Terms and nomenclature

In 1963, B. K. Forscher had a letter published in Science entitled ‘‘Chaos in the brickyard’’, in which he expressed concerns about the proliferation of meaningless studies that did not adhere to the high ideas of accuracy and sound theory building of science. This resonates with our similar concerns about terms and nomenclature that interfere with advancements in sport and exercise science. The introduction in 1960 of the Système International d’Unités should have established correct applications of mechanical constructs to describe and quantify the performance of exercise. In spite of attempts from authors such as Adamson and Whitney (1971), Knuttgen (1978), Rodgers and Cavanagh (1984), and Winter and Fowler (2009) to ensure that such applications occur, there are many instances where they do not. For example, in the context of body size, distinctions between weight and mass are frequently not made. Mass is the amount of matter in a body and weight is the force exerted by that body that arises from gravitational attraction. Body weight of humans should be reported in newtons (N) yet frequently it is misreported in the unit of mass (kg). If you want to lose weight, go to the moon and you will weigh about a sixth of what you weigh on earth. However, it is probably mass you want to lose and while you might well do so on the long extraterrestrial journey, there are simpler ways to achieve that requirement. Similarly, the terms ‘‘work’’, ‘‘power’’, and ‘‘efficiency’’ are often misused. In humans, the expenditure of energy does not always result in motion. For instance, recruited muscles can be active isometrically. Examples are suspension and balance in gymnastics, the scrum in both codes of rugby, and fine motor tasks involved in archery and shooting. Even so, the expenditure of energy can be considerable; for instance, try performing a Maltese Cross in gymnastics. Similarly, activities of daily living require isometric muscle actions exemplified by the tightening of screw-tops on jars or holding objects during domestic tasks. When motion does occur, mechanical work is done and for nutritional and other reasons, quantification of the amount of work that is performed can be valuable. Of more use, however, is the rate at which work is done (i.e. power output). But for reasons outlined by Knudson (2009), ‘‘power’’ is probably the second most abused term in sport and exercise – the first is likely ‘‘efficiency’’ (Winter, 2009) – and there are still legions who genuflect at the altar of vague calculations of power and efficiency oblivious to the misapplications that are being made. In projectile activities such as vertical or horizontal jumping where the body is the projectile or in throwing an implement or striking a ball, the decisive factor in determining performance is the velocity of the projectile as appropriate, at take-off, release or departure. This velocity is exactly determined by the preceding impulse that is imparted to the projectile (i.e. the force–time integral). Newton’s second law that is written as the impulse–momentum relationship clearly demonstrates and encapsulates the relationship. Here ‘‘velocity’’ is appropriate because it encompasses both magnitude and direction. For activity of long duration where laudable attempts are made to identify limits of tolerance to exercise, for nearly 50 years the term ‘‘critical power’’ has been used to describe these limits (Monod & Scherer, 1965). Unfortunately, ‘‘critical power’’ has limited applicability; it is an inappropriate use of the term ‘‘power’’. It cannot be used with activities such as running or swimming where performance is quantified either as time (t) or speed (m s); neither is the unit of power (i.e. the watt). The term ‘‘critical power’’ cannot be used when isometric muscle activity occurs because no external mechanical work is done, and hence there cannot be power output. Even in activities such as cycling where it is possible to assess a mean external power output on a bicycle or ergometer, if pedalling rate is increased, ‘‘critical power’’ is adversely affected. The reason is simple: more energy is required to move the limbs, and hence less is available for useful external output. The distinction between these internal and external Journal of Sports Sciences, July 2011; 29(10): 999–1000