avaliar, em mulheres idosas, os efeitos agudos do tempo sentado prolongado (TSP) de 5 horas na curva glicêmica e insulinêmica e comparar com os efeitos de diferentes padrões de interrupção do TSP por meio de atividade física (AF), nestes mesmos marcadores. Materiais e Métodos: participaram do estudo mulheres, com idade >= 65 anos, não obesas e não diabéticas. As voluntárias realizaram uma pré-avaliação na qual foram analisadas variáveis clínicas, antropométricas e padrão de AF espontânea. Em seguida, foram propostas 4 diferentes fases de intervenção. 1) TSP: composto por 300 minutos ininterruptos na postura sentada; 2) Intensidade Leve e Curta Duração (ILCD): TSP interrompido a cada 20 minutos por 2 minutos de AF de baixa intensidade (50 a 60% da FC máx prevista para a idade); 3) Intensidade Moderada e Curta Duração (IMCD): TSP interrompido a cada 20 minutos por 2 minutos de AF de moderada intensidade (65 a 75% da FC máx prevista para a idade); 4) Intensidade Moderada e Longa Duração (IMLD): TSP interrompido a cada 75 minutos por 10 minutos de AF de moderada intensidade (65 a 75% da FC máx prevista para a idade). As áreas sob a curva (ASC) glicêmica e insulinêmica foram verificadas por meio de coleta seriada de sangue, após a ingestão de refeição padrão e calculada pelo método do trapézio. Para as comparações entre os grupos foi proposto o modelo de regressão linear com efeitos mistos e controlado para idade, peso e classificação de NAF. Resultados: 16 idosas da comunidade com média de 69,2 ± 4 anos participaram do estudo. Na fase pré-avaliação as voluntárias passaram cerca de 9 horas/dia em posturas sedentárias. O TSP foi a fase de intervenção que apresentou os maiores valores de ASC de glicemia e insulina (555,9 ± 75,4 mg / dl) e (220,1 ± 76,2 µIU/mL), respectivamente. As fases de interrupção do TSP apresentaram menores valores de ASC de glicemia (ILCD: 514,0 ± 55,1; IMCD: 531,7 ± 69,1; IMLD: 530,0 ± 45,5 mg/dl) e insulina (ILCD: 155,0 ± 53,1; IMCD: 169,5 ± 81,7; IMLD: 164,9 ± 54,4 µIU/mL) em comparação com a fase de TSP (p < 0,05). No entanto, quando comparadas entre si, não houve diferença entre as fases ILCD, IMCD e IMLD (p > 0,05). Conclusão: o TSP foi relacionado a piora dos níveis de glicemia e insulinemia, enquanto a interrupção por meio de AF de intensidade leve ou moderada, de curta ou longa duração mostraram-se potenciais estratégias de redução desses marcadores de risco cardiovascular. Nenhum padrão de interrupção mostrou-se significativamente superior ao outro, sendo interrupções de curta duração e leve intensidade eficazes na redução dos níveis da ASC glicêmica e insulinêmica. / assess the acute effects of uninterrupted sitting time compared to sitting interrupted by physical activity (PA) bouts (light and moderate intensity, short and long duration) in relation to blood glucose and insulin responses, in older women. Subjects and Methods: community- dwelling women aged >= 65 years, non-obese and non-diabetic. The volunteers performed a pre-evaluation in which clinical, anthropometric and spontaneous PA patterns were analysed. Four different phases of intervention were proposed. 1) Uninterrupted sitting: 300 minutes in sitting posture 2) Sitting + 2 min Light Breaks: sitting time break every 20 minutes for 2 minutes of low intensity PA (50 to 60% of predicted HR max for age). 3) Sitting + 2 min Moderate Breaks: sitting time break every 20 minutes for 2 minutes of moderate intensity PA (65 to 75% of predicted HR max for age).4) Sitting + 10 min Moderate Breaks: sitting time break every 75 minutes for 10 minutes of moderate intensity PA (65 to 75% of predicted HR max for age). The glucose and insulin area under curve were verified by serial blood collection after the ingestion of a standard meal. Results: 16 older women, aged 69 ± 4 years were evaluated. In the pre-evaluation phase the volunteers spent about 9 hours / day in sedentary postures. The participants had lower values of blood glucose AUC during interrupted sitting time (2 min light 514.0 ± 55.1 vs 2 min moderate 531.7 ± 69.1 vs 10 min moderate 530.0 ± 45.5 mg / dl) and of insulin AUC ( 2 min light 155.0 ± 53.1 vs 2 min moderate 169.5 ± 81.7 vs 10 min moderate 164.9 ± 54.4 ?UI / mL) when compared to the uninterrupted phase (555.9 ± 75.4 mg / dl, 220.1 ± 76.2) (p <0.05). There was no significant differences between the different interruption patterns physical (p > 0.05). Conclusion: Uninterrupted sitting was associated with worsening blood glucose and insulin response, while breaking up prolonged sitting by bouts of short or long duration, light or moderate intensity showed to be potential strategies for improving blood glucose and insulin responses to a meal. No interruption pattern was found to be better than other, with even short breaks of light intensity being effective in reducing blood glucose and insulin levels.

