Assessment of physical activity with a pedometer and its relationship with VO2max among adolescents in Switzerland

Effect of Sex, Body Mass Index and Physical Activity Level on Peak Oxygen Uptake Among 14-19 Years Old Adolescents

The aim was to describe longitudinal trends in peak oxygen uptake (VO_2peak) among 14- to 19-year-old adolescents in Norway, and to examine effects of sex, body mass index (BMI), and physical activity (PA) level on VO_2peak during adolescence. Of 124 invited students from two lower secondary schools in Norway, 116 eighth-grade students (61 boys and 55 girls; 14 years old at baseline) volunteered to participate. The study has a longitudinal design with 6 yearly repeated measures of body height and mass, VO_2peak and PA level. VO_2peak allometrically scaled to body mass raised to the power of 0.67 was measured using a walking or running incremental test on a treadmill, whereas PA level was self-reported. Among 696 possible observations, 555 (79.7%) were valid. Multiple linear regression and linear mixed model analyses were used to examine the associations between age, sex, BMI, PA level and VO_2peak. VO_2peak showed a non-linear pattern from age 14 to 19, with a distinct increase for boys peaking at age 17, while the results provide a flatter and more stable curve for girls. Sex, BMI and PA level together explained 43–71% of the variance in VO_2peak at the different age levels. Sex and PA level contributed independently to explain a significant proportion of the variance in VO_2peak at all measurement occasions, while BMI did not. Adjusted sex differences in VO_2peak increased over time, from 26.5 ml·kg^−0.67·min⁻¹ at age 14 to 55.5 ml·kg^−0.67·min⁻¹ at age 19. The independent contribution from PA level to the variance in VO_2peak increased from age 14 to 16 and then decreased. While PA level explained 32.5% of the total variance in VO_2peak for 16-year-olds, this number was 14% in 19-year-olds. In conclusion, aerobic power showed a non-linear pattern during adolescence, peaking at age 17. Sex and PA level explained a large proportion of the variance in VO_2peak, each of them being an independent contributor to VO_2peak. Aerobic power is linked to improved health and seems to depend largely on sex and PA level in adolescents, emphasizing the importance of maintaining a sufficient PA level during adolescence.

Self-efficacy regarding physical activity is superior to self-assessed activity level, in long-term prediction of cardiovascular events in middle-aged men

Background

Self-efficacy has been determined to be a strong predictor of who will engage in physical activity. We aimed to evaluate the associations between self-efficacy to perform physical activity, self-reported leisure-time physical activity and cardiovascular events in a population-based cohort of middle-aged Swedish men with no previous cardiovascular disease, or treatment with cardiovascular drugs.

Methods

Analyses are based on 377 men randomly selected and stratified for weight and insulin sensitivity from a population sample of 58-year-old men (n = 1728) and who had answered a question about their competence to perform exercise (as an assessment of physical self-efficacy). The Saltin-Grimby Physical Activity Level Scale was used to assess self-reported levels of leisure-time physical activity. Cardiovascular events were recorded during 13-years of follow-up.

Results

The group with poor self-efficacy to perform physical activity had a significantly higher incidence of cardiovascular events compared with the group with good physical self-efficacy (32.1 % vs 17.1 %, p < 0.01). Multivariate analyses showed that poor physical self-efficacy was associated with an increased relative risk of 2.0 (95 % CI 1.2 to 3.0), of having a cardiovascular event during follow-up also after adjustments for co-variates such as waist to hip ratio, heart rate, fasting plasma glucose, serum triglycerides, systolic blood pressure, apoB/apoA-I ratio and leisure-time physical activity.

Conclusion

Self-efficacy to perform physical activity was strongly and independently associated with cardiovascular events and was superior to self-assessed physical activity in predicting cardiovascular events during 13-years of follow-up in a group of middle-aged men, without known CVD or treatment with cardiovascular drugs.

