Patterns of health behaviour associated with active travel: a compositional data analysis

ObjectiveWe sought to evaluate the performance of Fitbit in estimating ActiGraph‐derived moderate‐to‐vigorous physical activity (MVPA) and sedentary time in the knee osteoarthritis (OA) population.MethodsWe used data from two weeks of Fitbit and ActiGraph wear among knee OA subjects. In primary analyses, we used literature‐based ActiGraph thresholds of 200 and 1924 counts/min (triaxial vector magnitude) for sedentary and MVPA time as the gold standard to which we compared three sets of Fitbit thresholds informed by literature and data (Youden index). We also considered personalized, stride length–based Fitbit thresholds. In sensitivity analyses, we used uniaxial, vertical axis–based as well as personalized, BMI‐based ActiGraph thresholds. We calculated agreement, sensitivity, and specificity of Fitbit in classifying sedentary and MVPA time.ResultsIn the primary analysis (vector magnitude thresholds), maximum agreement for sedentary and MVPA time was 67.0% from the Youden index–based and 91.1% from the stride length–based Fitbit thresholds. For sedentary time, the 20 strides/min threshold had the highest sensitivity (97.6%), and Youden‐derived 1 stride/min had the highest specificity (51.6%). For MVPA, Youden‐derived 14 strides/min yielded 72.8% sensitivity, and using stride length yielded 98.6% specificity. MVPA time ranged from 49‐323 min/d, depending on threshold used, with literature‐based and personalized thresholds leading to more conservative estimates of MVPA than Youden‐derived thresholds.ConclusionUsing Fitbit for MVPA and sedentary time assessment may lead to inaccurate estimates of both. Fitbit MVPA estimates were generally more conservative than ActiGraph estimates. Incorporating individuals’ characteristics did not meaningfully improve Fitbit performance. Caution should be exercised when measuring activity using Fitbit.

Canadian physical activity guidelines recommend older adults accumulate 150 min of weekly moderate to vigorous physical activity (MVPA). Older adults who are insufficiently active may have reduced blood vessel health and an increased risk of cardiovascular disease. We tested this hypothesis in 11 older adults who did (7 female; age, 65 ± 5 years; MVPA, = 239 ± 81 min/week) and 10 older adults who did not (7 female; age, 68 ± 9 years; MVPA, 95 ± 33 min/week) meet MVPA guidelines. Flow-mediated dilation (FMD) in the brachial (BA) and popliteal (POP) arteries, as well as nitroglycerin-mediated dilation (NMD; endothelial-independent dilation) in the POP were assessed via ultrasonography. Aerobic fitness (peak oxygen uptake) was determined using a graded, maximal cycle ergometry test via indirect calorimetry. MVPA and sedentary time were assessed over 5 days using the PiezoRx and activPAL, respectively. There were no differences in peak oxygen uptake (26 ± 10 vs. 22 ± 10 mL O2/(kg·min); p = 0.26) or sedentary time (512 ± 64 vs. 517 ± 76 min/day; p = 0.87) between groups; however, those who achieved the MVPA guidelines had a higher BA-FMD (5.1% ± 1.3% vs. 3.6% ± 1.7%; p = 0.03), POP-FMD (2.6% ± 1.1% vs. 1.3% ± 0.8%; p = 0.006), and POP-NMD (5.1% ± 1.7% vs. 3.3% ± 2.1%; p = 0.04). In the pooled sample, MVPA was moderately correlated to both BA-FMD (r = 0.53; p = 0.01) and POP-NMD (r = 0.59; p = 0.005), and strongly correlated to POP-FMD (r = 0.85; p < 0.001). Collectively, our results provide supporting evidence that meeting MVPA guidelines is associated with better vascular function and may reduce the risk of developing cardiovascular disease in older adults. Furthermore, these data suggest that weekly MVPA time may have a greater impact on blood vessel function than aerobic fitness and weekly sedentary time.

