ABSTRACT: Pedometers may provide valuable information regarding the ambulatory patterns of adolescents, but the effects of BMI on pedometer accuracy in this population are unknown. PURPOSE: The purpose of this study was two-fold: 1) To determine if the New Lifestyles NL-2000 (NL) and the Digi-Walker SW-200 (DW) yield similar step counts as compared to an ankle-mounted criterion, StepWatch 3 (SW), when worn by early adolescents in a free-living environment and 2) to study whether BMI percentile affects the accuracy of waist-mounted pedometers in adolescents. METHODS: Seventy-four early adolescents (13.0 ± 1.1 y) wore the devices during one weekday. The study population included 33 normal weight, 21 overweight, and 20 obese participants. Two-way repeated measures ANOVAs was used to determine if BMI and device were related to number of steps per day and percent of actual steps. RESULTS: The NL and DW recorded fewer steps than the SW in each BMI category (P<0.05). In the obese group, the DW underestimated steps more than the NL (P<0.001). For the normal weight, overweight, and obese groups, the NL counted 89.1%, 89.1%, and 91.6% of the steps, respectively, while the DW counted 86.7%, 84.6% and 72.7%, respectively. CONCLUSION: Researchers must be cognizant of the limitations of waist-mountedpedometers, and carefully chose a device that suits the needs of their investigations. Because of the inaccuracies of the DW when measuring steps in obese adolescents, careful consideration must be given before choosing this device for research and interventions. The NL is a better device for assessment of adolescents' steps than the DW, especially for those whose are obese.
Medicine and science in sports and exercise 10/2012; · 3.71 Impact Factor
ABSTRACT: Activity monitors are widely used in research, and are currently being used to study physical activity (PA) trends in the US and Canada. The purpose of this study was to determine if body mass index (BMI) affects the step count accuracy of commonly used accelerometer-based activity monitors during treadmill walking.
Participants were classified into BMI categories and instructed to walk on a treadmill at 3 different speeds (40, 67, and 94 m·min-1) while wearing 4 accelerometer-based activity monitors (ActiGraph GT1M, ActiCal, NL-2000, and StepWatch).
There was no significant main effect of BMI on pedometer accuracy. At the slowest speed, all waist-mounted devices significantly underestimated actual steps (P < .001), with the NL-2000 recording the greatest percentage (72%). At the intermediate speed, the ActiGraph was the least accurate, recording only 80% of actual steps. At the fastest speed, all of the activity monitors demonstrated a high level of accuracy.
Our data suggest that BMI does not greatly affect the step-counting accuracy of accelerometer-based activity monitors. However, the accuracy of the ActiGraph, ActiCal, and NL-2000 decreases at slower speeds. The ankle-mounted StepWatch was the most accurate device across a wide range of walking speeds.
Journal of Physical Activity and Health 05/2012; 9(4):594-600.
ABSTRACT: This study compared the validity of a new Omron HJ-303 piezoelectric pedometer and 2 other pedometers (Sportline Traq and Yamax SW200).
To examine the effect of speed, 60 subjects walked on a treadmill at 2, 3, and 4 mph. Twenty subjects also ran at 6, 7, and 8 mph. To test lifestyle activities, 60 subjects performed front-back-side-side stepping, elliptical machine and stair climbing/descending. Twenty others performed ballroom dancing. Sixty participants completed 5 100-step trials while wearing 5 different sets of the devices tested device reliability. Actual steps were determined using a hand tally counter.
Significant differences existed among pedometers (P < .05). For walking, the Omron pedometers were the most valid. The Sportline overestimated and the Yamax underestimated steps (P < .05). Worn on the waist or in the backpack, the Omron device and Sportline were valid for running. The Omron was valid for 3 activities (elliptical machine, ascending and descending stairs). The Sportline overestimated all of these activities, and Yamax was only valid for descending stairs. The Omron andYamax were both valid and reliable in the 100-step trials.
The Omron HJ-303, worn on the waist, appeared to be the most valid of the 3 pedometers.
Journal of Physical Activity and Health 09/2011; 8(7):1014-20.
ABSTRACT: Pedometers could provide great insights into walking habits if they are found to be accurate for people of all weight categories.
the purposes of this study were to determine whether the New Lifestyles NL-2000 (NL) and the Digi-Walker SW-200 (DW) yield similar daily step counts as compared with the StepWatch 3 (SW) in a free-living environment and to determine whether pedometer error is influenced by body mass index (BMI) and speed of walking. The SW served as the criterion because of its accuracy across a range of speeds and BMI categories. Slow walking was defined as ≤80 steps per minute.
fifty-six adults (mean ± SD: age = 32.7 ± 14.5 yr) wore the devices for 7 d. There were 20 normal weight, 18 overweight, and 18 obese participants. A two-way repeated-measures ANOVA was performed to determine whether BMI and device were related to number of steps counted per day. Stepwise linear regressions were performed to determine what variables contributed to NL and DW error.
both the NL and the DW recorded fewer steps than the SW (P < 0.001). In the normal weight and overweight groups, error was similar for the DW and NL. In the obese group, the DW underestimated steps more than the NL (P < 0.01). DW error was positively related to BMI and percentage of slow steps, whereas NL error was linearly related to percentage of slow steps. A surprising finding was that many healthy, community-dwelling adults accumulated a large percentage of steps through slow walking.
the NL is more accurate than the DW for obese individuals, and neither pedometer is accurate for people who walk slowly. Researchers and practitioners must weigh the strengths and limitations of step counters before making an informed decision about which device to use.
Medicine and science in sports and exercise 02/2011; 43(2):350-6. · 3.71 Impact Factor