Physical activity has not been objectively measured in prospective cohorts with sufficiently large numbers to reliably detect associations with multiple health outcomes. Technological advances now make this possible. We describe the methods used to collect and analyse accelerometer measured physical activity in over 100,000 participants of the UK Biobank study, and report variation by age, sex, day, time of day, and season. Participants were approached by email to wear a wrist-worn accelerometer for seven days that was posted to them. Physical activity information was extracted from 100Hz raw triaxial acceleration data after calibration, removal of gravity and sensor noise, and identification of wear / non-wear episodes. We report age- and sex-specific wear-time compliance and accelerometer measured physical activity, overall and by hour-of-day, week-weekend day and season. 103,712 datasets were received (44.8% response), with a median wear-time of 6.9 days (IQR:6.5–7.0). 96,600 participants (93.3%) provided valid data for physical activity analyses. Vector magnitude, a proxy for overall physical activity, was 7.5% (2.35mg) lower per decade of age (Cohen’s d = 0.9). Women had a higher vector magnitude than men, apart from those aged 45-54yrs. There were major differences in vector magnitude by time of day (d = 0.66). Vector magnitude differences between week and weekend days (d = 0.12 for men, d = 0.09 for women) and between seasons (d = 0.27 for men, d = 0.15 for women) were small. It is feasible to collect and analyse objective physical activity data in large studies. The summary measure of overall physical activity is lower in older participants and age-related differences in activity are most prominent in the afternoon and evening. This work lays the foundation for studies of physical activity and its health consequences. Our summary variables are part of the UK Biobank dataset and can be used by researchers as exposures, confounding factors or outcome variables in future analyses.

The Microsoft Kinect sensor (Kinect) is potentially a low-cost solution for clinical and home-based assessment of movement symptoms in people with Parkinson's disease (PD). The purpose of this study was to establish the accuracy of the Kinect in measuring clinically relevant movements in people with PD. Nine people with PD and 10 controls performed a series of movements which were measured concurrently with a Vicon three-dimensional motion analysis system (gold-standard) and the Kinect. The movements included quiet standing, multidirectional reaching and stepping and walking on the spot, and the following items from the Unified Parkinson's Disease Rating Scale: hand clasping, finger tapping, foot, leg agility, chair rising and hand pronation. Outcomes included mean timing and range of motion across movement repetitions. The Kinect measured timing of movement repetitions very accurately (low bias, 95% limits of agreement 0.9 and Pearson's r>0.9). However, the Kinect had varied success measuring spatial characteristics, ranging from excellent for gross movements such as sit-to-stand (ICC=.989) to very poor for fine movement such as hand clasping (ICC=.012). Despite this, results from the Kinect related strongly to those obtained with the Vicon system (Pearson's r>0.8) for most movements. The Kinect can accurately measure timing and gross spatial characteristics of clinically relevant movements but not with the same spatial accuracy for smaller movements, such as hand clasping.

Ageing has become a significant area of interest in Human-Computer Interaction (HCI) in recent years. In this article we provide a critical analysis of 30 years of ageing research published across the ACM Special Interest Group on Computer-Human Interaction (SIGCHI) community. Discourse analysis of the content of 644 archival papers highlights how ageing is typically framed as a “problem” that can be managed by technology. We highlight how ageing is typically defined through an emphasis on the economic and societal impact of health and care needs of older people, concerns around socialisation as people age, and declines in abilities and associated reductions in performance when using technology. We draw from research within the fields of social and critical gerontology to highlight how these discourses in SIGCHI literature represent common stereotypes around old age that have also prevailed in the wider literature in gerontology. We conclude by proposing strategies for future research at the intersection of ageing and HCI.

The use of digital technologies is increasingly proposed in health and social care to address the aging population phenomenon but, in practice, the designers of these technologies are ill equipped to design for older people. We suggest participatory design as an approach to improving the quality of design for older people but, based on previous work and our own experiences, identify four central issues that participatory design approaches need to address. We describe an approach to early engagement in design with older people that address each of these issues and some of our experiences applying the approach in a variety of different design projects. We conclude by discussing some of the issues that have been highlighted when attempting apply this approach in different design contexts and the issues that have been raised when working with partners who are less committed to the idea of engaging with older adults in participatory design.

Probes have been adopted with great enthusiasm in both Design and HCI. The heterogeneity with which they have been used in practice reflects how the method has proved elusive for many. Originators and commentators of probes have discussed misinterpretations of the method, highlighting the lack of accounts that describe in detail the design of probes and their use with participants. This paper discusses our particular use of Design Probes as directed craft objects that are both tools for design and tools for exploration across a number of projects, spanning a decade, centered on self-identity and personal significance. In offering an example of what a framework for probe design and use might look like, we attempt to address the identified lacuna, providing a synthetic account of probe design and use over an extended period and conceptualizing the relationship between the properties of probes and their use in design projects.