Biomedical subjects

Catrine Tudor-Locke

Publications and source records attributed to Catrine Tudor-Locke.

30 records · Page 2Linked to original sources

PubMed2004

How many steps/day are enough? Preliminary pedometer indices for public health.

Pedometers are simple and inexpensive body-worn motion sensors that are readily being used by researchers and practitioners to assess and motivate physical activity behaviours. Pedometer-determined physical activity indices are needed to guide their efforts. Therefore, the purpose of this article is to review the rationale and evidence for general pedometer-based indices for research and practice purposes. Specifically, we evaluate popular recommendations for steps/day and attempt to translate existing physical activity guidelines into steps/day equivalents. Also, we appraise the fragmented evidence currently available from associations derived from cross-sectional studies and a limited number of interventions that have documented improvements (primarily in body composition and/or blood pressure) with increased steps/day.A value of 10000 steps/day is gaining popularity with the media and in practice and can be traced to Japanese walking clubs and a business slogan 30+ years ago. 10000 steps/day appears to be a reasonable estimate of daily activity for apparently healthy adults and studies are emerging documenting the health benefits of attaining similar levels. Preliminary evidence suggests that a goal of 10000 steps/day may not be sustainable for some groups, including older adults and those living with chronic diseases. Another concern about using 10000 steps/day as a universal step goal is that it is probably too low for children, an important target population in the war against obesity. Other approaches to pedometer-determined physical activity recommendations that are showing promise of health benefit and individual sustainability have been based on incremental improvements relative to baseline values. Based on currently available evidence, we propose the following preliminary indices be used to classify pedometer-determined physical activity in healthy adults: (i). <5000 steps/day may be used as a 'sedentary lifestyle index'; (ii). 5000-7499 steps/day is typical of daily activity excluding sports/exercise and might be considered 'low active'; (iii). 7500-9999 likely includes some volitional activities (and/or elevated occupational activity demands) and might be considered 'somewhat active'; and (iv). >or=10000 steps/day indicates the point that should be used to classify individuals as 'active'. Individuals who take >12500 steps/day are likely to be classified as 'highly active'.

Age Factors↗

PubMed2004

Utility of pedometers for assessing physical activity: construct validity.

Valid assessment of physical activity is necessary to fully understand this important health-related behaviour for research, surveillance, intervention and evaluation purposes. This article is the second in a companion set exploring the validity of pedometer-assessed physical activity. The previous article published in Sports Medicine dealt with convergent validity (i.e. the extent to which an instrument's output is associated with that of other instruments intended to measure the same exposure of interest). The present focus is on construct validity. Construct validity is the extent to which the measurement corresponds with other measures of theoretically-related parameters. Construct validity is typically evaluated by correlational analysis, that is, the magnitude of concordance between two measures (e.g. pedometer-determined steps/day and a theoretically-related parameter such as age, anthropometric measures and fitness). A systematic literature review produced 29 articles published since > or =1980 directly relevant to construct validity of pedometers in relation to age, anthropometric measures and fitness. Reported correlations were combined and a median r-value was computed. Overall, there was a weak inverse relationship (median r = -0.21) between age and pedometer-determined physical activity. A weak inverse relationship was also apparent with both body mass index and percentage overweight (median r = -0.27 and r = -0.22, respectively). Positive relationships regarding indicators of fitness ranged from weak to moderate depending on the fitness measure utilised: 6-minute walk test (median r = 0.69), timed treadmill test (median r = 0.41) and estimated maximum oxygen uptake (median r = 0.22). Studies are warranted to assess the relationship of pedometer-determined physical activity with other important health-related outcomes including blood pressure and physiological parameters such as blood glucose and lipid profiles. The aggregated evidence of convergent validity (presented in the previous companion article) and construct validity herein provides support for considering simple and inexpensive pedometers in both research and practice.

Adolescent↗

PubMed2003

Cross-sectional relationship of pedometer-determined ambulatory activity to indicators of health.

OBJECTIVE: To describe the cross-sectional relationship between an objective measure of walking (pedometer-determined steps/day) and general indicators of health, a prior diagnosis of one or more components of the metabolic syndrome, and self-reported occupational activity in a generally sedentary working population. RESEARCH METHODS AND PROCEDURES: Steps/day were compared with previous diagnosis of one or more components of the metabolic syndrome (by self-administered questionnaire) and with general health indicators including BMI, waist circumference, resting heart rate, and blood pressure in 182 subjects in Prince Edward Island, Canada. Study participants were volunteer employees recruited from five workplaces where, in general, the job types were moderately or highly sedentary. RESULTS: Steps/day were 7230 +/- SD 3447 for women (n = 153) and 8265 +/- 2849 (n = 21) for men. Pedometer-determined steps/day were associated inversely with BMI (r = -0.4005, p < 0.0001) in all participants and waist circumference in females only (r = -0.4303, p < 0.0001). There was a low correlation between steps/day and diastolic blood pressure in the whole sample (r = -0.2140, p = 0.0383). Participants who reported a prior diagnosis of one or more components of the metabolic syndrome (hypertension, hypercholesterolemia, heart disease, or type 2 diabetes) took fewer steps/day than healthy participants (p = 0.0254). Pedometer-determined steps/day were positively associated with self-reported occupational activity (p = 0.0002). DISCUSSION: Fewer steps/day are associated with increased BMI, waist circumference, diastolic blood pressure, and components of the metabolic syndrome. Low occupational activity is a contributing factor to low total ambulatory activity.