Benefits of pedometer-measured habitual physical activity in healthy women

This cross-sectional study aimed at (i) characterizing pedometer-determined physical activity and (ii) examining its associations with dietary intake and anthropometric and metabolic profile in healthy women. Anthropometric and metabolic profile was evaluated in 68 healthy women of reproductive age. Habitual physical activity was assessed using a pedometer for 6 consecutive days, including weekends. Participants were stratified into active and inactive according to the mean steps·day–1(≥6000 and <6000, respectively). Food consumption was evaluated by 24-h recall in a subsample of 35 participants. Thirty-eight women were defined as active and had significantly lower body mass index (BMI), fat percentage, waist circumference, sum of skinfold thickness, insulin, and HOMA than the sedentary group. Mean BMI was 27 kg·m–2(overweight) in active participants and 31 kg·m–2(class I obesity) in inactive participants. Active women consumed more carbohydrates (55.5% ± 9.4% vs. 46.3% ± 7.6%) and calories (2138 ± 679 vs. 1664 ± 558 kcal), and less protein (15.4% ± 4.2% vs. 19.9% ± 5.8%) and lipids (29.0% ± 7.2% vs. 33.8% ± 6.2%) than inactive individuals (p < 0.05). Fiber, cholesterol, and fatty acid intake was similar in both groups. The number of steps was lower on Sunday than on weekdays for the overall group. Using a pedometer for 3 days was sufficient to determine habitual physical activity (sensitivity: 94%; specificity 91% vs. 6 days of pedometer use). In the present study, nonstructured physical activity was associated with more adequate dietary consumption and contributed toward a healthier anthropometric and metabolic profile in young women, despite the high prevalence of overweight.

Physical activity and depressive symptoms in adolescents: a prospective study

BACKGROUND

The frequency of mental illness amongst adolescents and its potential long-term consequences make it an important topic to research in relation to risk and protective factors. Research on the relationship between physical activity and depressive symptoms in adolescents is limited. There is a particular lack of evidence from longitudinal studies. This study examines the relationship between depression and physical activity using the Research with East London Adolescents: Community Health Survey (RELACHS).

METHODS

This was a prospective cohort study. Participants were recruited from three Local Education Authority boroughs in East London in 2001 from year 7 (aged 11-12) and year 9 (aged 13-14) and were followed-up in 2003. All pupils in the 28 schools that took part were eligible for the study. Of the total 3,322 pupils eligible for the survey the overall response rate was 84% (2,789 pupils). A total of 2,093 (75%) pupils were also followed-up in 2003. The sample was multiethnic (73% of respondents were non-white) and deprived. Just under half of the sample was male (49%). Depressive symptoms were measured using the Short Moods and Feelings Questionnaire (SMFQ). Logistic regression analyses were used to examine the association between physical activity and depressive symptoms both cross-sectionally and longitudinally.

RESULTS

After adjustments, there was evidence for a cross-sectional association between physical activity and depressive symptoms for both boys and girls at baseline, with a decrease in the odds of depressive symptoms of about 8% for each additional hour of exercise undertaken per week (boys: odds ratio (OR) = 0.92, 95% CI 0.85 to 0.99; girls: OR = 0.92, 95% CI 0.85 to 1.00). There was no evidence for an association between a change in physical activity from baseline to follow-up and depressive symptoms at follow-up.

CONCLUSIONS

This study provides some evidence for an association between level of physical activity and decreased depressive symptoms in adolescents. Further longitudinal research of these associations is required before physical activity can be recommended as an intervention for depression in adolescents.

A comparison of two motion sensors for the assessment of free-living physical activity of adolescents

This study assessed and compared the daily step counts recorded by two different motion sensors in order to estimate the free-living physical activity of 135 adolescent girls. Each girl concurrently wore a Yamax pedometer and an ActiGraph accelerometer (criterion measure) every day for seven consecutive days. The convergent validity of the pedometer can be considered intermediate when used to measure the step counts in free-living physical activity; but should be considered with caution when used to classify participants’ step counts into corresponding physical activity categories because of a likelihood of ‘erroneous’ classification in comparison with the accelerometer.

