Comparison between warm-up and cool-down stretching programs on hamstring extensibility gains in primary schoolchildren

The purpose of this study was to compare the effects of a physical education-based stretching program performed during warm-up and cool-down periods on hamstring extensibility in schoolchildren aged 9-10 years. A sample of 73 schoolchildren, 36 boys and 37 girls, aged 9-10 years old from three classes were clustered randomly assigned to a no-training group (n = 24), warm-up group (n = 25), or cooldown group (n = 24). During physical education classes, the students of the warm-up and cool-down groups performed a four-minute stretching program twice a week for ten weeks during the warm-up and the cool-down periods, respectively. Hamstring extensibility was estimated by the classic sit-and-reach test at the beginning and at the end of the stretching intervention program. The results of the ANOVA showed that both the warm-up and cool-down students had statistically significant higher values on the hamstring extensibility than the no-training students (p < 0.05). The warm-up and cool-down groups did not show statistically significant differences. Nevertheless, the cool-down students obtained a slightly higher magnitude effect when compared with the warm-up group (g = 0.67 and g = 0.56, respectively). In addition to the slight higher improvement during the cool-down, due to the negative effect of static stretching on performance as previously found in the literature, it seems that physical education teachers should improve students´ flexibility during the cool-down period of the sessions