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Jocelyn F. Hafer, Mark S. Miller, Jane A. Kent and Katherine A. Boyer

Older females experience higher rates of disability than males, potentially due to sex-specific differences in gait and muscle function. The authors evaluated the effects of age and physical activity (PA) on gait mechanics and knee extensor muscle function in males and females. Three groups of 20 individuals (each 10 females) participated: young (21–35 y) and highly and less active older (55–70 y) adults. Knee extensor strength and joint mechanics during preferred speed gait were collected before and after 30 minutes of walking. Age by sex and PA by sex interactions indicated older and less active older females had lower concentric knee extensor muscle power and larger hip extension moments than males. After 30 minutes of walking, older less active adults had larger decreases in knee extensor power than their highly active older counterparts, and older adults of both sexes had decreases in ankle dorsiflexion moments while young adults did not. These results suggest that older, particularly less active, adults are susceptible to knee extensor muscle fatigue from moderate activity. For older adults, high levels of PA may be necessary to preserve gait mechanics in response to a bout of exercise. This new information may be important for targeting interventions in at-risk older adults.

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Paula R. Mesquita, Silvia G.R. Neri, Ricardo M. Lima, Eliane F. Manfio and Ana C. de David

Although previous reports have provided normative plantar pressure data for walking in children, evaluation during running is lacking. This study aimed to compare foot loading patterns during running and walking in children aged 4–10 years. Furthermore, the relationship between running baropodometric parameters and anthropometric measures was investigated. Foot loading of 120 volunteers was evaluated during running and walking using an Emed AT-4 pressure platform. Analyses were performed for 5 anatomical regions (rearfoot, midfoot, forefoot, hallux, and lesser toes). Higher peak pressure and maximum force values were seen under most foot regions during running in comparison with walking, whereas relative contact area tended to increase only in the midfoot. Data for running indicated that aging explained less than 23% of the variance of plantar loads and contact area. Running foot loads were more associated with height, body mass, and foot length. This study’s data described plantar loads under the feet of children were greater during running. Aging was associated with little increase in running plantar loads and larger contact areas. Results may be useful as reference to characterize foot loading during running and in the development of orthoses in clinical applications or products such as sport shoes for children.

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Jeff E. Goodwin

This investigation held concurrent visual feedback frequency at 50% in the acquisition phase and manipulated three different feedback schedules while comparing those to a 0% feedback frequency. In an assessment of dynamic postural stability, young, healthy adults performed 20 acquisition trials and four retention trials 48-hr later on a circular platform that moved in the anterior/posterior and medial/lateral axes simultaneously. Three concurrent feedback schedules were manipulated: a fade schedule consisting of high relative frequency of concurrent feedback early in the acquisition phase which was systematically reduced throughout acquisition (e.g., 100%, 75%, 50%, 25%, 0%), a constant schedule consisting of a uniform scheduling of concurrent feedback on every other acquisition trial, and a reverse fade group consisting of a schedule exactly opposite to that of the fade group. A no concurrent feedback group was also utilized to determine if feedback was necessary to learn the balance task. Acquisition and retention results revealed the concurrent groups performed with significantly greater accuracy and stability than the no concurrent feedback group. There were no significant differences between the three concurrent feedback schedules. Results indicate that manipulating concurrent feedback scheduling did not produce similar results to those investigations manipulating knowledge of results scheduling.

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Vera Ramos, Eliana V. Carraça, Teresa Paiva and Fátima Baptista

The aim of this study was to identify the best predictor of sleep quality (SQ) among physical behavior or capacity-related variables, namely physical activity, sedentary time, fitness, and physical function (activities of daily living) of independent elders using a representative sample of Portuguese aged 65 years and older (N = 437). SQ and activities of daily living were evaluated by a questionnaire, sedentary time, and physical activity through accelerometry, and physical fitness by means of the Senior Fitness Test. The logistic regression analysis revealed that activities of daily living measured by the Composite Physical Function was the only explanatory variable discriminating between poor SQ and good SQ. Receiver operating characteristic analysis showed that the best trade-off between sensitivity and specificity to discriminate older adults with poor SQ and good SQ was 20 points in the Composite Physical Function (sensitivity = 57.9%; specificity = 60.9%; area under the curve = 0.600, 95% confidence interval [0.536, 0.665], p = .003). Better physical function seems to be associated with better SQ in independent elders.

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Francesco Campa, Hannes Gatterer, Henry Lukaski and Stefania Toselli

Purpose: The exercise-induced increase in skin and body temperature, cutaneous blood flow, and electrolyte accumulation on the skin affects the validity of bioimpedance analysis to assess postexercise changes in hydration. This study aimed to assess the influence of a 10-min cold (22°C) shower on the time course of impedance measurements after controlled exercise. Methods: In total, 10 male athletes (age 26.2 [4.1] y and body mass index 23.9 [1.7] kg/m2) were tested on 2 different days. During both trials, athletes ran for 30 min on a treadmill in a room at 23°C. In a randomized crossover trial, the participants underwent a 10-min cold shower on the trial occasion and did not shower in the control trial. Bioimpedance analysis variables were measured before running (ie, baseline [T0]), immediately after exercising (T1), and 20 (T2), 40 (T3), and 60 min (T4) after the exercise. The shower was performed after T1 in the shower trial. Results: Body weight decreased similarly in both trials (−0.4% [0.1%], P < .001; −0.4% [0.1%], P < .001). Resistance and vector length returned to baseline at T2 in the shower trial, whereas baseline values were achieved at T3 in the control trial (P > .05). In the control trial, reactance remained at a lower level for the entire testing period (38.1 [6.9] vs 37.3 [6.7], P < .001). Forehead skin temperature returned to baseline values at T2 with shower, whereas it was still high at T4 without shower (P < .001). Conclusions: The present data show that a 10-min cold shower enables the stabilization of bioimpedance analysis measurements within 20 min after exercise, which might facilitate the assessment of hydration change after exercise.