Optimization of children's activity behaviors for skeletal health is a key public health priority, yet it is unknown how many hours of moderate to vigorous physical activity (MVPA), light physical activity (LPA), sedentary behavior, or sleep constitute the best day-the "Goldilocks Day"-for children's bone structure and function. To describe the best day for children's skeletal health, we used data from the cross-sectional Child Health CheckPoint. Included participants (n = 804, aged 10.7 to 12.9 years, 50% male) underwent tibial peripheral quantitative CT to assesses cross-sectional area, trabecular and cortical density, periosteal and endosteal circumference, polar moment of inertia, and polar stress-strain index. Average daily time-use composition (MVPA, LPA, sedentary time, and sleep) was assessed through 8-day, 24-hour accelerometry. Skeletal outcomes were regressed against time-use compositions expressed as isometric log-ratios (with quadratic terms where indicated), adjusted for sex, age, pubertal status, and socioeconomic position. The models were used to estimate optimal time-use compositions (associated with best 5% of each skeletal outcome), which were plotted in three-dimensional quaternary figures. The center of the overlapping area was considered the Goldilocks Day for skeletal health. Children's time-use composition was associated with all skeletal measures (all p ≤ 0.001) except cross-sectional area (p = 0.72). Days with more sleep and MVPA, less sedentary time, and moderate LPA were beneficially associated with skeletal measures, except cortical density, which was adversely associated. The Goldilocks daily time-use composition for overall skeletal health was center (range): 10.9 (10.5 to 11.5) hours sleep; 8.2 (7.8 to 8.8) hours sedentary time; 3.4 (2.8 to 4.2) hours LPA, and 1.5 (1.3 to 1.5) hours MVPA. Estimated optimal sleep duration is consistent with current international guidelines (9 to 11 hours), while estimated optimal MVPA exceeds recommendations of at least 60 min/d. This first study to describe optimal durations of daily activities for children's skeletal health provides evidence to underpin guidelines. © 2020 American Society for Bone and Mineral Research (ASBMR).

BackgroundFor people with prediabetes and type 2 diabetes it is important to be regularly physical active. Increasing and maintaining physical activity (PA) can be challenging. The aim of this study was to evaluate the effects of a pedometer-based intervention on PA, with a compositional data analysis (CoDA) approach, in individuals with prediabetes or type 2 diabetes.MethodsLongitudinal data on 188 participants with prediabetes and type 2 diabetes (40% female, mean age = 64.1 years) from a three-armed randomized controlled trail, the Sophia Step Study, was used. The three groups were a multi?component group (self?monitoring of steps with a pedometer, together with group (12 occasions) and individual counselling (10 occasions)), a single?component group (self?monitoring of steps with a pedometer, without counselling) and a standard care group. PA (moderate-to-vigorous PA (MVPA), light-intensity PA (LIPA) and sedentary behaviour (SB)) during the awake time were measured with ActiGraph GT1M accelerometer at baseline, 6, 12, 18 and 24 months. Relative time in MVPA, LIPA and SB for each participant at each measurement point was calculated by using the CoDA approach. Linear mixed models were used to evaluate the intervention effect between the three groups on the relative time in MVPA, LIPA and SB over the two-year period.ResultsIn total, 41% had ≤30 min MVPA at baseline. Significant group by time interactions were found for the multi-component group and the standard care group for the relative time in MVPA, at 6, 18 and 24 months. Differences in predicted group means between the groups were 1.2% at 6 months, 1.3% at 18 months and 0.9% at 24 months. Significant group by time interactions were also found for the single-component group and the standard care group for the relative time in MVPA at 24 months, with a difference in predicted group means of 0.8%. No significant interactions for LIPA or SB were found.ConclusionsThe multi-component group and the single-component component group maintained their relative time in MVPA, while the standard care group decreased their relative time in MVPA over the two-year period. This indicate that the Sophia Step Study intervention can prevent a decrease in MVPA in people with prediabetes and type 2 diabetes.

