Stacy A. Clemes

Methods of Measurement in epidemiology: Sedentary Behaviour

BACKGROUND Research examining sedentary behaviour as a potentially independent risk factor for chronic disease morbidity and mortality has expanded rapidly in recent years. METHODS We present a narrative overview of the sedentary behaviour measurement literature. Subjective and objective methods of measuring sedentary behaviour suitable for use in population-based research with children and adults are examined. The validity and reliability of each method is considered, gaps in the literature specific to each method identified and potential future directions discussed. RESULTS To date, subjective approaches to sedentary behaviour measurement, e.g. questionnaires, have focused predominantly on TV viewing or other screen-based behaviours. Typically, such measures demonstrate moderate reliability but slight to moderate validity. Accelerometry is increasingly being used for sedentary behaviour assessments; this approach overcomes some of the limitations of subjective methods, but detection of specific postures and postural changes by this method is somewhat limited. Instruments developed specifically for the assessment of body posture have demonstrated good reliability and validity in the limited research conducted to date. Miniaturization of monitoring devices, interoperability between measurement and communication technologies and advanced analytical approaches are potential avenues for future developments in this field. CONCLUSIONS High-quality measurement is essential in all elements of sedentary behaviour epidemiology, from determining associations with health outcomes to the development and evaluation of behaviour change interventions. Sedentary behaviour measurement remains relatively under-developed, although new instruments, both objective and subjective, show considerable promise and warrant further testing.

Office workers' objectively measured sedentary behavior and physical activity during and outside working hours.

Objective: To examine objectively determined sedentary behavior and physical activity (PA) during and outside working hours in full-time office workers. Methods: A total of 170 participants wore an ActiGraph GT1M accelerometer for 7 days. Time spent sedentary (<100 counts/min), in light-intensity PA (100 to 1951 counts/min), and moderate-to-vigorous PA (≥1952 counts/min) was calculated for workdays (including working hours and nonworking hours) and nonworkdays. Results: Participants accumulated significantly higher levels of sedentary behavior (68% vs 60%) and lower levels of light-intensity activity (28% vs 36%) on workdays in comparison with nonworkdays. Up to 71% of working hours were spent sedentary. Individuals who were most sedentary at work were also more sedentary outside work. Conclusions: Those who are most sedentary at work do not compensate by increasing their PA or reducing their sedentary time outside work. Occupational interventions should address workplace and leisure-time sedentary behavior.

Reactivity: an issue for short-term pedometer studies?

Objectives: To investigate the influence of wearing a pedometer and recording daily step counts on ambulatory activity. Methods: During the first visit to the laboratory, 50 healthy volunteers, blinded to the study aim, were provided with a sealed pedometer (New-Lifestyles NL-2000) and informed that it was a “body posture monitor” (sealed condition). Participants wore the pedometer throughout waking hours for one week. Upon returning to the laboratory step counts were downloaded and participants were informed that the device was actually a pedometer. They were requested to wear it unsealed for a second one-week period, and to record their step counts in an activity log (unsealed condition). Results: Mean (SD) daily step counts reported in the sealed condition (9541 (3186) steps/day) were significantly lower than step counts reported in the unsealed condition (11385 (3763) steps/day) (p<0.001). Conclusions: Step counts increased significantly in the unsealed condition. Possible mechanisms for this include the knowledge of wearing a pedometer, the visible step count display and the completion of the activity log. This has validity implications for short-term studies (duration ⩽1 week) investigating habitual pedometer-determined activity levels.

The relationship between sedentary behaviour and physical activity in adults: a systematic review.

To ascertain, through a systematic review, the associations between sedentary behaviour (SB) and physical activity (PA) among adults aged 18-60years. Studies published in English up to and including June 2013 were located from computerized and manual searches. Studies reporting on at least one measure of SB and an association with one measure of PA were included. 26 studies met the inclusion criteria. Six studies examined associations between SB and PA prospectively, and 20 were cross-sectional. The most commonly assessed subtype of sedentary behaviours were television viewing (11 studies), total sedentary time (10), total sitting time (4), general screen time (3) and occupational sedentary time (2). All studied types of SB were associated with lower levels of PA in adults. Findings of this review suggest inverse associations between SB and PA were weak to moderate. Objective monitoring studies reported larger negative associations between SB and light intensity activity. Current evidence, though limited, supports the notion that sedentary behaviour displaces light intensity activity.

