Doctoral Dissertations

Date of Award

8-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

David R. Bassett

Committee Members

Howley, Thompson, Truett

Abstract

This dissertation was designed to assess pedometer accuracy under both controlled and free-living conditions and to assess the efficacy and feasibility of the 10,000 steps per day exercise prescription in sedentary, overweight men vs. women. The specific aims were to 1) assess the accuracy of 10 electronic pedometers over the course of a 400-m walk; 2) compare the step values of multiple brands of pedometers over a 24-hour period; 3) compare the effects on body composition, cardiovascular risk factors and adherence in response to a 10,000 steps per day exercise prescription in overweight men vs. women. First, the accuracy and reliability of 10 electronic pedometers was assessed over the course of a 400-m walk. Ten males and 10 females ranging in body mass index (BMI) from 19.8 to 33.6 kg∙m-2 walked 400-m around an outdoor track while wearing two pedometers of the same model (one on the right and left sides of the body) for each of ten models. Four pedometers of each model were assessed in this fashion. The Kenz Lifecorder (KZ), New Lifestyles NL-2000 (NL), and the Yamax Digi-Walker SW-701 (DW) were the most accurate in counting steps, displaying values that were within ±3% of the actual steps taken, 95% of the time. The Sportline 330 (SL330) and the Omron HJ-105 (OM) were the least accurate, displaying values that were within ±37% of the actual steps, 95% of the time. The reliability within a single model (Chronbach’s alpha) was >0.80 for all pedometers with the exception of the SL330. The intra-model reliability was exceptionally high (>0.99) in the KZ, OM, NL, and the DW. Second, a comparison of 13 pedometer models was made over a 24-hour period. Ten males and ten females ranging in BMI from 19.8 to 35.4 kg∙m-2 wore two pedometers for a 24-hour period. The criterion pedometer Yamax Digi-Walker SW-200 (YX200) was worn on the left side of the body and a comparison pedometer was worn on the right. Steps counted by each device were recorded at the end of the day for each of the thirteen pedometers. Subjects took an average of 9,244 steps∙d-1. The KZ, YX200, NL, Yamax Digi-Walker SW-701 (YX701), and SL330 yielded mean values that were not significantly different from the criterion. The Freestyle Pacer Pro (FR), Accusplit Alliance 1510 (AC) Yamax Skeletone EM-180 (SK), Colorado on the Move (CO), and Sportline 345 (SL345) significantly underestimated steps (P<0.05) and the Walk4Life LS 2525 (WL), OM, and Oregon Scientific PE316CA (OR) significantly overestimated steps (P<0.05) when compared to the criterion. In addition, some pedometers underestimated by 25% while others overestimated by 45%. Third, a comparison of the effects on body composition, cardiovascular risk factors and adherence was made in response to a 10,000 steps per day exercise prescription in sedentary, overweight males vs. females. Fifteen men (46 ± 7 yrs) (mean ± SD) and twenty-four women (48 ± 5 yrs) who were overweight or obese participated in a 10,000 steps per day intervention for 36 weeks. Body weight, BMI, percent body fat, fat mass, fat-free mass, waist circumference, hip circumference, systolic blood pressure, diastolic blood pressure, and heart rate were determined at baseline, after 20 weeks and again after 36 weeks. A blood lipid profile was assessed at baseline and after 36 weeks. Men and women given a 10,000 steps per day exercise prescription experienced similarly significant improvements in body weight, BMI, percent body fat, fat mass, waist and hip circumferences, and HDL-C. When men and women were combined to explore the effect of adherence to the exercise prescription, the adherers significantly reduced body weight, BMI, percent body fat, fat mass, waist circumference, and hip circumference after 36 weeks while the non-adherers experienced little or no change in these variables. Thus, the 10,000 steps per day exercise prescription was effective at increasing daily walking volume which resulted in significant improvements in body weight and body composition in overweight, sedentary, middle-aged men and women.

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