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Lyle J. Micheli

The majority of injuries in exercising children affect the musculoskeletal system. These injuries result from two mechanisms: single, acute macrotrauma or repetitive microtrauma. The injuries resulting from repetitive microtrauma—overuse injuries—appear to be occurring with increased frequency in this age group. A number of risk factors for overuse injury from exercise have been identified, including training error, muscle imbalance, anatomic malalignment, footwear, surface, nutritional factors, and cultural factors. The development of scientific criteria for exercise prescription in this age group that will enhance fitness and avoid injury awaits techniques for noninvasive assessment of musculoskeletal tissue fitness. In the interim, many of these injuries can be prevented or decreased in severity by slow progression of exercise intensity and qualified adult supervision.

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Mariona A. Violan, Eric W. Small, Merrilee N. Zetaruk, and Lyle J. Micheli

The effect of 6 months of twice weekly karate training on flexibility, balance, and strength was evaluated in 14 boys who perform karate as beginners (age M = 10.3 ± 1.8) and a group of the same age who had never been involved in martial arts (n = 10; age M = 10.9 ± 1.4). All subjects were pretested and posttested on the following: flexibility of upper extremity (shoulder), hamstrings and quadriceps; strength, including handgrip strength and concentric flexion/extension of quadriceps; and balance, with eyes either open or closed. After 6 months, the tests were evaluated and compared by groups. The results showed the karate group made significant gains on quadriceps flexibility and balance with eyes closed. By improving flexibility, balance, and strength, karate improves three of the basic fitness components that are very important for preventing sport injuries in the growing years.

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Dai Sugimoto, Jessica C. LeBlanc, Sarah E. Wooley, Lyle J. Micheli, and Dennis E. Kramer

It is estimated that approximately 350,000 individuals undergo anterior cruciate ligament (ACL) reconstruction surgery in each year in the US. Although ACL-reconstruction surgery and postoperative rehabilitation are successfully completed, deficits in postural control remain prevalent in ACL-reconstructed individuals. In order to assist the lack of balance ability and reduce the risk of retear of the reconstructed ACL, physicians often provide a functional knee brace on the patients’ return to physical activity. However, it is not known whether use of the functional knee brace enhances knee-joint position sense in individuals with ACL reconstruction. Thus, the effect of a functional knee brace on knee-joint position sense in an ACL-reconstructed population needs be critically appraised. After systematically review of previously published literature, 3 studies that investigated the effect of a functional knee brace in ACL-reconstructed individuals using joint-position-sense measures were found. They were rated as level 2b evidence in the Centre of Evidence Based Medicine Level of Evidence chart. Synthesis of the reviewed studies indicated inconsistent evidence of a functional knee brace on joint-position improvement after ACL reconstruction. More research is needed to provide sufficient evidence on the effect of a functional knee brace on joint-position sense after ACL reconstruction. Future studies need to measure joint-position sense in closed-kinetic-chain fashion since ACL injury usually occurs under weight-bearing conditions.

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Avery D. Faigenbaum, Leonard D. Zaichkowsky, Wayne L. Westcott, Lyle J. Micheli, and Allan F. Fehlandt

The effectiveness of a twice-a-week strength training program on children was evaluated in 14 boys and girls (mean age 10.8 yrs) who participated in a biweekly training program for 8 weeks. Each subject performed three sets of 10 to 15 repetitions on five exercises with intensities ranging between 50 and 100% of a given 10-repetition maximum (RM). All subjects were pre- and posttested on the following measures: 10-RM strength, sit and reach flexibility, vertical jump, seated ball put, resting blood pressure, and body composition parameters. The subjects were compared to a similar group of boys and girls (n = 9; mean age 9.9 yrs) who were randomly selected to serve as controls. Following the training period, the experimental group made greater gains in strength (74.3%) as compared to the control group (13.0%) (p < 0.001), and differences in the sum of seven skinfolds were noted (−2.3% vs. +1.7%, respectively, p < 0.05). Training did not significantly affect other variables. These results suggest that participation in a short-term, twice-a-week strength training program can increase the strength and improve the body composition of young boys and girls.