BackgroundIdentifying leisure time activities performed before and after school that influence time in physical activity (PA) and/or time spent sedentary can provide useful information when designing interventions aimed to promote an active lifestyle in young people. The purpose of this study was to examine associations between mode of transportation to school, outdoor play after school, participation in exercise in clubs, and TV viewing with objectively assessed PA and sedentary behaviour in children.MethodsA total of 1327 nine- and 15-year-old children from three European countries (Norway, Estonia, Portugal) participated as part of the European Youth Heart Study. PA was measured during two weekdays and two weekend days using the MTI accelerometer, and average percent of time in moderate-to-vigorous PA (MVPA) and time spent sedentary were derived. Potential correlates were assessed by self-report. Independent associations between self-reported correlates with percent time in MVPA and percent time sedentary were analysed by general linear models, adjusted by age, gender, country, measurement period, monitored days and parental socio-economic status.ResultsIn 9-year-olds, playing outdoors after school was associated with higher percent time in MVPA (P < 0.01), while participation in sport clubs was associated with higher percent time in MVPA (P < 0.01) in 15-year-olds. No associations with percent time sedentary were observed in either age group.ConclusionFrequency of outdoor play after school is a significant correlate for daily time in MVPA in 9-year-olds, while this correlate is attenuated in favour of participation in sport and exercise in clubs in 15-year-olds. Targeting walking to school or reduced TV viewing time in order to increase time in daily MVPA in children is unlikely to be sufficient. Correlates related to time spent sedentary need further examination.

BackgroundThe aim of this study was to investigate how sleep, screen time, active school travel and sport and/or exercise participation associates with moderate-to-vigorous physical activity (MVPA) in nationally representative samples of Norwegian 9- and 15-y-olds, and whether these four behaviors at age nine predict change in MVPA from age nine to 15 years.MethodWe pooled cross-sectional accelerometer and questionnaire data from 9- (n = 2366) and 15-y-olds (n = 1554) that participated in the first (2005/06) and second (2011/12) wave of the Physical Activity among Norwegian Children Study to investigate cross-sectional associations. To investigate prospective associations, we used data from a sub-sample that participated in both waves (at age nine and 15 years, n = 517).ResultsCross-sectional analyses indicated a modest, inverse association between screen time and MVPA among 9- (− 2.2 min/d (95% CI: -3.1, − 1.3)) and 15-y-olds (− 1.7 min/d (95% CI: -2.7, − 0.8)). Compared to their peers with 0–5 min/d of active travel to school, 9- and 15-y-olds with ≥16 min/d accumulated 7.2 (95% CI: 4.0, 10.4) and 9.0 (95% CI: 3.8, 14.1) more min/d of MVPA, respectively. Nine-y-old boys and 15-y-olds reporting ≥8 h/week of sports and/or exercise participation accumulated 14.7 (95% CI: 8.2, 21.3) and 17.9 (95% CI: 14.0, 21.8) more min/d of MVPA, respectively, than those reporting ≤2 h/week. We found no cross-sectional association between sleep duration and MVPA in either age group. None of the four behaviors predicted change in MVPA from age nine to 15 years (p ≥ 0.102).ConclusionActive travel to school and sport/exercise participation may be important targets for future interventions aimed at increasing MVPA in children and adolescents. However, future studies are needed to determine causality.

