Once upon a time, health professionals seemed to be in agreement that body mass index (BMI) was the surest way to measure someone's health. But in recent years, this has been challenged by scientists who suggest that the test is outdated, throws up anomalies and hence should be ignored. We spoke to Tom Woolf, a former professional rugby player and the founder of PTX Performance Training in Dubai, about which system is the truest gauge of one's health.
BMI
What it is A measurement computed by taking one's mass in kilograms and dividing it by the square of one's height in metres. From this, 18.5 is considered underweight, between 18.5 and 24.9 is normal, 25 to 29.9 is overweight and 30 or more is clinically obese.
Pros It's simple to calculate, meaning anyone with a set of scales, a tape measure and calculator can figure it out.
Cons Tom Woolf explains: "Under the system, someone like [the former England rugby union player] Jonny Wilkinson would be deemed clinically obese because of his height to weight ratio and his bone and muscle density. Muscle is a lot denser than fat, so someone who has a lot of muscle can be heavy, even though they're extremely fit, so clearly [BMI] throws up a number of anomalies."
Body composition analysis
What it is Usually conducted with a modern, bioelectronic machine that forces a weak electric current through your body to reveal your fat content, bone density, muscle mass and water levels.
Pros It enables you to work out the exact proportion of various elements in the body, so it's a lot more accurate than BMI. "We use it when people are coming to us to get fitter, rather than just measuring absolute weight or BMI, as we can see exactly how our programmes are affecting them," says Woolf.
Cons "It is prone to a number of anomalies," says Woolf. "Someone like a sumo wrestler or a professional rugby prop forward are big, roly-poly guys with high fat content, but will score very highly in fitness tests, and probably be in the top one percentile globally."
Heart rate
What it is This is measured in one of two ways. First, as a resting heart rate, in which a lower result indicates a much stronger cardiac muscle, hence a better metabolic rate. A rate of between 60 and 90 beats per minute is considered normal, while elite athletes may register between 40 and 60 beats per minute. Second, as recovery, in which your heart's beats per minute are measured for a fixed period (usually one minute) after ceasing activity. The closer it is to one's pre-exercise heart rate, the fitter you are.
Pros "It's a very good indicator of aerobic capacity," says Woolf. "If someone is getting fitter, then both resting heart rate and recovery heart rate should decrease over time."
Cons "We find that it's not always accurate, as different climates can have different results on people. For example, someone who is from a European, cold environment who's not used to the climatic conditions over here would have a faster heart rate," says Woolf.
Waist-to-hip ratio
What it is A fitness measurement that's worked out by dividing the narrowest point of your waist by the widest point of your hips. According to some scientists, a ratio of 0.7 - or a waist measurement that is exactly 70 per cent of the hip circumference - is the ultimate goal for women.
Pros All you need is a tape measure and a calculator. For women, it takes into account that some voluptuous women may still be healthy, even though they have a comparatively high percentage of body fat.
Cons "We wouldn't use this as it's very reliant on genetic factors," says Woolf. "People store fat in different parts of their body, so it can skew the results in different ways. These are good for health practitioners to ascertain whether there will be longer-term risks, but they're not a good indicator of fitness."
VO2 Max test
What it is An analysis to ascertain the maximum amount of oxygen, in millimetres, one can use in a minute per kilogram of body weight. Those with high results can use oxygen more efficiently and thus exercise more intensely than those who are out of shape. Your average, untrained, young person will have a VO2 Max in the 40s, while an elite endurance athlete may record results in the 80s. Measuring VO2 Max accurately requires an all-out effort (usually on a treadmill or bicycle) with special breathing measurement equipment in a sports performance lab.
Pros It's a very scientific indicator of a person's aerobic capacity.
Cons Accurate results require a lab full of expensive equipment. Also, it fails to take into account the subject's strength. "We use this test to measure aerobic capacity," says Woolf, "but we also measure anaerobic capacity and strength. You need to take into account all of these when working out someone's fitness levels."