Pedometer-measured physical activity patterns of youth: a 13-country review

CONTEXT

Insufficient physical activity among young people aged 5-18 years is a global public health issue, with considerable disparities among countries. A systematic review was conducted to identify studies reporting pedometer daily steps (steps x day(-1)) in order to compile comparative, global cross-sectional data on youth physical activity patterns.

EVIDENCE ACQUISITION

Articles were included if they were in English, published by April 2009, and reported steps x day(-1) for boys and girls, separately, and reported steps x day(-1) for age groupings of no more than 4 years (e.g., 5-8 years) or combined no more than three grade levels (e.g., third- to fifth-graders). Studies could have been intervention-based but had to have reported baseline steps x day(-1), which would reflect unadulterated physical activity steps x day(-1) estimates. Inverse variance weighted estimates (steps x day(-1w)) were calculated for each country, and random effects models were estimated. Analyses were conducted in May and June 2009.

EVIDENCE SYNTHESIS

Forty-three studies, representing young people in 13 countries (N=14,200), were included. The majority of studies were from the U.S. (17/43). Overall, there was considerable variation within and among countries in steps x day(-1w). Boys and girls from European and Western Pacific regions had significantly more steps x day(-1w) than young people from the U.S. and Canada. Significantly lower steps x day(-1w) estimates for girls were observed for studies that combined measured steps x day(-1) for weekdays and weekend days, in comparison to weekdays only.

CONCLUSIONS

Limited sample sizes and non-population-based data preclude definitive statements regarding projected steps x day(-1) within countries. Nevertheless, these findings provide preliminary information for policymakers and researchers on the extent of the disparities among countries in the physical activity patterns of young people.

Measuring activity levels of young people: the validity of pedometers

The valid measurement of physical activity has the potential to be a very useful tool in countering the obesity epidemic. Previously, reviews have been carried out to investigate the validity of pedometers among adults. This paper aimed to carry out a similar review among children. A literature search was performed in PubMed, Web of Science, PsycINFO, CINAHL and SportDISCUS. Here, 25 papers investigating the validity, reliability and feasibility of pedometers for children were included in the study. Pedometers correlated highly in terms of both criterion (direct observation) and convergent validity (heart-rate monitor, accelerometer). Intra- and inter-unit reliability was also consistently high. Few studies report on feasibility issues of pedometer use in children, particularly compliance, reactivity and dealing with missing data. Given that they are both cheap and easy to use, pedometers can be effectively utilized as a valid determinant of physical activity levels among children and adolescents, particularly in large-scale epidemiological studies. There remains a need for accepted outliers and proper protocol regarding missing data.

Physical activity and hematologic cancer prevention

This chapter presents the epidemiologic evidence on the association between physical activity and hematologic cancers and related hypothesized biologic mechanisms. Some preliminary indications of a protective role for physical activity for non-Hodgkin's lymphoma, leukemia, multiple myeloma, and Hodgkin's lymphoma exist, but the level of epidemiologic evidence is still insufficient to make any definitive conclusions regarding the nature of these associations. Several plausible biologic mechanisms underlying the possible associations between physical activity and hematologic cancers have been proposed, including enhancement of immune function, reduction in obesity, improvement of antioxidant defense systems, impact on metabolic hormones, and anti-inflammatory effects. Future studies should improve the estimation of physical activity by using more reliable, valid, and comprehensive measurement tools, assessing all components of physical activity (type, intensity, and time period), and conducting intervention studies to evaluate the effect of physical activity on various biomarkers of cancer in order to provide further insight into plausible biologic mechanisms underlying the possible association between physical activity and hematologic cancers.

