Validity of SC-StepRx pedometer-derived moderate and vigorous physical activity during treadmill walking and running in a heterogeneous sample of children and youth.

BACKGROUND: The purpose of this study was to determine the validity of the SC-StepRx pedometer to assess moderate and vigorous physical activity during treadmill walking and running in a heterogeneous sample of children and youth aged 10-17 years. METHODS: Physical activity intensity assessed via indirect calorimetry served as the criterion standard. A convenience sample of 40 participants (20 boys, 20 girls) wore 6 SC-StepRx pedometers, 2 ActiGraph GT3X accelerometers, 2 Actical accelerometers, 1 Walk4Life MVP pedometer and 1 NL-1000 pedometer while walking/running at speeds approximating 2, 3, 4, 6 and 7 METs. Associations between indirect calorimetry and each activity monitor were assessed using linear regression analyses in SAS 9.2. RESULTS: Estimates of moderate and vigorous physical activity from all monitors were significantly associated with the criterion standard of indirect calorimetry. The strongest associations with the criterion measure were observed for the SC-StepRx with moderate/vigorous thresholds of 110/130 steps•minute(-1), and the NL-1000 (R2 = 0.82, p <0.05). The SC-StepRx with moderate/vigorous thresholds of 110/130 steps•minute(-1) also exhibited the highest combined sensitivity (92.9%) and specificity (96.5%) for correctly identifying a bout of moderate-to-vigorous physical activity. CONCLUSIONS: This study demonstrates that the SC-StepRx pedometer is a valid tool for the measurement of moderate and vigorous physical activity in children and youth.

Combinations of physical activity, sedentary behaviour and sleep: relationships with health indicators in school-aged children and youth.

The purpose of this systematic review was to determine how combinations of physical activity (PA), sedentary behaviour (SB), and sleep were associated with important health indicators in children and youth aged 5-17 years. Online databases (MEDLINE, EMBASE, SPORTdiscus, CINAHL, and PsycINFO) were searched for relevant studies examining the relationship between time spent engaging in different combinations of PA, SB, and sleep with the following health indicators: adiposity, cardiometabolic biomarkers, physical fitness, emotional regulation/psychological distress, behavioural conduct/pro-social behaviour, cognition, quality of life/well-being, injuries, bone density, motor skill development, and self-esteem. PA had to be objectively measured, while sleep and SB could be objectively or subjectively measured. The quality of research evidence and risk of bias for each health indicator and for each individual study was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework. A total of 13 cross-sectional studies and a single prospective cohort study reporting data from 36 560 individual participants met the inclusion criteria. Children and youth with a combination of high PA/high sleep/low SB had more desirable measures of adiposity and cardiometabolic health compared with those with a combination of low PA/low sleep/high SB. Health benefits were also observed for those with a combination of high PA/high sleep (cardiometabolic health and adiposity) or high PA/low SB (cardiometabolic health, adiposity and fitness), compared with low PA/low sleep or low PA/high SB. Of the 3 movement behaviours, PA (especially moderate- to vigorous-intensity PA) was most consistently associated with desirable health indicators. Given the lack of randomized trials, the overall quality of the available evidence was low.

Associations between active school transport and physical activity, body composition, and cardiovascular fitness: a systematic review of 68 studies.

BACKGROUND: The impact of active school transport (AST) on daily physical activity (PA) levels, body composition and cardiovascular fitness remains unclear. METHODS: A systematic review was conducted to examine differences in PA, body composition and cardiovascular fitness between active and passive travelers. The Medline, PubMed, Embase, PsycInfo, and ProQuest databases were searched and 10 key informants were consulted. Quality of evidence was assessed with GRADE and with the Effective Public Health Practice Project tool for quantitative studies. RESULTS: Sixty-eight different studies met the inclusion criteria. The majority of studies found that active school travelers were more active or that AST interventions lead to increases in PA, and the quality of evidence is moderate. There is conflicting, and therefore very low quality evidence, regarding the associations between AST and body composition indicators, and between walking to/from school and cardiovascular fitness; however, all studies with relevant measures found a positive association between cycling to/from school and cardiovascular fitness; this evidence is of moderate quality. CONCLUSION: These findings suggest that AST should be promoted to increase PA levels in children and adolescents and that cycling to/ from school is associated with increased cardiovascular fitness. Intervention studies are needed to increase the quality of evidence.

