Test, measurement and evaluation
These three words are often mixed up. They are three different steps.
- Test: a tool, task or question used to collect information. Example: a 50 m sprint, a weighing scale.
- Measurement: the number we get from the test. Example: 7.4 seconds, 52 kg.
- Evaluation: judging the measurement, often by comparing it with a standard (a norm). Example: "7.4 s is good for your age".
Why they matter
- They show a person's present fitness and health.
- They help a coach pick players and plan training.
- They show progress over time and keep people motivated.
- They help find health risks early.
Body Mass Index (BMI)
BMI compares body mass with height. Formula: BMI = mass (kg) ÷ height (m)². The unit is kg/m².
Steps: 1) change height to metres (160 cm = 1.6 m). 2) square it (1.6 × 1.6 = 2.56). 3) divide the mass by that number.
Adult BMI chart (WHO)
- Below 18.5: underweight
- 18.5 to 24.9: healthy (normal)
- 25.0 to 29.9: overweight
- 30.0 and above: obese
Some Asian health bodies, including in India, use lower cut-offs (overweight from 23) because risk starts earlier. For children and teens, BMI is compared with age-and-sex charts (percentiles), not with the adult chart.
Limits of BMI
BMI cannot tell muscle from fat. A muscular athlete may show "overweight" while being very fit. It also says nothing about where the fat is.
Waist-hip ratio and skinfold measurement
Waist-hip ratio (WHR)
Measure the waist at its narrowest point (around the belly button) and the hips at their widest point, in the same unit. WHR = waist ÷ hip. It has no unit.
Common risk guide: above about 0.90 for men and 0.85 for women means more belly fat and higher risk of heart disease and diabetes.
Skinfold test
A tool called a skinfold caliper pinches a fold of skin and the fat under it and measures its thickness in millimetres. Common sites are the triceps (back of the upper arm), biceps, below the shoulder blade (subscapular) and above the hip bone (suprailiac). The sum of several sites is put into a formula or table to estimate body fat percentage. Use the right side, take each reading 2 times and use the average.
Somatotypes (body types)
A somatotype is a person's body shape type. The scientist W. H. Sheldon described three types:
- Endomorph: round and soft body, wide hips, gains fat easily. Often good at events needing mass, such as shot put or sumo.
- Mesomorph: muscular, broad shoulders, narrow waist, gains muscle easily. Often good at sprinting, gymnastics, wrestling.
- Ectomorph: thin, long arms and legs, little fat and muscle. Often good at long-distance running, high jump, basketball.
Most people are a mix. A somatotype is written as three numbers from 1 to 7, like 2-6-2 (mostly mesomorph).
Measuring health-related fitness
Health-related fitness has five parts. Each has a simple test:
- Body composition: BMI, waist-hip ratio, skinfold.
- Cardiovascular endurance: 600 m run/walk or a step test.
- Muscular strength: grip strength with a hand dynamometer.
- Muscular endurance: partial curl-ups or push-ups in a set time.
- Flexibility: sit-and-reach test.
Use the same method each time, warm up first, and record the results to compare later.
Try it at home
With an adult's help, measure your height (stand against a wall, no shoes) and your mass on a scale. Work out your BMI on paper, then check it with the slider in the 3D. Next, measure your waist and hips with a soft tape and find your waist-hip ratio. Remember: for students under 18, a doctor uses an age chart, so treat your number as practice, not a diagnosis.
Key formulas and definitions
- BMI = mass (kg) ÷ [height (m)]²
- Adult BMI: < 18.5 underweight · 18.5–24.9 healthy · 25–29.9 overweight · ≥ 30 obese
- Waist-hip ratio = waist circumference ÷ hip circumference
- Higher risk: WHR > 0.90 (men), > 0.85 (women)
- Somatotypes: endomorph (round) · mesomorph (muscular) · ectomorph (thin)
- Test → measurement → evaluation
Worked examples
1. Riya has a mass of 50 kg and a height of 1.60 m. Find her BMI and category (adult chart).
Height² = 1.6 × 1.6 = 2.56. BMI = 50 ÷ 2.56 ≈ 19.5 kg/m². This is in 18.5–24.9, so healthy.
2. A man is 175 cm tall and weighs 92 kg. Find his BMI.
175 cm = 1.75 m. 1.75² = 3.0625. BMI = 92 ÷ 3.0625 ≈ 30.0 kg/m². This is 30 or above, so obese on the adult chart.
3. A woman's waist is 84 cm and her hips are 96 cm. Find her waist-hip ratio. Is it in the higher-risk range?
WHR = 84 ÷ 96 = 0.875. For women, above 0.85 is higher risk, so yes, she should reduce belly fat.
4. What mass would a 1.80 m tall adult have at a BMI of exactly 25?
Mass = BMI × height² = 25 × 3.24 = 81 kg.
Common mistakes
- Using height in centimetres. 64 ÷ 160² gives a tiny wrong number. Always change to metres first.
- Forgetting to square the height. Divide by height × height, not by height once.
- Thinking a high BMI always means fat. Muscular athletes can have a high BMI and little fat.
- Mixing up test and measurement. The test is the tool or task; the measurement is the number.