Regular use of pedometer does not enhance beneficial outcomes in a physical activity intervention study in type 2 diabetes mellitus

The aim of the present study was to investigate whether the use of pedometer increases walking and/or enhances beneficial outcomes in a physical intervention study in type 2 diabetes mellitus. Seventy persons with type 2 diabetes mellitus were randomized to a pedometer and a nonpedometer group (P and non-P groups). All participants were seen by a nurse at a baseline visit (V1), after 1 month, after 3 months, and after 6 months and were then encouraged to increase walking. Subjects in the P group additionally registered pedometer steps 3 days twice per month for 6 months. After V1 and the visit at 6 months, aerobic capacity (VO2peak) was measured; and subjects reported perceived physical fitness and activity. Twenty-two subjects did not complete the study (dropouts). The VO2peak at V1 was lower in dropouts than in subjects who completed the study (completers) (P=.003). In the P group, the number of steps per day did not increase from month 1 to month 6 (P=.65). In completers, taken together, there was a decrease in body weight (P=.005), hemoglobin A1c (P=.034), fasting blood glucose (P=.033), triglycerides (P=.002), and diastolic blood pressure (P=.048) and an increase in high-density lipoprotein cholesterol (P<.001), with no difference between the P group and non-P group for these variables (all P values>.38). Perceived improvement in physical and mental state correlated with improvement in VO2peak (r=0.45, P=.008 and r=0.38, P=.03, respectively; n=34). We conclude that the use of pedometer did not increase walking or enhance beneficial metabolic outcomes. The low aerobic capacity in dropouts indicates that persons most needy of physical exercise are the least compliant in exercise programs.

Pedometer-assessed physical activity in young adolescents

The purpose of this study was to evaluate the physical activity (PA) patterns of children. Forty-four 7th-grade students (19 boys, 25 girls) recorded pedometer data for 2 consecutive weeks. Separate 2 x 3 repeated measures analyses of variance were used to examine differences in total steps/day between boys and girls and between after-school activity participants and nonparticipants. The relative contribution of physical education (PE) and after-school activity (ASA) to weekday steps/day was evaluated as a proportion, for example (steps taken in PE class/total daily steps taken on a PE class day) * 100. The total sample mean was 11,392 steps/day, SD = 4112; for boys, M = 12,490 steps/day, SD=3910, versus girls, M = 10,557 steps/day, SD=4142; F=(1, 42) 4.365, p = .043. The sample population averaged 2046 steps, SD=945, during PE class; boys=2379 steps, SD=1115, versus girls=1782, SD=703; t (42) = 2.15, p = .038, d = .65, which represented 18% of the total steps/day on PE days. In comparison, the participants accumulated an average of 5366 steps, SD=2590; ASA for boys=5897 steps/day, SD=2738, versus girls=4963 steps/day, SD=2450; t (42) = 1.190, p = .241, d = .36), representing 46% of the steps/day on all weekdays and 47% of the total on PE days. Expressed as a rate, the sample population took 45.5 steps/min (SD=21) during PE class and 13.1 steps/min (SD = 4.7) in ASA on all weekdays. The relative stability of day-to-day behavior in youth is a preliminary finding but noteworthy. Although the absolute contribution ofPE class to daily PA was less than ASA (i.e., 18 vs. 47%, respectively), the importance of the condensed contribution in class was evident when these two activities were expressed as rates (i.e., steps/min). These data indicate that youth involved in ASA accumulated a greater number of steps on all days, weekend days, and health education days when compared to youth not involved in ASA.

Clinimetric review of motion sensors in children and adolescents

BACKGROUND AND OBJECTIVES

To review the clinimetric quality of motion sensors used to assess physical activity in healthy children and adolescents (2-18 years).

METHODS

A systematic literature search was performed in PubMed, Embase, and SpycINFO. The clinimetric quality of two pedometers (Digi-Walker, Pedoboy), four one-dimensional accelerometers (LSI, Caltrac, Actiwatch, CSA/ActiGraph), and three three-dimensional accelerometers (Tritrac-R3D, RT3, Tracmor2) was evaluated and compared using a 20-item checklist.

RESULTS

Overall, the quality of the studies (n = 35), and therefore the level of evidence for the reproducibility, validity, and feasibility of the motion sensors was modest (mean = 6.4 +/- 1.6 out of 14 points). There was strong evidence for a good reproducibility of the Caltrac in adolescents (12-18 years), a poor reproducibility of the Digi-Walker in children (8-12 years), a good validity of the CSA/ActiGraph in children and adolescents (8-18 years), and a good validity of the Tritrac-R3D in children (8-12 years).

