What basic measurements do fitness professionals rely on?

There are four basic measurements:

1. Body Mass Index (BMI)

2. Blood Pressure (BP)

3. Resting Heart Rate (RHR)

4. Waist-to-Hip Ratio (WHR)

Below is an outline of these measurements, their units, and the charts used to evaluate a given measurement.

Body Mass Index (BMI)

What is it?

The BMI is the relationship between a person’s weight and their height squared, and is a rule of thumb used to broadly categorize a person as underweight, normal weight, overweight, or obese.

What is the measurement unit?

BMI is measured in kilograms per metres squared (kg/m²)

How is a given measurement evaluated?

Blood Pressure (BP)

What is it?

Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels, mostly resulting from the heart pumping blood through the circulatory system.

Systolic pressure refers to the pressure when your heart is beating, while diastolic pressure refers to the pressure between heartbeats.

What is the measurement unit?

Blood pressure is measured in millimetres of mercury (mmHg) above the surrounding atmospheric pressure.

The unit mmHg comes from an experiment by Italian physicist, Evangelista Torricelli. In the experiment, Torricelli would dip a glass tube filled with mercury into a bowl also filled with mercury, keeping the open end of the tube submerged. While gravity would act on the mercury inside the tube by pulling down, leaving a partial vacuum at the top end of the tube, the air pressure surrounding the bowl would keep the mercury in the tube afloat, specifically at a height of 760 millimetres (at sea level). This unit has ever since been used as a way of describing pressure. Hence, the name of the unit is millimetres of mercury (mmHg).

How is a given measurement evaluated?

Resting Heart Rate (RHR)

What is it?

Your heart rate is the number of times your heart beats per minute. A normal heart rate is between 60 and 100 bpm while you are resting.

What is the measurement unit?

Beats per minute (bpm)

How is a given measurement evaluated?

A low resting heart rate usually means your heart muscle is in better condition, and doesn’t have to work as hard to maintain a steady beat.

Your Maximum Heart Rate (MHR) is approximately 220 minus your age.

Your Target Heart Rate (THR) is 50-70% of your maximum heart rate. You should aim to exercise with your heart rate between these two figures to make sure you increase your fitness and strength safely.

Waist-to-Hip Ratio (WHR)

What is it?

Waist-to-hip ratio is the dimensionless ratio of the circumference of the waist to the circumference of the hips.

What is the measurement unit?

According to the World Health Organization (WHO), the waist and hips should be measured as follows:

• Waist circumference should be measured at the midpoint between the lower margin of the last palpable ribs and the top of the iliac crest. The measurement should also be taken at the end of an exhale.

• Hip circumference should be measured around the widest portion of the buttocks.

How is a given measurement evaluated?

According to WHO, a healthy waist-to-hip ratio is:

• 0.9 or less in men

• 0.85 or less for women

More specifically, the cut-off points for waist circumference and waist-to-hip ratio, and their indications, are as follows:

Men

• A waist circumference cut-off point that is > 94 cm indicates an Increased Risk of metabolic complications.

• A waist circumference cut-off point that is > 102 cm indicates a Substantially increased risk of metabolic complications.

• A Waist-to-Hip Ratio cut-off point that is ≥ 0.90 indicates a Substantially increased risk of metabolic complications.

Women

• A waist circumference cut-off point that is > 80 cm indicates an Increased Risk of metabolic complications.

• A waist circumference cut-off point that is > 88 cm indicates a Substantially increased risk of metabolic complications.

• A Waist-to-Hip Ratio cut-off point that is ≥ 0.85 indicates a Substantially increased risk of metabolic complications.