Investigating balance reactions following continuous, multidirectional, support surface perturbations is essential for improving our understanding of balance control in moving environments. Segmental motions are often incorporated into rapid balance reactions following external perturbations to balance, although the effects of these motions during complex, continuous perturbations have not been assessed. This study aimed to quantify the contributions of body segments (ie, trunk, head, upper extremity, and lower extremity) to the control of center-of-mass (COM) movement during continuous, multidirectional, support surface perturbations. Three-dimensional, whole-body kinematics were captured while 10 participants experienced 5 minutes of perturbations. Anteroposterior, mediolateral, and vertical COM position and velocity were calculated using a full-body model and 7 models with reduced numbers of segments, which were compared with the full-body model. With removal of body segments, errors relative to the full-body model increased, while relationship strength decreased. The inclusion of body segments appeared to affect COM measures, particularly COM velocity. Findings suggest that the body segments may provide a means of improving the control of COM motion, primarily its velocity, during continuous, multidirectional perturbations, and constitute a step toward improving our understanding of how the limbs contribute to balance control in moving environments.
You are looking at 101 - 110 of 26,604 items for :Clear All
Alison Schinkel-Ivy, Vicki Komisar and Carolyn A. Duncan
Mhairi J. MacDonald, Samantha G. Fawkner and Ailsa G. Niven
Background: In order to promote walking, researchers have sought to identify the required step rate to maintain a health-enhancing walking intensity However, there is limited evidence regarding the stepping rate required to promote moderate-intensity walking in adolescent girls. Purpose: To identify the step rate equivalent to moderate-intensity physical activity (MPA) in adolescent girls and to explore the influence that different anthropometric measures may have on the step rate equating to MPA in this population. Methods: A total of 56 adolescent girls (mean age = 13.8[0.7] y) were recruited to the study. Anthropometric variables and resting metabolic rate were assessed, followed by 3 overground walking trials on a flat surface at approximately 2, 3, and 4 mph, each lasting a minimum of 4 minutes. Oxygen uptake was assessed using a portable gas analyzer and subsequently converted into metabolic equivalents (METs). Step count was assessed by real-time direct observation hand tally. Results: Employing the linear regression between step rate and METs (r 2 = .20, standard error of estimates = 0.003) suggests that 120 steps per minute was representative of an MPA (3 METs) equating to 7200 steps in 60 minutes. Multiple regression and mixed-model regression confirmed weight-related variables and maturity were significant predictors of METs (P < .01). Conclusion: The results suggest that, at population level, a step rate of 120 steps per minute may be advocated to achieve MPA in adolescent girls; although, due to the small sample size used, caution should be applied. At an individual level, other factors, such as age and weight, should be considered.
Alejandra Jáuregui, Selene Pacheco-Miranda, Armando García-Olvera and Emanuel Orozco-Núñez
Background: Quality physical education (QPE) is part of a whole-of-school approach for school-based physical activity promotion. The United Nations Educational, Scientific and Cultural Organization QPE Policy Project supported 4 countries to develop QPE policies. The authors summarize the process, progress, successes, setbacks, and lessons learned during the implementation of the project in Mexico. Methods: The project was developed from August 2016 to April 2018 following the methodology proposed by the United Nations Educational, Scientific and Cultural Organization. Adaptations to the methodology were made to meet local needs. Results and Discussion: The project successfully implemented the United Nations Educational, Scientific and Cultural Organization methodology and prepared a national strategy for the provision of QPE in Mexico. The national strategy progressed despite the change in presidential administration. Successes included the use of a QPE policy evaluation framework, the inclusion of stakeholders representing extreme PE views and from all regions in the country, and the presence of international agencies in the national team. Setbacks included difficulties in engaging key organizations and a weak communication campaign. Lessons learned are discussed. Conclusions: The QPE project in Mexico served as a pilot project to test the feasibility of implementing a QPE policy revision process. The experience and lessons learned in Mexico can be drawn on to inform the work of other stakeholders interested in advocating for a national QPE policy.
Christopher C. Moore, Aston K. McCullough, Elroy J. Aguiar, Scott W. Ducharme and Catrine Tudor-Locke
Background: The authors conducted a scoping review as a first step toward establishing harmonized (ie, consistent and compatible), empirically based best practices for validating step-counting wearable technologies. Purpose: To catalog studies validating step-counting wearable technologies during treadmill ambulation. Methods: The authors searched PubMed and SPORTDiscus in August 2019 to identify treadmill-based validation studies that employed the criterion of directly observed (including video recorded) steps and cataloged study sample characteristics, protocol details, and analytical procedures. Where reported, speed- and wear location–specific mean absolute percentage error (MAPE) values were tabulated. Weighted median MAPE values were calculated by wear location and a 0.2-m/s speed increment. Results: Seventy-seven eligible studies were identified: most had samples averaging 54% (SD = 5%) female and 27 (5) years of age, treadmill protocols consisting of 3 to 5 bouts at speeds of 0.8 (0.1) to 1.6 (0.2) m/s, and reported measures of bias. Eleven studies provided MAPE values at treadmill speeds of 1.1 to 1.8 m/s; their weighted median MAPE values were 7% to 11% for wrist-worn, 1% to 4% for waist-worn, and ≤1% for thigh-worn devices. Conclusions: Despite divergent study methodologies, the authors identified common practices and summarized MAPE values representing device step-count accuracy during treadmill walking. These initial empirical findings should be further refined to ultimately establish harmonized best practices for validating wearable technologies.