UK adults exhibit higher step counts in summer compared to winter months

Background: Seasonal differences in step counts have been observed in a limited number of studies conducted on US adults. Due to the diverse global climate, assessment and interpretation of seasonal patterns in ambulatory activity may vary between countries, and regionally specific studies are necessary to understand global patterns. Currently, no studies have assessed whether a seasonal trend is present when ambulatory activity is measured objectively in adults living in the UK. Aim: The present study investigated whether pedometer-determined step counts of adults living in the UK vary between summer and winter. Subjects and methods: Ninety-six adults (52% male, age = 41.0 ± 12.3 years, BMI = 26.1 ± 5.1 kg m–2) completed a within-subject bi-seasonal pedometer study. All participants completed two 4-week monitoring periods; one during the summer and one the following winter. The same Yamax SW-200 pedometer was worn throughout waking hours during both seasons, and daily step counts were recorded in an activity log. Intra-individual seasonal changes in mean daily steps were analysed using a paired samples t-test. Results: Summer mean daily step counts (10 417 ± 3055 steps day–1) were significantly higher than those reported during the winter (9132 ± 2841 steps day–1) (p < 0.001). A follow-up study conducted the subsequent summer in a sub-sample (n = 28) reinforced this trend. Summer step counts were significantly higher than winter step counts on all days of the week (p ≤ 0.001). A significant day of the week effect was present in both seasons, with step counts reported on a Sunday being on average 1500 steps day–1 lower than those reported Monday through to Saturday. Conclusion: Step counts in the sample of UK adults surveyed decreased significantly in the winter compared to the summer, suggesting future pedometer surveillance studies should capture step counts throughout the year for a non-biased reflection of habitual ambulatory activity. Public health initiatives should target these seasonal differences, and opportunities should be provided that encourage individuals to increase their activity levels during the colder, darker months of the year.

What constitutes effective manual handling training? A systematic review

BACKGROUND Injuries caused by manual handling are a major burden to society. Manual handling training programmes have been designed to reduce the likelihood of injury among the workforce; however, concerns have been raised over the efficacy of current manual handling training methods. AIMS To undertake a systematic review of the literature examining the effectiveness of different approaches to training in manual handling. METHODS Peer-reviewed publications along with published conference proceedings published in English, between 1980 and 2009, on the topic of manual handling training comprised the search criteria. A published checklist for reviewing papers was selected, which formed the basis for assessing the quality of the papers reviewed. RESULTS A total of 1827 papers were located. Following elimination of duplicates, 221 papers were collected and reviewed. Of these, 53 papers were intervention studies with the primary aim of investigating the effectiveness of manual handling training. The review identified little evidence supporting the effectiveness of both technique- and educational-based manual handling training. In addition, there was considerable evidence supporting the idea that the principles learnt during training are not applied in the working environment. Strength and flexibility training shows promise; however, further research is needed to ascertain whether such an intervention is sustainable over the long term. CONCLUSIONS The evidence collected indicates that manual handling training is largely ineffective in reducing back pain and back injury. High priority should be given to developing and evaluating multidimensional interventions, incorporating exercise training to promote strength and flexibility, which are tailored to the industrial sector.

How Many Days of Pedometer Monitoring Predict Monthly Ambulatory Activity in Adults

PURPOSE To determine how many days of pedometer monitoring are necessary to estimate monthly ambulatory activity in adults. METHODS Two hundred and twelve adults (64% female; age = 38.3 +/- 13.3 yr; body mass index = 27.9 +/- 5.3 kg x m(-2)) wore a pedometer (SW-200) for 28 consecutive days. About 76.4% were randomly allocated to a reliability group, whereas the remainder (n = 50) comprised a confirmation group. Mean step counts calculated over the 28-d period served as the criterion. Using the reliability group, intraclass correlations (ICC) were computed for the entire 4-wk period, for 3, 2, and 1 wk, and for different combinations of any 6, 5, 4, 3, and 2 d. The reliability of the recommended time frame was tested in the confirmation group using regression analysis. RESULTS In the reliability group, the ICC for any single given day was 0.41. All combinations including 6 d or more had ICC above 0.80. The inclusion of participant characteristics into a regression, alongside mean steps reported during 1 wk of monitoring, failed to strengthen the prediction. When tested in the confirmation group, there was a significant relationship between mean step counts calculated from the first week of monitoring and the criterion (adjusted R2 = 0.91, P< 0.001). CONCLUSION It is recommended that researchers collect pedometer data over a 7-d period for a reliable estimate of monthly activity in adults. A 7-d period is recommended, as opposed to 6 d (where ICC > 0.80) because: 1) step counts are characteristically lower on a Sunday; thus, for a reliable estimate of habitual activity, Sunday activity should always be included; and 2) in the event of missing data (1 d), data collected on 6 d will remain sufficiently reliable to estimate mean monthly activity.