Background: Ageing is a life-long process characterized by a progressive loss of physical fitness compromising strength, flexibility, and agility. The purpose of this study was to use accelerometry to examine the relationship between sedentary time, light physical activity (LPA), and moderate to vigorous physical activity (MVPA) with the elderly’s physical fitness. Additionally, we aimed to examine the association between the aforementioned variables on older adults who fulfilled global recommendations on physical activity for health and on those who did not fulfil these recommendations. Methods: Eighty-three elderly (mean ± SD: 72.14 ± 5.61 years old) of both genders volunteered to participate in this cross-sectional study, being divided into an active group (n = 53; 71.02 ± 5.27 years old) and an inactive group (n = 30; 74.13 ± 5.72 years old) according to the established guidelines. Sedentary and physical activity times were assessed using an ActiGraph® GT1M accelerometer, whereas physical fitness was evaluated with the Senior Fitness Test. Results: MVPA time was correlated with lower body mass index (BMI) ((rs = −0.218; p = 0.048; −0.3 < r ≤ −0.1 (small)) and shorter time to complete the agility test ((rs = −0.367; p = 0.001; −0.5 < r ≤ −0.3 (low)). Moreover, MVPA time was positively correlated with aerobic endurance ((rs = 0.397; p = 0.000; 0.5 < r ≤ 0.3 (low)) and strength ((rs = 0.243; p = 0.027; 0.3 < r ≤ 0.1 (small)). In the inactive group, MVPA time was positively correlated with upper limb flexibility ((rs = 0.400; p = 0.028; 0.5 < r ≤ 0.3 (low)); moreover, sedentary time was negatively correlated with upper limb flexibility ((r = −0.443; p = 0.014; −0.5 < r ≤ −0.3 (low)), and LPA time was negatively correlated with BMI ((r = −0.423; p = 0.020; −0.5 < r ≤ −0.3 (low)). In the active group, MVPA time was correlated with lower BMI ((rs = −0.320; p = 0.020; −0.5 < r ≤ −0.3 (low)), and shorter time to complete agility test ((rs = −0.296; p = 0.031; −0.3 < r ≤ −0.1 (small)). Conclusions: Our results reinforce the importance of promoting MVPA practice among the elderly, thereby allowing physical fitness maintenance or improvement.

Spending more time active (and less sedentary) is associated with health benefits such as improved cardiovascular health and lower risk of all-cause mortality. It is unclear whether these associations differ depending on whether time spent sedentary or in moderate-vigorous physical activity (MVPA) is accumulated in long or short bouts. In this study, we used a novel method that accounts for substitution (i.e., more time in MVPA means less time sleeping, in light activity or sedentary) to examine whether length of sedentary and MVPA bouts associates with all-cause mortality. We used data on 79,503 adult participants from the population-based UK Biobank cohort, which recruited participants between 2006 and 2010 (mean age at accelerometer wear 62.1 years [SD = 7.9], 54.5% women; mean length of follow-up 5.1 years [SD = 0.73]). We derived (1) the total time participants spent in activity categories-sleep, sedentary, light activity, and MVPA-on average per day; (2) time spent in sedentary bouts of short (1 to 15 minutes), medium (16 to 40 minutes), and long (41+ minutes) duration; and (3) MVPA bouts of very short (1 to 9 minutes), short (10 to 15 minutes), medium (16 to 40 minutes), and long (41+ minutes) duration. We used Cox proportion hazards regression to estimate the association of spending 10 minutes more average daily time in one activity or bout length category, coupled with 10 minutes less time in another, with all-cause mortality. Those spending more time in MVPA had lower mortality risk, irrespective of whether this replaced time spent sleeping, sedentary, or in light activity, and these associations were of similar magnitude (e.g., hazard ratio [HR] 0.96 [95% CI: 0.94, 0.97; P < 0.001] per 10 minutes more MVPA, coupled with 10 minutes less light activity per day). Those spending more time sedentary had higher mortality risk if this replaced light activity (HR 1.02 [95% CI: 1.01, 1.02; P < 0.001] per 10 minutes more sedentary time, with 10 minutes less light activity per day) and an even higher risk if this replaced MVPA (HR 1.06 [95% CI: 1.05, 1.08; P < 0.001] per 10 minutes more sedentary time, with 10 minutes less MVPA per day). We found little evidence that mortality risk differed depending on the length of sedentary or MVPA bouts. Key limitations of our study are potential residual confounding, the limited length of follow-up, and use of a select sample of the United Kingdom population. We have shown that time spent in MVPA was associated with lower mortality, irrespective of whether it replaced time spent sleeping, sedentary, or in light activity. Time spent sedentary was associated with higher mortality risk, particularly if it replaced MVPA. This emphasises the specific importance of MVPA. Our findings suggest that the impact of MVPA does not differ depending on whether it is obtained from several short bouts or fewer longer bouts, supporting the recent removal of the requirement that MVPA should be accumulated in bouts of 10 minutes or more from the UK and the United States policy. Further studies are needed to investigate causality and explore health outcomes beyond mortality.

