Athletes worried about injuries should stay away from spring football, according to statistics compiled by the National Athletic Injury Illness Reporting System. By this measurement, it's in a class by itself as a source of injuries and is more than twice as dangerous as autumn football. Using what NAIRS calls "athlete exposures" -- the number participating times the number of sessions at risk of injury -- to enable comparison of sports with different lengths of seasons, K.S. Clarke and W. Buckley came up with the figures. Grouping the sports "to avoid spurious comparisons of minute differences," the researchers found that women's basketball and women's gymnastics ranked right up there among the men's contact sports in generating "significant" injuries. The two defined a "significant" injury as one which caused the athlete to miss a week of competition. The rates of significant injuries per 1,000 athlete exposures are: spring football (m), 6.3; wrestling (m), 4.2; fall football (m), 3.0; gymnastics (w), 2.7; ice hockey (m), 2.5; basketball (w), 2.5; lacrosse (m), 2.5; soccer (m), 2.6; track and field (w), 2.2; basketball (m), 2.1; volleyball (w), 2.1; track and field (m), 1.9; softball (w), 1.8; gymnastics (m), 1.5; baseball (m), 1.3; field hockey (w), 1.0; tennis (w), 3.6; swinning and diving (m), 0.6; swimming and diving (w), 0.2.