The increasing evidence of associations between sedentary behaviour and low levels of physical activity in adults and both immediate and long term health implications is of public health concern. There is a need to further our understanding of adult's health behaviours, to facilitate the development of behaviour change strategies promoting healthy behaviours. This thesis provides four independent but interlinked studies focusing on adult s sedentary behaviour and physical activity in the context of measurement and behaviour change. Chapter 1 provides an introduction to the thesis where the scene is set for the placement of the studies in this thesis in the field of sedentary behaviour, physical activity, and measurement methods. Chapter 2 describes a systematic review of the relationship between sedentary behaviour and physical activity in adults. This systematic review is of primary importance as it was instrumental in shaping and informing the direction of the research described in later chapters. Chapter 3 describes a laboratory study investigating the measurement of energy expenditure during common sitting and standing tasks and also examines the 1.5 MET definition of sedentary behaviour. This study provides evidence that the 1.5 MET threshold for sedentary behaviours seems reasonable however some sitting-based activities may be classified as non-sedentary in people of differing weight status. This study raised some important questions on the validity of objective measurement devices for differentiating between sitting and standing postures. Thus, Chapter 4 of this thesis describes a laboratory study investigating the validity of the ActiGraph inclinometer algorithms for differentiating between sitting and standing postures. Chapter 5 is an intervention investigating sedentary behavior and physical activity compensation outside working hours in a sample of office workers exposed to sit-to-stand desks in the workplace. This thesis found that light physical activity, especially standing, could be one of the most efficient and feasible behaviours to replace sedentary behaviour. Such findings add considerably to the existing literature. Targeting such facets of adults behaviour and specially office workers holds great potential for behaviour change strategies.

Sedentary behaviour (SB) is prevalent across all ages, but particularly in older adults aged 50 years and above. Given that older adults spend more than 60% of waking hours sedentary, enhancing our understanding of the correlates of SB will be important to inform the development of interventions to reduce SB in mid-age and older adults. This thesis provides five studies focusing on the correlates of SB in mid-age and older adults. Firstly, Chapter 2 presents a literature review using behaviour epidemiology framework to examine the existing evidence on sedentary behaviour in general adults in order to identify the gap of current knowledge in sedentary behaviour. Chapter 3 presents a systematic review which included the existing evidence on correlates of SB in mid-age and older adults and provides evidence-based conclusions on the topic. Chapter 4 presents a study examining the association of demographics and physical activity (PA) with daily sitting time in mid-age and older adults, and found behavioural correlates of SB and PA in mid-age and older adults. Chapter 5 presents a secondary data analysis using the data of the older office worker from the Stormont study. This chapter uses the results from the cross-sectional and longitudinal data to examine the association of demographics and behaviours with domain-specific sitting time among the older office workers. In this study, differences were found in demographic and behavioural correlates according to the studied domain of sitting. Chapter 6 presents a 6-month longitudinal study, which was designed to fill the gaps of our understanding of the associations between demographics, health and PA with SB in older adults aged 65 years and above. This chapter also looked into the changes of sitting time and its correlates. Together, these four studies provide adequate evidence on the demographics and behavioural correlates of SB and also identified the determinants of SB in mid-age and older adults. This thesis found that demographics had limited associations with SB, and sociodemographics were associated with work-related sitting time. Health behaviour was generally inversely associated with SB. These findings provide information to the correlates and determinants of mid-age and older adults SB and will inform further research on behaviour change strategies.

