We are a lazy lot when it comes to physical activity. Most adults take little physical exercise. Swimming is popular, but often only on holiday. And why do so many teenage girls hate sport? This picture stimulates discussion about sport, health, exercise and behaviour.

Swimming

Swimming is the third most common physical activity among boys (after football and cycling) and the second most common with girls (after cycling). Why do people like swimming (clean exercise; simple to arrange, no team or equipment needed; healthy for the heart; no stresses and strains on joints; relaxing)? Why does the national curriculum expect 11-year-olds to be able to swim 25 metres (most people who drown are non-swimmers)?

Safety

Stress danger of (a) riptides pulling you out to sea (don’t ignore red flag or warning notice); (b) getting out of your depth on an inflatable without a life jacket; (c) young adults drinking alcohol and drowning; (d) inury if you dive into shallow water.

Sport

Guess what percentage of boys and girls aged 14 to 15 say they like sport “a lot” (58 per cent of boys, 28 per cent of girls). Why do boys enjoy football, while so many girls switch off sport? What sort of activities might appeal more (aerobics? dance? badminton? Ones for which you wear a leotard or football shirt instead of gym kit?)? What sport helps the heart most (doctors say it is healthy to get your heartbeat above 140 a minute for 20 minutes three times a week by, for instance, running, vigorous dancing, aerobics, but not slow walking or watching television!)?

Biomechanics

How do our limbs move? In swimming we try to displace water with each stroke, so what helps and hinders performance (we can rotate arms full circle, but not legs; we can bend elbows and knees in one direction only; long arms and legs help in swimming and throwing because of leverage; tall people have an advantage in basketball)?