Taking Height, Weight and ‘BMI’ Measurements

Taking weight measurements

To ensure you take reliable measurements using body weight scales you must:

1. Zero the scales before the client steps onto them
2. Ask the client to remove any ‘heavy’ items from their pockets (key’s, wallets etc) and remove any heavy items of clothing or apparel (big jackets, shoes, woollen jerseys etc)
3. Ensure you note the clients state and time of day for testing to ensure any subsequent tests can be taken under identical conditions (check state of hydration, food consumed recently etc)
4. When measuring weight – ask client to look straight ahead and stay still on the scales.  Wait for the needle/digital screen to settle before recording the measurement

Taking height measurements

Ideally height measurements will be taken using a ‘drop down’ tape measure fixed at about 2metres on a wall or a specific piece of measuring equipment as shown adjacent.  A reliable measurement could be taken without this equipment by marking a point (top of clients head) against a wall and measuring up to it.

When taking measurements of height you must:

• Ask your client to remove their shoes prior to taking the measurement
• Ask your client to stand with their back to the wall and look directly forward.  The back of their feet, calves, bottom, upper back and the back of their head should all be in contact with the wall.  They should be positioned directly underneath the drop down measuring device.
• Lower the measuring device until it rests gently on the top of your clients head and record the measurement

Calculating BMI (body mass index)

A very common method of measuring bodyweight as a risk factor (cardiovascular disease, diabetes etc) is BMI (Body Mass Index).  The calculation is based on comparing a person's weight against their height. It applies equally to men and women.

The equation for BMI is:

BMI =             Weight (kg)

                      Height (m)²

The following table categorises people according to their BMI results:

BMI – The Pros

Measuring BMI is an inexpensive method which can be used to assess if a clients body weight compared to their height is healthy or not.  It can also be used to assess their weight as a risk factor for the development of diseases.  BMI is also easy to calculate and the results are repeatable and consistent.

BMI  – The Cons

The BMI is not very valid. For instance, it is possible for a healthy, muscular person with very  low body fat to be classified obese using the BMI formula. This is because muscle weighs more than fat.  BMI assumes that any excess weight is bad regardless of whether that weight is fat or muscle, as BMI doesn’t differentiate between the fat and muscle.

Summary

As fitness professionals, BMI is one of the least valid tests you can use in order to programme effectively and motivate your clients as there is no specific measure of changes such as a reduction in size and body fat rather than just a reduction in weight.  BMI is used to show changes in large populations over time – it has very little use when applied to individuals.

The following chart can be used as an alternative for calculating clients BMI, by finding their height and following it across until it meets the line of their weight.