Emerging evidence suggests that sedentary behaviour is independently associated with cardiometabolic disease risk in school-aged children and youth. This thesis includes 4 related studies in the pursuit of 2 objectives: 1) To determine the cross-sectional association of sedentary time, interruptions in sedentary time, sedentary bout length, and total movement variability with markers of cardiometabolic disease risk among children and youth, and 2) To examine the impact of 1-day of prolonged sedentary behaviour, with and without interruptions or structured physical activity, on markers of cardiometabolic disease risk, hunger, food intake and spontaneous physical activity levels in children and youth. In Study 1, we found that interruptions in sedentary time and short bouts of sedentary time were beneficially associated with clustered cardiometabolic disease risk in boys and girls aged 8-11 years, independent of total sedentary time, moderate-and-vigorous physical activity (MVPA), and other confounders (all p<0.05), while the opposite was true for screen based sedentary behaviours. In Study 2, we found that movement variability (minute-to-minute changes in movement intensity) was negatively associated with clustered cardiometabolic disease risk and systolic blood pressure independent of MVPA, sedentary time and other covariates in a representative sample of American children and youth aged 12-17 years (all p<0.05). In Studies 3 and 4, we found that prolonged sitting, with or without interruptions and structured MVPA did not result in acute changes in markers of cardiometabolic disease risk, nor subsequent ad libitum food intake or physical activity levels in healthy children aged 10-14 years (all p ≥0.05). Taken together, the studies that make up this thesis suggest that optimal levels of cardiometabolic disease risk are most likely to be seen in children who limit their time engaging in screen-based sedentary behaviours, who frequently interrupt their sedentary time, and who have high levels of variability in their movement behaviours.

Yes / Purpose: To assess physical activity outcomes of a pedometer-based physically active learning (PAL) intervention in primary school children. Methods: Six paired schools were randomly allocated to either a 6-week teacher-led pedometer-based physically active learning intervention or a control (n = 154, female = 60%, age = 9.9 [0.3] y). Accelerometers assessed total daily sedentary time, light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA). Preintervention mean daily MVPA minutes grouped participants as Low Active (<45 min/d) and High Active (≥45 min/d). Results: From the final sample size, the intervention (n = 52) significantly improved LPA versus control (n = 31, P = .04), by reducing sedentary time. More intervention (+10%) than control (+3%) pupils met the 60 minutes per day guidelines. In both intervention subgroups, pupils spent less time in LPA (P < .05) versus control. The greatest nonsignificant increase was found in the Low Active pupils MVPA levels. Conclusions: Improvements in LPA were statistically significant in the intervention versus control group. In subgroup analysis, Low Active pupils in the intervention showed the greatest beneficial effects and the Most Active pupils may have replaced MVPA and sedentary time with LPA. The intervention group housed clusters of pupils showing variable responsiveness, justifying routine examination of subgroup variability in future studies.

