The effects of gait speed and step length on the required coefficient of friction (COF) confound the investigation of age-related differences in required COF. The goals of this study were to investigate whether age differences in required COF during self-selected gait persist when experimentally-controlling speed and step length, and to determine the independent effects of speed and step length on required COF. Ten young and 10 older healthy adults performed gait trials under five gait conditions: self-selected, slow and fast speeds without controlling step length, and slow and fast speeds while controlling step length. During self-selected gait, older adults walked with shorter step lengths and exhibited a lower required COF. Older adults also exhibited a lower required COF when walking at a controlled speed without controlling step length. When both age groups walked with the same speed and step length, no age difference in required COF was found. Thus, speed and step length can have a large influence on studies investigating age-related differences in required COF. It was also found that speed and step length have independent and opposite effects on required COF, with step length having a strong positive effect on required COF, and speed having a weaker negative effect.
Dennis E. Anderson, Christopher T. Franck and Michael L. Madigan
Jeanette Gustat, Christopher E. Anderson and Sandy J. Slater
Background: Spaces that promote play are important for the physical, social, and psychological growth of children. Public spaces, including playgrounds, provide an important venue for children to engage in play. A simple tool is needed to evaluate playground features and conditions. Methods: A simple play space audit instrument to assess the presence and condition of playground features was tested on a sample of 70 playgrounds during the summer of 2017, in Chicago, IL. Duplicate observations were collected on 17 playgrounds. Frequencies of features were tabulated, and reliability of variables was assessed using percent agreement and kappa statistic. Scores were created to summarize playground “playability,” overall and within domains of general overview, surface, path, and play equipment/structure features. Results: The tool demonstrated acceptable reliability with high kappa values between .79 and .90 for all items in domains. The overall score, general overview score, and play equipment/structure scores were correlated with mean playground usage. Conclusions: This brief instrument allows reliable assessment of playground features and their conditions. The scoring method generates a summary of playground conditions and features, which facilitates comparison of playgrounds. This tool has the potential to assist communities in evaluating their play spaces and identifying where to focus resources for improvements.
Ashley L. Kapron, Stephen K. Aoki, Christopher L. Peters, Steve A. Maas, Michael J. Bey, Roger Zauel and Andrew E. Anderson
Accurate measurements of in-vivo hip kinematics may elucidate the mechanisms responsible for impaired function and chondrolabral damage in hips with femoroacetabular impingement (FAI). The objectives of this study were to quantify the accuracy and demonstrate the feasibility of using dual fluoroscopy to measure in-vivo hip kinematics during clinical exams used in the assessment of FAI. Steel beads were implanted into the pelvis and femur of two cadavers. Specimens were imaged under dual fluoroscopy during the impingement exam, FABER test, and rotational profile. Bead locations measured with model-based tracking were compared with those measured using dynamic radiostereometric analysis. Error was quantified by bias and precision, defined as the average and standard deviation of the differences between tracking methods, respectively. A normal male volunteer was also imaged during clinical exams. Bias and precision along a single axis did not exceed 0.17 and 0.21 mm, respectively. Comparing kinematics, positional error was less than 0.48 mm and rotational error was less than 0.58°. For the volunteer, kinematics were reported as joint angles and bone-bone distance. These results demonstrate that dual fluoroscopy and model-based tracking can accurately measure hip kinematics in living subjects during clinical exams of the hip.
Jeanette Gustat, Christopher E. Anderson, Keelia O’Malley, Tian Hu, Rachel G. Tabak, Karin Valentine Goins, Cheryl Valko, Jill S. Litt and Amy A. Eyler
Background: To assess how perceptions of the community built environment influence support for community policies that promote physical activity (PA). Methods: A national cross-sectional survey assessed perceptions of the local built environment and support of community policies, including school and workplace policies, promoting PA. A random digit–dialed telephone survey was conducted in US counties selected on Behavioral Risk Factor Surveillance System data for high or low prevalence of obesity and inactivity. A total of 1208 subjects were interviewed, 642 from high-prevalence counties and 566 from low-prevalence counties. Analyses were stratified by county prevalence of obesity and inactivity (high or low). Linear models adjusted for covariates were constructed to assess the influence of built environment perceptions on policy support. Results: Perception of more destinations near the residence was associated with increased support for community policies that promote PA, including tax increases in low-prevalence (obesity and inactivity) counties (P < .01). Positive perception of the workplace environment was associated (P < .001) with increased support for workplace policies among those in high-, but not low-, prevalence counties. Conclusions: Support for community policies promoting PA varies by perception of the built environment, which has implications for policy change.