Adult↗

PubMed2003

Ambulatory activity and simple cardiorespiratory parameters at rest and submaximal exercise.

The purpose of this study was to explore the relationship between objectively determined ambulatory activity and simple cardiorespiratory parameters (heart rate and blood pressure at rest and during submaximal exercise) in individuals who were stratified for self-reported participation (yes/any vs. no/none) in vigorous physical activity (PA). Ninety-eight subjects (African Americans: 7 M, 16 F; Caucasians: 33 M, 42 F; mean age 46.4 +/- 15.4 yrs; mean BMI 26.7 +/- 4.8) wore a pedometer for 21 consecutive days and completed a 10-min submaximal treadmill graded exercise test with HR (beats/min) and BP (mmHg) measured while walking at 4.8 km/hr and a 10% grade. Subjects averaged 7,618 +/- 3.045 steps/day. There were no differences in steps/day by self-reported vigorous PA strata. There was an inverse relationship (r = -0.35, p = 0.03) between steps/day and resting HR in subjects who reported no vigorous PA. There was an inverse relationship (r = -0.22, p = 0.04) between steps/day and submaximal HR in all subjects. When stratified for self-reported vigorous PA, the inverse relationship between steps/day and submaximal HR was stronger for those reporting no vigorous PA (r = -0.39, p = 0.01) vs. those reporting any vigorous PA (r = -0.28, p = 0.05). There was no relationship between steps/day and BP at rest or during exercise in this normotensive sample.

Adolescent↗

PubMed2003

Objective physical activity of filipino youth stratified for commuting mode to school.

PURPOSE: The Cebu Longitudinal Health and Nutrition Survey included self-report measures and objective measures (Caltrac accelerometer) of Filipino adolescent (ages 14-16) physical activity (PA) in 1998-99. The purpose of this subanalysis was to compare objectively monitored PA of adolescents who differed by their self-reported habitual commuting mode to school, specifically commuting by walking, motorized transport, or a combination of the two. METHODS: Descriptive analysis included the proportion of adolescents who reported commuting to school by the different modes, participating in sport/exercise during or after school, or currently working. ANCOVA was used to estimate and compare adjusted mean Caltrac-derived energy expenditure (kcal.d ) by commuting mode for each gender. Covariates were age, weight, and height. RESULTS: The analysis sample of 1518 Filipino adolescents included 691 male (BMI = 18.5 +/- 2.5) and 827 female subjects (BMI = 18.7 +/- 2.3). A total of 323 male subjects (46.8% of all male subjects) walked to school, 160 (23.2%) took motorized transport, and 208 (30.0%) used a combination of the two modes. The corresponding values for female subjects were 303 (36.6%), 177 (21.4%), and 347 (42.0%). The absolute difference in Caltrac-derived energy expenditure that appeared to be due to active commuting was 44.2 kcal.d for Filipino male adolescents and 33.2 kcal.d for female adolescents. These differences between commuting modes could not be explained by participation in sport/exercise or by current employment. CONCLUSIONS: Assuming 200 school days in a year, the difference in energy expended due to active commuting translates to a 8840 kcal and 6640 kcal in male and female subjects, respectively. For those youth who commute to school by motorized transport a yearly positive energy balance (i.e., weight gain) of 2-3 lb would be anticipated, all other things being held constant.

Adolescent↗

PubMed2003

Comparison of pedometer and accelerometer accuracy under controlled conditions.

