Dismiss the myth: No. 6: Fitness tests are accurate (part 1)
Physical fitness is an elusive concept that is difficult to define, but it may be conceived as 11 components grouped into two broad categories - the agility, balance, co-ordination, power, speed and reaction time related to physical fitness; and the aerobic (or cardiovascular) fitness, muscle strength and endurance, flexibility and body composition related to health.
In this series I'll focus on health-related fitness.
The assessment and interpretation of young people's health-related fitness is one of the most complex problems in applied physiology. And fitness tests, suitable for use in schools, which provide valid measures of fitness, are currently not available. Fitness tests used in schools tend to measure performance, rather than underlying physiological processes. Only part of the score obtained from performance tests - shuttle runs, sit-ups, press-ups, flexed arm-hangs - concerns health-related fitness. For example, the 20 metre shuttle run - the bleep test - is the most popular test of aerobic fitness, but although related to aerobic fitness, it is also dependent on other factors, which include motivation, running efficiency, clothing, footwear, running surfaces, body mass and composition, the weather and anaerobic capacity.
The key weakness of all performance tests is that they do not take into account students' motivation to do well. All performance tests depend on the enthusiasm of the student. This was vividly illustrated 50 years ago in the USby a physiologist called Schwab. He required students to hang from a horizontal bar to test muscle endurance. Told to hold on as long as possible, students managed an average of less than one minute. The test was repeated with the same students, but this time they were offered a $5 reward if they hung on longer than before. On average, they hung on for nearly two minutes. So their muscle endurance doubled with a financial inducement!
Motivation, however, is not the overriding reason to be extremely wary of fitness tests. Children's biological clocks run at different rates and with a class of 13-year-old boys, a teacher may be testing a group in which 10 per cent are pre-pubertal, 10 per cent are almost fully mature and the remainder are somewhere in between.
Next week I'll explore the effects of growth and maturation on fitness tests and show why comparing students' fitness test scores is grossly unfair.
Professor Neil Armstrong is the director of the Children's Health and Exercise Research Centre, Exeter University