Seasonal variation in physical activity, sedentary behaviour and sleep in a sample of UK adults

Abstract Background: Physical activity (PA), sedentary behaviour (SB), sleep and diet have all been associated with increased risk for chronic disease. Seasonality is often overlooked as a determinant of these behaviours in adults. Currently, no study has simultaneously monitored these behaviours in UK adults to assess seasonal variation. Aim: The present study investigated whether PA, SB, sleep and diet differed over season in UK adults. Subjects and methods: Forty-six adults (72% female; age = 41.7 ± 14.4 years, BMI = 24.9 ± 4.4 kg/m2) completed four 7-day monitoring periods; one during each season of the year. The ActiGraph GT1M was used to monitor PA and SB. Daily sleep diaries monitored time spent in bed (TIB) and total sleep time (TST). The European Prospective Investigation of Cancer (EPIC) food frequency questionnaire (FFQ) assessed diet. Repeated measures ANOVAs were used to identify seasonal differences in behaviours. Results: Light-intensity PA was significantly higher in summer and spring (p < 0.001). SB and TIB were significantly higher in winter (p < 0.01). There were no seasonal variations detected in moderate–vigorous PA, TST or diet (p > 0.05). Conclusions: Findings support the concept that health promotion campaigns need to encourage year-round participation in light intensity PA, whilst limiting SB, particularly during the winter months.

Sitting time and step counts in office workers

BACKGROUND Technological advances mean that many adults are now employed in sedentary occupations. Given evidence linking prolonged sitting to chronic disease risk, understanding sitting and physical activity in and outside the workplace may usefully inform effective interventions. AIMS To assess sitting time and physical activity during and outside working hours in full-time office workers. METHODS Participants wore a pedometer and recorded sitting times and step counts during and outside working hours for 7 days. Participants were divided into tertiles based on the proportion of time spent sitting at work. Sitting times and step counts reported outside work were compared between groups, using one-way analysis of variance. RESULTS There were 72 participants. Almost two-thirds (65%) of time at work was spent sitting. The sample accumulated 3742±2493 steps at work and 5159±2474 steps outside work on workdays. Participants in the highest tertile for workplace sitting reported sitting for longer than those in the lowest tertile during transport (64±59 versus 21±16min), after work (154±30 versus 126±51min) and at weekends (382±133 versus 288±124min, all P < 0.05). Work duration and steps reported outside work did not differ between groups. CONCLUSIONS Office workers who sit for a large proportion of their working day also report sitting for longer outside work. They do not compensate for their sedentary behaviour at work by being more active outside work. Occupational health interventions should focus on reducing workplace and leisure-time sitting in sedentary office workers.

Evaluation of a commercially available pedometer used to promote physical activity as part of a national programme

Objective To assess the accuracy of a pedometer (manufactured by Silva) currently being used as part of a national programme to promote physical activity in the UK. Methods Laboratory study: 68 participants (aged 19.2 years (SD 2.7), body mass index (BMI) 22.5 kg/m2 (SD 3.3)) wore two Silva pedometers (over the right and left hips) while walking on a motorised treadmill at 2, 2.5, 3, 3.5 and 4 mph. Pedometer step counts were compared with actual steps counted. Free-living study: 134 participants (aged 36.4 years (SD 18.1), BMI 26.3 kg/m2 (SD 5.1)) wore one Silva pedometer, one New-Lifestyles NL-1000 pedometer and an ActiGraph GT1M accelerometer (the criterion) during waking hours for one day. Step counts registered by the Silva and NL-1000 pedometers were compared with ActiGraph step counts. Percentage error of the pedometers were compared across normal-weight (n = 58), overweight (n = 45) and obese (n = 31) participants. Results Laboratory study: Across the speeds tested percentage error in steps ranged from 6.7 (4 mph) to 46.9% (2 mph). Free-living study: Overall percentage errors of the Silva and NL-1000 pedometers relative to the criterion were 36.3% and 9%, respectively. Significant differences in percentage error of the Silva pedometer were observed across BMI groups (normal-weight 21%, overweight 40.2%, obese 59.2%, p<0.001). Conclusion The findings suggest the Silva pedometer is unacceptably inaccurate for activity promotion purposes, particularly in overweight and obese adults. Pedometers are an excellent tool for activity promotion; however, the use of inexpensive, untested pedometers is not recommended as they will lead to user frustration, low intervention compliance and adverse reaction to the instrument, potentially impacting future public health campaigns.