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Deborah Salvo, Rodrigo S. Reis, Adriano A.F. Hino, Pedro C. Hallal and Michael Pratt

Background:

There is little understanding about which sets of environmental features could simultaneously predict intensity-specific leisure-time physical activity (LTPA) among Brazilians. The objectives were to identify the environmental correlates for intensity-specific LTPA, and to build the best-fit linear models to predict intensity-specific LTPA among adults of Curitiba, Brazil.

Methods:

Cross sectional study in Curitiba, Brazil (2009, n = 1461). The International Physical Activity Questionnaire and Abbreviated Neighborhood Environment Assessment Scale were used. Ninety-two perceived environment variables were categorized in 10 domains. LTPA was classified as walking for leisure (LWLK), moderate-intensity leisure-time PA (MLPA), vigorous-intensity leisure-time PA (VLPA), and moderate-to-vigorous intensity leisure-time PA (MVLPA). Best fitting linear predictive models were built.

Results:

Forty environmental variables were correlated to at least 1 LTPA outcome. The variability explained by the 4 best-fit models ranged from 17% (MLPA) to 46% (MVLPA). All models contained recreation areas and aesthetics variables; none included residential density predictors. At least 1 neighborhood satisfaction variable was present in each of the intensity-specific models, but not for overall MVLPA.

Conclusions:

This study demonstrates the simultaneous effect of sets of perceived environmental features on intensity-specific LTPA among Brazilian adults. The differences found compared with high-income countries suggest caution in generalizing results across settings.

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Jennifer R. O’Neill, Russell R. Pate and Michael W. Beets

Background:

The aims of this study were to describe the physical activity levels of girls during dance classes and to identify factors associated with moderate-to-vigorous physical activity (MVPA) in those classes.

Methods:

Participants were 137 girls (11 to 18 years-old) enrolled in ballet, jazz, or tap dance classes from 11 dance studios. Participants wore an accelerometer during the selected dance class on 2 separate days. Factors hypothesized to be associated with MVPA were dance style, instructional level, instructor’s experience, percent of class time spent in choreography, and participants’ age, race/ethnicity, BMI-for-age percentile, and years of dance training. Data were analyzed using generalized linear mixed models.

Results:

Girls engaged in 9.8 minutes of MVPA, 6.0 minutes of moderate, 3.8 minutes of vigorous, 39.3 minutes of light, and 10.9 minutes of sedentary behavior per hour of dance class participation. Jazz/tap classes provided more MVPA than ballet classes, and intermediate level classes provided more MVPA than advanced level classes. Girls with more dance training obtained more MVPA than girls with less dance training.

Conclusion:

Dance classes provide valuable opportunities for adolescent girls to be physically active.

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Nabil Ilmane and Jacques LaRue

The aim of this experiment was to explore the behavioral effects of various temporal pressures on the anticipatory postural adjustments (APAs) in a complex task. Eighteen handball players performed a handball direct throw in three conditions of temporal pressure: (1) a reactive condition (RC), the throw was initiated as quickly as possible following a visual stimulus; (2) an anticipation-coincidence condition (AC), by synchronizing the impact of the ball with the passage of a visual mobile on a target; and (3) a self-initiated (SI) throw. The whole-body postural oscillation and the acceleration of the wrist were measured before and during the throwing action. Results showed that the delays between the onsets of the postural and focal activities were significantly different between RC and both the SI and the AC conditions. Movement time, time to peaks (negative and positive), are shorter in the RC, intermediate in the AC, and longer in the SI condition. Variability was significantly larger in AC in comparison with RC and SI. These results support the existence of different control modes triggered by the temporal pressure; they demonstrate that these control modes can be generalized to complex intentional movements such as the throwing skill and to an anticipation-coincidence situation.

