Physical inactivity is a major contributor to non-communicable diseases and many adults and children are insufficiently active to maintain good health. The proportion of children who meet the United Kingdom recommendations for physical activity (at least 60 minutes of moderate-vigorous intensity physical activity each day) has been reported to be as low as 3% for boys and 2% for girls. Systematic reviews on interventions to promote physical activity in childhood have shown that although physical activity is modifiable to some degree most interventions have had only modest and short-term impacts on physical activity. Therefore, novel approaches to physical activity promotion in childhood are required. Dog ownership is a significant societal factor that may be used to encourage and sustain health behaviour change at individual and population levels. A number of observational studies have reported that dog ownership and/or dog walking are associated with increased levels of physical activity. However, evidence is lacking as to whether and how interventions with families and their dogs can be used to promote physical activity. Therefore, the major aim of this thesis was to assess the feasibility, acceptability and potential efficacy of a theory-driven, family-based, dog walking intervention for 9–11 year old children and their families. However, prior to this it was essential to develop ActiGraph cut-points for measuring physical activity intensity in dogs. The ability to measure the intensity of dog physical activity accurately was important as it allows for the effectiveness of dog walking interventions to be tested, therefore another aim of this thesis was to calibrate and cross-validate ActiGraph cut points that can be used to describe physical activity in dogs by intensity. Similarly, no studies have been published previously that assess which factors are related to dog physical activity when measured using ActiGraph accelerometry. It was therefore desirable to explore whether body condition score, breed, age, and neutered status are associated with ActiGraph measured dog physical activity. Furthermore, no published studies have described the spontaneous changes in dog physical activity during substantial weight loss; therefore, another aim of this thesis was to explore changes in physical activity in dogs during a 6 month calorie controlled weight loss programme. Using Receiver Operating Curve analyses Chapter 2 showed that the ActiGraph GT3X can accurately measure the amount of time a dog spends sedentary, in light-moderate intensity physical activity and in vigorous intensity physical activity. The sensitivity and specificity of the cut-points developed when using both the integrated axes and vertical axis accelerometry data were high. Agreement between the accelerometer data and direct observation in the cross-validation subset was also ‘very good’ (as measured by Cohen’s Kappa). This indicates that the ActiGraph GT3X accelerometer is accurate when measuring the intensity of physical activity in dogs, facilitating the use of the ActiGraph GT3X to describe the frequency, intensity and duration of dog physical activity in Chapters 3-6 of this thesis. Chapter 3 shows that, in a sample of dogs of varying breed and body condition scores, obese dogs spend significantly less time in ActiGraph measured vigorous intensity physical activity than ideal weight dogs (6 ± 3minutes/day versus 20 ± 14 minutes/day). Chapter 4 focussed on the factors related with physical activity in the two most commonly registered dog breeds in the United Kingdom, Labrador Retrievers and Cocker Spaniels. Five potential correlates (age, sex, breed, neuter status, body condition score) were tested with associations with ActiGraph measured physical activity. Age and breed were associated with total volume of physical activity, light-moderate intensity physical activity and sedentary behaviour in the final models and age was also associated with vigorous intensity physical activity. Unlike Chapter 3 body condition score was not related with any physical activity variables. Chapter 5 explored the changes in physical activity and sedentary time during weight loss in dogs enrolled in a 6 month calorie controlled weight loss programme. Despite an average weight loss of 15% body weight from baseline there was no marked increase in any ActiGraph measured physical activity variable. Chapter 6 describes the results of the Children Parents and Pets Exercising Together (CPET) Study. CPET was the first exploratory randomised controlled trial to develop and evaluate an intervention aimed at dog-based physical activity promotion in children, their parents and pet dogs. The results show that the CPET intervention was both feasible and acceptable to study participants. Eighty-nine percent of families enrolled in CPET were retained at follow up. Ninety-five percent of intervention sessions were delivered and ActiGraph measured physical activity data were collected for 100% of children, 96% of parents and 96% of dogs at baseline, and 100% of children, 96% of parents and 96% of dogs available at follow up. Despite the apparent feasibility and acceptability of CPET there was no significant change in the primary outcome measure (child physical activity) or the majority of the secondary measures. This thesis shows that the ActiGraph GT3X accelerometer is capable of accurately measuring the intensity of dog physical activity. It also shows that obesity may be related to lower levels of objectively measured vigorous intensity physical activity and the physical activity levels in dogs decline with age and vary by breed. However, it appears that physical activity levels do not increase spontaneously as dogs lose substantial amounts of body weight. Using pet dogs as the agent of lifestyle change in physical activity interventions in children and their parents is both feasible and acceptable; however, the lack of any apparent increase in child physical activity suggests that the intervention may need to be modified in a future, more definitive trial. In summary, the findings of this thesis have important implications for the measurement of physical activity intensity in dogs, the understanding of factors associated with dog physical activity and for the development of dog-walking interventions in children and their parents.

