Sport is the leading cause of injury in youth, with the lower extremity being the most common injury location. Additionally, more injuries occur during the period of peak growth and maturation and are more prominent in females compared to males. In order to reduce injury risk, injury prevention (IP) programs have been developed and successfully implemented in youth. However, there is limited research specifically targeted at youth females, including what components of an IP program are most beneficial in this group. The overall purpose of this thesis was to examine the effects of an IP program embedded in the school curriculum on injury risk factors, injury rates and athletic performance measures in youth females. Additionally, there was a focus on better describing injuries in this population, possible association between injury and the phases of the menstrual cycle, and the role strength plays in performance.

To better understand the rate of injuries in this population and to see if an association existed between injuries and phase of the menstrual cycle, an online questionnaire (using an all physical problem definition of injury) was used to record training and competition exposure and self-reported injuries over 30 weeks. On average, girls trained 3.4 hours/week and competed for one hour/week. During the study, 74 participants reported 595 injuries. The average weekly prevalence of all injuries was 20.7% (95% CI: 20.0-21.3), of which 8.6% (95% CI: 8.3-9.0) were acute injuries and 12.0% (95% CI: 11.4-12.6) were gradual onset/overuse injuries. The overall rate of sport and PE injuries was 10.4 injuries/1000 hours of exposure. The most common acute injury involved the ankle (35%), whereas the most common gradual onset/overuse injury involved the knee (51%). There was no significant association between the stage of the menstrual cycle and the likelihood of injury (P = 0.18). There were significant differences between strength groups (strong, average and weak as measured by isometric mid-thigh pull) for all performance measures. Strong girls (SG) had significantly faster sprint times than average girls (AG). Additionally, SG and AG performed significantly better than weak girls in all assessments. The results from both studies demonstrate the need for an IP program targeting the lower extremity.

Finally, the effect of an IP program, integrated into the school curriculum, on injury risk factors and athletic performance measures in youth females was examined [intervention (INT) n = 43, control (CON) n = 49]. The INT group completed a 23 week IP program whereas the CON group continued normal physical education class. The overall adherence to the IP program was 82%. Significant improvements were found in movement skill (approximately 80% more likely to have an improved movement skill as measured by the back squat assessment and drop vertical jump) and balance (as measured by the y-balance) for the INT group compared to the CON group [mean difference (95% CI) = 2.07 cm (0.48 to 3.66 cm) and 2.66 cm (1.03 to 4.29 cm), respectively]. A significant difference was found in weekly training and competition hours with the INT group (who competed at a much higher level of competition) reporting greater sports participation than the CON group (4.15 vs 2.19 training hours and 0.77 vs 0.55 competition hours). There was no significant difference found in any of the injury rates between the two groups.

These findings highlight that a long-term IP program integrated into the school curriculum can improve movement quality and balance in youth females and it may be protective against increased injury risk for youth females competing at higher levels of competition. It is recommended that practitioners implementing this program should ensure good adherence, individual progression and a focus on movement technique.