Scandinavian Journal of Public Health, 2010; 38(Suppl 5): ORIGINAL ARTICLE

Scandinavian Journal of Public Health, 2010; 38(Suppl 5): 105 118 ORIGINAL ARTICLE Does a variation in self-reported physical activity reflect variation in objectively measured physical activity, resting heart rate, and physical fitness? Results from the Tromsø study AINA EMAUS 1,2, JORID DEGERSTRØM 3, TOM WILSGAARD 3, BJØRGE HERMAN HANSEN 4, CHRISTINA M. DIELI-CONWRIGHT 2, ANNE-SOFIE FURBERG 3,5, SVEIN ARNE PETTERSEN 6, LARS BO ANDERSEN 4,7, ANNE ELISE EGGEN 3, LESLIE BERNSTEIN 2 & INGER THUNE 1 1 Department of Oncology, Oslo University Hospital, Ullevål, Norway, 2 Division of Cancer Etiology, Department of Population Sciences, Cty of Hope National Medical Center, Duarte, USA, 3 Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, Norway, 4 Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway, 5 Department of Microbiology and Infection Control, University Hospital of North Norway, Norway, 6 Humanities, Social Science and Education, Department of Education, University of Tromsø, Norway, and 7 University of Southern Denmark, Institute of Sports Science and Clinical Biomechanics, Denmark Abstract Aims: To study the association between self-reported physical activity (PA) and objectively measured PA, resting heart rate, and physical fitness. Methods: During 2007 08, 17 men and 57 women aged 30 69 years attended the sixth survey of the Tromsø study. Self-reported PA during leisure-time and work were assessed and resting heart rate was measured. In a sub-study, the activity study, PA (Actigraph LLC) and physical fitness (VO 2max ) were objectively measured among 313 healthy men and womenaged40 44years.Results: Self-reported leisure PA was significantly correlated with VO 2max (ml/kg/min) (women 0.40, p < 0.001, men 0.44 p < 0.001) and moderate-to-vigorous PA (42000 counts/min) (women 0.28, p < 0.01, men 0.25, p < 0.01). The intra-class correlation coefficient between self-reported leisure PA and overall PA (counts/min) measured by accelerometer was 0.62 (95% CI 0.51, 0.71) for women and 0.59 (95% CI 0.47, 0.69) for men, and for VO 2max the intra-class correlation coefficient was 0.86 (95% CI 0.81, 0.90) for both sexes. Among all participants, an inverse dose response relationship was observed between self-reported leisure PA and resting heart rate for both men and women (p < 0.0001). More women than men met the international recommendations of 10,000 step counts/day (27% vs. 22%) and the recommendation of at least 30 minutes/day of moderate-to-vigorous intensities (30% vs. 22 %). Conclusions: The Tromsø physical activity questionnaire has acceptable validity and provides valid estimates of high-intensity leisure activity. However, these results underscore the need for collecting objectively PA measurements in large epidemiological studies. Key Words: Physical activity, general population, self-reported, objective Introduction Observational studies and short-term randomised controlled clinical trials have shown that physical activity results in biological processes [1 3] involved in risk, development, and mortality of several chronic diseases [4 7]. Furthermore, studies have observed inter-individual differences in biomarker response to exercise training, suggesting variation in an individual s susceptibility, supporting gene environment relationships [8]. Such associations may be a consequence of thefactthatourgeneswereselectedinanenvironment enhancing bouts of high-intensity physical activity. The benefits of physical activity on biomarkers and diseases have resulted in concern regarding declines in physical activity in Western populations [9,10]. Correspondence: Aina Emaus, Department of Oncology, Oslo University Hospital, Ullevål, Oslo 1062, Norway. E-mail: aina.emaus@medisin.uio.no (Accepted 26 June 2010) ß 2010 the Nordic Societies of Public Health DOI: 10.1177/1403494810378919

106 A. Emaus et al. Large health surveys collect self-reported information on physical activity levels in order to study the association between physical activity and biomarkers of disease [1,3,11] or disease outcomes [4,12 14]. These self-reported data on physical activity during leisure time are often categorised into sedentary, some physical activity, and sufficient physical activity to meet recommended physical activity levels, with 20 % of the study population in each category. However, physical activity is a complex behaviour and self-reported physical activity is often plagued by variation in recall accuracy. Therefore, objective measurement devices such as accelerometers, which measure movement duration, intensity, and frequency of activities, offer an important tool for understanding the true variation in physical activity and to validate self-reported physical activity [15]. In large health surveys, only smaller subgroups can be measured by objective measurements, i.e. using accelerometers and tests of physical fitness, due to the necessity of collecting detailed individual data. Physical activity questionnaires remain the most practical data collection method in large studies, but need to be reliable, valid, and relevant for the time period and for the population under study. Thus, to study whether the specific physical activity questions that are used in many Norwegian studies capture the true effects of physical activity and can be used in both large and small studies, the present validation study was conducted. The survey questions