The calculator multiplies moving mass by gravitational acceleration and elevation gain. Measured power can also be converted into joules. Mechanical work is then divided by efficiency. This estimates metabolic cost from useful external work.
Distance and Hybrid Use
A distance model is helpful for walking and running checks. A simple rule uses body weight times kilometers traveled. It is not perfect, but it gives a practical field estimate. The hybrid method compares major outputs and applies a thermic addition. This can represent extra processing cost after activity.
Interpreting Results
No algorithm is exact for every person. Heat loss, fitness, terrain, technique, and device error matter. Treat the result as an engineering estimate. Use consistent inputs when comparing sessions. For lab work, record assumptions beside each calculation. For training plans, compare trends more than single values.