Globally, public health policies are targeting modifiable lifestyle behaviors. We explore the independent association of moderate-to-vigorous physical activity (MVPA) and sedentary behavior on the risk of childhood overweight/obesity. A cross-sectional survey of children aged 8-11 years (N = 826). Objective body mass index was used to classify children as normal weight or overweight/obese. Children wore wrist-worn Geneactiv accelerometers for 7-days and thresholds were applied to categorize MVPA and sedentary time. Screen time (ST) was parent reported. Poisson regression examined the independent association of (1) MVPA (2), objective sedentary time and (3) ST on the risk of overweight/obesity. Overall, 23.7% (95% CI, 20.8-26.6%) of children were overweight/obese. On average, children spent 10.8% of waking time at MVPA and 61.3% sedentary. One-fifth (22.1%, 95% CI, 19.3-25.0%) of children achieved MVPA recommendations (≥ 60 min each day) and 17.5% (95% CI, 14.9-20.1%) met ST recommendations (<2 hr per day). Time spent at MVPA was inversely associated with the risk of overweight/obese independent of total sedentary time. Total time spent sedentary was not associated with overweight/obese independent of MVPA. ST was associated with an increased risk of overweight/obese independent of physical activity. Few schoolchildren met physical activity and screen time recommendations suggesting population based measures are needed.

BackgroundPast cross-sectional studies have reported a positive association between moderate-to-vigorous physical activity (MVPA) and academic achievement in children and adolescents. Despite this, the influence of variations in MVPA over time on academic achievement remains yet to be definitively understood. Therefore, this study aims to track the patterns of MVPA and examine how they are associated with academic achievement over a three-year period among Chinese primary school students.MethodsThe longitudinal study examined the MVPA and academic achievement of a cohort of 202 primary school children over a three-year period. MVPA was assessed via accelerometers and analysed using Compositional Data Analysis (CoDA). Academic achievement was quantified using standardised test scores in reading, mathematics, and language. Group-Based Trajectory Models (GBTMs) were used to identify patterns of MVPA. Covariates such as demographics, sleep duration, and attitudes towards sports were adjusted in the Generalized Estimating Equations (GEEs) used to examine associations with academic achievement. All statistical analyses were conducted using R and SAS 9.4 software.ResultsThis study identified three distinct MVPA trajectories: Low (74.8%), Decline (13.2%), and High (12.0%). At baseline, the High MVPA group had better academic achievement with mean scores of 89.8 in reading, 94.5 in mathematics, and 94.7 in language, compared to the Low MVPA group with mean scores of 80.4, 83.0, and 84.9, respectively. After adjustment for confounders, GEE models showed significant associations between MVPA trajectories and improved academic achievement. Compared to the Low MVPA group, the Decline MVPA group exhibited significant score increases in reading (β = 4.11, 95% CI: 1–7.21) and mathematics (β = 2.79, 95% CI: 0.09–5.5). The High MVPA group exhibited significant score increases in reading (β = 11.3, 95% CI: 7.93–14.67), mathematics (β = 12.32, 95% CI: 9.61–15.02), and language (β = 11.53, 95% CI: 8.99–14.06). Additionally, notable gender differences in MVPA trajectories were observed, and a positive association was found between favorable sports attitudes and improved academic achievement.ConclusionsThis study reveals three distinct MVPA trajectories among Chinese primary school children and demonstrates that those with high MVPA trajectories showcase superior academic achievements, particularly in reading, mathematics, and language. This highlights the vital role of MVPA in supporting academic excellence.

