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Concurrent Validity of Lower Limb Muscle Strength by Handheld Dynamometry in Children 7 to 11 Years Old

Ryan Mahaffey, Megan Le Warne, Stewart C. Morrison, Wendy I. Drechsler, and Nicola Theis

Context: The assessment of pediatric muscle strength is necessary in a range of applications, including rehabilitation programs. Handheld dynamometry (HHD) is considered easy to use, portable, and low cost, but validity to measure lower limb muscle strength in children has not been assessed. Objective: To determine the concurrent validity of lower limb torque from HHD compared with isokinetic dynamometry (ID) in children aged from 7 to 11 years old. Design: A descriptive assessment of concurrent validity of lower limb joint torques from HHD compared with ID. Methods: Sixty-one typically developing children underwent assessment of maximal hip, knee, and ankle isometric torque by HHD and ID using standardized protocols. Joint positions were selected to represent maximal strength and were replicated between devices. Concurrent validity was determined by Pearson correlation, limits of agreement, and Bland–Altman plots. Results: Correlations between HHD and ID were moderate to large for knee extension (r 95% CI, .39 to .73), small to large for plantar flexion (r 95% CI, .29 to .67), knee flexion (r 95% CI, .16 to .59), hip flexion (r 95% CI, .21 to .57), hip extension (r 95% CI, .18 to .54), and hip adduction (r 95% CI, .12 to .56), and small to moderate for dorsiflexion (r 95% CI, −.11 to .39) and hip abduction (r 95% CI, −.02 to .46). Limits of agreement for all joint torques were greater than 10% indicating large error in HHD measured torque compared with ID. A positive proportional bias was detected for plantarflexion, indicating that HHD underestimated torque to a greater extent in participants with higher torque values. Conclusions: Maximal torque values from HHD and ID are consistent with those previously reported in the literature. Poor concurrent validity of HHD may have arisen from issues around joint position, joint stabilization, and the experience of the tester to prevent an isokinetic contraction. Pediatric lower limb muscle strength assessed by HHD should be interpreted with caution.

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Variability in Normalization Methods of Surface Electromyography Signals in Eccentric Hamstring Contraction

Juan Guerrero-Henriquez, Claudio Tapia, and Martin Vargas-Matamala

Context: In human movement analysis, normalization of a surface electromyography signal is a crucial step; therefore, parameter selection for this procedure must be adequately justified. The aim of this research was to determine the variability of electromyography signals in eccentric hamstring contraction under different normalization parameters. Design: Cross-sectional study. Methods: Nine university rugby players (age 21.50 [3.61] y; body mass index 21.50 [4.95]) and no history of recent hamstring injury. Values from maximum voluntary isometric contraction protocol and task related (ie, Nordic hamstring exercise) were used for surface electromyography signal normalization. Intersubject and intrasubject variation coefficients were used for normalization method variability and for signal reproducibility, respectively. Results: Intrasubject variation coefficient value indicates acceptable reproducibility of surface electromyography (less than 12%) for all normalization procedures. Lower values of intersubject variation coefficient value were achieved for normalization procedures using task-related values. Conclusion: Parameters extracted from task execution provided less variability for surface electromyography amplitude normalization in eccentric hamstring muscle contractions.

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Association Between Nondominant Leg-Side Hip Internal Rotation Restriction and Low Back Pain in Male Elite High School Soft Tennis Players

Toru Tanabe, Takumi Watabu, Hiroichi Miaki, Naoyuki Kubo, Tiharu Inaoka Pleiades, Tomonari Sugano, and Katsunori Mizuno