used were first developed for use among men [16] and further developed for use in the Oslo study [17] and later chosen as the assessment tool for the Norwegian Counties study [18], the Tromsø study [1,19], and even in smaller clinical studies, like the EBBA study [3]. The Tromsø study is a unique population-based health survey, which began in 1974 and has been conducted six times in the same population [1,20 23]. The study includes approximately 40,000 men and women and provides solid data for evaluating selfreported physical activity during work and leisure. In previous Tromsø surveys, an association between selfreported leisure activity and work load (physical fitness) among women were observed [22] and heart rate and metabolic profiles were strongly associated with repeated assessments of self-reported leisure activity 7 years apart in men and women [1]. In order to study whether the Tromsø activity questions captures high-intensity physical activity, inclusions of indirect markers of performed physical activity such as resting heart rate and maximal oxygen uptake (VO 2max ) as a measure of cardiorespiratory fitness were included. The ability to perform aerobic exercise is influenced by an individual s maximal oxygen uptake, which is widely recognised as one of the most important indices of aerobic fitness. Heart rate is a marker of cardiac capacity, reflecting autonomic function observed by variability in heart rate [24,25]. In order to study whether the questionnaire reflects performed physical activity, we included 7 days with accelerometer measurement. To promote and maintain an optimal physical activity level in the general population, it is recommended that healthy adults perform moderate-intensity aerobic (endurance) physical activity for a minimum of 30 minutes preferably on every day of the week [26,27]. The aims of the present study were to elucidate the patterns and associations between self-reported physical activity (the Tromsø study questionnaire) during leisure and work time and the resting heart rate, objectively measured physical activity (accelerometer), and fitness (VO 2max ) in men and women. Additionally, we wanted to use these various selfreported and objective physical activity measures to estimate what proportion of participants met recommended physical activity guidelines. Materials and methods Study population The study subjects were men and women who participated in the sixth population-based health survey of the Tromsø study carried out in 2007 08. Some of the participants were invited to participate in a sub-study, the activity study (2008 09) (Figure 1). Each participant received a written invitation to participate, together with a general questionnaire including history of chronic diseases and physical activity. The population of Tromsø reflects the distribution of sex, levels of education, number of children, and average income in Norway overall, but the population is somewhat younger [28]. The sixth survey of the Tromsø study invited all subjects in Tromsø aged 40 42 and 87 years, a 40% random sample aged 43 59 years, and a 10% random sample aged 30 39 years. In addition to the random sample, 295 participants were invited because they attended the second visit in the fourth survey in 1994. In the age group 30 69 years, 10,624 men and women attended (attendance rate 67.3 %) and 2435 subjects aged 40 44 years attended (attendance rate 58%). In the Tromsø activity sub-study, a sample of 746 men and women aged 40 44 years who already had participated in the Tromsø study were invited by mail. The participants were randomly selected from those who attended during the last 3 months of the core examination of the sixth Tromsø study. A total of 391 (52%) persons responded and 313 persons were eligible to participate (Figure 1).

Physical activity, self-reported vs. objectively measured, general population 107 The Tromsø study Sixth survey, 2007 2008 30 87 years, n=12984 Main study population a 30 69 years, n=10,624 57 women, 17 men 40 44 years, n=2,367 1 292 women, 1 075 men Population 40 44 years b n=2054 1 134 women, 920 men The activity study c 2008 2009, n=313 158 women, 1 men Physical activity Accelerometer n=2 d 138 women, 132 men Physical fitness VO 2max n=305 e 154 women, 151 men Figure 1. The study population a Participating men and women 30 69 years. b Population 40 44 years, n ¼ 2 054; of whom n ¼ 1 621 not invited to the activity study, n ¼ 3 invited but non responders, n ¼ 78 could not be included. c Invited to the activity study, n ¼ 746: responders, n ¼ 391 (52.4%); included ¼ 313 (42.0%). d Included in accelerometer analyses, n ¼ 2. Exclusions: Instrument malfunction/missing information (n ¼ 27), not achieving 3 or more days registration (n ¼ 16). e Included in fitness analyses, n ¼ 305. Inclusion criteria: respiratory exchange ratio 1.05 or the ability to demonstrate a VO 2 plateau, defined as a failure of oxygen uptake to increase by greater than 2.0 ml kg-1 min-1 with treadmill speed/inclination increase. Excluded, n ¼ 8. Ethics Each subject gave written informed consent prior to participation. The Regional Committee of Medical and Health Research Ethics recommended the protocol and the Norwegian Data Inspectorate approved the study. Physical activity assessments Self-reported physical activity (questionnaires) and resting heart rate The main questionnaire covering physical activity was filled in at home and checked by trained personnel at the survey for