Promoting a shift from using cars towards walking and cycling (a modal shift) has the potential to improve population health by reducing the adverse health effects associated with exposure to motor traffic and increasing the population level of physical activity through active travel. However, little is known about the effects of interventions which might achieve this by changing urban design, transport infrastructure or other putative determinants of population travel behaviour. I conducted a systematic review of the best available evidence about the effects of interventions to promote a modal shift. I searched twenty electronic literature databases as well as websites, bibliographies and reference lists and invited experts to contribute additional references. I identified 69 relevant studies and devised a two-dimensional hierarchy of study utility based on study design and study population with which I selected a subset of studies for inclusion. I appraised the quality of these studies; extracted data on the effects of interventions on choice of mode of transport, how these effects were distributed in the population, and associated effects on measures of individual and population health and wellbeing; and produced a narrative synthesis of the findings. Twenty-two studies were included. These comprised three randomised controlled trials, seven non-randomised controlled prospective studies, 11 uncontrolled prospective studies, and one controlled retrospective study of interventions applied to urban populations or areas in which outcomes were assessed in a sample of local people. I found some evidence that targeted behaviour change programmes could change the behaviour of motivated subgroups, resulting (in the largest study) in a modal shift of around 5% of all trips at a population level. Single studies of commuter subsidies and a new railway station also showed positive effects. The balance of best available evidence about other types of intervention such as publicity campaigns, traffic calming and cycling infrastructure suggested that they had not been effective. Participants in trials of active commuting experienced short term improvements in certain measures of health and fitness, but I found no good evidence about health effects associated with any effective intervention at population level. Most relevant studies were not found in mainstream health or social science literature databases. Further analysis of the 47 excluded studies did not change the overall conclusions about effectiveness, but did identify additional categories of intervention that merit further research and provided evidence to challenge assumptions about the actual effects of progressive urban transport policies. The contributions of internet publications, serendipitous discoveries and the initially-excluded studies to the total set of relevant evidence suggested that undertaking a comprehensive search may have provided unique evidence and insights that would not have been obtained using a more focused search. I identified an evaluative bias whereby the effects of population-level interventions were less likely than those of individual-level interventions to have been studied using the most rigorous study designs. Understanding of how environmental and policy factors may influence active travel and physical activity currently relies heavily on evidence from cross-sectional studies of correlates rather than intervention studies. I therefore took advantage of the opportunity presented by a local ‘natural experiment’ — the construction of a new urban section of the M74 motorway in Glasgow — to design, develop and complete the cross-sectional (baseline) phase of a new primary study of the effects of a major environmental intervention. Using a combination of census data, geographical data and field visits, I delineated an intervention study area close to the proposed route of the new motorway and two matched control areas elsewhere in Glasgow. I collected and described data from residents in the three study areas (n=1322) on socioeconomic status, the local environment, travel behaviour, physical activity and general health and wellbeing using a postal questionnaire incorporating two established instruments (the SF-8 and the short-form International Physical Activity Questionnaire), a travel diary and a new 14-item neighbourhood rating scale whose test–retest reliability I established in a subset of respondents (n=125). I then analysed the correlates of active travel and physical activity using logistic regression. Using travel diary data from Scottish Household Survey respondents (n=39067), I also compared the characteristics and travel behaviour of residents living close to the proposed route with those living in the rest of Scotland and analysed the correlates of active travel using logistic regression. Overall data quality and the test–retest reliability of the new neighbourhood scale appeared acceptable. Local residents reported less car travel than expected from national data. In the local study area, active travel was associated with being younger, being an owner-occupier, not having to travel a long distance to work and not having access to a car, whereas overall physical activity was associated with living in social-rented accommodation and not being overweight. After adjusting for individual and household characteristics, neither perceptions of the local environment nor the objective proximity of respondents’ homes to motorway or major road infrastructure appeared to explain much of the variance in active travel or overall physical activity, although I did find a significant positive association between active travel and perceived proximity to shops. Apart from access to local amenities, therefore, environmental characteristics may be of limited relevance as explanatory factors for active travel in this comparatively deprived urban population which has a low level of car ownership and may therefore have less capacity for making discretionary travel choices than the populations studied in most published research on the environmental correlates of physical activity. The design and baseline data for the M74 study now provide the basis for a controlled longitudinal study, which could not otherwise have been carried out, of changes in perceptions of the local environment, active travel, physical activity, and general health and wellbeing associated with a major intervention in the built environment. This will, in time, contribute to addressing calls to produce better evidence about the health impacts of natural experiments in public policy.

