The main findings of the present study were as follows: (1) 9.1% of adolescent amateur weightlifters had received orthopaedic treatment, and spine-related injuries were the the most frequently treated injuries (44.4%). There were no significant sexual differences. (2) Of the adolescent weightlifters who did not receive orthopaedic treatments, 31.1% had pain in the spine or lower extremities that had lasted for > 4weeks, and 65% of weightlifters with LBP had positive findings on the Kemp test. There were no significant sexual differences. (3) There were significant sexual differences in the tightness of quadriceps and dorsiflexion of the ankle joint between male and female adolescent weightlifters.
Several studies have reported on the injuries among adult elite weightlifters, noting that the shoulder, spine, and knee were the most common injury locations [4, 8, 31]. Calhoonn et al. reported that acute injuries accounted for 59.6% of injuries, while chronic injuries accounted for 30.4% [32]. According to a systematic review, the incidence of injuries in weightlifters was similar to that in other non-contact athletes [8]. To the best of our knowledge, the present study was the first and largest population study to evaluate injuries and physical characteristics in adolescent amateur weightlifters. Spine-related pain and injuries were the most prevalent in adolescent weightlifters, similar to findings in elite adult weightlifters [8, 31, 32]. Almost 20% of young weightlifters had LBP for > 4weeks, and 65% of those weightlifters with LBP had positive findings on the Kemp test. LBP is a common symptom in young athletes, and Micheli et al. reported that spondylolysis was the most common cause of LBP, accounting for 47% of cases [33]. It was reported that 91.7% of young weightlifters had abnormal findings of the spine on magnetic resonance imaging (MRI) at the end of a 3-year cohort study [11]. Sakai et al. reported that the bone healing rate was 93.8% in early-stage spondylolysis [34]. Therefore, screening of LBP, especially for the early detection of spondylolysis, may be needed to protect young weightlifters. It was reported that the prevalence of injuries and positive findings of physical examinations were the highest in weightlifting among the 4 sports activities [20]. Thus, orthopaedic medical examinations are recommended for screening injuries in adolescent weightlifters.
The results of the present study demonstrated no significant sexual differences in the incidence of injury, pain in the spine or lower extremities, or the findings of physical examinations. It was reported that young female athletes sustained more injuries to the spine and lower extremities than young male athletes due to a retrospective review of 2,133 young athletes [14]. Some authors have found that female athletes had a greater risk of knee injuries than males [35, 36]. The sexual differences in the incidence and type of sports-related injuries are influenced by a number of factors [15–19]. Especially during puberty, different growth patterns between the sexes, including the bone mineral density, can influence on the sports related injuries [37]. Quatman et al. reported sexual differences in “weightlifting” related injuries among non-weightlifters [5]. However, no studies have evaluated the sexual differences in injuries among competitive weightlifters. In the present study, female weightlifters showed a significantly lower dorsiflexion of the ankle joints than male weightlifters. Restricted dorsiflexion of the ankle joint is associated with increased knee valgus, a decreased knee flexion angle, and increased ground reaction forces on landing [38–40]. Therefore, limited dorsiflexion of the ankle may be a risk factor for knee injuries, such as anterior cruciate ligament injury and patellofemoral pain [39, 40]. Bell et al. reported that medial knee displacement during squatting was reduced by improving the dorsiflexion of the ankle joint [41]. Therefore, intervention to improve the dorsiflexion of the ankle joint may be necessary to prevent injuries in female weightlifters. However, the current study was unable to draw conclusions concerning sexual differences in weightlifters due to its retrospective design and limited population size. Further studies are thus needed to investigate sexual differences in young weightlifters as well as in adult weightlifters in order to individualize prevention and treatment strategies for weightlifting.
Whether or not early specialization is required for weightlifters remains controversial. All of the participants in this study had early specialized in weightlifting. Early sports specialization may be necessary for some sports, including gymnastics and figure skating, because the best performance is achieved before physical maturation [42, 43]. However, early sports specialization is associated with an increased risk of overuse injuries, burnout, and depression [43–47]. Bush et al. reported that 68.8% of adult elite weightlifters did not think early specialization necessary to achieve elite status [12]. Furthermore, the American Academy of Pediatrics recommended that preadolescents and adolescents should avoid maximal lifting before physical and skeletal maturity [7]. More studies will be required to evaluate the influence of early specialization on physical and psychological problems in adolescent weightlifters.
There were several limitations to the present study. First, the orthopaedic medical examinations in this study did not evaluate the upper extremities. Shoulder injuries are common in weightlifters [4, 5], therefore, future studies will be required to evaluate the injuries and physical characteristics of upper extremities in adolescent weightlifters. Second, the number of adolescent female athletes included in this study was not large. However, few female weightlifters specialize in competitive weightlifting at an early age, so this may have been unavoidable. Third, the orthopaedic medical examinations were performed cross-sectionally (annually). Therefore, the influence of early specialization on the career of weightlifters was not evaluated. Despite these limitations, the present study provided useful information regarding young amateur weightlifters for clinicians and researchers as well as weightlifters and their healthcare providers.