inconsistencies and incomplete data. The participants indicated their usual level of leisure activity in the past year using one of four response categories (see Appendix) [12]: level 1: reading, watching television, or engaging in sedentary activities; level 2: at least 4 hours a week walking, bicycling, or engaging in other types of physical activity; level 3: at least 4 hours a week exercising to keep fit and participating in recreational athletics; and level 4: regular, vigorous training or participating in competitive sports several times a week). This physical activity assessment method used in surveys from 19/1980s and also recently, has been observed to reflect heart rate, fitness, and metabolic profile [1,3,22]. The self-reported level of physical activity during work time in the past year was also graded in a four-point scale: a grade of 1 was assigned to those whose work was mostly sedentary; a grade 2 to those whose job involved a lot of walking; a grade 3 to those whose job required a lot of lifting and walking; a grade 4 to those engaged in heavy manual labour. Resting heart rate was derived from the median pulse-to-pulse interval in a sitting position during the time of the blood pressure measurement (automated device, Dinamap Pro care 300 Monitor). Three readings were taken, separated with 1-minute interval. The mean of the two latest measurements recorded was used in the present study. Objective assessment of physical activity Objective measurements of physical activity were collected using GT1M-Activity Monitor (Actigraph LLC, Pensacola, Florida). The GT1M-Actigraph is a lightweight, electronic motion sensor comprising a single plane accelerometer. The accelerometer is small (3.8 3.7 1.8 cm) and light (27 g) and was worn on an elastic belt on the right hip. Study investigators gave monitors to participant in

108 A. Emaus et al. a face-to-face meeting. The participants were asked to wear the Actigraph during waking hours for 7 consecutive days. Each Actigraph was programmed to start at 07:00 on the day after delivery. The accelerometer allows detailed investigation of patterns of activity. Movement in the vertical plane is detected as a combined function of the frequency and intensity of the movement. Movement counts are averaged over specified epochs (time-intervals) and these data are stored in memory and subsequently downloaded to a computer. The sum of the activity counts in a given epoch is related to activity intensity and can be categorised by intensity (e.g., sedentary, light, moderate and vigorous, vigorous) on the basis of validated activity count cut points [29 31]. Actigraphs were programmed to measure 15-second epochs and accelerometer data were integrated up from 15 seconds to 1 minute in dataanalysis. The software program CSA Analyzer (csa.svenssonsport.dk) was used to extract data. Night activity (midnight to 06:00) and sequences of 410 minutes of consecutive zero counts, indicating that the accelerometer was not in use, were excluded from the recordings. A minimum of 10 hours activity per day were set to be included in the analyses. To assess potential differences in activity levels between individuals with different numbers of assessment days, we calculated physical activity levels separately for individuals with 3, 4, and 5 days of valid activity recordings. Because no differences were found (data not shown), all participants with at least 3 days and at least 10 hours of activity per day of individual data are included in the analyses. Of 313 participants in the activity study, a total of 286 participants provided valid Actigraph recordings for (1 7 days). Reasons for exclusion were: not wearing ActiGraph (n ¼ 15), instrument malfunction (n ¼ 6), and missing identity number (n ¼ 6). All in all, 2 participants achieved a minimum of 3 days of assessment and were included in analyses regarding accelerometer data. Of these, 2 participants had data from weekdays and 224 (83%) participants had weekend accelerometer data. Objective measurement of physical fitness VO 2max is defined as the highest rate of oxygen consumption attainable during maximal exercise [25]. Normally aerobic power (VO 2max ) is expressed by dividing measured values by body mass (ml/kg/min) making it possible to compare the fitness level between individuals of different body mass. The participants completed an incremental VO 2max test performed until total exhaustion, administered by two trained study assistants [32]. The beginning pace varied by individual, starting with a speed that elicited a heart rate of approximately 145 (beats/min). Since running technique differs, participants could choose if they preferred having speed increased, level of incline increased, or a combination of both to enhance workload. Every minute, the workload was increased (1 km/h or two grades incline increments). Towards the end of the test, workload was increased individually to motivate test subjects to continue when changing to a heavier stage. Heart rates were monitored with a Polar S 610 I (Finland) wrist watch. Expired air was analysed continuously for O 2 and carbon-dioxide (CO 2 ) by a Erich Jaguar Oxycon Pro (Jaeger Viasys, Healthcare, Hoechberg, Germany) oxygen analyser, calibrated with standardised gases before each test. The subjects breathed through a Hans Rudolph valve (20 series) with registration of ventilation, VO 2, CO 2, and respiratory exchange ratio at an average of every 30 seconds. Subjects had