Robert Turick, Anthony Weems, Nicholas Swim, Trevor Bopp and John N. Singer
One prominent, well-debated issue in the American higher education system is whether university officials should remove the names of individuals with racist pasts from campus buildings/structures that bear their namesake. The purpose of this study was to analyze basketball and football facilities at Division I Football Bowl Subdivision institutions to explore the racialized history of the people whom these facilities are named after. Utilizing a collective case study approach, the authors identified 18 facilities that were named after athletic administrators, coaches, and philanthropists who engaged in racist activities or harbored racist views. The authors argue, using critical race theory and systemic racism theory as interpretative lenses, that naming buildings after racist persons legitimizes their legacies, rationalizes systemic racism, and continues to unjustly enrich this particular group.
Tanya K. Jones
Liam D. Corr, Adam Field, Deborah Pufal, Jenny Killey, Tom Clifford, Liam D. Harper and Robert J. Naughton
Polyphenol consumption has become a popular method of trying to temper muscle damage. Cocoa flavanols (CF) have attracted attention due to their high polyphenol content and palatability. As such, this study will investigate whether an acute dose of CF can aid recovery following exercise-induced muscle damage. The study was a laboratory-based, randomized, single-blind, nutrient-controlled trial involving 23 participants (13 females and 10 males). Participants were randomized into either control ∼0 mg CF (n = 8, four females); high dose of 830 mg CF (CF830, n = 8, five females); or supra dose of 1,245 mg CF (CF1245, n = 7, four females). The exercise-induced muscle damage protocol consisted of five sets of 10 maximal concentric/eccentric hamstring curls and immediately consumed their assigned drink following completion. To measure muscle recovery, maximal voluntary isometric contraction (MVIC) of the knee flexors at 60° and 30°, a visual analog scale (VAS), and lower-extremity function scale were taken at baseline, immediately, 24-, 48-, and 72-hr postexercise-induced muscle damage. There was a main effect for time for all variables (p < .05). However, no significant differences were observed between groups for all measures (p ≥ .17). At 48 hr, there were large effect sizes between control and CF1245 for MVIC60 (p = .17, d = 0.8); MVIC30 (p = .26, d = 0.8); MVIC30 percentage change (p = .24 d = 0.9); and visual analog scale (p = .25, d = 0.9). As no significant differences were observed following the consumption of CF, there is reason to believe that CF offer no benefit for muscle recovery when ingested acutely.
Cédric Leduc, Jason Tee, Mathieu Lacome, Jonathon Weakley, Jeremy Cheradame, Carlos Ramirez and Ben Jones
Purpose: To investigate the convergent validity, reliability, and sensitivity over a week of training of a standardized running test to measure neuromuscular fatigue. Methods: Twenty male rugby union players were recruited for the study, which took place during preseason. The standardized running test consisted of four 60-m runs paced at ~5 m·s−1 with 33 seconds of recovery between trials. Data from micromechanical electrical systems were used to calculate a running-load index (RLI), which was a ratio between the mechanical load and the speed performed during runs. RLI was calculated by using either the entire duration of the run or a constant-velocity period. For each type of calculation, either an individual directional or the sum of the 3 components of the accelerometer was used. A measure of leg stiffness was used to assess the convergent validity of the RLI. Results: Unclear to large relationships between leg stiffness and RLI were found (r ranged from −.20 to .62). Regarding reliability, small to moderate (.47–.86) standardized typical errors were found. The sensitivity analysis showed that the leg stiffness presented a very likely trivial change over the course of 1 week of training, whereas RLI showed very likely small to a most likely large change. Conclusions: This study showed that RLI is a practical method to measure neuromuscular fatigue. In addition, such a methodology aligns with the constraint of elite team-sport setup due to its ease of implementation in practice.
Thomas D. Raedeke, Victoria Blom and Göran Kenttä
This study evaluated the relationship of perfectionism and self-perceptions with burnout and life satisfaction in aesthetic performers (N = 254) recruited in Sweden. Cluster analysis revealed four groups: perfectionistic with maladaptive self-perceptions, perfectionistic (parent-driven) with maladaptive self-perceptions, achievement-oriented with adaptive self-perceptions, and nonperfectionistic with adaptive self-perceptions. Performers in both maladaptive clusters reported characteristics suggesting they were perfectionistic compared to their peers. They also reported relatively high contingent self-worth and low basic self-esteem. In contrast, those in the nonperfectionistic with adaptive self-perceptions cluster scored relatively low on perfectionism and reported relatively high basic self-esteem and low contingent self-worth. The performers in the achievement-oriented with adaptive self-perceptions cluster reported average scores across most variables, moderately high personal standards, and higher basic self-esteem compared with contingent self-worth. Overall, performers in both maladaptive clusters reported the highest burnout and lowest life satisfaction. Study findings underscore the importance of perfectionism and self-perceptions when considering burnout and life satisfaction.