Context: The incidence of low back pain (LBP) is high among high school male soft tennis players. In some sports for which the rotational component of the body is important, an association between restricted hip internal rotation of the nondominant leg and LBP has been reported; however, whether this association holds in soft tennis is unknown. Therefore, this study aimed to evaluate the association between hip internal rotation, hip external rotation, hamstring flexibility, iliopsoas flexibility, and LBP incidence. Design: This study was designed as a cross-sectional study, conducted at a sports training center. Methods: Participants comprised 113 male elite high school soft tennis players (age: 16.1 [0.7] y) from 9 elite-level teams. The main outcome measures were the hip internal and external rotation range of motion, hamstring flexibility on the straight leg raise test, and iliopsoas flexibility on the Thomas test. Multiple logistic regression analysis was performed to examine the influence of main outcomes on LBP incidence in the past 1 year. Results: A total of 35 participants had LBP (LBP group); 78 participants did not have LBP (non-LBP group). Multiple logistic regression analysis revealed that the odds ratio for height was 1.08 (95% confidence interval, 1.00–1.16; P = .043) and for the hip internal rotation range of motion in the nondominant leg was 0.90 (95% confidence interval, 0.85–0.95; P < .001), indicating significant associations with LBP. Conclusion: Hip internal rotation range of motion in the nondominant leg and height were crucial factors related to LBP in male elite high school soft tennis players.

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Association of Cycling Kinematics With Anterior Knee Pain in Mountain Bike Cyclists

Guilherme R. Branco, Renan A. Resende, Felipe P. Carpes, and Luciana D. Mendonça

Context: Comfort and pain in cyclists are often discussed as a result of the posture on the bike, and bike fit, including motion analysis, is advocated as a strategy to minimize these conditions. The relationship between cycling kinematics, comfort, and pain is still debatable. Objectives: To investigate the association of ankle, knee, and trunk kinematics with the occurrence of anterior knee pain (AKP) in mountain bike cyclists. Design: Cross-sectional study. Methods: Fifty cross-country mountain bike cyclists (26 with AKP and 24 without AKP) had their pedaling kinematics assessed. Linear and angular data from trunk, hip, knee, ankle, and foot from cyclists with and without AKP were recorded using Retül motion analysis system. Results: The binary logistic regression model showed that kinematic variables such as peak ankle plantar flexion, peak knee flexion, and forward trunk lean were significant predictors of AKP. Both larger peak plantar flexion and knee flexion decreased the probability of reporting AKP. On the other hand, larger forward trunk lean increased the probability of reporting AKP. Conclusions: Ankle, knee, and trunk sagittal kinematics may predict AKP in cross-country mountain bike cyclists, whereas hip, knee, and ankle alignment in the frontal plane showed no association with occurrence of AKP. In other words, cyclists with larger ankle plantar flexion and knee flexion are less likely to have AKP, whereas those with increased trunk forward lean are more likely to have AKP.

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Instrument-Assisted Soft Tissue Mobilization Increased Hamstring Mobility

Jeffrey R. Doeringer, Ramon Ramirez, and Megan Colas

Context: Limited research reveals that the use of different soft tissue mobilization techniques increases tissue mobility in different regions of the body. Objective: The purpose of this study was to determine whether there is a difference between administering instrument-assisted soft tissue mobilization (IASTM) and therapeutic cupping (TC) on hamstring tightness. Design: Subjects attended one session wherein treatment and leg order were randomized before attending the session. A statistical analysis was completed using a 2 (intervention) × 2 (time) repeated-measures analysis of variance at α level ≤ .05. Participants : Thirty-three subjects between the age of 18–35 years old with bilateral hamstring tightness participated in this study. Interventions : The IASTM and TC were administered on different legs for 5 minutes and over the entire area of the hamstring muscles. One TC was moved over the entire treatment area in a similar fashion as the IASTM. Main Outcome Measures: The intervention measurements included soreness numeric rating scale, Sit-n-Reach (single leg for side being tested), goniometric measurement for straight-leg hip-flexion motion, and superficial skin temperature. The timeline for data collection included: (1) intervention measurements for the first randomized leg, (2) 5-minute treatment with the first intervention treatment, (3) intervention measurements repeated for postintervention outcomes, and (4) repeat the same steps for 1 to 3 with the contralateral leg and the other intervention. Results: There was a main effect over time for Sit-n-Reach, measurement (pre-IASTM—29.50 [8.54], post-IASTM—32.11 [8.31] and pre-TC—29.67 [8.21], post-TC—32.05 [8.25]) and goniometric measurement (pre-IASTM—83.45 [13.86], post-IASTM—92.73 [13.20] and pre-TC—83.76 [11.97], post-TC—93.67 [12.15]; P < .05). Conclusion: Both IASTM and TC impacted hamstring mobility during a single treatment using only an instrument-assisted soft tissue mobilization technique without any additional therapeutic intervention.