PURPOSE: The purpose of this investigation was to compare the concurrent accuracy of the CSA accelerometer and the Yamax pedometer under two conditions: 1) on a treadmill at five different speeds and 2) riding in a motorized vehicle on paved roads. METHODS: In study 1, motion sensor performance was evaluated against actual steps taken during 5-min bouts at five different treadmill walking speeds (54, 67, 80, 94, and 107 m.min-1). In study 2, performance was evaluated during a roundtrip (drive 1 and drive 2) motor vehicle travel on paved roads (total distance traveled was 32.6 km or 20.4 miles). Any steps detected during motor vehicle travel were considered error. RESULTS: In study 1, the Yamax pedometer detected significantly (P < 0.05) fewer steps than actually taken at the slowest treadmill speed (54 m.min-1). Further, the pedometer detected fewer steps than the accelerometer at this speed (75.4% vs 98.9%, P < 0.05). There were no differences between instruments compared with actual steps taken at all other walking speeds. In study 2, the CSA detected approximately 17-fold more erroneous steps than the pedometer (approximately 250 vs 15 steps for the total distance traveled, P < 0.05). CONCLUSIONS: The magnitude of the error (for either instrument) is not likely an important threat to the assessment of free-living ambulatory populations but may be a problem for pedometers when monitoring frail older adults with slow gaits. On the other hand, CSA accelerometers erroneously detect more nonsteps than the Yamax pedometer under typical motor vehicle traveling conditions. This threat to validity is likely only problematic when using the accelerometer to assess physical activity in sedentary individuals who travel extensively by motor vehicle.

Acceleration↗

PubMed2002

Comparison of pedometer and accelerometer measures of free-living physical activity.

PURPOSE: The purpose of this investigation was 1) to evaluate agreement between dual-mode CSA accelerometer outputs and Yamax pedometer outputs assessed concurrently under free-living conditions; 2) to determine the relationship between pedometer-steps per day and CSA-time spent in inactivity and in light-, moderate-, and vigorous-intensity activities; and 3) to identify a value of pedometer-steps per day that corresponds with a minimum of 30 CSA-min x d(-1) of moderate ambulatory activity. METHODS: Data were analyzed from 52 participants (27 men, 25 women; mean age = 38.2 +/- 12.0 yr; mean BMI = 26.4 +/- 4.5 kg x m(-2)) who were enrolled in the International Physical Activity Questionnaire study and wore both motion sensors during waking hours for 7 consecutive days. RESULTS: Participants averaged 415.0+/-159.5 CSA-counts x min(-1) x d(-1), 357,601 +/- 138,425 CSA-counts x d(-1), 11,483 +/- 3,856 CSA-steps x d(-1), and 9,638 +/- 4,030 pedometer-steps x d(-1). There was a strong relationship between all CSA outputs and pedometer outputs (r = 0.74-0.86). The mean difference in steps detected between instruments was 1845+/-2116 steps x d(-1) (CSA > pedometer; t = 6.29, P < 0.0001). There were distinct differences (effect sizes >0.80) in mean CSA-time (min x d(-1)) in moderate and vigorous activity with increasing pedometer-determined activity quartiles; no differences were noted for inactivity or light activity. Approximately 33 CSA-min x d(-1) of moderate activity corresponded with 8000 pedometer-steps x d(-1). CONCLUSION: Differences in mean steps per day detected may be due to differences in set instrument sensitivity thresholds and/or attachment. Additional studies with different populations are needed to confirm a recommended number of steps per day associated with the duration and intensity of public health recommendations for ambulatory activity.

Acceleration↗

PubMed2002

Utility of pedometers for assessing physical activity: convergent validity.

Valid assessment of physical activity is important to researchers and practitioners interested in surveillance, screening, programme evaluation and intervention. The validity of an assessment instrument is commonly considered its most important attribute. Convergent validity is the extent to which an instrument's output is associated with that of other instruments intended to measure the same exposure of interest. A systematic review of the literature produced 25 articles directly relevant to the question of convergent validity of pedometers against accelerometers, observation, and self-reported measures of physical activity. Reported correlations were pooled and a median r-value was computed. Pedometers correlate strongly (median r = 0.86) with different accelerometers (specifically uniaxial accelerometers) depending on the specific instruments used, monitoring frame and conditions implemented, and the manner in which the outputs are expressed. Pedometers also correlate strongly (median r = 0.82) with time in observed activity. Time in observed inactivity correlated negatively with pedometer outputs (median r = -0.44). The relationship with observed steps taken depended upon monitoring conditions and speed of walking. The highest agreement was apparent during ambulatory activity (running, walking) or during sitting (when both observation and pedometers would register few steps taken). There was consistent evidence of reduced accuracy during slow walking. Pedometers correlate moderately with different measures of energy expenditure (median r = 0.68). The relationship between pedometer outputs and energy expenditure is complicated by the use of many different direct and indirect measures of energy expenditure and population samples. Concordance with self-reported physical activity (median r = 0.33) varied depending upon the self-report instrument used, individuals assessed, and how pedometer outputs are expressed (e.g. steps, distance travelled, energy expenditure). Pedometer output has an inverse relationship with reported time spent sitting (r = -0.38). The accumulated evidence herein provides ample support that the simple and inexpensive pedometer is a valid option for assessing physical activity in research and practice.