The term sedentary refers to a distinct class of activities which involve sitting or reclining and which do not cause an increase in energy expenditure above resting levels. Observational studies have reported positive associations between both sedentary time and the number of hours spent sitting per day, with risk for a number of health outcomes that are independent of moderate to vigorous physical activity (MVPA). The total time spent sitting can be amassed in different patterns (long and short bouts) and different types (watching TV, driving, working at a computer) that may have differential associations with health outcomes as well as different confounders that have yet to be properly explored. Further, limitations in current measures used to quantify sedentary behaviour and the possibility of residual confounding, mean that it is unclear whether the posture of sitting itself represents a risk to health or whether sitting is actually a proxy for low energy expenditure. This thesis aimed to examine; the associations between five separate sitting types with health risk, the prevalence of sitting behaviour in England, and the biological mechanisms which might underpin the observed negative health consequences of sitting. Using data from the Whitehall II cohort study the first four studies of this thesis examined prospective associations between sitting at work, TV viewing, non-TV leisure time sitting, total leisure time sitting (TV and non-TV leisure sitting combined) and total sitting from work and leisure, with four health outcomes; mortality, cardiovascular disease, type II diabetes and obesity. No association between any of the sitting indicators with risk for mortality or incident cardiovascular disease was found. TV viewing and total sitting were associated with an increase in risk for type II diabetes following adjustment for sociodemographic covariates and MVPA, but were attenuated following further adjustment for body mass index. None of the five sitting indicators were associated with incident obesity but being obese prior to the measurement of sitting was associated with the number of reported hours of daily TV viewing. The final study of this thesis examined the acute effect of sustained versus interrupted sitting on glucose and insulin metabolism. Interrupting sitting with repeated short bouts of light intensity walking significantly improved insulin sensitivity while repeated short bouts of standing did not. Sitting is a prevalent behaviour in English adults and varies by socio-demographic characteristics. Previously reported associations between sitting time and health risk may be confounded by light intensity physical activity and obesity. The absence of an effect of repeated standing bouts (a change in posture without a change in energy expenditure) suggests that promoting reductions in sitting without also promoting increases in movement are not likely to lead to improvements in metabolic health. New measures of sedentary behaviour are required that can be used in population studies, and can discriminate between the posture of sitting, standing and very low levels of physical activity of a light intensity. This would permit further studies that are needed to clarify the precise nature of the association between sitting and health.

Regular physical activity is associated with improved physiological and psychological wellbeing, by reducing the risk of chronic illnesses such as cardiovascular disease, cancer, obesity, diabetes, osteoporosis and depression. There is a common perception that physical activity levels in the population are declining, and one of the biggest changes affecting this is occupational based activity. Since adults spend on average over 50% of their waking hours at work, work sites have the potential to be an important setting for health promotion initiatives. Cognitions and behaviours are key causal factors behind many of today s most widespread health problems and illnesses. The stage of change model has been highlighted as having intuitive appeal because it considers the dynamic nature of attitudes and behaviour change. This thesis is concerned with the application of the stage of change model to an occupational health intervention promoting physical activity. Several research studies were undertaken to explore the experiences of employees with workplace health initiatives and investigate the strategies and practices used by occupational health to promote healthy behaviours. These research studies highlighted the barriers and facilitators to successful health interventions and contributed towards the design, development and implementation of an activity promotion intervention. Additional research was also conducted to develop information materials based on the stage of change model. The stage approach was simplified and intervention materials were classified based on whether employees were thinking about making a change or not thinking about making a change to their activity levels. In order to test the materials, a twelve month intervention was implemented in ten work sites across the UK that were allocated to one of three groups. Two groups received information materials and one group received no information during the intervention period (control group). The difference between the two groups who received information was that one group received standard activity promotion information (standard group) and the second group received tailored information based on their stage of change construct (staged group). Participants in the staged intervention group demonstrated significant decreases in body mass index, fat percentage, waist circumference, blood pressure and resting heart rate following the twelve month intervention. In contrast, reductions were identified for the standard intervention group for waist circumference and diastolic blood pressure. Finally, there were no long-term significant improvements identified for the control group. However, group comparisons revealed there were no significant differences between the intervention conditions. The intervention also recorded self-reported psychological outcomes, which demonstrated variations throughout the intervention period for all groups. The potential reasons for these inconsistent outcomes are discussed. A process evaluation following the intervention demonstrated employees valued the health screenings and identified issues relating to knowledge, behaviour change and health implications that were important outputs of the intervention. Based on these findings, the research concludes there is scope to make physical activity interventions in the workplace more effective by applying the stage of change approach. Using the process of simplifying the stages and focusing on whether employees want to change their behaviours or not allows occupational health to deliver information that could be more meaningful and have a significant impact on behaviour change. By understanding employees readiness to change their activity behaviours and targeting information based on their beliefs, attitudes and intentions to change may produce significant improvements in health outcome measures compared to standard information. The results also suggest there is potential for this type of tailored intervention to be extended to other occupational health issues.

