Effect of Sex and Maturation on Knee Extensor and Flexor Strength in Adolescent Athletes

Lower Extremity Strength Relative to Body Mass in Pediatric Female Athletes: Implications for Anterior Cruciate Ligament Injury

This study compared lower extremity (LE) muscular strength by 3 groups of female athletes using chronological age and consideration of age of peak height velocity (PHV). Isometric quadriceps, hamstrings, and hip abductors strength were assessed from physically active, pediatric females. The body mass normalized isometric strength (N m/kg) was compared by the 3 age groups. There were 388 young female athletes (<10 years [14.2%], 11-14 years [48.7%], and 15-18 years [37.1%]). The body mass normalized LE strength was lower in 11-14 years compared with <10 years (quadriceps [P = .001], hamstrings [P = .001], and hip abductors [P = .037]) as well as in 15-18 years relative to <10 years in quadriceps (P = .001) and hamstrings (P = .001). The analysis results were consistent with both chronological age alone and incorporating effects of age of PHV. In short, body mass normalized LE strength (quadriceps, hamstrings, and hip abductors) of 11-14 years females was lower than <10 years females.

Identifying modifiable risk factors and screening strategies associated with anterior cruciate ligament injury risk in children aged 6 to 13 years: A systematic review

Growing anterior cruciate ligament (ACL) injury incidence is reported in countries across Europe, North America and in Australia for 5-14-year-olds, yet research on injury risk reduction predominantly focuses on populations aged > 13 years. For injury risk reduction, it is crucial to understand (i) which modifiable risk factors are associated with ACL injury in children (6-13 years) and (ii) how these risk factors are assessed. Articles were grouped according to sex/gender and/or maturational/age differences and examined modifiable risk factors during different physical screening tasks. The included articles (n = 40) predominantly examined intrinsic risk factors in girls aged 10-13 years. Factors mechanically linked to increased ACL loading at this age included increased peak knee adductor moments, knee valgus angles, hip and knee extension, and ground reaction forces. Assessment focused on laboratory-based assessments (e.g., motion capture, force plates). This review concluded that modifiable risk factors are present in children aged 6-13 years and that injury risk reduction strategies should be implemented as early as possible regardless of sex/gender. Further, screening strategies need updating to be childhood specific and feasible for the wide community. Additional research on extrinsic risk factors, norm values and children aged 6-9 years could allow for more targeted risk reduction strategies.