to achieve at least one of the two following criteria: (1) the ability to demonstrate a VO 2 plateau, defined as a failure of oxygen uptake to increase by greater than 2.0 (ml/kg/min) with increasing treadmill speed/incline, (2) respiratory exchange ratio 1.05. In addition, the test-administrator evaluated the following characteristics of maximal performance: test subject expressed orally or in terms of body language that he or she was totally exhausted or the test subject could not continue to run properly, was blanching and in danger of falling due to exhaustion. The highest oxygen uptake reached (30 seconds average) was recorded as VO 2max. A total of 305 participants are included in the analyses regarding fitness data. Statistical analyses Data analyses were conducted using SAS version 9.2 (SAS Institute, Cary, NC). Statistical analyses were performed in order to study the association between self-reported leisure-time and work activity, objectively measured physical activity, resting heart rate, and physical fitness. Continuous variables were assessed for normality and reported as mean and standard deviation (SD) and proportions were noted for categorical variables. The study population aged 40 44 years was compared with the participants in the activity study in regards to descriptive characteristic (Table I). Spearman rank-order correlation coefficients were used to determine the association between the questionnaire variables for self-reported physical activity (work and leisure-time) and the direct objectively measured accelerometer data, resting heart rate, and physical fitness (Table II). Test retest reliability of self-reported leisure time

physical activity according to objectively measures of physical activity and physical fitness was assessed using intra-class correlation coefficients (ICC) (Table III). The strength of agreement for the ICC was interpreted as follows; < 0.00, poor; 0.00 0.20, slight, 0.21 0.40, fair, 0.41 0., moderate; 0.61 0.80, substantial; and 0.81 1.00, almost perfect [33,34]. We used general linear models to compare objectively tested physical activity and fitness by level of self-reported leisure time and work activity (Tables IV and V) and calculated least squared means and conducted trend tests by fitting ordinal values for self-reported activity in the regression models. Physical activity, self-reported vs. objectively measured, general population 109 Several objective physical activity variables were derived. Overall activity was the average accelerometer counts/min over the full period of valid recording. Time (minutes) spent in different intensity levels of physical activity was estimated and activity cutpoints ranges were computed: no activity describing minutes without any objectively measured movements [0 counts/min], light physical activity (LPA; 1 2000 counts/min), moderate and vigorous physical activity (MVPA; 42000 counts/minute), and vigorous physical activity (VPA; 400 counts/minute) [29 31]. The MVPA defined as42000 counts/min is equivalent to three metabolic equivalents (METs) and a walking pace at 4 km/h. Step counts per day was measured using the Actigraph. Table I. Descriptive characteristics, the Tromsø study (n ¼ 10 624). Main study population (30 69 years, n ¼ 10,624) Study population (40 44 years, n ¼ 2054) Participants in the activity study (40 44 years, n ¼ 313) p-value a Women, no. 57 1134 158 Demography Age, years (SD) 53.1 (10.1) 41.5 (1.23) 42.3 (1.38) <0.0001 Married, no. (%) 3206 (57.2) 582 (51.3) 83 (52.5) 0.78 Higher education, no. (%) 2322 (41.4) 638 (56.3) 100 (63.3) 0.09 Household income 4E,245, no. (%) b 2364 (42.2) 688 (.7) 111 (.3) 0.02 Children, mean (SD) 2.14 (1.17) 1.96 (1.10) 2.15 (1.22) <0.05 Resting heart rate, beats/min (SD) 66.1 (10.0).6 (9.90) 64.4 (10.5) 0.16 Self-reported leisure activity, no. (%) Sedentary 936 (17.8) 210 (19.0) 21 (13.5) 0.09 Moderate 3541 (67.5) 677 (61.2) 95 (.9) 0.94 Hard 719 (13.7) 197 (17.8) 35 (22.4) 0.16 Vigorous 54 (1.03) 22 (2.00) 5 (3.21) 0.32 Self-reported work activity, no. (%) Sedentary 2011 (49.9) 514 (49.9) 79 (53.4) 0.42 Moderate 1199 (29.7) 280 (27.2) 43 (29.1) 0.63 Hard 780 (19.3) 228 (22.1) 25 (16.9) 0.15 Heavy manual work 44 (1.09) 9 (0.87) 1 (0.68) 0.81 Men, no. 17 920 1 Demography Age, years (SD) 53.8 (10.0) 41.4 (1.18) 42.1 (1.41) <0.0001 Married, no. (%) 3157 (62.9) 462 (.2) 90 (58.1) 0.07 Higher education, no. (%) 2123 (42.3) 426 (46.3) 85 (54.8) <0.05 Household income 4E,245, no. (%) b 2685 (53.5) 0 (.2) 115 (74.2) 0.03 Resting heart rate, beats/min (SD) 64.5 (10.7) 64.1 (10.3) 63.2 (10.6) 0.31 Self-reported leisure activity, no. (%) Sedentary 1004 (20.9) 224 (24.9) 24 (15.6) 0.01 Moderate 2441 (.8) 389 (43.3) (35.7) 0.08 Hard 1226 (25.5) 247 (27.5) 67 (43.5) <0.0001 Vigorous 134 (2.79) 38 (4.23) 8 (5.19) 0.58 Self-reported work activity, no. (%) Sedentary 2234 (56.3) 451 (52.0) 83 (58.9) 0.013 Moderate 842 (21.2) 187 (21.5) 27 (19.2) 0.52 Hard 676 (17.0) 177 (20.4) 29 (20.6) 0.96 Heavy manual work 217 (5.47) 53 (6.11) 2 (1.42) 0.02 a p-value for differences in means and proportions between population 40 44 years and the activity study. b Household income 4NOK 5,000, US$ 96,5. SD standard deviation. Numbers may vary due to missing information.

