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Yi-Ju Tsai, Chieh-Chie Chia, Pei-Yun Lee, Li-Chuan Lin, and Yi-Liang Kuo

Context: Core control and strength are important for reducing the risk of lower-extremity injury. Current evidence on the effect of core training in male adolescent athletes is limited, and other investigations into the effects of core training often emphasized core strength only. Objective: To examine whether core training emphasizing both control and strength of the trunk and hip would improve joint kinematics during landing, sports performance, and lower-extremity muscle strength in adolescent male volleyball athletes. Design: Single group pretest and posttest design. Setting: University laboratory. Participants: Sixteen male participants (age: 13.4 [1] y, height: 167.8 [8.6] cm, mass: 58.6 [13.9] kg, and volleyball experience: 3.8 [1.5] y) from a Division I volleyball team at a junior high school. Main Outcome Measurements: Kinematics of the trunk and lower-extremity during box landing and spike jump landing tasks, volleyball-related sports performance, and isokinetic strength of hip and knee muscles were assessed before and after a 6-week core training program. Results: After training, the participants demonstrated decreased trunk flexion angle (P = .01, Cohen’s d = 0.78) during the box landing task and reduced the maximum knee internal rotation angle (P = .04, Cohen’s d = 0.56) during the spike jump landing task. The average isokinetic strength of hip flexors and external rotators, and knee flexors and extensors also significantly increased (P = .001, Cohen’s d = 0.98; P = .04, Cohen’s d = 0.57; P = .02, Cohen’s d = 0.66; P = .003, Cohen’s d = 0.87, respectively); however, sports performance did not show significant changes. Conclusions: A more erect landing posture following training suggests that the core training program may be beneficial for improving core stability. The long-term effect of core training for knee injury prevention needs further investigation.

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Li-Xin Guo, Zhao-Wen Wang, Yi-Min Zhang, Kim-Kheng Lee, Ee-Chon Teo, He Li, and Bang-Chun Wen

The aim of this study is to investigate the effect of material property changes in the spinal components on the resonant frequency characteristics of the human spine. Several investigations have reported the material property sensitivity of human spine under static loading conditions, but less research has been devoted to the material property sensitivity of spinal biomechanical characteristics under a vibration environment. A detailed three-dimensional finite element model of the human spine, T12– pelvis, was built and used to predict the influence of material property variation on the resonant frequencies of the human spine. The simulation results reveal that material properties of spinal components have obvious influences on the dynamic characteristics of the spine. The annulus ground substance is the dominant component affecting the vertical resonant frequencies of the spine. The percentage change of the resonant frequency relative to the basic condition was more than 20% if Young’s modulus of disc annulus is less than 1.5 MPa. The vertical resonant frequency may also decrease if Poisson’s ratio of nucleus pulposus of intervertebral disc decreases.

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Ching-Yi Wang, Ming-Hsia Hu, Hui-Ya Chen, and Ren-Hau Li

To determine the test–retest reliability and criterion validity of self-reported function in mobility and instrumental activities of daily living (IADL) in older adults, a convenience sample of 70 subjects (72.9 ± 6.6 yr, 34 male) was split into able and disabled groups based on baseline assessment and into consistently able, consistently disabled, and inconsistent based on repeat assessments over 2 weeks. The criterion validities of the self-reported measures of mobility domain and IADL-physical subdomain were assessed with concurrent baseline measures of 4 mobility performances, and that of the self-reported measure of IADL-cognitive subdomain, with the Mini-Mental State Examination. Test–retest reliability was moderate for the mobility, IADL-physical, and IADL-cognitive subdomains (κ = .51–.66). Those who reported being able at baseline also performed better on physical- and cognitive-performance tests. Those with variable performance between test occasions tended to report inconsistently on repeat measures in mobility and IADL-cognitive, suggesting fluctuations in physical and cognitive performance.

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Li Yi, Tyler B. Mason, Chih-Hsiang Yang, Daniel Chu, and Genevieve F. Dunton

Background: Cross-sectional studies have shown positive associations between neighborhood park access and children’s physical activity (PA); however, research that examines the relationship longitudinally is lacking. This study investigates how neighborhood park access affects the longitudinal trajectory of PA in 192 children across 3 years. Methods: Accelerometer-assessed PA data of children (N = 202) were collected across 6 semi-annual waves (7 d each) between 2014 and 2018. Geographical information systems was used to measure neighborhood park access (ie, coverage, density, and proximity) at baseline. Mixed-effects models examined the associations of park access with children’s baseline and trajectory of moderate to vigorous PA (MVPA) minutes across 3 years and whether the associations differed by sex or weekends versus weekdays. Results: Higher neighborhood park density, coverage, and proximity were positively associated with children’s baseline MVPA minutes per day. Longitudinally, higher park coverage was associated with smaller decreases in children’s MVPA minutes per day, but only during weekends. Park density and proximity were not associated with change in MVPA minutes per day. The above associations did not differ by sex. Conclusions: Having access to more neighborhood parklands protected against age-related declines in children’s PA. These findings suggest that neighborhood park coverage should be considered by urban planners when evaluating the health impacts of their policies.

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Li Yi, Shirlene D. Wang, Daniel Chu, Aditya Ponnada, Stephen S. Intille, and Genevieve F. Dunton

Background: Recent studies have shown potentially detrimental effects of the COVID-19 pandemic on physical activity (PA) in emerging adults (ages 18–29 y). However, studies that examined the effects of COVID-19 on PA location choices and maintenance for this age group remain limited. The current study investigated changes in PA location choices across 13 months during the pandemic and their associations with PA maintenance in this population. Methods: Emerging adults (N = 197) living in the United States completed weekly survey on personal smartphones (May 2020–June 2021) regarding PA location choices and maintenance. Mixed-effects models examined the main effects of PA location choice and its interaction with weeks into the pandemic on participants’ PA maintenance. Results: On a given week, participants performing PA on roads/sidewalks or at parks/open spaces were 1½ and 2 times as likely to maintain PA levels, respectively. Moreover, after September 2021, weeks when individuals performed PA on roads/sidewalks had a protective effect on PA maintenance. Conclusions: Performing PA on roads/sidewalks and at parks/open spaces was associated with PA maintenance during the COVID-19 pandemic. PA promotion and intervention efforts for emerging adults during large-scale disruptions to daily life should focus on providing programmed activities in open spaces to maintain their PA levels.