CONCLUSIONS

The CSA/ActiGraph and the Caltrac are the only motion sensors in which the reproducibility, validity, and feasibility have been examined in different age groups. Further studies of the reproducibility of motion sensors in preschool children, improvement of the quality of clinimetric studies, and evaluation of the acceptability of motion sensors are warranted.

Steps counts among middle school students vary with aerobic fitness level

The purpose of this study was to examine if steps/day taken by middle school students varied based on aerobic fitness classification. Middle school students (N = 223; 112 girls, 111 boys) were assigned to three aerobic fitness categories (HIGH, MOD, LOW) based on results of the FlTNESSGRAM PACER test. Four weekdays of pedometer monitoring determined activity levels (steps/day). Boys accumulated significantly more steps/day than girls, 11,589 +/- 3,270 and 10,232 +/- 2,517 steps/day, respectively; F(1,219) = 16.0, p < .001, eta2 = .055. There were no differences in steps/day between grades. HIGH fit participants accumulated significantly more steps/day, F(2, 217) = 12.2, p < .101, eta2 = .101, than moderately fit and low fit participants (approximately 1,491 and ; 2,867 steps/day, respectively). Middle school students who participated in sports in addition to physical education (PE) accumulated significantly more steps/day (approximately 980 steps/day) than those participating in PE only, F(1, 219) = 10.0, p < .01, eta2 = .044. Although the relationship between physical activity and aerobic fitness was moderate (0.35; p < .01), these data demonstrated significant differences in accumulated steps/day among youth of varying aerobic fitness levels. Whether improved fitness levels were the result of additional activity or the cause of it remains to be determined. Regardless, the fittest middle school students were also the most active and accumulated a significant amount of steps/day through organized extracurricular physical activities.

Graded associations between cardiorespiratory fitness, fatness, and blood pressure in children and adolescents

OBJECTIVE

To measure the graded relation between cardiorespiratory fitness and sum of skinfolds, waist circumference, and blood pressure in children and adolescents participating in the European youth heart study.

METHODS

The participants were 4072 children and adolescents (aged 9 and 15) from Denmark, Portugal, Estonia, and Norway. Cardiorespiratory fitness was indirectly determined using a maximal ergometer cycle test. The sum of four skinfolds, waist circumference, and blood pressure were assessed with a standardised protocol. Linear regression analysis was used to test the graded relation between cardiorespiratory fitness and the dependent variables adjusted for pubertal stage, sex, and country.

RESULTS

A significant curvilinear graded relation was found between cardiorespiratory fitness and waist circumference and sum of skinfolds (partial r2 for cardiorespiratory fitness was 0.09-0.26 for the different sexes and age groups). Systolic and diastolic blood pressure also showed a curvilinear relation with cardiorespiratory fitness, and fitness explained 2% of the variance in systolic blood pressure. The difference in systolic blood pressure between the least and most fit was 6 mm Hg.

CONCLUSION

A curvilinear graded relation was found between cardiorespiratory fitness and waist circumference, sum of skinfolds, and systolic blood pressure. The greatest difference in these health variables was observed between low and moderate fitness levels.

Relationship between pedometer-registered activity, aerobic capacity and self-reported activity and fitness in patients with type 2 diabetes

AIM

The aim of this study is to investigate the relationship between pedometer-registered activity, aerobic capacity (VO(2 max)) and self-reported activity and fitness in patients with type 2 diabetes before and after a 12-week exercise programme.

METHODS

Twenty-nine men with type 2 diabetes (age=57.4 (7.8) years, BMI=31.7 (2.8) kg/m(2)) underwent exercise testing, registered pedometer activity and reported their physical fitness and activity in a questionnaire. Participants were randomly allocated to an exercise (EX) group (n=15) or a control (CO) group (n=14). Participants in EX group were offered supervised exercise twice a week for 12 weeks. At the end of the study, participants again underwent exercise testing, fasting blood tests and registration of pedometer activity.