110 A. Emaus et al. Table II. Spearman s correlation coefficient by sex for resting heart rate, objectively tested physical fitness (VO 2 ) and physical activity, stepcounts and self-reported physical activity, the Tromsø study (n ¼ 313). Objectively tested fitness a Objectively tested physical activity b Self-reported activity c Physical activity assessment comparison Heart rate VO 2 (ml/kg/min) Overall activity Light PA Moderate- Vigorous PA Vigorous PA Step Work Leisure Women (self-reported) Leisure activity 0.24 e 0.40 f 0.23 d 0.22 d 0.28 e 0.27 e 0.12 0.23 e Work activity 0.07 0.07 0.11 0.40 f 0.05 0.13 0.15 0.23 e 0.39 f 0.17 a 0.06 0.15 a 0.28 e 0.13 0.07 0.24 d Men (self-reported) Leisure activity 0.17 d 0.44 f 0.23 e 0.23 d 0.25 e 0.25 e 0.29 e 0.17 a Work activity 0.02 0.02 0.08 0.29 e 0.04 0.15 0.14 0.17 g 0.34 f 0.17 a 0.05 0.14 0.28 e 0.13 0.02 0.17 a Objectively tested fitness: maximal treadmill-test, VO 2, oxygen uptake. b Objectively assessed physical activity (PA): light physical activity, 1 2000 counts/min; moderate to vigorous physical activity, above 2000 counts/min; vigorous physical activity, above 00 counts/min. c Self-reported work physical activity: three levels; self-reported leisure time activity: four levels. Numbers may vary due to missing information. d p < 0.05. e p < 0.01. f p < 0.001. g p ¼ 0.05 0.10. Table III. Intra-class correlation (ICC) coefficients for test retest reliability of self-reported leisure activity, according to objectively measures of physical activity, and physical fitness by sex, the Tromsø study (n ¼ 313). Women Men Variable ICC 95% CI ICC 95% CI Accelerometer data a Overall activity (counts/min) 0.62 (0.51, 0.71) 0.59 (0.47, 0.69) Weekend activity (counts/min) 0.61 (0.48, 0.71) 0.06 (0.00, 0.24) Weekdays activity (counts/min) 0. (0.36, 0.62) 0.61 (0.49, 0.71) No activity (min/day) 0.15 (0.00, 0.31) 0.48 (0.34, 0.) Light PA (min/day) 0.31 (0.15, 0.45) 0.47 (0.33, 0.59) Moderate-to-vigorous PA (min/day) 0. (0.54, 0.74) 0.48 (0.34, 0.) Vigorous PA (min/day) 0.75 (0.67, 0.81) 0.40 (0.25, 0.53) Step (counts/day) 0.29 (0.12, 0.44) 0.64 (0.52, 0.73) Fitness data b VO 2 max (l/min) 0.71 (0.62, 0.78) 0.74 (0., 0.81) VO 2 max (ml/kg/min) 0.86 (0.81, 0.90) 0.86 (0.81, 0.90) a Objectively assessed physical activity (PA): accelerometer: no activity, 0 counts/min; light physical activity, 1 2000 counts/min; moderate to vigorous physical activity, above 2000 counts/min; vigorous physical activity, above 00 counts/min. b Objectively tested fitness: maximal treadmill-test, VO 2, oxygen uptake. Numbers may vary due to missing information. We used all four categories of the self-reported leisure and work activity variables when studying the main outcomes. However, for analysis that stratified on these variables to assess the effects of objectively measured physical activity and work activity, heavy lifting, and walking was combined with heavy manual labour as only three subjects reported heavy manual labour. We studied the variation in resting heart rate for men and women in quartiles of step counts, MVPA and VO 2max, and four categories of self-reported leisure activity (Figure 2) and tested for trend across categories. The patterns of activity bouts were determined by summing continuous minutes of MVPA in modified 10-minute bouts. The Actigraph data were further classified according to achievement of the specific physical activity recommendations, in particular, whether the activity achieved the recommended pattern of 430 min/day accumulated in one

Physical activity, self-reported vs. objectively measured, general population 111 Table IV. Objectively tested physical activity and fitness for total group and by levels of self-reported leisure activity, the Tromsø study (n ¼ 313). a Data are presented as means (SD). Self-reported physical activity Total group Sedentary Moderate Hard Very hard p trend Women Accelerometer data (N) b 136 19 83 31 3 Actigraph use (days) 5.80 (1.24) 5.58 (1.43) 5.77 (1.22) 6.06 (1.12) 4.67 (1.51) 0. Actigraph use (hours/day) 13.1 (1.02) 12.8 (0.79) 13.2 (1.04) 13.1 (1.08) 12.2 (0.53) 0.95 Overall activity (counts/min) 402.4 (133.5) 347.9 (115.0) 391.4 (120.4) 443.0 (124.3) 6.7 (325.2) 0.0002 Weekend activity (counts/min) 410.0 (178.5) 319.4 (140.6) 387.6 (148.9) 1.0 (219.3) 829.2 <0.0001 Weekdays activity (counts/min) 401.0 (138.3) 354.8 (111.6) 392.8 (131.8) 434.4 (126.8) 618.6 (347.6) 0.003 No activity (min/day) 234.1 (48.1) 225.9 (47.2) 233.5 (48.7) 247.3 (35.9) 246.3 (35.6) 0.09 Light PA (min/day) 515.1 (84.6) 513.7 (.4) 524.7 (86.8) 489.5 (74.8) 413.9 (54.1) 0.03 Moderate- vigorous (min/day) 37.6 (22.8) 28.1 (18.1) 35.2 (20.3) 47.4 (26.0) 72.7 (31.3) <0.0001 Vigorous PA (min/day) 2. (5.71) 0.61 (1.24) 2.33 (4.42) 3.10 (3.45) 19.1 (27.9) 0.0005 Step (counts/day) 8727 (2591) 7904 (2417) 86 (2495) 9518 (2886) 10,400 (2511) 0.018 Resting heart rate (beats/min) 64.1 (10.1).1 (10.7).9 (9.) 59.7 (9.53) 52.6 (8.76) 0.0007 Fitness data (N) c 152 19 94 34 5 VO 2max (l/min) 2.37 (0.35) 2.33 (0.27) 2.30 (0.33) 2.52 (0.36) 2.71 (0.44) 0.001 VO 2max (ml/kg/min) 35.6 (6.32) 32.0 (5.72) 34.7 (5.26) 39.6 (6.29) 43.4 (8.81) <0.0001 Men Accelerometer data (N) b 132 23 48 6 Actigraph use (days) 5.88 (1.14) 5.27 (1.45) 5.75 (1.01) 6.18 (1.00) 6.00 (1.26) 0.002 Actigraph use (hours/day) 13.0 (1.12) 12.6 (1.27) 12.9 (0.94) 13.3 (1.14) 13.2 (1.25) 0.02 Overall activity (counts/min) 416.8 (148.1) 364.0 (115.2) 387.9 (135.7) 452.8 (159.2) 463.1 (153.6) 0.005 Weekend activity (counts/min) 432.7 (208.8) 394.8 (181.4) 394.4 (167.9) 463.4 (242.3) 479.2 (141.5) 0.11 Weekdays activity (counts/min) 388.0 (142.8) 3.8 (115.9) 384.3 (138.1) 449.1 (145.5) 458.0 (164.1) 0.004 No activity (min/day) 231.9 (54.7) 248.8 (33.7) 237.8 (.7) 219.6 (58.1) 249.6 (58.5) 0.08 Light PA (min/day) 512.4 (91.5) 478.5 (91.3) 2.2 (84.4) 534.4 (94.5) 491.2 (73.7) 0.03 Moderate-to-vigorous PA (min/day) 36.8 (23.1) 30.8 (20.4) 32.3 (22.2) 41.1 (23.8) 48.1 (24.5) 0.01 Vigorous PA (min/day) 3.20 (7.03) 0.97 (2.12) 2.20 (5.95) 4.43 (8.58) 6.40 (6.) 