Combined associations between moderate to vigorous physical activity and sedentary behaviour with cardiometabolic risk factors in children.

The objective of this study was to examine the combined associations between time spent in moderate- to vigorous-intensity physical activity (MVPA) and time spent sedentary in relation to cardiometabolic risk factors in a cohort of Canadian children. A cross-sectional study was conducted on 536 white children aged 8-10 years with at least 1 obese biological parent. Time spent in MVPA and sedentary behaviour over 7 days was measured using accelerometry and participants were stratified by tertiles. Daily screen time over 7 days was also self-reported by the child. Outcomes included waist circumference, systolic and diastolic blood pressure, fasting triglycerides, high-density lipoprotein cholesterol, and glucose concentrations. Analyses of covariance comparing tertiles of sedentary time/MVPA showed that higher levels of MVPA were associated with lower waist circumference, fasting triglycerides and diastolic blood pressure, and higher high-density lipoprotein (HDL) cholesterol, irrespective of sedentary time. In linear regression, MVPA was inversely associated with waist circumference and diastolic blood pressure and positively associated with HDL cholesterol, independent of covariates including sedentary time. In contrast, sedentary time was positively associated with diastolic blood pressure but after adjustment for MVPA the association was no longer statistically significant. Self-reported screen time was positively associated with waist circumference and negatively associated with HDL cholesterol independent of covariates including MVPA. Overall, a high level of MVPA was associated with reduced cardiometabolic risk in this sample of children, regardless of their amount of sedentary behaviour. The type of sedentary behaviour (i.e., screen time) might be more important than overall sedentary time in relation to cardiometabolic risk.

Associations of sedentary behavior, sedentary bouts and breaks in sedentary time with cardiometabolic risk in children with a family history of obesity.

BACKGROUND: Although reports in adults suggest that breaks in sedentary time are associated with reduced cardiometabolic risk, these findings have yet to be replicated in children. PURPOSE: To investigate whether objectively measured sedentary behavior, sedentary bouts or breaks in sedentary time are independently associated with cardiometabolic risk in a cohort of Canadian children aged 8-11 years with a family history of obesity. METHODS: Data from 286 boys and 236 girls living in Quebec, Canada, with at least one biological parent with obesity (QUALITY cohort) were collected from 2005-2008, and analyzed in 2013. Sedentary behavior, light and moderate-to-vigorous physical activity were measured over 7 days using accelerometry. Leisure time computer/video game use and TV viewing over the past 7 days were self-reported. Outcomes included waist circumference, body mass index Z-score, fasting insulin, fasting glucose, triglycerides, HDL-cholesterol, C-reactive protein and a continuous cardiometabolic risk score. RESULTS: After adjustment for confounders, breaks in sedentary time and the number of sedentary bouts lasting 1-4 minutes were associated with reduced cardiometabolic risk score and lower BMI Z-score in both sexes (all p<0.05). The number of sedentary bouts lasting 5-9 minutes was negatively associated with waist circumference in girls only, while the number of bouts lasting 10-14 minutes was positively associated with fasting glucose in girls, and with BMI Z-score in boys (all p<0.05). Leisure time computer/video game use was associated with increased cardiometabolic risk score and waist circumference in boys, while TV viewing was associated with increased cardiometabolic risk, waist circumference, and BMI Z-score in girls (all p<0.05). CONCLUSIONS: These results suggest that frequent interruptions in sedentary time are associated with a favourable cardiometabolic risk profile and highlight the deleterious relationship between screen time and cardiometabolic risk among children with a family history of obesity.

Physiological and health implications of a sedentary lifestyle.

Sedentary behaviour is associated with deleterious health outcomes, which differ from those that can be attributed to a lack of moderate to vigorous physical activity. This has led to the field of "sedentary physiology", which may be considered as separate and distinct from exercise physiology. This paper gives an overview of this emerging area of research and highlights the ways that it differs from traditional exercise physiology. Definitions of key terms associated with the field of sedentary physiology and a review of the self-report and objective methods for assessing sedentary behaviour are provided. Proposed mechanisms of sedentary physiology are examined, and how they differ from those linking physical activity and health are highlighted. Evidence relating to associations of sedentary behaviours with major health outcomes and the population prevalence and correlates of sedentary behaviours are reviewed. Recommendations for future research are proposed.