RESULTS

At baseline, pedometer activity correlated with VO(2 max) (r=0.43, p=0.02) and with perceived physical fitness (r=0.48, p=0.02). After, but not before, intervention, pedometer activity and VO(2 max) additionally correlated with perceived everyday activity (r=0.62, p<0.01 and r=0.49, p=0.03, respectively). Both EX and CO groups tended to increase pedometer activity. In EX group, weight decreased by 2.7% (p=0.01), VO(2 max) increased 10.6% (p=0.03) and HbA1c decreased by 5.2% from baseline (p=0.02). In EX group, an increase in pedometer activity correlated with a fall in HbA1c (r=0.84, p<0.01) and in diastolic blood pressure (r=0.77, p=0.025).

CONCLUSIONS

Pedometer activity correlates with VO(2 max) in type-2 diabetic patients. Our exercise programme was well tolerated; it produced favourable effects on body weight, aerobic capacity and metabolic control. The use of pedometer may lead to more realistic assessment of perceived everyday physical activity.

A preliminary study of one year of pedometer self-monitoring

BACKGROUND

Long-term pedometer monitoring has not been attempted.

PURPOSE

The purpose of this project was to collect 365 days of continuous self-monitored pedometer data to explore the natural variability of physical activity.

METHODS

Twenty-three participants (7 men, 16 women; M age = 38 +- 9.9 years; M body mass index = 27.7 +- 6.2 kg/m2) were recruited by word of mouth at two southern U.S. universities. Participants were asked to wear pedometers at their waist during waking hours and record steps per day and daily behaviors (e.g., sport/exercise, work or not) on a simple calendar. In total, participants wore pedometers and recorded 8,197 person-days of data (of a possible 8,395 person-days, or 98%) for a mean of 10,090 +- 3,389 steps/day. Missing values were estimated using the Missing Values Analysis EM function in SPSS, Version 11.0.1.

RESULTS

A mean of 10,082 +- 3,319 steps/day was computed. Using the corrected data, differences in steps/day were significant for season (summer > winter, F = 7.57, p = .001), day of the week (weekday > weekend, F = 3.97, p = .011), type of day (workday vs. nonworkday, F = 9.467, p = .008), and participation in sport/exercise (day with sport/exercise > day without sport/exercise, F = 102.5, p < .0001).

CONCLUSIONS

These data suggest that surveillance should be conducted in the spring/fall or that an appropriate correction factor should be considered if the intent is to capture values resembling the year-round average.

Patterns of walking for transport and exercise: a novel application of time use data

Background

Walking for exercise is a purposeful or structured activity that can be captured relatively easily in surveys focused on leisure time activity. In contrast, walking for transport is an incidental activity that is likely to be missed using these same assessment approaches. Therefore, the purpose of this analysis was to utilize 1997 Australian Bureau of Statistics (ABS) Time Use Survey diary data to describe nationally representative patterns of walking for transport and for exercise.

Methods

Household members ≥ 15 years of age were recruited from over 4,550 randomly selected private dwellings in Australia. Time use diaries were collected for two designated days during all four seasons over the calendar year. 3,471 males and 3,776 females (94% household response rate and 84% person response rate) provided 14,315 diary days of data. The raw diary data were coded and summarized into bouts and minutes that included walking for transport and for exercise.

Results

Walking for transport was indicated on a higher proportion of days compared to walking for exercise (20 vs. 9%). Based on participant sub-samples ('doers'; those actually performing the activity) walking for transport was performed over 2.3 ± 1.4 bouts/day (12.5 minutes/bout) for a total of ≈28 mins/day and walking for exercise over 1.2 ± 0.5 bouts/day (47 minutes/bout) for a total of ≈56 mins/day.

Conclusion

Although walking for transport is typically undertaken in multiple brief bouts, accumulated durations approximate public health guidelines for those who report any walking for transport.

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.