Weight, Muscle & Body Fat
Hawley, J., and L. Burke. Changing body size and shape. In: Peak Performance: training and nutritional strategies for sport by J. Hawley and L. Burke. Sydney: Allen & Unwin, 1998, p. 233-260.
Burke, L. Swimmers: body fat mystery! Sportscience News Nov-Dec 1997.
In some sports, particularly those based on skill (eg golf, archery and shooting), performance is largely independent of body fatness. Both selection and conditioning factors tend to allow higher body fat levels in these athletes. In fact, top performers in these sports may actually be overweight (or over-fat) by community standards. At the other end of the spectrum there are sports in which a low body mass, and in particular a low body fat level, are a distinct advantage to performance. The advantages of a low body fat level include physical and mechanical gains due to an increased power to mass ratio, or simply to a reduction in the 'dead weight' that must be moved by the athlete. This is a particular advantage where the athlete has to transport their own body mass over long distances (eg distance runners, triathletes, road cyclists) or to move vertically against greater gravity effects (gymnasts, jumpers, basketball players, or cyclists riding a hilly course). Higher body fat levels are seen in endurance athletes, most notably swimmers, who perform in a weight-supported sport. A high 'power to mass' ratio plays a role in 'stop-start' sports by increasing speed, agility and the ability to change direction quickly. In some team sports, players in mobile field positions or with a mobile playing style are often observed to have lower body fat levels than their team-mates. On the other hand, particularly in sports involving physical contact, a higher body fat level may be less problematic for 'set position' players. A certain level of body fat may help to protect body organs against injury from body contact, and to provide bulk against tackling. Nevertheless, a high body mass should be achieved principally through an increase in muscle mass.
Swimmers, especially female swimmers, face an energy balance conundrum. Elite swimmers typically undertake 4000-20,000 m per day in training, burning thousands of calories. However, the typical body fat levels of these athletes are significantly higher than runners or cyclists who expend similar or even smaller amounts of energy in their training. Many female swimmers have fought well-publicized battles with their body fat levels and with their coaches! They are generally prescribed "land training" (running or cycling) in addition to their many laps of the pool in the belief that it is a necessary treatment to produce lower skinfold levels.