Falls and fall-related injuries are among the most common, serious, and medically-expensive problems facing the growing older population. Regular physical activity has been proposed to reduce falls, but no research has examined the efficacy of compliance with official recommended amounts of physical activity over the adult life-course and falls in community dwelling older adults. From the development and implementation of a new questionnaire to assess guideline related lifetime physical activity levels and falls history with a sample of 314 community-dwelling older adults, it was identified that lifetime adherence to the 2004 Department of Health physical activity guidelines offered no protective benefit for reduction in falls, fear of falling or fall outcome. A sub-sample of the 314 participants was then invited to participate in three laboratory investigations. Biomechanical measures of stability were utilised in studies investigating quiet standing, straight line walking and performing a 360º standing turn with groups of young adults (n = 15), older non-fallers (n = 15), older single fallers (max n = 13) and older multiple fallers (n = 14). During standing, young adults placed their centre of mass (COM) anterior to their centre of pressure (COP), whilst older adults primarily placed their COM posterior to their COP. There were no differences between faller groups and it was therefore concluded that quiet standing was not a challenging enough task to differentiate faller status. During walking, multiple fallers displayed greater COM-COP separation than the non-fallers and single fallers, and greater COM acceleration than the non-fallers at heel strike in the antero-posterior direction thus identifying both measures as capable of i differentiating between faller status groups in similar populations. At the initiation of the 360º standing turn, multiple fallers demonstrated a significantly shorter latency between reorientation onset of the thorax and the pelvis compared to all the other groups and thus exhibited a more en-bloc strategy of turning. Therefore, the onset of body segment reorientation was identified as capable of differentiating between fallers and non-fallers in otherwise healthy, community dwelling older adults. Discussion of and conclusions drawn from the findings of the four empirical studies identify the need for future research to identify more appropriate falls-related physical activity recommendations for public health messages for adults, and recommend the use of biomechanical variables such as COM-COP separation, COM acceleration and the assessment of segment reorientation in future falls-related research and as outcome measures for the efficacy of physical activity intervention programmes for fall prevention.

Motion segmentation plays an important role in human motion analysis. Understanding the intrinsic features of human activities represents a challenge for modern science. Current solutions usually involve computationally demanding processing and achieve the best results using expensive, intrusive motion capture devices. In this thesis, research has been carried out to develop a series of methods for affordable and effective human motion assessment in the context of stand-up physical exercises. The objective of the research was to tackle the needs for an autonomous system that could be deployed in nursing homes or elderly people's houses, as well as rehabilitation of high profile sport performers. Firstly, it has to be designed so that instructions on physical exercises, especially in the case of elderly people, can be delivered in an understandable way. Secondly, it has to deal with the problem that some individuals may find it difficult to keep up with the programme due to physical impediments. They may also be discouraged because the activities are not stimulating or the instructions are hard to follow. In this thesis, a series of methods for automatic assessment production, as a combination of worded feedback and motion visualisation, is presented. The methods comprise two major steps. First, a series of key body poses are identified upon a model built by a multi-class classifier from a set of frame-wise features extracted from the motion data. Second, motion alignment (or synchronisation) with a reference performance (the tutor) is established in order to produce a second assessment model. Numerical assessment, first, and textual feedback, after, are delivered to the user along with a 3D skeletal animation to enrich the assessment experience. This animation is produced after the demonstration of the expert is transformed to the current level of performance of the user, in order to help encourage them to engage with the programme. The key body pose identification stage follows a two-step approach: first, the principal components of the input motion data are calculated in order to reduce the dimensionality of the input. Then, candidates of key body poses are inferred using multi-class, supervised machine learning