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Amy K. Hegarty, Max J. Kurz, Wayne Stuberg and Anne K. Silverman

The goal of this pilot study was to characterize the effects of gait training on the capacity of muscles to produce body accelerations and relate these changes to mobility improvements seen in children with cerebral palsy (CP). Five children (14 years ± 3 y; GMFCS I-II) with spastic diplegic CP participated in a 6-week gait training program. Changes in 10-m fast-as-possible walking speed and 6-minute walking endurance were used to assess changes in mobility. In addition, musculoskeletal modeling was used to determine the potential of lower-limb muscles to accelerate the body’s center of mass vertically and forward during stance. The mobility changes after the training were mixed, with some children demonstrating vast improvements, while others appeared to be minimal. However, the musculoskeletal results revealed unique responses for each child. The most common changes occurred in the capacity for the hip and knee extensors to produce body support and the hip flexors to produce body propulsion. These results cannot yet be generalized to the broad population of children with CP, but demonstrate that therapy protocols may be enhanced by modeling analyses. The pilot study results provide motivation for gait training emphasizing upright leg posture, mediolateral balance, and ankle push-off.

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Bert Steenbergen and John van der Kamp

We investigated attentional processes that support the performance of high-skilled soccer players with hemiparetic cerebral palsy. Participants (N = 10) dribbled a slalom course as quickly and accurately as possible under two attentional-focus manipulation conditions. In the task-relevant focus condition, they attended to the foot that was in contact with the ball, whereas in the task-irrelevant focus condition, they monitored a series of words played on a tape. The time taken to complete the slalom course was registered. Performances of individuals with left and right hemiparesis were compared to explore differential effects of hemispheric lesion. The high-skilled players with congenital hemiparesis showed similar attentional-focus effects as those previously reported in the literature for high-skilled players without neurological disorders (Beilock et al., 2002; Ford et al., 2005). Task-relevant focus increased dribbling time, whereas a task-irrelevant focus did not result in a significant change in dribbling time. These findings generalized to each of the five participants with left hemiparesis (i.e., damage to the right hemisphere). By contrast, the effects of a task-relevant focus were less consistent for participants with right hemiparesis (i.e., left-hemisphere damage). This corroborates suggestions that the reinvestment of procedural knowledge is a left-lateralized function. The implications for the training of individuals with congenital brain damage are discussed.

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Gurtej S. Grewal, Rachel Baisch, Jacqueline Lee-Eng, Stephaine Wu, Beth Jarrett, Neil Humble and Bijan Najafi

Context:

Improvements in postural stability in figure skaters can play a significant role in performance, as well as reducing fall risk.

Objective:

To explore the effect of custom foot insoles on postural stability in advanced figure skaters.

Design:

Exploratory study.

Setting:

Out of laboratory.

Participants:

Nine advanced figure skaters were recruited and 7 completed the study (age 38 ± 18.5 y, body-mass index 25 ± 3.6 kg/m2).

Intervention:

Custom foot insoles.

Main Outcome Measures:

Primary outcome of changes in postural stability (PS) quantified by center-of-mass sway with secondary outcomes of ankleand hip-joint sway and joint range of motion. Sway measurements were assessed using body-worn sensors while participants wore skates on ice. PS was assessed in single-leg stance, as well as during gliding on the dominant foot.

Results:

A significant improvement in static PS was observed after 6-wk use of custom insoles. Center-of-mass sway reduced significantly on average by 48.44% (P = .023), and ankle-joint sway reduced by 45.7% (P = .05) during single-leg-stance balance measurements. During the gliding maneuver nonsignificant changes were observed for both ankle- and knee-joint range of motion.

Conclusion:

The results of this study suggest proof of concept toward benefits of custom insoles in improving postural stability in advanced figure skaters. To generalize the findings, randomized controlled trials with larger sample sizes are warranted.

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Alex C. Garn, Alexandre J.S. Morin, Jeffrey Martin, Erin Centeio, Bo Shen, Noel Kulik, Cheryl Somers and Nate McCaughtry

This study investigated a reciprocal effects model (REM) of children’s body fat self-concept and physical self-concept, and objectively measured school physical activity at different intensities. Grade four students (N = 376; M age = 9.07, SD = .61; 55% boys) from the midwest region of the United States completed measures of physical self-concept and body fat self-concept, and wore accelerometers for three consecutive school days at the beginning and end of one school year. Findings from structural equation modeling analyses did not support reciprocal effects. However, children’s body fat self-concept predicted future physical self-concept and moderate-to-vigorous physical activity (MVPA). Multigroup analyses explored the moderating role of weight status, sex, ethnicity, and sex*ethnicity within the REM. Findings supported invariance, suggesting that the observed relations were generalizable for these children across demographic groups. Links between body fat self-concept and future physical self-concept and MVPA highlight self-enhancing effects that can promote children’s health and well-being.

