Philippa M. Dall

Frequency of the sit to stand task: An observational study of free-living adults

The sit to stand movement is a key determinant of functional independence. Knowledge of the frequency with which the sit to stand movement is performed throughout the day could inform workplace ergonomics, but has rarely been examined. Healthy adults (n=140) were recruited from the general population. Free-living activity for each participant was reported using an activity monitor. On average, participants performed 60 (+/-22) sit to stand movements each day. Participants in indoor sedentary occupations performed significantly more sit to stand movements per day than participants in outdoor active occupations (66 vs. 54; n=102; p=0.003). Participants (n=33) performed significantly more sit to stand movements on working days than on non-working days (65 vs. 55; p=0.018). This analysis provides contemporary data for sit to stand frequency in a predominantly working population, and demonstrates that work and employment have a significant effect on that frequency.

Sitting patterns at work: objective measurement of adherence to current recommendations

Long uninterrupted sedentary periods, independent of total sedentary time, are risk factors for poor health. There is little objective data relating to workplace sedentary behaviour and adherence to current recommendations. The sitting behaviour of office workers (n = 83) was quantified objectively using body-worn accelerometers (activPAL™) over a working week. Adherence to three different recommendations (maximum length of a sitting event of: 20 min; 30 min; 55 min) were assessed. Participants were seated at work for 5.3 ± 1.0 h/d (mean ± 1 SD), equivalent to 66 ± 12% of the working day, accrued in 27 ± 7events/d individual sitting events. Dependent on the recommendation applied, 5–20% of sitting events and 25–67% of time was accumulated in sitting events longer than current guidelines. No participants met the 20 or 30 min recommendations on every working day but seven (8%) participants met the 55 min recommendation. In conclusion, office workers spend a considerable period of their day sitting, accumulated in uninterrupted sitting events longer than current recommendations. Statement of Relevance: Emerging evidence suggests prolonged sitting has negative health effects. In this study of office workers, 25–67% of time sitting was accumulated in events longer than minimum recommended durations. Adverse sitting behaviour is prevalent in the office, making it an appropriate setting to target the reduction of this behaviour.

Development and validation of a physical activity monitor for use on a wheelchair

Study design:Keeping physically active is important for people who mobilize using a wheelchair. However, current tools to measure physical activity in the wheelchair are either not validated or limited in their application. The purpose of this study was to develop and validate a monitoring system to measure wheelchair movement.Methods:The system developed consisted of a tri-axial accelerometer placed on the wheel of a wheelchair and an analysis algorithm to interpret the acceleration signals. The two accelerometer outputs in the plane of the wheel were used to calculate the angle of the wheel. From this, outcome measures of wheel revolutions, absolute angle and duration of movement were derived and the direction of movement (forwards or backwards) could be distinguished. Concurrent validity was assessed in comparison with video analysis in 14 people with spinal cord injury using their wheelchair on an indoor track and outdoor wheelchair skills course. Validity was assessed using intraclass correlation coefficients (ICC(2,1)) and Bland–Altman plots.Results:The monitoring system demonstrated excellent validity for wheel revolutions, absolute angle and duration of movement (ICC(2,1)>0.999, 0.999, 0.981, respectively) in both manual and powered wheelchairs, when the wheelchair was propelled forwards and backwards, and for movements of various durations.Conclusion:This study has found this monitoring system to be an accurate and objective tool for measuring detailed information on wheelchair movement and manoeuvring regardless of the propulsion technique, direction and speed.

Individuals with chronic low back pain have a lower level, and an altered pattern, of physical activity compared with matched controls: an observational study

QUESTION Is there a difference in the level and pattern of free-living physical activity between individuals with chronic low back pain and matched controls? DESIGN Observational, cross-sectional study. PARTICIPANTS Fifteen individuals with chronic low back pain and fifteen healthy controls matched for age, gender, and occupation. OUTCOME MEASURES Participants wore an activity monitor for seven days. Level of physical activity was measured as time standing and walking, and number of steps averaged over a 24-hour day (midnight to midnight), day time (9.00 am - 4.00 pm), and evening time (6.00 pm - 10.00 pm), and work days versus non-work days. Pattern of physical activity was measured as number of steps and cadence during short (< 20 continuous steps), moderate (20-100 continuous steps), long (> 100-499 continuous steps), and extra long walks (>or= 500 continuous steps). RESULTS Over an average 24-hour day, the chronic low back pain group spent 0.7 fewer hours (95% CI 0.3 to 1.1) walking, and took 3480 fewer steps (95% CI 1754 to 5207) than the healthy controls. They took 793 fewer steps/day (95% CI -4 to 1591) during moderate walks, and 1214 fewer steps/day (95% CI 425 to 2003) during long walks, and 11 fewer steps/min (95% CI 4 to 17) during extra long walks than the healthy controls. CONCLUSION Individuals with chronic low back pain have a lower level, and an altered pattern, of physical activity compared with matched controls.