techniques from a set of training samples. Finally, cluster analysis is used to refine the result. Key body pose identification is guaranteed to be invariant to the repetitiveness and symmetry of the performance. Results show the effectiveness of the proposed approach by comparing it against Dynamic Time Warping and Hierarchical Aligned Cluster Analysis. The synchronisation sub-system takes advantage of the cyclic nature of the stretches that are part of the stand-up exercises subject to study in order to remove out-of-sequence identified key body poses (i.e., false positives). Two approaches are considered for performing cycle analysis: a sequential, trivial algorithm and a proposed Genetic Algorithm, with and without prior knowledge on cyclic sequence patterns. These two approaches are compared and the Genetic Algorithm with prior knowledge shows a lower rate of false positives, but also a higher false negative rate. The GAs are also evaluated with randomly generated periodic string sequences. The automatic assessment follows a similar approach to that of key body pose identification. A multi-class, multi-target machine learning classifier is trained with features extracted from previous motion alignment. The inferred numerical assessment levels (one per identified key body pose and involved body joint) are translated into human-understandable language via a highly-customisable, context-free grammar. Finally, visual feedback is produced in the form of a synchronised skeletal animation of both the user's performance and the tutor's. If the user's performance is well below a standard then an affine offset transformation of the skeletal motion data series to an in-between performance is performed, in order to prevent dis-encouragement from the user and still provide a reference for improvement. At the end of this thesis, a study of the limitations of the methods in real circumstances is explored. Issues like the gimbal lock in the angular motion data, lack of accuracy of the motion capture system and the escalation of the training set are discussed. Finally, some conclusions are drawn and future work is discussed.

Background: Tower Hamlets is a socioeconomically disadvantaged borough, home to the UK’s largest South Asian population, a group at increased risk of obesity-related diseases. Previous studies in this population have reported high levels of adiposity and inactivity. No borough-wide study has been conducted objectively measuring physical activity patterns. This study aimed to investigate pedometer-determined activity levels of Tower Hamlets' schoolchildren, their association with adiposity and differences according to ethnicity and socioeconomic status (SES). The study was preceded by reviews investigating the association between step counts and adiposity in children and investigating the validity of pedometers as a measure of physical activity in young people. Methods: Participants were recruited from Tower Hamlets' secondary schools (n=884; 584 boys, 300 girls). A pedometer was worn for 7 days. Internationally recognised mean daily step count cut-offs (boys = 15000, girls = 12000) were used to define activity level. Body mass index (BMI), bioelectrical impedance analysis (BIA)-determined percentage body fat (%bf) and waist circumference (WC) were all measured. Children were classified as being of normal weight, overweight or obese according to international cut-off points. A questionnaire was administered to establish socioeconomic status and ethnicity. Results: A total of 884 schoolchildren were recruited (66% boys, 34% girls). Of this, 657 (74%) provided a full set of pedometer, anthropometric and socio-demographic data. Sixty-five percent of all participants were South Asian and 55% received free school meals. Significant differences in anthropometric variables were observed according to gender, ethnicity and school. The prevalence of overweight/obesity ranged widely for boys (35%, 53% and 65%) and girls (33%, 55% and 55%) according to BMI, %bf and WC, respectively. The majority of participants provided 4 or 5 days of activity data, with 15% providing data for 7 days. Inactivity was high, 83% of boys and 72% of girls failed to meet the minimum recommended daily step counts. Activity was greater during the week compared to the weekend and those that were most active during the week were also more active at the weekend. Boys (11580±3560) took significantly more steps than girls (10062±3239) and differences were also observed between schools. No significant differences in activity levels were observed according to ethnicity, SES or adiposity levels. Conclusion: The vast majority of schoolchildren in Tower Hamlets fail to reach current physical activity recommendations, irrespective of ethnicity or socioeconomic class. Inactivity is greater at the weekend. The prevalence of overweight/obesity is also higher than national averages. Intervention strategies to increase physical activity and tackle overweight/obesity in this cohort are required.

