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Ricky Watari, Blayne Hettinga, Sean Osis and Reed Ferber

The purpose of this study was to validate measures of vertical oscillation (VO) and ground contact time (GCT) derived from a commercially-available, torso-mounted accelerometer compared with single marker kinematics and kinetic ground reaction force (GRF) data. Twenty-two semi-elite runners ran on an instrumented treadmill while GRF data (1000 Hz) and three-dimensional kinematics (200 Hz) were collected for 60 s across 5 different running speeds ranging from 2.7 to 3.9 m/s. Measurement agreement was assessed by Bland-Altman plots with 95% limits of agreement and by concordance correlation coefficient (CCC). The accelerometer had excellent CCC agreement (> 0.97) with marker kinematics, but only moderate agreement, and overestimated measures between 16.27 mm to 17.56 mm compared with GRF VO measures. The GCT measures from the accelerometer had very good CCC agreement with GRF data, with less than 6 ms of mean bias at higher speeds. These results indicate a torsomounted accelerometer provides valid and accurate measures of torso-segment VO, but both a marker placed on the torso and the accelerometer yield systematic overestimations of center of mass VO. Measures of GCT from the accelerometer are valid when compared with GRF data, particularly at faster running speeds.

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Erika Rees-Punia, Charles E. Matthews, Ellen M. Evans, Sarah K. Keadle, Rebecca L. Anderson, Jennifer L. Gay, Michael D. Schmidt, Susan M. Gapstur and Alpa V. Patel

feasible and cost-effective option for large-scale epidemiologic studies ( Haskell, 2012 ; Masse & de Niet, 2012 ; Sallis & Saelens, 2000 ). Given these issues, it is important to conduct validity studies of PA surveys to understand how measurement error may affect results of future association studies

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Serkan Usgu, Günseli Usgu, Fatma Uygur and Yavuz Yakut

) assess athletic injuries or functional limitations and successfully identify foot- and ankle-related impairments. 12 The FAAM is a reliable and valid instrument used to measure physical function 13 in sport and high-intensity daily living activities. 14 Notably, the sport subscale of the FAAM

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Liang Hu, Edward McAuley and Steriani Elavsky

This study was designed to address whether the Perceived Physical Ability (PPA) subscale of the Physical Self-Efficacy Scale (PSES; Ryckman, Robbins, Thornton, & Cantrell, 1982) measures self-efficacy or self-esteem. Secondary analyses of four previously reported data sets were conducted to examine the extent to which the PPA overlaps with multidimensional self-esteem measures. Once the factor structure of the PPA was confirmed, multitrait-multimethod analyses were employed to establish convergent and discriminant validity of the PPA and task-specific self-efficacy measures with self-esteem measures. The results support the position that the PPA may be more reflective of esteem than efficacy. Additionally, task-specific self-efficacy measures demonstrated stronger associations with behavioral outcomes than did the PPA. It is recommended that if the PPA is to be used for research purposes, it may have greater utility as a measure of physical self-esteem rather than self-efficacy.

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Loren Z.F. Chiu, Brian K. Schilling, Andrew C. Fry and Lawrence W. Weiss

Displacement-based measurement systems are becoming increasingly popular for assessment of force expression variables during resistance exercise. Typically a linear position transducer (LPT) is attached to the barbell to measure displacement and a double differentiation technique is used to determine acceleration. Force is calculated as the product of mass and acceleration. Despite the apparent utility of these devices, validity data are scarce. To determine whether LPT can accurately estimate vertical ground reaction forces, two men and four women with moderate to extensive resistance training experience performed concentric-only (CJS) and rebound (RJS) jump squats, two sessions of each type in random order. CJS or RJS were performed with 30%, 50%, and 70% one-repetition maximum parallel back squat 5 minutes following a warm-up and again after a 10-min rest. Displacement was measured via LPT and acceleration was calculated using the finite-difference technique. Force was estimated from the weight of the lifter-barbell system and propulsion force from the lifter-barbell system. Vertical ground reaction force was directly measured with a single-component force platform. Two-way random average-measure intraclass correlations (ICC) were used to assess the reliability of obtained measures and compare the measurements obtained via each method. High reliability (ICC > 0.70) was found for all CJS variables across the load-spectrum. RJS variables also had high ICC except for time parameters for early force production. All variables were significantly (p < 0.01) related between LPT and force platform methods with no indication of systematic bias. The LPT appears to be a valid method of assessing force under these experimental conditions.

