Test, Measurement and Evaluation III: Anthropometric Measurements, Landmarks and the Measurement of Body Segments, Height, Sitting Height, Weight, Diameters, Circumferences and Skinfolds, the Body Mass Index and Ponderal Index, Somatotype and Posture Evaluation, the Testing of Physiological Phenomena, and Tests for Psychological Variables

The body mass index, BMI = weight in kilograms ÷ (height in metres)², relates weight to height: a 72 kg athlete 1.80 m tall has a BMI of 72 ÷ 3.24 ≈ 22.2. Its classification bands and limitations were given in Unit VI; for athletes its main limitation is that it cannot separate muscle from fat. The ponderal index relates height to the cube root of weight. In the form used in physique studies, it is height ÷ ∛weight; with height in centimetres and weight in kilograms, a person 180 cm tall weighing 64 kg (whose cube root is 4) has a ponderal index of 180 ÷ 4 = 45. In this form it is also called the height–weight ratio (HWR) and is the basis of the ectomorphy rating in the Heath–Carter somatotype; Sheldon used the same ratio with height in inches and weight in pounds (a 72-inch person weighing 216 lb has 72 ÷ 6 = 12), so values depend on the units. A higher value means a more linear, slender build. The name "ponderal index" is also used in paediatrics for a different quantity, weight ÷ height³ (Rohrer's index, in kg/m³), so the formula and units should always be stated.

Somatotype is the quantification of body shape and composition. William Sheldon (1940) described three components: endomorphy (relative fatness, roundness and softness), mesomorphy (relative musculoskeletal robustness, a muscular, broad-shouldered build) and ectomorphy (relative linearity and slenderness). Each is rated, and the somatotype is written as three numbers always in that order, endomorphy–mesomorphy–ectomorphy: a 1–7–1 is an extreme mesomorph, a 2–5–2 a balanced mesomorph, and a 7–1–1 an extreme endomorph. Sheldon rated physique from standardised photographs on a 1–7 scale for each component and considered it largely fixed. The Heath–Carter method (Barbara Heath and J. E. Lindsay Carter, 1967), now standard, can be applied by anthropometry: endomorphy from the sum of the triceps, subscapular and supraspinale skinfolds, corrected for height; mesomorphy from the biepicondylar breadths of the humerus and femur, the flexed arm girth and calf girth (each corrected for skinfold) and height; and ectomorphy from the height–weight ratio. Its scale is open-ended and in half units, and the somatotype can change with training and nutrition. Ratings are plotted on a two-dimensional somatochart. Somatotype is used to describe athletes, since elite performers in many sports cluster in characteristic regions (throwers and sprinters towards mesomorphy, distance runners and high jumpers towards ecto-mesomorphy), and in talent identification.

Posture is evaluated by observation against a plumb line, from the side (ear lobe, shoulder tip, greater trochanter, just in front of the knee and just in front of the lateral malleolus) and from behind (the line should bisect the head, spine and the space between the heels, with the shoulders and hips level). The New York State Posture Rating Chart rates thirteen body areas, each scored 5 (good), 3 (fair) or 1 (poor) against illustrated standards. Other methods include photographs and silhouettes on a grid, the conformateur, flexible rulers and inclinometers for spinal curves, Adam's forward-bend test for scoliosis (a rib hump on bending forward suggests a structural curve), and footprint (podograph) tests for flat foot. Suspected structural deformities should be referred for medical examination.

Blood pressure is measured with a sphygmomanometer and stethoscope by the auscultatory method: the cuff is inflated above systolic pressure and slowly deflated, and the first Korotkoff sounds mark the systolic pressure and their disappearance the diastolic pressure; a typical adult resting value is about 120/80 mmHg, and the difference between the two is the pulse pressure (120 − 80 = 40 mmHg). Breathing frequency is counted, unobtrusively, over a full minute; a typical resting adult rate is about 12–20 breaths per minute. Vital capacity, the largest volume that can be exhaled after a maximal inhalation, is measured with a spirometer and equals tidal volume + inspiratory reserve volume + expiratory reserve volume: 0.5 + 3.0 + 1.2 = 4.7 litres in a typical young man; it is larger in taller people and in men. Heart rate is the number of heartbeats per minute and pulse rate the number of arterial pulsations felt, normally the same; the pulse is taken at the radial artery at the wrist or the carotid at the neck, counted for 15 seconds and multiplied by 4 or for 30 seconds and multiplied by 2 (18 beats in 15 seconds is 72 per minute), or recorded with heart-rate monitors. Body temperature is about 37 °C orally, slightly lower at the armpit and higher rectally, and is measured with clinical, digital or infrared thermometers.

Body composition, the proportions of fat mass and fat-free mass, is measured by several methods. Hydrostatic (underwater) weighing, long the reference field-laboratory method, calculates body density from the loss of weight in water and converts it to percentage fat by equations such as Siri's, % fat = (495 ÷ density) − 450: a density of 1.060 g/cm³ gives 495 ÷ 1.060 − 450 ≈ 467.0 − 450 = 17.0 per cent. Air-displacement plethysmography (the Bod Pod) measures body volume by displaced air. Dual-energy X-ray absorptiometry (DEXA) measures fat, lean and bone mass regionally. Skinfold equations (such as those of Jackson and Pollock or Durnin and Womersley) predict density from skinfold thicknesses, and bioelectrical impedance analysis (BIA) estimates body water, and hence fat-free mass, from the resistance of the body to a small electrical current, which is affected by hydration.

Psychological inventories are self-report instruments, so their results depend on honest answers and are open to social desirability, faking and the athlete's mood on the day. They should be used with their published instructions and norms, by people competent to interpret them, with the athlete's consent and with confidentiality; they are best used to understand and help athletes, for example in planning psychological skill training, rather than to select or exclude them. Indian adaptations and translations should be checked for their own reliability and validity.