Observations of human behaviour show a tendency for avoiding energy expenditure through stair climbing where possible. Similarities between demographic influences in stair avoidance and explicit perceptions of geographical slant outlined in the ‘economy of action’ account (Proffitt, 2006) suggest that this avoidance behaviour might be due to a perceptual bias. Chapter two of this thesis investigated measures of slant perception linked to action. It appears that these ‘haptic’ measures tap into a perceptual process that is more in touch with the physical reality of the environment than conscious awareness. Chapter four demonstrated that fundamentals of the economy of action account generalise to the perception of staircases, and to a newly developed laboratory setting. Depletion of energetic resources, manipulated through fatigue, resulted in steeper explicit estimates of staircase steepness. In reaction to published criticisms of the methodology used in this field, chapter five took a new approach to testing the effect of resources on perception. Two quasi-experimental field studies, designed to circumvent methodological issues challenging the validity of previous studies, demonstrated that available energy resources affects consciously perceived steepness in the built environment. Chapters six and seven built on this by testing the economy of action account as a model that explains stair avoidance behaviour. Encouragingly, across two different points-of-choice between stair climbing and avoidance, explicit measures of perceived geographical slant were linked to reported prior stair climbing behaviour at one site (chapter six) and objectively measured behaviour at another (chapter seven). Collectively, these findings suggest that available energetic resources dictate the exaggeration of perceived geographical slant experienced at an individual level, and that this in turn influences stair choice behaviour, biasing those with less resources towards stair avoidance and energy preservation.

There is a large inter-subject variability in the capacity to oxidise fat (MFO) during exercise and this could have important implications for metabolic health. Chapter 3 of this thesis was designed to explore the relationship between MFO with 24-h fat oxidation and insulin sensitivity. This study showed that MFO during exercise is significantly and positively associated with 24-h fat oxidation and insulin sensitivity. Chapter 4 investigated relationships between selected plasma metabolites, hormones and overnight-fasted resting fat oxidation rates, with MFO. Plasma lipolytic markers, plasma insulin, resting fat oxidation and aerobic capacity were important modulators of the inter-subject variability in MFO. Chapter 5 explored the influence of meal timing around exercise on substrate utilisation, lipolytic markers and insulin, and intra-muscular triglyceride (IMTG) use in obesity. This study found that Fasted- as compared with Fed-state exercise augments exercise fat oxidation, and the circulating concentration of plasma glycerol and NEFA during exercise. This thesis generates new data that contributes to our understanding of the links between MFO and metabolic risk, as well as the factors that influence the inter-subject variability in MFO during exercise. It also shows that fasted exercise augments exercise fat oxidation, which could have meaningful implications for optimising metabolic health.

Over two thirds of the UK population do not meet physical activity (PA) recommendations set by the Department of Health (2011) to improve or maintain health. It is therefore essential to focus research on effective and efficient methods to promote autonomous reasons to engage and persist in PA. Employing a variety of research designs this thesis explores the social contextual and environmental determinants, predominantly from a Self-Determination Theory perspective, of PA adoption, persistence and psychological well-being (Study 1; qualitatively). Study 2 and 3 examined unique sources of support from within and beyond a PA programme including human and non-human sources (i.e., technology). Study 3 employed an intervention focusing on the effect of autonomy supportive text messages on PA behaviour and well-being. Deriving from findings of Study 1, the final study (4) investigated the effect of the physical environment and PA levels on affective states. Results highlight the importance and relevance of socio-contextual (considering each unique contribution of individual sources of support) and environmental determinants (moderate intensity PA within a natural outdoor environment being key for positive high activation) in the promotion of PA. Findings carry important practical implications for those involved in promotion of long-term PA behaviour.

