( Feito, Bassett, & Thompson, 2012 ). Piezoelectric accelerometer-based pedometers have been reported to have better accuracy in obese individuals as compared to mechanical spring-levered devices ( Tyo, et al., 2013 ; Tyo, et al., 2011 ). Crouter et al found that a spring-levered device (Digi-Walker SW
Brian Tyo, Rebecca Spataro-Kearns and David R. Bassett Jr.
Scott Duncan, Kate White, Losi Sa’ulilo and Grant Schofield
The aim of this study was to assess the convergent validity of a new piezoelectric pedometer and an omnidirectional accelerometer for assessing children’s time spent in moderate to vigorous physical activity (MVPA). A total of 114 children (51 boys, 63 girls) aged 5–11 years wore a sealed NL-1000 piezoelectric pedometer (New Lifestyles Inc, Lee’s Summit, MO) and an Actical accelerometer (Mini Mitter, Bend, OR) over one school day. The NL-1000 pedometers were randomized to one of two manual intensity thresholds used to define MVPA (1): Level 3 = 2.9 metabolic equivalent test (MET) and (2) Level 4 = 3.6 MET. Compared with the Actical, the NL-1000 underestimated the time spent in MVPA by 37% and 45% at intensity levels 3 and 4, respectively. In addition, the 95% limits of agreement were wide at both intensity levels (level 3 = -144%, 70%; level 4 = -135%, 45%), indicating a low level of precision.
Donghui Fu, Zhende Hou, Qing-Hua Qin, Lianyun Xu and Yanjun Zeng
The piezoelectric properties of bone play an important role in the bone remodeling process and can be employed in clinical bone repair. In this study, the piezo-voltage of bone between two surfaces of a bone beam under bending deformation was measured using an ultra-high-input impedance bioamplifier. The influence of shear stress on the signs of piezo-voltages in bone was determined by comparing and contrasting the results from three-point and four-point bending experiments. From the three-point bending experiment, the study found that the signs of piezo-voltages depend only on shear stress and are not sensitive to the normal stress.
Jeffrey P. Broker and Robert J. Gregor
In light of substantial interest in the measurement of rider-induced loads, a new bicycle pedal instrumentation system is presented. The system employs dual piezoelectric transducers and permits the measurement of three components of a uniaxial load, moments about the pedal’s vertical axis, and the point of application of the applied load. Force and moment patterns derived from pedal output agree with previously reported data. Unique to this design, however, is the determination of center of pressure—and these data indicate that the applied load location varies during the pedaling cycle, with a significant effect on the calculated pedal moment.
Jeffrey B. Wheeler, Robert J. Gregor and Jeffrey P. Broker
In response to the popularity of clipless bicycle pedals with float designs, an instrumented force pedal system with multicompatibility for different shoe/pedal interfaces is presented. A dual piezoelectric element pedal has been modified for use with popular clipless pedal interfaces. The dual transducer arrangement permits measurement of three components of uniaxial load, location of the applied load, and calculation of the moment Mz about an axis through the position of the applied load and orthogonal to the pedal surface. Quantification of lower extremity kinetics using float feature pedals and the investigation of the pathomechanics of lower extremity cycling overuse injuries, especially knee injuries, is warranted. Qualitative descriptions of lower extremity pathomechanics related to overuse injuries have suggested that foot constraint may induce undesirable knee kinematics and kinetics. The instrumented force pedal system described here permits a comparison between pedal kinematics and kinetics of popular shoe/pedal interfaces with varying degrees of float allowance.
E. Andrew Pitchford and Joonkoo Yun
The purpose of this study was to examine the accuracy of spring-levered and piezoelectric pedometers for adults with and without Down syndrome (DS). Twenty adults with DS and 24 adults without a disability walked for two minute periods on a predetermined indoor course at a self-selected, slower and faster pace. Pedometer recorded and criterion observed steps were compared to determine pedometer error. There was a significant interaction between pedometer model and walking speed. Piezoelectric pedometers demonstrated significantly less measurement error than spring-levered pedometers, particularly at slower walking speeds. There were also significant differences in pedometer error between adults with and without DS. The study concludes that pedometer measurement error is significantly different for adults with DS but also that piezoelectric pedometers can be used in the future to measure walking activity for adults with and without DS.
The oscillations of a hand-held tennis racket and a racket with its handle firmly clamped were measured by striking the racket with a ball and observing the output voltage from a thin piezoelectric film wrapped around the handle. The oscillations of the racket in these two cases were quite different, with the hand-held racket displaying vibrational modes similar to those of a completely free racket.
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.
Sandra C. Webber, Sheila M. Magill, Jenessa L. Schafer and Kaylie C.S. Wilson
The purpose was to compare step count accuracy of an accelerometer (ActiGraph GT3X+), a mechanical pedometer (Yamax SW200), and a piezoelectric pedometer (SC-StepMX). Older adults (n = 13 with walking aids, n = 22 without; M = 81.5 years old, SD = 5.0) walked 100 m wearing the devices. Device-detected steps were compared with manually counted steps. We found no significant differences among monitors for those who walked without aids (p = .063). However, individuals who used walking aids exhibited slower gait speeds (M = 0.83 m/s, SD = 0.2) than non–walking aid users (M = 1.21 m/s, SD = 0.2, p < .001), and for them the SC-StepMX demonstrated a significantly lower percentage of error (Mdn = 1.0, interquartile range [IQR] = 0.5−2.0) than the other devices (Yamax SW200, Mdn = 68.9, IQR = 35.9−89.3; left GT3X+, Mdn = 52.0, IQR = 37.1−58.9; right GT3X+, Mdn = 51.0, IQR = 32.3−66.5; p < .05). These results support using a piezoelectric pedometer for measuring steps in older adults who use walking aids and who walk slowly.
Jeffrey P. Broker, Robert J. Gregor and Richard A. Schmidt
This study evaluated the retention of a cycling kinetic pattern using two different feedback schedules and evaluated the potential for feedback dependency in a continuous-task learning environment. Eighteen inexperienced cyclists rode a racing bicycle mounted to a fixed-fork Velodyne Trainer, with pedal forces monitored by dual piezoelectric transducers. Subjects received right-pedal shear force feedback and a criterion pattern emphasizing “effective” shear. Concurrent feedback (CFB) subjects received concurrent feedback 140 ms after the completion of every other revolution, while summary feedback (SFB) subjects received averaged feedback between trials. All subjects performed 10 retention trials without feedback 1 week later. Both groups improved significantly during practice, and performance decay in retention was negligible. Group differences during all phases were not significant. High CFB group proficiency in retention indicated that the detrimental aspects of frequent feedback were not significant. High SFB proficiency in retention suggests that large changes in kinetic patterning are achievable with relatively few feedback presentations.