Background: Medical students are at risk for poor mental health and burnout compared to the general population (Dyrbye et al., 2014). A preponderance of research has examined predictors of mental illness in medical students (Brazeau et al., 2014; Hope & Henderson, 2014). However, few studies have investigated predictors of mental health, and no studies to our knowledge have compared predictors of mental health and burnout in medical students. Further, several studies have assessed physical activity and burnout in medical students but these have neither examined specific intensities of physical activity nor have considered the role of sedentary behaviour in predicting medical student burnout (Dyrbye, Satele, & Shanafelt, 2017b; Wolf & Rosenstock, 2017). Thus, there is a dearth of knowledge on how demographics relate to mental health and burnout, and how mild, moderate, and vigorous physical activity, and sedentary behaviour relate to burnout in medical students. Purpose: To investigate and compare demographic predictors (gender, ethnicity, age, level of education, year of study, and proposed specialty) of mental health and burnout, to examine behavioural predictors (mild, moderate, vigorous, and total physical activity, and sedentary behaviour) of burnout, and to investigate moderate-to-vigorous physical activity as a moderator of the relationship between sitting and burnout in first to fourth year medical students. Methods: The sample consisted of 129 first to fourth year medical students at two large Canadian universities. Participants were recruited through electronic newsletters, medical student Facebook groups, and an in-class announcement. This study used a cross-sectional design. Data were collected through online surveys of validated self-report questionnaires measuring demographics, mild, moderate, vigorous, and total physical activity, sitting, mental health, and burnout. Results: Third year of study was a significant negative predictor of mental health while female gender, ‘other’ ethnicity and third year of study were significant positive predictors of burnout. Moreover, female gender, ‘other’ ethnicity, and fourth year of study predicted mental health differently from burnout. Second and third year of study predicted mental health and burnout similarly. Mild physical activity and sitting were significant negative predictors of burnout. Moderate-to-vigorous physical activity was not a significant moderator of the relationship between sitting and burnout. Conclusions: Findings of this study support Keyes’ Dual Continua Model (2014) and Maslach’s theorization of burnout (Maslach, Jackson, & Leiter, 1996) and can inform targeted programs to prevent poor mental health and burnout in medical students. Future research is recommended on these key topics.

Les sociétés actuelles montrent un déclin toujours plus important du niveau d’activité physique, associé à une progression alarmante des comportements sédentaires. Compte tenu de la mutation inéluctable des activités professionnelles, le milieu du travail a récemment été suggéré comme un environnement pertinent et intéressant pour favoriser l’activité physique. Dans ce contexte, l’objectif principal de ce travail de doctorat était d’évaluer la faisabilité de mise en place et l’efficacité de programmes d’activité physique conduits en entreprise sur les principaux indicateurs de santé d’employés du secteur tertiaire. Si les premiers résultats soulignent bien la faisabilité de ce type d’approche et viennent confirmer leurs bienfaits sur la santé, ce travail vient enrichir la littérature dans le domaine de nouveaux résultats particulièrement importants à considérer : i) le haut niveau de sédentarité semble influencer le niveau de santé des employés ; ii) la mise en place de ce type de programme se confronte à un faible taux d’adhésion qui semble déterminé à la fois par le profil initial de participant et par les effets à court terme du programme. De manière importante, nos résultats mettent clairement en avant que la santé générale des employés de ce secteur tertiaire ne peut pas être uniquement améliorée par l’accroissement du niveau d’activité physique, mais également très certainement par la réduction concomitante de leur temps de sédentarité. Si les travaux conduits jusqu’alors se sont intéressés de manière isolée à la promotion du niveau d’activité physique ou à cette rupture de sédentarité, des approches combinées doivent