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Biopsychosocial Experiences of Elite Athletes Retiring From Sport for Career-Ending Injuries: A Critically Appraised Topic

Haley S. Moore, Samuel R. Walton, Morgan R. Eckenrod, and Melissa K. Kossman

Clinical Scenario: Injuries cause individuals varying amounts of time loss from participation, which may depend on injury and sport-specific factors such as level of participation. Athletes who never return to sport either choose or are forced to retire due to numerous factors. At elite levels of play, when an athlete chooses retirement, they have the opportunity to create and execute a retirement plan; however, if unexpected (eg, due to career-ending injury), athletes may struggle to transition out of sport effectively, impacting physical, mental, and social health. The biopsychosocial model looks at the relationship between biology, psychology, and socio-environmental factors. Therefore, the purpose of this study was to better understand the biopsychosocial experiences elite athletes face after a career-ending injury so that sport stakeholders can develop and implement strategies to support a healthy transition. Clinical Question: How does suffering a career-ending injury affect elite athletes’ biopsychosocial experiences during retirement from sport? Summary of Key Findings: All studies found that a career-ending injury negatively impacted athlete’s biopsychosocial health during the transition period. In addition, social support was identified as a positive coping mechanism and research highlighted the role of education in promoting successful transitions. Sport stakeholders should educate athletes regarding the importance of creating secondary plans. By creating a culture of athletic and nonathletic identity, athletes can feel empowered to navigate different phases of their life despite transition being forced upon them due to injury. Clinical Bottom Line: Career-ending injuries negatively impact the biopsychosocial experiences of elite athletes as they transition out of sport. Athletes may face many transitional challenges including a loss of identity, a lack of external support, and/or mental health decline; those more closely identifying with their role as an athlete tend to have a harder transition. Therefore, it is important for all athletes to be adequately prepared for sport retirement, especially given the uncertainty about when and how retirement may occur. Strength of Recommendation: Collectively, the body of evidence included to answer the clinical question aligns with the strength of recommendation of C.

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Is Myofascial Decompression Effective at Increasing Hamstring Flexibility in the Athletic Population? A Critically Appraised Topic

Julia Spellman, Rachel Eldredge, Melissa Nelson, Jennifer Ostrowski, and Jennifer Concannon

Clinical Scenario: There are a variety of therapeutic modalities used to treat flexibility issues in athletes, which can be the main cause of hamstring injuries. Myofascial decompression is one modality used to treat these patients. Focused Clinical Question: Is myofascial decompression effective at increasing hamstring flexibility in the athletic population? Summary of Search, “Best Evidence” Appraised, and Key Findings: The literature was searched for studies of level 2 evidence or higher that investigated the use of myofascial decompression to increase hamstring flexibility, that were published in the last 5 years. Two high-quality randomized controlled trials were included and one cohort study. Clinical Bottom Line: There is not enough consistent, clinically significant, high-level evidence to support the use of myofascial decompression to increase hamstring flexibility. Strength of Recommendation: There is level B evidence to support that myofascial decompression is effective at increasing hamstring flexibility.