Association of Patterns of Moderate-to-Vigorous Physical Activity Bouts With Pain, Physical Fatigue, and Disease Severity in Women With Fibromyalgia: the al-Ándalus Project

PurposePhysical inactivity is a known risk factor for worsening pain, yet accelerometry-based assessment of sedentary behaviour (SED), physical activity (PA) and time-in-bed (as a proxy for sleep) in individuals with temporomandibular disorders (TMD) are still scarce. We aimed to document and compare the 24-hour time-use compositions of physical behaviours of women with TMD during weekdays and weekends.MethodsBehaviours were monitored over 7 days using a thigh-worn accelerometer in 44 women with TMD according to the Diagnose Criteria for TMD (mean age 29.6 ± 7.2 years). Daily time-use compositions were exhaustively described in terms of SED in short (<30 min) and long (≥30 min) bouts, light PA (LPA), moderate-to-vigorous PA (MVPA), and time-in-bed. Following a compositional data analysis, isometric log-ratios (ilr) were calculated; ilr1 – time-in-bed relative to time spent awake, ilr2 – SED (short and long bouts) relative to LPA and MVPA, ilr3 – SED in short relative to long bouts, and ilr4 – LPA relative to MVPA. Differences between weekday and weekend data were examined using repeated-measures MANOVA, followed by univariate post-hoc tests of pairwise differences.ResultsDuring the week, women with TMD appeared to spend more time SED in short bouts (241 min), more time SED in long bouts (416 min), less time in LPA (241 min), less time in MVPA (62 min), and more time-in-bed (480 min) than on the weekend (223, 379, 276, 70 and 493 min, respectively). The MANOVA showed that the set of ilrs as a whole for weekdays and weekend differed significantly (ηp2 = 0.25, p = 0.02). The post-hoc tests showed that time spent SED in short and long bouts relative to LPA and MVPA (ilr2) was larger during the week than at the weekend (Cohen’s d = 0.31, p = 0.04).ConclusionsWomen with TMD behaved differently during weekdays and weekends, whether this relates to days with/without pain or to other factors is still unclear. Further research is required to understand whether these differences in behaviours are part of everyday life or a consequence of musculoskeletal pain.

In recent years, there has been a migration toward the use of glycated hemoglobin (HbA1c) in determining glycemic control. This study aimed to quantify the associations between changes in body weight, sedentary time, and moderate to vigorous physical activity (MVPA) time with HbA1c levels for a 3-yr period among adults at high risk of type 2 diabetes. This study reports baseline and 3-yr follow-up data from the Walking Away from Type 2 Diabetes study. ActiGraph GT3X accelerometers captured sedentary time and MVPA. Linear regression examined the independent associations of changes in sedentary time, MVPA, and body weight with HbA1c between baseline and 3-yr follow-up. The sample composed of 489 participants (mean age = 64.2 ± 7.3 yr, body mass index = 31.7 ± 5.1, 63.4% male) with valid baseline and follow-up accelerometer, body weight, and HbA1c data. After adjustment for known confounders, an increase in MVPA time (per 30 min·d) was associated with a decrease in HbA1c percentage (β = -0.11 [-0.18 to -0.05], P = 0.001), and an increase in body weight (per 6 kg) was associated with an increase in HbA1c percentage (β = 0.08 [0.04-0.12], P < 0.001). The presence of dysglycemia at baseline (HbA1c ≥ 6.0%) strengthened these associations (P < 0.001 for interactions). Change in sedentary time was not significantly associated with change in HbA1c after adjustment for change in MVPA time. Increases in MVPA and body weight were associated with a reduction and increase in HbA1c, respectively, particularly in those with dysglycemia. Quantifying the effect that health behavior changes have on HbA1c can be used to inform prevention programs.