être maintenant conduites et ce de manière individualisée. / Current societies show a continuous decline of physical activity level associated with an alarming progression of sedentary behaviors. Considering the inevitable shift in professional activities, workplace has recently been suggested as a relevant and interesting setting for the promotion of physical activity. In this context, the main objective of this PhD thesis was to evaluate the feasibility, implementation and effectiveness of physical activity programs conducted within companies on the main health indicators of tertiary employees. If our first results underline the feasibility of such an approaches and confirm their health benefits, this work enriches the literature in the field of new results particularly important to consider : i) the high level of sedentary time seems to influence the employees’ health level despite increased physical practice ; ii) the introduction of this program type is confronted to a high attrition rate which seems determined by both the initial participants' profile and the short-term effects of the program. Importantly, our results clearly point out that the employees’ general health in the tertiary sector can not only be improved by increasing the physical activity level, but needs a concomitant reduction of their sedentary time. If the work carried out until now has been independently focusing on the promotion of physical activity or on anti-sedentary time strategies, combined individualized approaches must now be carried out.

Bakgrund: Graviditetsdiabetes är den vanligaste metabola sjukdomen hos gravida. Sjukdomen ökar drastiskt relaterat till ökat stillasittande. Åtgärder inkluderar kostråd, råd om fysisk aktivitet, stöd att förbättra levnadsvanor samt vid behov insulinbehandling. Trots att forskning visar att fysisk aktivitet har flera positiva effekter på graviditetsdiabetes är mindre än hälften av populationen så fysiskt aktiva som de rekommenderas vara. För att bättre kunna stötta dessa kvinnor i sitt fysiska aktivitetsbeteende behövs mer information om deras kunskap och utfallsförväntningar avseende fysisk aktivitet. Syfte: Att undersöka hur fysiskt aktiva gravida med graviditetsdiabetes är, vilken kunskap och vilka utfallsförväntningar de har avseende fysisk aktivitet vid graviditetsdiabetes samt undersöka eventuella samband mellan kunskap, utfallsförväntningar och fysisk aktivitetsnivå. Metod: Observationsstudie av icke experimentell design genomfördes med webbenkät skapad i Google Forms. Bekvämlighetsurval från specialistmödravården samt sluten Facebook-grupp. Resultat: Majoriteten ägnade mindre än 30 minuter åt fysisk träning en vanlig vecka, uppfyllde inte rekommendationerna för vardagsmotion samt var stillasittande hela dagen. Majoriteten av deltagarna hade mer än häften rätt på kunskapsfrågorna och var säkra på att fysisk aktivitet är hälsosamt. Korrelationsberäkningarna var inte statistiskt signifikanta. Slutsats: Deltagarna hade kunskaper och höga utfallsförväntningar avseende fysisk aktivitet men låg fysisk aktivitetsnivå. Ytterligare forskning krävs för att undersöka eventuell korrelation. / Background: Gestational diabetes mellitus (GDM) is the most common metabolic disease in pregnant women. GDM increases drastically related to sedentary behaviour. Treatment includes dietary advice, advice on physical activity and if necessary, insulin therapy. Objective: The purpose was to examine how physically active women with GDM are, their knowledge and outcome expectations on physical activity during GDM and whether there is any correlation between knowledge, outcome expectations and level of physical activity. Method: Observation study of non-experimental design was performed with a web-based questionnaire created in Google Forms. Study participants from Specialistmödravården at Akademiska sjukhuset Uppsala and a closed Facebook group. Results: The majority devoted less than 30 minutes to physical exercise a regular week, did not meet the recommendations for everyday exercise and were sedentary throughout the day. Most of the participants answered more than half of the questions correctly and were confident that physical activity is healthy. No significant correlations were found. Conclusion: The study participants had knowledge and high outcome expectations regarding physical activity, but their physical activity level was low. Further research on correlations is required.