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Women’s College Volleyball Players Exhibit Asymmetries During Double-Leg Jump Landing Tasks

Jeffrey B. Taylor, Anh-Dung Nguyen, Audrey E. Westbrook, Abigail Trzeciak, and Kevin R. Ford

Context: Women’s volleyball requires frequent and repetitive jumping that when performed with altered biomechanics, including kinematic or kinetic asymmetry, may place the athlete at high risk for injury. This study identified and analyzed lower-extremity biomechanical asymmetries in college women’s volleyball players during standard and sport-specific double-leg landing tasks. Design: Cross-sectional laboratory study. Methods: Eighteen female college volleyball players were analyzed using standard 3D motion capture techniques during a drop vertical jump and an unanticipated lateral reactive jump task. Repeated-measures multivariate analysis of variance identified asymmetries in kinematic and kinetic variables of each task. Results: Average symmetry indices ranged from 9.3% to 31.3% during the drop vertical jump and 11.9% to 25.6% during the reactive jump task. During the drop vertical jump, the dominant limb exhibited lower knee abduction moments (P = .03), ankle dorsiflexion moments (P = .02), ankle eversion moments (P = .003) and vertical ground reaction forces (P = .03), and greater ankle inversion moments (P = .001). Both kinematic (λ = 0.27, P = .03) and kinetic (λ = 0.12, P = .008) asymmetries were identified during the reactive jump task. The dominant limb exhibited greater peak knee flexion (P = .003) and ankle dorsiflexion (P = .02) angles, and greater ankle dorsiflexion (P = .005) and inversion (P = .03) moments than the nondominant limb. Conclusions: These asymmetries observed during double-leg landing tasks may predispose volleyball athletes to unilaterally higher ground reaction or muscle forces and ultimately a greater risk of injury during landing.

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Erratum. The Single Hop for Distance Test: Reviewing the Methodology to Measure Maximum and Repeated Performance

Human Kinetics, Inc.

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Association Between Knee Extension Strength at 3 and 6 Months After Anterior Cruciate Ligament Reconstruction

Sho Mitomo, Junya Aizawa, Kenji Hirohata, Shunsuke Ohji, Takehiro Ohmi, Toshiyuki Ohara, Hideyuki Koga, and Kazuyoshi Yagishita

Context: Deficits in knee extension strength after anterior cruciate ligament reconstruction have been a major problem. The inadequate recovery of the knee extension strength of surgical limb reportedly delays return to sports and increases reinjury risk. Accordingly, the early detection of knee extension strength deficits after reconstruction may help plan early interventions to manage impairment. This study aimed to clarify the association between knee extension strength at 3 and 6 months after anterior cruciate ligament reconstruction. Design: Retrospective study. Methods: Fifty patients who underwent primary anterior cruciate ligament reconstruction using hamstring grafts were included. At 3 months postoperatively, the limb symmetry index (LSI) of isokinetic knee extension strength (IKE) at 60°/s, degree of swelling, passive range of motion of knee flexion and extension, and anterior leg reach distance were measured. At 6 months postoperatively, the LSI of IKE was measured at 60°/s, which was used as the main outcome. A correlation analysis was performed with the LSI of IKE at 6 months postoperatively as the dependent variable and the LSI of IKE at 3 months postoperatively as the independent variable. Subsequently, a multiple regression analysis was performed, with LSI of IKE at 6 months postoperatively as the dependent variable; LSI of IKE at 3 months postoperatively as the independent variable; and other variables, demographic information, and surgical data as covariates. Results: The correlation analysis revealed that the LSIs of IKE at 3 and 6 months postoperatively were correlated (r = .535, P < .001). In the multiple regression analysis, the LSI of IKE at 3 months postoperatively was significantly associated with that at 6 months postoperatively, even when other variables were included as covariates (R 2 = .349, P = .004). Conclusion: Asymmetry of knee extension strength at 3 months postoperatively could be more useful than other variables related to knee strength in predicting the asymmetry of knee extension strength at 6 months postoperatively.