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Sofie Martien, Christophe Delecluse, Jan Seghers and Filip Boen

The primary purpose of this study was to assess the validity of two motion sensors in measuring steps in institutionalized older adults during daily life activities. Sixty-eight nursing home residents (85.8 ± 5.6 years) were equipped with a hip-worn and ankle-worn piezoelectric pedometer (New Lifestyles 2000) and with an arm-mounted multisensor (SenseWear Mini). An investigator with a hand counter tallied the actual steps. The results revealed that the multisensor and hip- and ankle-worn pedometer significantly underestimated step counts (89.6 ± 17.2%, 72.9 ± 25.8%, and 20.8 ± 24.6%, respectively). Walking speed accounted for 41.6% of the variance in percent error of the ankle-worn pedometer. The threshold value for accurate step counting was set at 2.35 km/hr, providing percent error scores within ± 5%. The ankle-worn piezoelectric pedometer can be useful for accurate quantification of walking steps in the old and old-old (> 85 years) walking faster than 2.35 km/hr.

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Lydia Kwak, Maria Hagströmer and Michael Sjostrom

Background:

To be able to draw any conclusions regarding the health effects of occupational physical activity (OPA), more information is needed regarding valid measures to assess OPA. Aims were to compare OPA as assessed with the International Physical Activity Questionnaire long version (IPAQ-L) with OPA assessed with an accelerometer and to assess the contribution of OPA to total PA.

Methods:

Working adults (n = 441; mean age = 49.4 yrs; 44% males) wore an accelerometer for 7 days in free-living situations and completed the IPAQ-L. Comparisons were made between IPAQ-L-work and accelerometer data limited to working time (Moderate and Vigorous PA (accelerometer-MVPA-work) and average intensity). Subgroup analyses were performed.

Results:

Spearman correlation was r = .46 (P < .01) between IPAQ-L-work and accelerometer-MVPA-work. Correlations ranged from r = .27 to r = .55 in respectively obese and overweight subjects. The contribution of IPAQ-L-work to IPAQ-total was 24.7%.

Conclusions:

The IPAQ-L work domain is a moderately good measure of time spent on MVPA at work and can be used to assess the contribution of OPA to total PA. This study provides valuable information regarding the use of the IPAQ-L in assessing work domain specific PA, and underscores the importance of assessing OPA, as it can contribute for a substantial part to total PA.

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Carlos Balsalobre-Fernández, Hovannes Agopyan and Jean-Benoit Morin

based on opto-electronic devices and accelerometers. 11 , 13 , 14 Among these, the Optojump Next (Microgate, Bolzano, Italy) is probably the most widely used because of its high degree of validity and reliability compared with force platforms. 15 , 16 Moreover, contact and aerial times can be used

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Jason Lake, Peter Mundy, Paul Comfort, John J. McMahon, Timothy J. Suchomel and Patrick Carden

dual-plate system yields a typical measurement range upper limit of 8.8 kN with protection up to 13.2 kN. Although it appears that this portable force plate system may provide a realistic alternative to established systems, nothing is known about its reliability and concurrent validity. Currently, a 1

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Jennifer J. Sherwood, Cathy Inouye, Shannon L. Webb and Jenny O

who are not yet disabled or those with early disability at risk of progression are most likely to benefit from exercise intervention. It is in this population that reliable, valid, and age-appropriate tools are needed to monitor lower limb muscular power. Currently, community exercise programs screen