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Dai Sugimoto, Benton E. Heyworth, Jeff J. Brodeur, Dennis E. Kramer, Mininder S. Kocher, and Lyle J. Micheli

Context: Recent epidemiology studies indicated a steady increase of anterior cruciate ligament (ACL) injury in young athletes. ACL reconstruction (ACLR) is currently a standard of care, but the effect of ACLR graft including bone patellar tendon bone (BTB), hamstring tendon (HT), or iliotibial band (ITB) on balance and hop performance is understudied. Objective: To compare balance and hop deficits between uninvolved and reconstructed limbs in each autograft type (aim 1) and among the 3 autograft groups (aim 2). Setting: Biomechanical laboratory. Participants: Male ACLR patients who are younger than 22 years (total N = 160; BTB: N = 19, HT: N = 108, ITB: N = 33). Intervention: Approximately 6 to 9 months following ACLR, Y-balance and 4 types of hop tests were measured bilaterally. Main Outcome Measures: Limb symmetry index of balance and hop tests within each graft type and between the 3 graft types. Results: In the BTB group, significant anterior reach, single hop, triple hops, and cross-over hops deficits were observed on the ACLR limb compared with the uninvolved limb. The HT group showed significant deficits in single hop, triple hops, and cross-over hops on the ACLR limb relative to the uninvolved limb. Compared with the uninvolved limb, significantly decreased triple hops and 6-m timed hop deficits in the ACLR limb were recorded in the ITB group. When controlling for confounders and comparing among the 3 autograft types, the only significant difference was anterior reach, in which the BTB group showed significant deficits. Conclusion: Compared with the uninvolved limb, significant hop deficits in ACLR limb were prevalent among adolescent ACLR at ∼6 to 9 months postoperatively. After controlling covariates, significantly reduced anterior reach balance was found in the BTB group compared with the HT and ITB groups.

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Dai Sugimoto, Benton E. Heyworth, Brandon A. Yates, Dennis E. Kramer, Mininder S. Kocher, and Lyle J. Micheli

Context: To treat anterior cruciate ligament (ACL) injury, ACL reconstruction (ACLR) surgery is currently a standard of the care. However, effect of graft type including bone–patellar tendon–bone (BTB), hamstring tendon, or iliotibial band (ITB) on thigh size, knee range of motion (ROM), and muscle strength are understudied. Objective : To compare postoperative thigh circumference, knee ROM, and hip and thigh muscle strength in adolescent males who underwent ACLR, based on the 3 different autograft types: BTB, hamstring (HS), and ITB. Setting: Biomechanical laboratory. Participants: Male ACLR patients who are younger than 22 years of age (total N = 164). Intervention: At 6- to 9-month postoperative visits, thigh circumference, knee ROM, and hip and thigh muscle strength were measured. Main Outcome Measures: Deficits of each variable between the uninvolved and ACLR limb were compared for pediatric and adolescent ACLR males in the BTB, HS, and ITB cohorts. Baseline characteristics, including physical demographics and meniscus tear status, were compared, and differences identified were treated as covariates and incorporated in analysis of covariance. Results: Data were from 164 adolescent male ACLR patients [mean age 15.7 (1.2) years]. There were no statistical differences in thigh circumference, knee ROM, hip abductor, and hip-extensor strength among the 3 autografts. However, patients with BTB demonstrated 12.2% deficits in quadriceps strength compared with 0.5% surplus in HS patients (P = .002) and 1.2% deficits in ITB patients (P = .03). Patients with HS showed 31.7% deficits in hamstring strength compared with 5.4% deficits in BTB (P = .001) and 7.7% deficits in ITB (P = .001) groups at 6- to 9-month postoperative visits. Conclusion: Adolescent male ACLR patients with BTB and HS autografts demonstrated significant deficits in quadriceps and hamstring strength, respectively, at 6 to 9 months postoperatively. Minimal lower-extremity strength deficits were demonstrated in pediatric male ACLR patients undergoing ITB harvest.