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Francisco Javier Alonso, Publio Pintado and José María Del Castillo

The use of the Hodrick-Prescott (HP) filter is presented as an alternative to the traditional digital filtering and spline smoothing methods currently used in biomechanics. In econometrics, HP filtering is a standard tool used to decompose a macroeconomic time series into a nonstationary trend component and a stationary residual component. The use of the HP filter in the present work is based on reasonable assumptions about the jerk and noise components of the raw displacement signal. Its applicability was tested on 4 kinematic signals with different characteristics. Two are well known signals taken from the literature on biomechanical signal filtering, and the other two were acquired with our own motion capture system. The criterion for the selection of cutoff frequency was based on the power spectral density of the raw displacement signals. The results showed the technique to be well suited to filtering biomechanical displacement signals in order to obtain accurate higher derivatives in a simple and systematic way. Namely, the HP filter and the generalized cross-validated quintic spline (GCVSPL) produce similar RMS errors on the first (0.1063 vs. 0.1024 m/s2) and second (23.76 vs. 23.24 rad/s2) signals. The HP filter performs slightly better than GCVSPL on the third (0.209 vs. 0.236 m/s2) and fourth (1.596 vs. 2.315 m/s2) signals.

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Melody Oliver, Scott Duncan, Celia Kuch, Julia McPhee and Grant Schofield

Background:

Aims were to investigate sex, ethnicity, and age differences in achieving daily step count and television (TV) watching recommendations in schoolchildren.

Methods:

Participants were 615 children (n = 325) and adolescents (n = 290) aged 5 to 16 years. Activity was assessed over 5 days using pedometers; TV time was collected via parental proxy-report and self-report. Ethnic, sex, and age differences in step counts, TV time, and odds of meeting TV and step count recommendations were examined for weekdays, weekend days, and overall using generalized estimation equation modeling.

Results:

Overall, boys were more active than girls (P < .001). Adolescents were more active than children (P = .044), watched more TV (P = .005), and were less likely to meet TV watching recommendations (P = .004). Non-European children watched significantly more TV (P = .008), and were significantly less likely to meet TV recommendations than non-European children (P = .001). Participants watched more TV and accumulated less steps on weekend days than weekdays.

Conclusions:

Multifaceted interventions focusing on both increasing activity and decreasing TV time are needed, especially on weekends. Children and girls may benefit more from activity interventions, while ethnic-specific interventions focusing on TV habits may be most efficacious for adolescents.

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Ryan D. Burns, Timothy A. Brusseau and James C. Hannon

Background:

Optimal levels of moderate-to-vigorous physical activity (MVPA) have been shown to improve health and academic outcomes in youth. Limited research has examined MVPA trajectories throughout a daily middle school physical education (PE) curriculum. The purpose of this study was to examine MVPA trajectories over a daily PE curriculum and the modifying effects of sex, body composition, and cardiorespiratory endurance.

Methods:

One hundred 7th- and 8th-grade students participated in daily PE lessons. There were 66 lessons throughout the semester. MVPA was monitored during each lesson using NL-1000 piezoelectric pedometers. Students were classified into FITNESSGRAM Healthy Fitness Zones using estimated VO2 Max and Body Mass Index (BMI). A population averaged generalized estimating equation was employed to examine MVPA trajectories.

Results:

On average, students’ MVPA decreased over time (β = –0.35, P < .001). Poor student VO2max classification significantly modified the trajectories (β = –0.14, P < .001), however poor BMI classification did not have a modifying effect (β = 0.03, P = .158).

Conclusions:

MVPA decreased in daily PE over time and cardiorespiratory endurance significantly modified the trajectories. The results support that extra efforts have to be made by teachers and students to sustain MVPA behaviors over a semester.