0.01 Step (counts/day) 8109 (2799) 6954 (2466) 77 (24) 8882 (2839) 9284 (3832) 0.002 Resting heart rate (beats/min) 62.9 (10.3).4 (8.13) 64.3 (11.3) 61.2 (10.1) 59.8 (8.05) 0.03 Fitness data (N) c 1 23 53 66 8 VO 2max (l/min) 3.67 (0.) 3.38 (0.39) 3. (0.51) 3.80 (0.58) 4.22 (0.31) <0.0001 VO 2max (ml/kg/min) 43.4 (7.) 37.2 (5.11) 41.7 (6.86) 46.2 (7.35) 48.4 (6.01) <0.0001 a Fitness data, n ¼ 305; accelerometer data, n ¼ 2; numbers may vary due to missing information. b Objectively assessed physical activity (PA): no activity, 0 counts/min; light physical activity, 1 2000 counts/min; moderate to vigorous physical activity, above 2000 counts/min; vigorous physical activity, above 00 counts/min. c Objectively tested fitness, maximal treadmill-test, VO 2, oxygen uptake. continuous bout or in several short modified 10-minute bouts [27]. Results Among 57 women (mean age 53.1 years) and 17 men (mean age 53.8 years) participating in the main study, 14.7% of the women and 28.3% of the men reported hard and vigorous activity during leisure time, while 20.4% of the women and 22.5 % of the men reported hard and heavy manual work activity (Table I). Comparing those aged 40 44 years who participated in the activity study with those who did not participate, more men who participated in the activity study reported hard leisure activity (p men < 0.0001, p women ¼ 0.16), compare to those who did not participate. To assess the association between self-reported physical activity, resting heart rate, and objectively measured physical activity and fitness, Spearman correlation coefficients were calculated for men and women (Table II). Self-reported leisure activity was significantly correlated with the objectively measurements for fitness and activity, and the strongest correlations were shown with VO 2max (ml/kg/min) (women 0.40, p < 0.001, men 0.44 p < 0.001) and MVPA (women 0.28, p < 0.01, men 0.25, p < 0.01). Resting heart rate was negatively correlated with VO 2max (ml/kg/min) (women 0.39, p < 0.001, men 0.34, p < 0.001) (Table II). In the main study population (30 69 years, n ¼ 10,624) the correlation

112 A. Emaus et al. Table V. Objectively tested physical activity and fitness in levels of self-reported work activity, the Tromsø study (n ¼ 313). a Data are presented as mean (SD). Work activity Sedentary Moderate Hard p trend Women Accelerometer data (N) b 69 39 22 Actigraph use (days) 5.81 (1.30) 5.85 (1.09) 5.73 (1.39) 0.85 Actigraph use (hours/day) 12.9 (0.93) 13.2 (1.02) 13.6 (1.26) 0.01 Overall activity (counts/min) 393.2 (146.9) 414.1 (113.6) 428.4 (123.3) 0.24 Weekend activity (counts/min) 423.6 (194.1) 407.6 (181.8) 366.7 (130.0) 0.25 Weekdays activity (counts/min) 387.0 (147.1) 411.8 (119.8) 448.7 (137.8) 0.07 No activity (min/day) 2.6 (33.7) 211.6 (51.9) 205.4 (42.8) <0.0001 Light PA (min/day) 482.2 (67.9) 539.8 (90.2) 572.3 (90.7) <0.0001 Moderate to vigorous PA (min/day) 38.8 (24.7) 38.4 (21.5) 36.2 (20.9) 0.69 Vigorous PA (min/day) 2.90 (6.84) 2.67 (5.18) 1.97 (3.14) 0.54 Step (counts/day) 8452 (2736) 9267 (2279) 9206 (2248) 0.13 Resting heart rate (beats/min) 63.3 (9.63) 63.1 (9.66).2 (11.6) 0.48 Fitness data (N) c 69 39 22 VO 2max (l/min) 2.37 (0.41) 2.43 (0.30) 2.23 (0.20) 0.20 VO 2max (ml/kg/min) 36.5 (6.93) 35.4 (5.87) 34.3 (5.27) 0.11 Men Accelerometer data (N) b 73 22 26 Actigraph use (days) 5.81 (1.16) 5.77 (1.27) 6.38 (0.85) 0.05 Actigraph use (hours/day) 12.9 (1.12) 12.7 (1.05) 13.5 (1.12) 0.66 Overall activity (counts/min) 415.8 (138.0) 419.4 (191.5) 449.2 (136.3) 0.35 Week-end activity (counts/min) 456.8 (216.4) 417.5 (227.9) 426.7 (171.8) 0.49 Week-days activity (counts/min) 408.9 (135.7) 414.6 (175.6) 451.9 (133.3) 0.21 No activity (min/day) 243.7 (.0) 225.1 (.4) 206.8 (49.5) 0.003 Light PA (min/day) 493.4 (96.1) 6.9 (73.9) 562.2 (85.1) 0.002 Moderate to vigorous PA (min/day) 39.5 (22.7) 32.4 (19.6) 38.7 (25.7) 0.66 Vigorous PA (min/day) 3.36 (6.44) 4.23 (10.4) 2.63 (6.32) 0.77 Step (counts/day) 8017 (22) 7892 (2493) 9307 (3184) 0.08 Resting heart rate (beats/min) 62.3 (10.4).4 (10.4) 62.1 (10.9) 0.83 Fitness data (N) c 80 27 31 VO 2max (l/min) 3. (0.) 3.74 (0.62) 3.57 (0.63) 0.36 VO 2max (ml/kg/min) 43.7 (7.) 45.8 (7.46) 42.5 (6.75) 0. a Fitness data, n ¼ 305; accelerometer data, n ¼ 2; numbers may vary due to missing information. b Objectively assessed physical activity (PA): accelerometer: no activity, 0 counts/min; light physical activity, 1 2000 counts/min; moderate to vigorous physical activity, above 2000 counts/min; vigorous physical activity, above 00 counts/min. c Objectively tested fitness: maximal treadmill-test, VO 2, oxygen uptake. % meeting recommendations 100 90 80 40 30 20 10 0 86.5 84.4 Self reported leisure activity 30.4 Accelerometer, MVPA Women Men 27 22 22.1 Step count Figure 2. Percentage of adults meeting physical activity guidelines: self-reported leisure time activity, level 2 4; accelerometer, accumulation 30 min/day or more of moderate to vigorous physical activity (MVPA), in either one continuous bout, or several shorter bouts lasting i.e. 10 minutes; step count, minimum 10 000 steps per day; the Tromsø activity study (n ¼ 2).