Mental toughness (MT) originated within elite sport and was identified as an attribute of success. MT has emerged as being important for enhancing health-related lifestyle factors (HRLF; e.g., physical activity). Investigating the healthiness of one’s lifestyle appears a timely area to research given the current health status of the population. Therefore, the aim of this thesis was to investigate MT in relation to HRLF and weight loss. Study One investigated MT and HRLF in university students (n = 167). Self-reported MT, physical activity, exercise barriers, dietary behaviour, and psychological wellbeing were recorded. MT was significantly different between regular exercisers (M = 3.43 ± .42) and non-regular exercisers (M = 3.24 ± .54, p < .05). Components of eating identity, exercise barriers, and psychological wellbeing, were significantly correlated with MT. Study Two longitudinally investigated weight loss progress, and adherence to a weight loss support group, in slimming club members who were pursuing a weight loss goal (n = 132). MT and eating identity were assessed at baseline, three-months, and six-months, and weight was recorded at weekly meetings. Overall MT was not significantly related to weight loss (r = -.15, p > 0.05) or adherence to the service (r = .03, p > 0.05). Study Three sampled individuals who held a weight loss goal, but were not attending a weight loss support club (n = 78). Overall MT was not significantly related to weight loss (r = -.21, p > 0.05). MT was not significantly different between weight loss goal achievers (M = 3.62 ± .49) and non-goal achievers (M =3.42 ± .38, p > 0.05). Thus, irrespective of whether structured support is received, overall MT was not related to weight loss progress. II Study Four investigated the experiences of high (n = 9) and low (n = 7) mentally tough individuals pursing a weight loss goal. High and low MT individuals, identified using the MTQ48, were interviewed. Thematic analysis revealed that amongst the high mentally tough individuals, those who prioritised leading a healthy lifestyle reported weight loss success compared to those who prioritised other goals. Strategies to overcome low levels of MT (e.g., control), as well as receive additional support, appeared crucial for successful weight loss in low MT individuals. Study Five further investigated the low MT individuals’ (n = 7) perceptions, experiences, and attitudes, towards weight loss. Low MT individuals were sampled based on their MT score assessed via the MTQ48. Vignette based interviews extended the findings in Study Four. Thematic analysis revealed key findings, including the potential to change low MT individuals’ perceptions to enhance behaviour change. Overall, this thesis expanded the understanding of MT; the processes that one experiences when trying to lose weight appears to differentiate between high and low MT individuals, which offers an explanation as to why MT did not appear to play a significant role in weight loss outcomes. These findings challenged the predominant contemporary understanding of MT and demonstrated that MT was not associated with behaviour change to achieve weight loss.

The increasing evidence of associations between physical activity, sedentary behaviour, sleep duration and diet and both immediate and long term health implications is of public health concern. There is a need to further our understanding of the patterns of these behaviours and how they affect poor health indicators individually and simultaneously. This thesis aims to advance the current literature by investigating associations between multiple lifestyle behaviours and indicators for poor health and identifying patterns of physical activity, sedentary behaviour, sleep duration and dietary intake. Anthropometric measurements and bioelectrical impedance analysis were collected from 72 UK adults. These participants were asked to wear an ActiGraph GT1M accelerometer to objectively measure their physical activity and sedentary behaviour across 7 consecutive days. Over these 7 days, participants also completed a self-report daily sleep diary and a food frequency questionnaire. Participants were asked to complete these measurements at 4 different time points across the year in order to capture these behaviours over each season; 46 participants completed all 4 seasons. Using the data collected from the 72 participants who completed at least 1 season, regression analyses were conducted to identify associations between lifestyle behaviours and indicators for poor health. Repeated measures ANOVAs were conducted on data from 52 participants who provided the full 7 days of data during their initial measurement period to assess day of the week variations in physical activity, sedentary behaviour and sleep patterns. Repeated measures ANOVAs were also conducted on physical activity, sedentary behaviour, sleep and dietary intake data provided by the 46 participants who provided 4 seasons of data to assess seasonal variation. This thesis demonstrated that in a sample of relatively active, UK adults, time spent in moderate-vigorous physical activity and sedentary behaviour had a negative association with BMI and body fat percentage, increased time spent in moderate-vigorous physical activity was also associated with decreases in waist circumference. Light intensity physical activity had a positive association with BMI, body fat percentage and diastolic blood pressure. There were significant day of the week variations in light intensity physical activity, sedentary behaviour and time spent in bed, with light intensity physical activity and time in bed being significantly higher on a Sunday, whilst sedentary behaviour was significantly lower on a Sunday in this sample of UK adults. In addition to day of the week variations, there were seasonal variations in light intensity physical activity, sedentary behaviour and time spent in bed and sleep durations (weekdays only). Over the winter months, light intensity physical activity was significantly lower, whilst sedentary behaviour, time in bed and total sleep time was significantly higher. No seasonal variations in time spent in moderate-vigorous intensity physical activity or diet were observed in the present sample. This thesis demonstrates that lifestyle behaviours that have been found to affect health do vary over the week and across different seasons. This research has implications for surveillance studies which estimate these behaviours at one time point throughout the year, and also for interventions aimed at improving these behaviours which are implemented at just one time period of the year. Strategies for overcoming barriers to PA under unfavourable environmental conditions will be needed for this to be achieved, in addition to interventions reducing SB, even in the winter months.