The incidence of hamstring injuries per athlete-seasons was 137.9 for period 1, 60.6 for period 2, and 6.7 for period 3, with the incidence decreasing significantly for each of the 3 periods (w2(2) ¼ 31.78, P < .001; effect size: Cramer V ¼ 0.23, 1 b ¼ 0.999).