between self-reported leisure activity and resting heart rate was 0.15 (p < 0.0001) for women and 0.23 (p < 0.0001) for men (data not shown in tables). The test retest intra-class correlation (ICC) with its 95 % confidence interval for the self-reported leisure-time activity is shown in Table III. The ICC estimates ranged from 0.15 to 0.86 in women and 0.06 to 0.86 in men. The ICC was classified as moderate, substantial, or almost perfect for all variables except for weekend activity in men and no activity, LPA, and step count in women. Table IV presents objectively assessed physical activity and measured physical fitness for the total group and by levels of self-reported leisure activity. Overall activity measured in counts/min did not differ significantly between men and women (417 and 402 counts/min respectively, p ¼ 0.40). In contrast, women tended to have a higher number of step count per day compared to men (8727 and 8109 step count/day, respectively, p ¼ 0.07). After dividing the objectively assessed step counts/min into different intensity categories of activities, women spent on average 515 minutes in LPA and 37.6 minutes in moderate activities (MVPA), while men spent on average 512 minutes and 36.8 minutes in LPA and MVPA, respectively. The mean (SD) maximal oxygen uptake for women was 35.6 (6.32) ml/kg/ min, and for men was 43.4 (7.) ml/kg/min (Table IV). We observed a positive association between overall activity (counts/min) and level of leisure activity with a dose response association across four categories for both men and women (p trend women ¼ 0.0002, p trend men ¼ 0.005) (Table IV). This association was also observed in moderate-tovigorous (MVPA) and vigorous (VPA) intensity activity for both men and women. Maximal oxygen uptake was positively associated with increasing level of self-reported leisure activity for both men and women [VO 2max (ml/kg/min) p women < 0.0001, p men < 0.0001)]. When dividing men and women into three categories of self-reported work activity no association was observed for VO 2max or overall activity (counts/min) (Table V). We observed a negative association between the objective measures of no activity and self-reported work activity (p women < 0.0001, p men < 0.0001) and a positive association between light physical activity and self-reported work activity (p women < 0.0001, p men < 0.0001). Figure 3 shows the association between resting heart rate and different subjective and objective measures of physical activity. Heart rate was negatively associated with increasing level of selfreported leisure activity for both women and men Physical activity, self-reported vs. objectively measured, general population 113 in all three study groups; main study population, 30 69 years and 40 44 years; (p trend women < 0.0001, p trend men < 0.0001) and in the activity sub-study, (p trend women ¼ 0.0007, p trend men ¼ 0.03). An inverse dose response relationship was observed for heart rate over quartiles of VO 2max (p trend women ¼ 0.0002, p trend men ¼ 0.0001). The proportion of the participants who met the physical activity recommendation of accumulating at least 30 min/day or more of MVPA in either one continuous bout or several shorter bouts lasting 10 minutes was 30.4% for women and 22.0% for men (Figure 2). 27.0% of women met the recommended level of more than 10,000 steps/day, among men this percentage was 22.1%. Discussion In this study, we compared objectively assessed physical activity (based on accelerometer), resting heart rate and fitness (VO 2max ) with self-reported physical activity. We observed a positive correlation between self-reported leisure activity and overall activity counts/min, with a positive dose response among adult men and women. We also found a positive association between self-reported leisure activity and moderate-to-vigorous accelerometer activity for both men and women. Participating men and women seemed able to rate their leisure time activity level in correspondence with their objectively measured physical activity. Moreover, in test retest reliability we observed a substantial agreement between self-reported leisure activity and VO 2max, also supported with a strong dose response association for both men and women, indicating that the questionnaire provides valid estimates of high-intensity leisure activity. Participating men and women were able to rate their leisure activity level in accord with their objectively measured VO 2max. These results corresponds to others showing moderate correlations between self-reported physical activity and VO 2max [35,36]. There was no such association between self-reported work activity and VO 2max, supporting the premise that work activity in this population is not associated with aerobic capacity. However, recent results support that total physical activity independent of physical fitness may play a role in cardiovascular disease risk suggesting a role for work activity [37]. Heart rate is an important clinical measure and easy to assess in clinical settings when evaluating general health among patients seeking healthcare advice. The observed association between heart rate and hard and vigorous physical activity, with less reduction in heart rate in relation to moderate

114 A. Emaus et al. a) Main study population (30 69 years) Women Ptrend<0.0001 1 2 3 4 Men Ptrend <0.0001 1 2 3 4 Self reported leisure time physical activity Self reported leisure time physical activity b) Study population (40 44 years) Ptrend<0.0001 1 2 3 4 Ptrend <0.0001 1 2 3 4 Self reported leisure time physical activity Self reported leisure time physical activity c) The activity study (40 44 years) 1 2 3 4 Self reported leisure time activity Ptrend =0.38 q1 q2 q3 q4 Step (counts/day) in quartiles Ptrend =0.0007 Ptrend =0.03 1 2 3 4 Self reported leisure time physical activity Ptrend =0.32 q1 q2 q3 q4 Step (counts/day) in quartiles Ptrend =0.12 q1 q2 q3 q4 MVPA (min/day) in quartiles Ptrend =0.27 q1 q2 q3 q4 MVPA (min/day) in quartiles Ptrend =0.0002 q1 q2 q3 q4 VO 2 (ml/kg/min) in quartiles Ptrend =0.0001 q1 q2 q3 q4 VO 2 (ml/kg/min) in quartiles Figure 3. Mean resting heart rate (beats/min) in different levels of objectively tested physical activity, fitness and self-reported leisure activity among participants in: (a) main study population, 30 69 years, 57 women, 17 men; (b) study population 40 44 years, 1134 women, 920 men; (c) the activity study, 158 women, 1 men. Numbers may vary due to missing information. MVPA; moderate-tovigorous physical activity. VO 2, oxygen uptake.