Active school travel (AST), such as walking or biking to/from school, involves physical effort and situational awareness, making it a potentially health-enhancing cognitive activity. However, whether AST is related to cognitive functioning among children has rarely been explored. Hence, this study aims to examine associations between AST and spatial cognitive functions and explore potential moderating factors. Cross-sectional study. Primary caregivers of 510 children aged 8–12 years from Australia reported patterns of AST. Children completed three visuospatial cognitive tests: working memory, mental rotation, and situational awareness (recalling route landmarks and directions). Adjusted linear regressions were conducted to test associations. Interaction terms were used to explore moderation by gender, independent travel experience, moderate-to-vigorous physical activity (MVPA), and team sports participation. Adjusted regression analysis showed no significant associations between AST and cognitive outcomes. MVPA moderated the association between walking to school and route directions (B = −0.59, 95% CI [−0.99, −0.19], p = 0.004), with weak evidence of moderation of the association between biking to school and route landmarks (B = −0.90, 95% CI [−1.98, 0.17], p = 0.099). Team sports moderated the association between biking and working memory (B = 8.71, 95% CI [2.01, 15.42], p = 0.011). While regular AST was not directly linked to better spatial cognition, some moderating effects of MVPA and team sport were found. Future research should include longitudinal or experimental study designs, incorporate objective active (school) travel measures, and explore additional dimensions like distance, duration, speed, and cognitive engagement. • Children who engaged in active school travel did not show better spatial cognitive skills compared to other children. • The Route Recall Task proved to be feasible and applicable for assessing situational awareness during active travel. • The association between AST and working memory was more favourable for those who did team sports. • Some associations were slightly more favourable among those with lower MVPA.

BackgroundTime spent in sleep, sedentary behaviour (SB), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA) all impact child health. The aim of this study was to investigate cross-sectional and longitudinal associations between time use and adiposity and cardio-respiratory fitness (CRF) in school-aged children.MethodsCross-sectional (n = 281) and longitudinal (n = 305) data were used from the Life on Holidays study with assessments over three time periods (two consecutive school years, and the interleaving summer holiday period). 24-h time use was measured using wrist-worn accelerometers. Adiposity was assessed as BMI z-score from measured weight and height, using World Health Organization reference data, and from body fat percentage (%BF) measured via bioelectrical impedance. CRF was operationalised as estimated VO2max from the 20-m shuttle run test. Compositional data analysis in conjunction with linear mixed-effects models was used to investigate the associations between time-use composition and outcomes after controlling for covariates. Cross-sectional models used baseline measures, and longitudinal models used rates of change in each outcome. Sensitivity analyses explored relationships for moderate physical activity (MPA) and vigorous physical activity (VPA) separately.ResultsIn cross-sectional analyses, time spent in MVPA was favourably associated with all adiposity and fitness outcomes (all p < 0.01) whereas time in LPA was unfavourably associated with all outcomes (all p < 0.01). Sleep was favourably associated with %BF, whereas SB was unfavourably associated (both p = 0.02). In longitudinal models, only MVPA was significantly associated with any of the three outcomes. 30 min/day more time spent in MVPA was associated with a decrease in %BF rate of change (-0.60 to -0.48) when time was reallocated from LPA or SB, and with an increase in VO2max (+ 0.89 to + 1.01) when time was reallocated from any other behaviour. Sensitivity analyses showed VPA was significantly associated with changes in %BF and VO2max.ConclusionsAll behaviours displayed cross-sectional associations with adiposity and CRF. However, only MVPA (and in particular VPA) was significantly associated with changes in %BF or VO2max in longitudinal models. Future efforts should focus on increasing participation in MVPA with school-aged children to see the most benefit to health.