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Brian Hanley, Trent Stellingwerff and Florentina J. Hettinga

Purpose: This was the first study to analyze high-resolution pacing data from multiple global championships, allowing for deeper and rigorous analysis of pacing and tactical profiles in elite-standard middle-distance racing. The aim of this study was to analyze successful and unsuccessful middle-distance pacing profiles and variability across qualifying rounds and finals. Methods: Finishing and 100-m-split speeds and season’s best times were collected for 265 men and 218 women competing in 800- and 1500-m races, with pace variability expressed using coefficient of variation. Results: In both events, successful athletes generally separated themselves from slower athletes in the final 200 m, not by speeding up but by avoiding slowing compared with competitors. This was despite different pacing profiles between events in the earlier part of the race preceding the end spurt. Approximately 10% of athletes ran season’s best times, showing a tactical approach to elite-standard middle-distance racing and possible fatigue across rounds. Men’s and women’s pacing profiles were remarkably similar within each event, but the previously undescribed seahorse-shaped profile in the 800-m (predominantly positive pacing) differed from the J-shaped negative pacing of the 1500-m. Pacing variability was high compared with world records, especially in the finals (coefficient of variation: 5.2–9.1%), showing that athletes need to be able to vary pace and cope with surges. Conclusions: The best athletes had the physiological capacity to vary pace and respond to surges through successive competition rounds. In competition-specific training, coaches should incorporate several sessions in which pace changes frequently and sometimes unexpectedly.

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Heontae Kim and Minsoo Kang

Background: To establish evidence for the validity of the Sedentary Behavior Record (SBR) instrument using a criterion measure through a proxy of direct observation. Methods: A total of 27 study participants (aged ≥18 y; 15 male) participated in this study. Throughout a 4-day measurement period, each participant recorded their sedentary behavior using the SBR in 10-minute blocks every night. During the measurement period, participants also wore wearable Autographer cameras as a proxy for direct observation. Autographer data were aggregated into 10-minute intervals. To establish evidence of validity, contingency (C) and Kappa (K) coefficients were calculated between the SBR and the Autographer data. For C and K, agreements were determined between 2 measures every cell. The coefficient C was compared across domains, types, and time of day, and K was compared across types of day and times of day. Results: Overall, the coefficients C and K were acceptable (C = .70) and substantial (K = .64), respectively. Among all domains, the highest C was reported for work-related sitting (C = .87). Values of C ranged from .49 to .91 among all activities; the highest accuracy was for work-related, screen-based sitting. Conclusions: This study suggests that the SBR is an acceptable self-report measure of sedentary behavior in adults.

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Aitor Iturricastillo, Cristina Granados, Raúl Reina, José Manuel Sarabia, Ander Romarate and Javier Yanci

Purpose: To analyze the relationship between mean propulsive velocity (MPV) of the bar and relative load (percentage of the 1-repetition maximum [%1RM]) in the bench-press (BP) exercise and to determine the relationship of power variables (ie, mean concentric power [MP], mean propulsive power [MPP], and peak power [PP]) in change-of-direction ability, linear sprint, and repeated-sprint ability. Methods: A total of 9 Spanish First Division wheelchair basketball players participated in the study. All participants performed an isoinertial BP test in free execution mode, a 505 change-of-direction ability test, linear sprint test (20 m), and repeated-sprint ability test. Results: A nearly perfect and inverse relationship was observed for the BP exercise between the %1RM and MPV (r = −.97, R 2 = .945, P < .001). The maximum loads for MP, MPP, and PP were obtained between 48.1% and 59.4% of the 1RM. However, no significant correlations were observed between strength and wheelchair performance. Conclusions: Wheelchair basketball players with different functional impairments showed a nearly perfect and inverse relationship for the BP exercise between the %1RM and MPV; thus the MPV could be used to estimate the %1RM. This finding has important practical applications for velocity-based resistance training in that coaches would be able to prescribe and monitor training load. Conversely, the absence of association between BP performance and field tests might be due to other factors such as the wheelchair–user interface, trunk-muscle activity, or propulsion technique, apart from strength variables.

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Xiangli Gu, Senlin Chen and Xiaoxia Zhang

The purpose of this study was to examine the associations between fundamental motor skills (FMS; including locomotor and object-control skills), moderate-to-vigorous physical activity (MVPA), and sedentary behavior among young Hispanic and non-Hispanic children. Using the prospective research design spanning one academic school year, we recruited 671 children (6.96 ± 1.6 years, 46% girls) from four primary schools in North Texas, 300 of whom were Hispanic and 371 non-Hispanic children, with 90% of the Hispanic and 74% of the non-Hispanic children from low-income families. All participants completed the PE Metrics FMS assessment and wore Actical accelerometers. Hispanic children demonstrated a lower level of MVPA on school days than their non-Hispanic peers. After adjusting for sociodemographic variables, both locomotor and object-control skills significantly predicted school-based MVPA for the non-Hispanic groups, while only object-control skills significantly predicted MVPA for the Hispanic group. For both ethnic groups, locomotor skills significantly predicted school-based sedentary behavior. The findings shed light on future motor competence–based interventions for physical activity promotion and obesity prevention among young Hispanic as well as non-Hispanic children.