Healthy Pediatric Athletes Have Significant Baseline Limb Asymmetries on Common Return-to-Sport Physical Performance Tests

Abstract

Background: Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction in children is associated with a much higher risk (∼30%) of subsequent ACL injury than in adults. Most RTS testing protocols use a limb symmetry index (LSI) ≥90% on physical performance tests (PPTs) to assess an athlete’s readiness for sport. This assumes that, in a healthy state, the physical performances across both lower extremities are and should be equal. Purpose: To determine the prevalence of limb asymmetries >10% in the uninjured pediatric population on common PPTs as well as to explore the relationship between athlete variables, limb preference, and LSI values. Study Design: Cross-sectional study; Level of evidence, 3. Methods: This study included healthy volunteers (N = 100) evenly distributed between the ages of 6 and 18 years (mean age, 11.7 ± 3.6 years; 52% female). Participants performed 9 common PPTs. For analysis, we developed a composite score for each limb by averaging trials. We then calculated the LSI for each test. Univariable and multivariable linear regression analyses were performed to assess the relationship between athlete variables (age, sex, height, and weight) and LSI for each PPT. Results: Instances of poor baseline limb symmetry (<90% LSI) were common across all PPTs. The single-leg timed hop had the highest percentage of participants, with LSI ≥90% at 73%, while the stork on a Bosu ball had the lowest percentage at 23%. After adjusting for age, female sex showed a significant association with LSI for the stork test ( P = .010) and the quadrant hop–counterclockwise ( P = .021). Additionally, after adjusting for sex, increasing age showed a significant association with LSI for the stork test ( P < .001), single-leg squat on a Bosu ball ( P = .010), quadrant hop–clockwise ( P = .016), and quadrant hop–counterclockwise ( P = .009). Conclusion: The majority of healthy athletes 18 years and younger demonstrated significant (<90%) limb asymmetries. Limb symmetry was not consistently affected by participant age or sex, and the effect sizes of these relationships were small. These findings should encourage clinicians and coaches to exercise caution in using the LSI as an isolated measure of RTS readiness after injury in pediatric athletes.

Good physical function but reduced quality of life in children 3 years after ACL reconstruction

“…An LSI of >90% in the hop tests is a generally accepted goal following ACL reconstruction. However, in healthy children (6–18 years old) [26], a relatively large asymmetry between the right and left legs in hop tests has been reported (SL = 67% LSI, 6 M = 73% LSI and CO = 65% LSI) [26]. Others reported that only 75% of children 9–15 years old had an LSI above 85%, which is considered normal in healthy adults, and that only about 60% of healthy children had an LSI above 90% [4, 45].…”

“…The incidence of anterior cruciate ligament (ACL) injuries in children and adolescents is increasing worldwide [41,7,19,23,26]. During the last two decades, there has been a 2.3% increase per year in ACL injuries among 6-to 18-year-olds, now accounting for more than 10% of all sports-related injuries among 13-to 17-yearolds [22,29,39,40].…”

“…A significant factor for this is an increased participation in sports among children, compared to earlier. Additionally, there has been a tendency towards early specialisation and intensified sports training at an early age [14,26,31,38,45,46,48].…”

“…Comprehensive rehabilitation is an essential part of regaining physical function and being able to return to sports (RTSs) after surgery. Several tests are used to measure function and evaluate the ability to RTSs activities, but there is no agreement on how this is best achieved [26, 27]. There is little evidence to support any specific strategy for the treatment of ACL injuries in children, and long‐term follow‐ups are sparse [2].…”

Female Collegiate Dancers’ Physical Fitness across Their Four-Year Programs: A Prospective Analysis

“…Scores range from 0% to 100%, where 100% suggests full functional symmetry [ 35 ]. The LSI is commonly used for return-to-activity decisions with a target of 85% LSI before full return-to-activity [ 35 , 36 , 37 ], and asymmetries greater than 15% being associated with an increased injury risk [ 36 ]. In the current study, the LSI was calculated as (higher value/lower value) × 100 across legs at two time points: freshman and senior scores [ 38 ].…”