Objective assessment of mobility of the spinal cord injured in a free-living environment

Study design:An exploratory study of the practicality and feasibility of an instrument.Objectives:To adapt an activity monitor for use on a wheelchair to assess long-term mobility in a free-living environment in the spinal cord injury (SCI) population, and to explore the utility of the data collected.Setting:Glasgow, UK.Methods:An activity monitor was adapted for use on a wheelchair wheel. The monitor was used to assess, for 1 week, the wheelchair mobility of seven participants with SCI who only used a wheelchair. In conjunction with a second monitor on the thigh the mobility of seven participants with SCI who used a wheelchair and upright mobility, and five healthy non-wheelchair users, were assessed for 1 day.Results:The adapted monitor collected 1260 h of data and was suitable for use on both manual and electric wheelchairs. During 1 week, participants with SCI who only used a wheelchair spent between 4 and 13 h moving in the wheelchair, covering a distance of between 7 and 28 km. Distinct differences in mobility were shown between participants with an SCI and non-wheelchair users. The differences in time spent in mobility activities between the groups of participants with SCI were smaller.Conclusions:The system was successfully used in this group of participants with SCI, and could provide useful information on the mobility of people with SCI in a free-living environment.

Step accumulation per minute epoch is not the same as cadence for free-living adults

PURPOSE The term cadence has been used interchangeably to describe both the rate of stepping and the number of steps in a minute epoch. This is only strictly true if walking is continuous within that epoch. This study directly compared these two outcomes in minute epochs of data from free-living adults to assess the scale of any difference between them. METHODS A convenience sample of healthy adults wore an activPAL activity monitor for 7 d. The event record output of the activPAL, providing the start time and duration of each stride to the nearest 0.1 s, was used to calculate step accumulation (number of steps), duration of walking, and cadence (number of steps/duration of walking) for each minute of measurement. RESULTS Data from 117 individuals (78 females; mean age, 46 ± 16 yr; mean body mass index, 24.9 ± 3.7 kg·m-2) were analyzed. Twenty-one percent of minutes (n = 310d-1) contained walking. The distribution (most minutes fewer than 40 steps per minute) and mean (34 ± 9 steps per minute) of step accumulation were very different from that of cadence (most minutes between 60 and 100 steps per minute; mean, 76 ± 6 steps per minute). Only 12% of minutes with stepping were walked continuously, whereas 69% of minutes with stepping contained less than 30 s of walking. This is key to the difference between step accumulation and cadence, and means that cadence cannot be reconstructed from step accumulation without also knowing the duration that was walked. CONCLUSION Step accumulation, the number of steps in a fixed period, and cadence, the rate of stepping while walking, are not interchangeable outcome measures. It is vitally important that unambiguous terminology is used to describe the rate of stepping so that the outcomes of studies can be correctly interpreted.

Daily and hourly frequency of the sit to stand movement in older adults: a comparison of day hospital, rehabilitation ward and community living groups

Background and aims: The sit to stand (STS) movement is commonly performed in daily life, and can be used as an indicator of activity. This study aimed to quantify the usual frequency and distribution of the STS movement performed by older adults in both home and rehabilitation settings. Methods: Three groups of older adults were recruited; healthy older adults living in the community, older adults living in the community attending rehabilitation services at a day hospital, and frail older patients in a rehabilitation ward. Participants wore an activity monitor, which reported posture continuously for a week. The number of STS movements was the primary outcome measure, and mean values of daily STS frequency were reported. The pattern of activity was investigated using median values of STS hourly rate. Results: Healthy older adults living in the community performed significantly more STS movements per day (n=20; 71±25) than either older adults attending a day hospital (n=20; 57±23) or frail older patients in a rehabilitation ward (n=30; 36±16). For all participants, the hourly rate of STS movements ranged from zero to 48, although the median hourly rate was two (healthy older adults) and one (both rehabilitation groups). Conclusion: Measurement of the number of STS movements performed over the course of a week in three groups of older adults, demonstrated significant differences in daily number of STS movements and in the hourly pattern between the groups. Activity patterns can provide additional information on clinically relevant aspects of physical activity and function to daily averages.

