School-age swimmers who want to follow Rebecca Adlington's Olympic gold medal feats will be subjected to an unacceptably heavy training regime, say researchers at Leeds Metropolitan University. By the age of 11 or 12, top athletes are expected to swim up to 32 miles a week - up to 27 hours in the pool. By 14, many are swimming 40 miles, equivalent to running 160 miles. A netball player of similar age and ability would train for only four and a half hours a week. Researchers say an excessive regime can inhibit bone growth and cause mental and physical burnout.