Last reviewed 1 Oct 2026 · 8 min read
What is ergonomics?
Ergonomics (human engineering, human factors) is the study of the relationship between the worker, the machine and the working environment, so that machines are designed to fit people — improving comfort, safety, efficiency and health and reducing fatigue and accidents.
In agriculture the operator's body (hands, feet, back, eyes, ears), the machine's controls and seat, and the environment (heat, noise, dust, vibration) are all considered.
Anthropometry
Anthropometry is the measurement of body dimensions. Designers use percentiles of a user population:
- 5th percentile (small people) for reach distances (so small users can reach controls);
- 95th percentile (large people) for clearance (legroom, door and overhead space);
- 50th percentile for average adjustments.
Key dimensions: stature, sitting height, elbow height, knee height, functional (grip) reach, hand length and width, foot length. Indian farm workers are generally smaller than the Western populations on which many tractors were first designed, so Indian data (ICAR studies) are used for seat height, control reach and pedal force.
Human power capacity
| Activity | Typical power |
|---|---|
| Continuous manual work (8 h) | about 0.1 kW (≈ 0.13 hp) |
| Short-period peak (seconds) | up to 1 kW or more |
| Sustained pedalling | about 75 W for a fit worker |
| Animal (bullock) | about 0.5–0.75 hp each |
- Maximum aerobic capacity (VO₂ max) of Indian male workers: roughly 2.0–3.0 L of oxygen per minute (about 35–45 mL/kg/min); women are about 70–80 % of that.
- Acceptable workload for an 8-hour day is generally taken as about 35–40 % of maximum aerobic capacity (for continuous work).
Physiological measurement of work
| Parameter | Measurement | Use |
|---|---|---|
| Heart rate | Counted at the wrist, chest strap or monitor | Simple index of workload: the heart-rate increase over rest is nearly linear with the oxygen uptake |
| Oxygen consumption | Douglas bag, respirometer or gas analyser | Energy cost: about 20.9 kJ (5 kcal) per litre of oxygen |
| Energy expenditure | kJ/min or kcal/min | Classifies the work |
| Rate of perceived exertion | Scale of effort | Subjective |
| Body temperature, sweat | — | Heat stress |
Classification of workload (energy expenditure — adult men, typical limits)
| Class | Heart rate (beats/min) | Oxygen uptake (L/min) | Energy (kcal/min) |
|---|---|---|---|
| Light | up to about 100 | up to ~0.5–1.0 | up to ~2.5 |
| Moderate | 100–125 | ~1.0–1.5 | ~2.5–5.0 |
| Heavy | 125–150 | ~1.5–2.0 | ~5.0–7.5 |
| Very heavy | 150–175 | ~2.0–2.5 | ~7.5–10 |
| Extremely heavy | above 175 | above 2.5 | above 10 |
(Class limits vary slightly between authors; the principle is that ploughing with a bullock team, manual digging and threshing are heavy, while tractor driving is moderate.)
A worker's oxygen uptake while operating a manual seeder is 1.2 L/min. With an energy value of about 20.9 kJ per litre of oxygen,
Energy expenditure ,
which lies in the heavy class. For comfortable 8-hour work the worker needs rest breaks — an acceptable continuous level is about 5 kcal/min (moderate).
If the average acceptable energy expenditure is (about 5 kcal/min for continuous work), a task of kcal/min and resting energy (about 1.5 kcal/min), the rest allowance (fraction of time) is
With , and , — about 22 % of the time should be rest.