Quantifying the cadence of free-living walking using event-based analysis

PURPOSE Free-living walking occurs over a wide range of durations and intensities (cadence). Therefore, its characterisation requires a full description of the distribution of duration and cadence of these walking events. The aim was to use event-based analysis to characterise this in a population with intermittent claudication (IC) and a healthy matched control group. METHODS Seven-day walking activity was recorded using the activPAL activity monitor in a group of people with IC (n=30) and an age-matched control group (n=30). The cadence, number of steps and duration of individual walking events were calculated and outcomes were derived, and compared (p<0.05), based on thresholds applied. RESULTS Both groups had similar number of walking events per day (392±117 vs 415±160). The control group accumulated a greater proportion of their walking at higher cadences and 32% of their steps were taken at a cadence above 100 steps/min, for the IC group this was 20%. Longer walking events had higher cadences and the IC group had fewer of these. As walking events became longer the cadence increased but the inter-event cadence variability decreased. More purposeful walking might occur at a higher cadence, and be performed at a preferred cadence. Individuals with IC had a smaller volume of walking, but these differences occurred almost entirely above a cadence of 90 steps/min. CONCLUSIONS This is the first study which has quantified the cadence of continuous periods of free-living walking. The characteristics (duration, number of steps and cadence) of all the individual walking events were used to derive novel outcomes, providing new insights into free-living walking behaviour.

Ethnic differences in and childhood influences on early adult pulse wave velocity: The determinants of adolescent, now young adult, social wellbeing, and health longitudinal study

Early determinants of aortic stiffness as pulse wave velocity are poorly understood. We tested how factors measured twice previously in childhood in a multiethnic cohort study, particularly body mass, blood pressure, and objectively assessed physical activity affected aortic stiffness in young adults. Of 6643 London children, aged 11 to 13 years, from 51 schools in samples stratified by 6 ethnic groups with different cardiovascular risk, 4785 (72%) were seen again at aged 14 to 16 years. In 2013, 666 (97% of invited) took part in a young adult (21–23 years) pilot follow-up. With psychosocial and anthropometric measures, aortic stiffness and blood pressure were recorded via an upper arm calibrated Arteriograph device. In a subsample (n=334), physical activity was measured >5 days via the ActivPal. Unadjusted pulse wave velocities in black Caribbean and white UK young men were similar (mean±SD 7.9±0.3 versus 7.6±0.4 m/s) and lower in other groups at similar systolic pressures (120 mm Hg) and body mass (24.6 kg/m2). In fully adjusted regression models, independent of pressure effects, black Caribbean (higher body mass/waists), black African, and Indian young women had lower stiffness (by 0.5–0.8; 95% confidence interval, 0.1–1.1 m/s) than did white British women (6.9±0.2 m/s). Values were separately increased by age, pressure, powerful impacts from waist/height, time spent sedentary, and a reported racism effect (+0.3 m/s). Time walking at >100 steps/min was associated with reduced stiffness (P<0.01). Effects of childhood waist/hip were detected. By young adulthood, increased waist/height ratios, lower physical activity, blood pressure, and psychosocial variables (eg, perceived racism) independently increase arterial stiffness, effects likely to increase with age.

How does light-intensity physical activity associate with adult cardiometabolic health and mortality? Systematic review with meta-analysis of experimental and observational studies

Aim To assess the relationship between time spent in light physical activity and cardiometabolic health and mortality in adults. Design Systematic review and meta-analysis. Data sources Searches in Medline, Embase, PsycInfo, CINAHL and three rounds of hand searches. Eligibility criteria for selecting studies Experimental (including acute mechanistic studies and physical activity intervention programme) and observational studies (excluding case and case–control studies) conducted in adults (aged ≥18 years) published in English before February 2018 and reporting on the relationship between light physical activity (<3 metabolic equivalents) and cardiometabolic health outcomes or all-cause mortality. Study appraisal and synthesis Study quality appraisal with QUALSYST tool and random effects inverse variance meta-analysis. Results Seventy-two studies were eligible including 27 experimental studies (and 45 observational studies). Mechanistic experimental studies showed that short but frequent bouts of light-intensity activity throughout the day reduced postprandial glucose (−17.5%; 95% CI −26.2 to −8.7) and insulin (−25.1%; 95% CI −31.8 to –18.3) levels compared with continuous sitting, but there was very limited evidence for it affecting other cardiometabolic markers. Three light physical activity programme intervention studies (n ranging from 12 to 58) reduced adiposity, improved blood pressure and lipidaemia; the programmes consisted of activity of >150 min/week for at least 12 weeks. Six out of eight prospective observational studies that were entered in the meta-analysis reported that more time spent in daily light activity reduced risk of all-cause mortality (pooled HR 0.71; 95% CI 0.62 to 0.83). Conclusions Light-intensity physical activity could play a role in improving adult cardiometabolic health and reducing mortality risk. Frequent short bouts of light activity improve glycaemic control. Nevertheless, the modest volume of the prospective epidemiological evidence base and the moderate consistency between observational and laboratory evidence inhibits definitive conclusions.