Activities of Daily Living↗

PubMedDate not supplied

In their own voices: definitions and interpretations of physical activity.

Terms such as physical activity, exercise, and leisure are perceived and interpreted differently by people differing in gender, class, and sociocultural factors. We accessed multiple diverse data sources (including qualitative data recently collected in research and evaluation studies) to explore African-American and American Indian women's (age 40+) definitions, meanings, and interpretations of "physical activity". These women reported that physical activity is typically considered to be structured "exercise" and not incidental activities of daily life. The term "leisure" was interpreted from a cultural perspective as being lazy. These women also had difficulty understanding the meaning of "intensity" (e.g., "moderate", "vigorous"). Researchers must acknowledge and understand inconsistencies that arise and how these might influence design of, and responses to, self-report assessment of physical activity.

Adult↗

PubMedDate not supplied

Suitability of commuting by bicycle to Arizona elementary schools.

PURPOSE: To determine the biking suitability (i.e., bikeability) of and prevalence of biking in 14 elementary schools representing two extremes of bused students (2.4% vs. 53.6%). METHODS: Street segments (within 0.25-mile radius of school) were scored for bikeability. Bikes in racks per school student population established biking prevalence. Mann-Whitney U-test compared bikeability and prevalence of biking between groups. RESULTS: A total of 12.5 +/- 2.2 streets per school were assessed. Thirteen schools scored very good (< 3.0) and one scored fair (4.0-4.9). Median bikeability score was 0.69 for the low-busing schools and 0.53 for the high-busing schools (nonsignificant). Median biking prevalence was 3.1% in the low-busing schools and 1.3% in the high-busing schools (p < .05). CONCLUSION: Streets surrounding schools were adequate for biking. Biking prevalence was significantly higher in low-busing schools but was relatively low in both low- and high-busing schools. Other factors, including intraindividual, social, school, and community, likely contribute to choice of biking to school.

Arizona↗

PubMedDate not supplied

Evaluation of quality of commercial pedometers.

BACKGROUND: The purpose of this study was to: 1) evaluate the quality of promotional pedometers widely distributed through cereal boxes at the time of the 2004 Canada on the Move campaign; and 2) establish a battery of testing protocols to provide direction for future consensus on industry standards for pedometer quality. METHODS: Fifteen Kellogg's* Special K* Step Counters (K pedometers or K; manufactured for Kellogg Canada by Sasco, Inc.) and 9 Yamax pedometers (Yamax; Yamax Corporation, Tokyo, Japan) were tested with 9 participants accordingly: 1) 20 Step Test; 2) treadmill at 80m x min(-1) (3 miles x hr(-1)) and motor vehicle controlled conditions; and 3) 24-hour free-living conditions against an accelerometer criterion. RESULTS: Fifty-three percent of the K pedometers passed the 20 Step Test compared to 100% of the Yamax. Mean absolute percent error for the K during treadmill walking was 24.2+/-33.9 vs. 3.9+/-6.6% for the Yamax. The K detected 5.7-fold more non-steps compared to the Yamax during the motor vehicle condition. In the free-living condition, mean absolute percent error relative to the ActiGraph was 44.9+/-34.5% for the K vs. 19.5+/-21.2% for the Yamax. CONCLUSIONS: K pedometers are unacceptably inaccurate. We suggest that research grade pedometers: 1) be manufactured to a sensitivity threshold of 0.35 Gs; 2) detect +/-1 step error on the 20 Step Test (i.e., within 5%); 3) detect +/-1% error most of the time during treadmill walking at 80m x min(-1) (3 miles x hr(-1)); as well as, 4) detect steps/day within 10% of the ActiGraph at least 60% of the time, or be within 10% of the Yamax under free-living conditions.

Adult↗

PubMedDate not supplied

Proximal impact of Canada on the Move: the relationship of campaign awareness to pedometer ownership and use.

OBJECTIVE: Despite increased participation in leisure-time physical activity, inactivity remains an important public health problem. This study examines the immediate impact of the Canada on the Move initiative to promote walking through pedometer use among adult Canadians. METHODS: Data from a rolling monthly sample were collected via the Canadian Fitness and Lifestyle Research Institute's Physical Activity Monitor between November 2003 and September 2004. Prevalence rates were compared using Bonferroni-adjusted confidence intervals. Correlates of campaign recall and pedometer ownership were estimated using odds ratios adjusted for age, sex, income and education. RESULTS: Message recall and awareness as well as ownership and use of pedometers increased over the campaign and coincided with promotional activity. There was some evidence of a dose response between the number of messages recalled and pedometer use. DISCUSSION: The increased awareness and usage of pedometers among adult Canadians is encouraging; it indicates that these proximal targets are realistic and achievable for health promotion campaigns and contribute to opportunities for increasing physical activity behaviours.

Adolescent↗