Participants with higher IKDC scores demonstrated an increased likelihood of presenting with greater involved limb quadriceps strength and better Q-LSI. Based on the results of this study, a patient-reported outcome measure, such as the IKDC, may be able to serve as a valuable screening tool for the identification of quadriceps strength deficits in this population; however, it should not be considered an accurate surrogate for isokinetic dynamometry. Furthermore, a score of ≥94.8 on the IKDC is likely to indicate that a patient's quadriceps strength is at an acceptable RTS level.

Both the ACLR-U and the ACLR-B groups demonstrated side-to-side deficits during functional hop tests; however, these deficits were not identified according to the clinically accepted LSI values of ≥90%, calling into question the efficacy of current RTS criteria. At the time of RTS, only individuals in the ACLR-U group demonstrated an altered LSI in quadriceps strength. Significantly lower quadriceps strength of both limbs in the ACLR-B group was seen compared with the CTRL group, despite no LSI deficits in quadriceps strength. Current use of LSIs during strength and performance tests may not be an appropriate means of identifying residual deficits in female patients after bilateral ACLR at time of RTS. Furthermore, a better indicator of strength performance in this population may need to include a comparison of strength performance values to the normative values of healthy controls.

Context:The rising incidence of physical activity– and sports-related injuries has prompted the present-day investigation of resistance training as a potential means of injury prevention and physical literacy development among youth.Evidence Acquisition:Relevant studies on the topics of athlete development, physical literacy, resistance training, and injury prevention in children and adolescents were reviewed (PubMed and Sports Discus, 1982-2016). Recommendations from consensus guidelines and position statements applicable to resistance training and injury prevention in youth, in addition to young athlete development, were reviewed. Additionally, hand searches, expert requests, article reference lists, and gray literature were utilized and reviewed for pertinent content.Study Design:Clinical review.Level of Evidence:Level 4.Results:Youth throughout the physical activity spectrum are at risk for physical activity– and sports-related injury. Of highest priority are early specializers, physically inactive youth, and young girls, owing to increased injury rates. Resistance training among these at-risk populations has been shown to reduce injury risk by up to 68% and improve sports performance and health measures, in addition to accelerating the development of physical literacy. Recent recommendations, position statements, and national initiatives advocate for the incorporation of resistance training with qualified instruction among these groups.Conclusion:Resistance training in addition to free play and other structured physical activity training can serve as a protective means against injury and a positive catalyst for the development of physical literacy to offset the impact of diminishing physical activity and early sport specialization in today’s youth.

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