self-reported leisure activity compared to sedentary leisure activity, is consistent with the possibility that men and women may overestimate their leisure activity when reporting moderate leisure activity; this has also been observed by others [38,39]. This may also explain why self-reported leisure activity was only weakly correlated with overall activity based on accelerometer data (men and women 0.23, p < 0.001) and heart rate (women 0.22, p < 0.001, men 0.17 p < 0.05). When analysing objectively measured physical activity and fitness by level of leisure time activity, we used all four categories even though there were low numbers in the very hard exercise group, as we believe they refer to top athletes and they will always be few in a general population study, but can add interesting information. Recent studies suggest that even a simple questionnaire like the Tromsø physical activity questions provides a reasonable valid measure [15,40] of physical activity. Furthermore, our observation that self-reported leisure activity had a moderate correlation with VO 2max supports the observation that our self-reported questionnaire reflects aerobic training and moderate or vigorous exercise. The mean VO 2max for those reporting the lowest levels of leisure activity was almost two standard deviations lower than the mean for those reporting the highest level, which supports that the Tromsø PA questionnaire is a reasonable and valid measure of vigorous activity. Interestingly, those participants who reported hard or very hard levels of leisure activity had a 21.7% higher overall number of step counts. This association was also observed for moderate and hard intensity activity (MVPA and VPA) for both men and women, and supports that the amount of activity was fairly accurately reported in the two highest self-reported intensity levels of leisure activity. This also supports our previous results where we observed a moderate association between fitness (maximum workload) and self-reported physical activity using the same questionnaire [1,22]. Moreover, we have previously reported that changes in self-reported leisure activity over a 7-year time period influenced metabolic profiles especially among those reporting high-intensity activities [1]. Therefore, the present study provides reassuring information that our questionnaire accurately represents high-intensity activity. These findings are important as physical fitness has been observed to be a stronger predictor of disease risk than physical activity [11]. Our observation that accelerometer data recorded a higher overall number of counts/min per day among those reporting hard work activity than among those reporting sedentary work activity underscores that Physical activity, self-reported vs. objectively measured, general population 115 also work activity contributes to the objectively performed amount of total activity. However, selfreported work activity was not associated with heart rate or VO 2max, which suggests that work activity reflects the amount of performed activity and not high-intensity level activity, also observed by others [41]. The Tromsø physical activity questionnaire was developed to measure various level of work activity from sedentary heavy manual work. Due to technical improvement there has been a change in type of work. This may imply that the present questionnaire reports lower levels of work activity and that this activity does not influence heart rate and fitness. Another possibility is that work activity has not been accurately reported and less difference was observed related to heart rate and fitness. Our observations are consistent with other regarding using the same type of accelerometer [15,42]. However, the most appropriate choice of accelerometer epoch for physical activity assessment is unclear. Early accelerometer studies used 1-minute epochs almost exclusively. This practice was employed in most cases to optimise the recording and storage capacity of the monitors. However, with greater memory capacities, the epoch length has declined. Our choice of 15-second epoch is based on this. The trunk location (hip or lower back) has become the most common placement for the accelerometer and no calibration study has used sites other than the trunk to derive the equation for interpreting accelerometer output [43]. For this reason we standardised our protocol and asked our participants to wear the monitor on the right hip. The right hip may be most convenient because most people are right handed [43]. We found no significant differences in activity levels between individuals with different numbers of assessment days (3, 4, and 5 days) and all participants with at least 3 days of individual data are included in the analyses. In a study among children, Mattocks et al. found that measures tended to be higher on the first day of recording and if children wore the monitor for fewer days, but these differences were small [44]. Among adults, at least 3 5 days of monitoring are required to estimate habitual physical activity [45]. However, 5 7 days would have been preferred if possible. Differences regularly observed between weekday and weekend activities suggest that for most age-groups, a standard 7-day monitoring protocol is a sensible choice [45]. Our choice of accelerometer cut-points in LPA, MVPA, and VPA were based on previously studies in comparable populations [29 31]. The amount of minutes in the different categories is sensitive for the choice of cut-points, but the association to other variables is not affected greatly.

116 A. Emaus et al. The international physical activity recommendations of 10,000 step-counts/day will fit differentially for people with different work-related activity; however, it is a specific and easy recommendation. Of note is our observation that about one out of four men and women met the recommendations of 10,000 step-counts/day and at least 30 minutes/day of moderate to vigorous intensities (43 METS). Interestingly, self-reported leisure activity resulted in a higher fraction of the population who met the physical activity guidelines. Taking into consideration that moderate leisure activity seems to be overestimated, the figures for the accelerometer data may be more appropriate and are in accordance with recently published data in comparable population [42,46,47]. In our study we found women to be more active than men when regarding step counts. One explanation for our findings may be that the Norwegian women in this age category is still having a type of work in where they need to do more walking than men, i.e. healthcare work. In Norway, heavy manual work activities for men have been changed into use of more technical equipment. Thus, men do not always need to use their body as much as before compared to women. The attendance rate in this population-based study was high and supports the generalisation of the results presented and also reflects the variation in Norwegian population. It also reduces the likelihood of major biases in the estimates of self-reported leisure and work activity, resting heart rate, or objectively assessed activity data using accelerometer. Our face-to-face personal interaction with participants when delivering the accelerometers strengthens the adherence to wearing the accelerometers. Moreover, it gave us the opportunity to inform the participants about use of the accelerometer and to answer any questions before data-collection started. The use of three different objective methods; resting heart rate, accelerometer, and maximum oxygen uptake to validate the physical activity questionnaire strengthen confidence in this validation study. The consistent pattern that we observed across these different methods strengthens our findings. In conclusion, our results support the utility of the physical activity questions used in the Tromsø study for future health surveys and clinical trials in which biomarkers and disease outcome are studied. Moreover, our results show that over-reporting of self-reported leisure activity may underestimate the potential role of even moderate physical activity on biomarkers and disease outcomes when using this questionnaire. The variation in heart rate and fitness support these findings. Finally, about one out of four men and women met the recommended levels of step-counts of 10,000/day and 30 minutes of moderate activity/day. These observations support continuously studying the benefits of physical activity for health in order to understand the need to target physical activity in prevention of major chronic diseases and to encourage the general population to be more physically active. Funding The study was mainly supported by the Norwegian Research Council (181809) and Norwegian Cancer Society (PR 2008 0176). Acknowledgement The authors would like to thank all the participants in the activity study, Sissel Andersen, and Institute of Community Medicine, University of Tromsø, for assistance with organisation, the test lab at The University of Tromsø for testing facilities, and SATS for offering the participants a free lesson with a personal trainer. We are thankful to the Norwegian School of Sport Science for sharing information from the KAN1 study. 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