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Thorlene Egerton, Kade Paterson, and Jorunn L. Helbostad

This study aimed to determine if temporal-spatial gait characteristics are associated with free-living ambulatory physical activity in relatively-healthy older people. A total of 630 women and 593 men had valid data from gait tests and activity monitoring. Gait speed alone was associated with daily step count. Gait speed along with cadence, walk ratio, step length, step time, and swing time were associated with measures of higher intensity activity and overall activity. Those who walked slower were less active. After controlling for gait speed, shorter step length, shorter step time, shorter swing time, and higher cadence were associated with less activity. This finding may be an indication of the functional consequences of a breakdown in the stride length–cadence relationship and/or compensations to increase stability. Asymmetry measures at preferred and fast walking speeds showed no association with physical activity levels. Gait speed was the only predictor of change in activity over the subsequent 12 months.

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Alan K. Bourke, Espen A. F. Ihlen, and Jorunn L. Helbostad

Background: This study aims to perform a concurrent criterion validation of the activPAL3 activity monitor, in the detection of physical activity, steps, and postural transfers in older adults using video observation. Method: Twenty community-dwelling older adults performed both an unsupervised free-living activity protocol in their home environment, recorded using body-worn cameras, and a semi-structured supervised protocol in a smart-home setting, recorded using wall mounted cameras, with an activPAL3 attached to the thigh. Percentage of agreement and typical statistical accuracy metrics were calculated by comparing the activPAL3 output and the video observation gold-standard (0.04 s resolution). Results: The activPAL3 provided a valid measure of standing, sitting, lying, and purposeful walking, including stair climbing. Shuffling, picking, transition, and kneeling were not consistently classified when compared to video observation and were thus confounding activities for the activPAL3. Sedentary behavior was better identified in a free-living scenario than during the semi-structured protocol. Step detection during stair ascending and descending achieved a high percentage of agreement (>89%). Steps detected during walking were underreported (80.2% free-living, 72.9% laboratory-based). Many steps were not detected during shuffling and transitions; overall, the percentage of agreement was low (59.5% free-living, 58% laboratory-based). Good sensitivity, specificity, and accuracy (>85%) were achieved for laboratory-based activities and good to excellent sensitivity, specificity, and accuracy (>89%) were achieved for free-living activities. Percentage of agreement was higher for free-living activities (85.2%) compared to laboratory-based activities (69.15%). Conclusion: This validation study provided a detailed insight into the physical activities that the activPAL3 classifies in its three main activity categories, step detection and postural transition analysis in a laboratory and a free-living setting. Caution is advised when measuring relatively more intensive physical activity protocols (e.g., in-lab), assessing postural transfer quantity, or during sedentary behavior analysis, as some short-duration sedentary bouts are ignored and postural transfers underreported.

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Kristin Taraldsen, Beatrix Vereijken, Pernille Thingstad, Olav Sletvold, and Jorunn L. Helbostad

The aim of the study was to investigate the precision of estimated upright time during one week in community-dwelling older adults after hip fracture when monitoring activity for different numbers of consecutive days. Information about upright time was collected by thigh-worn accelerometers during 7 consecutive days in 31 older adults (mean age 81.8 years ± 5.3) 3 months after hip-fracture surgery. Mean time in upright position, including both standing and walking, was 260.9 (±151.2) min/day. A cutoff value of half an hour was used to provide recommendations about number of recording days. Large variability between participants between days, as well as a nonconstant within-participant variability between days indicates that at least 4 consecutive days of recording should be used to obtain a reliable estimate of upright time for individual persons. However, at a group level, one day of recording is sufficient.

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Thorlene Egerton, Jorunn L. Helbostad, Dorthe Stensvold, and Sebastien F.M. Chastin

Fatigue has been associated with reductions in daily activity of older people. Summary measures of daily physical activity provide limited understanding of how fatigue affects physical activity behavior. This study examined the hour-by-hour energy expenditure estimated from accelerometry data to provide insight into physical activity behaviors of older people experiencing fatigue. Fatigued participants were matched to ‘not fatigued’ participants by age, sex, and BMI. Each group consisted of 86 people with a mean age 73.8 years (SD 2.0), BMI 26.5 kg⋅m–2 (SD 3.9) and 61% female. The phase-space plot, constructed to express rate of change of average vertical axis counts per hour as a time series, showed fatigued participants deviated from the not fatigued participants during the morning period, when hour-by-hour activity was increasing. Older people who feel fatigued have a different morning activity pattern, which appears to lead to the lower overall levels of physical activity.