Instrument 04
Converts any activity and duration into MET-hours, then returns the duration of every other activity that costs the same energy. The comparison a single-activity calculator structurally cannot make.
MET values assume level ground and no carried load. Gradient, soft surfaces and a pack raise the true cost substantially.
Gross expenditure for —.
One metabolic equivalent is defined as oxygen consumption of 3.5 ml per kilogram of body mass per minute. MET values are drawn from the Compendium of Physical Activities. Energy cost follows the standard conversion: MET × 3.5 × body mass in kg ÷ 200 × minutes.
Equivalent durations are computed by holding MET-hours constant across activities. Forty-five minutes at 6 METs is 4.5 MET-hours, which matches 27 minutes at 10 METs.
The 3.5 ml/kg/min resting reference is a population average that overestimates resting metabolic rate for many people, particularly at higher body mass. Individual movement economy varies. Terrain, gradient, wind, temperature and carried load are all excluded from the published values.
The result is that absolute calorie figures carry a realistic error band of 10 to 25 percent for an individual. Relative comparisons between activities are considerably more reliable, because the systematic errors largely cancel when both sides use the same assumptions.
Use the ratio. Treat the calorie total as an order-of-magnitude figure.
| Condition | Multiplier on the horizontal cost |
|---|---|
| Firm dirt trail | 1.05–1.1 |
| Gravel | 1.2–1.3 |
| Rough or rocky trail | 1.3–1.5 |
| Soft sand | 1.6–2.1 |
| Unbroken snow | 1.6–2.5 |
For ascent, add roughly 0.5 to 0.6 kcal per kilogram of total mass — body plus pack — per 100 metres climbed.