Abstract
This study describes engagement in and stability of physical activity and sedentary behaviors in early life, and assesses associations with sex, maternal education, and developmental stage.
Abstract
Maternal-report data at child age 4-, 9-and 20-months were collected from 542 families in the Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program. Parents estimated average daily time their child spent in pursuits that were active or restricted movement. With increasing age, children generally spent more time in active pursuits and watching television, and less time in situations that restrict movement. Associations were found with age of developmental milestone attainment but not sex or maternal education.
Abstract
Stability over time was strongest for television viewing (β=0.34-0.38) and time spent outdoors (β=0.27-0.33). Contrary to guidelines, television viewing increased and showed stability suggesting a need to target this behavior very early in life to achieve optimal longer term outcomes.
Introduction
Health behaviors such as physical activity and sedentary behavior develop early in life.
Introduction
observed in older children due to the rapid physical, cognitive and social development during that life phase. Information on very young children is crucial to inform the need for and development of strategies to optimise levels of physical activity and reduce sedentary behaviors from early life.
Introduction
With only three disparate studies having reported physical activity levels in children aged 0-2, it is difficult to have a clear picture of activity levels in this population. Parents in Greece reported their 1-2 year olds spent just over one hour/week in physical activity. (Manios, 2006) Direct observation of 2-3 year old Dutch children showed 41% and 69% of time indoors and outdoors, respectively, was spent active. (Gubbels et al., 2011) Objective assessment by accelerometry found 19-month old Australian children spent 231 minutes/day in physical activity (of light-to vigorous-intensity). (Hnatiuk et al., 2012) Whether physical activity levels in early life are important for later health is likely to be partially contingent on the stability of these behaviors over time. While physical activity tracks moderately over the shorter term in older children,(Kwon, Janz, & International Children's Accelerometry Database, 2012) no studies have investigated stability over the first years of life.
Introduction
Studies investigating sedentary behavior in young children focus on television viewing.
Introduction
Parents of 0-2 year olds report average viewing times from 12 to 153 minutes/day. (Barr, Danziger, Hilliard, Andolina, & Ruskis, 2010; Christakis & Garrison, 2009; Dennison, Erb, & Jenkins, 2002; Kourlaba, Kondaki, Liarigkovinos, & Manios, 2009; Mendelsohn et al., 2008; Rideout & Hamei, 2006; Ruangdaraganon et al., 2009; Schmidt, Rich, Rifas-Shiman, Oken, & Taveras, 2009; Thompson & Christakis, 2005; Tomopoulos et al., 2010; Vandewater et al., 2007; Zimmerman, Christakis, & Meltzoff, 2007) These vastly different estimates may be due to age variations in the samples as despite the narrow age band, within samples, viewing time was higher in older children. Low to moderate tracking of sedentary behaviors in children have been reported, (Biddle, Pearson, Ross, & Braithwaite, 2010 As well as understanding prevalence and stability, it is important to identify characteristics of children who engage in less physical activity and more sedentary behavior to assist in identifying those most at risk of poor outcomes and in need of intervention. In older children, boys are consistently found to be more physically active than girls. (Sallis, Prochaska, & Taylor, 2000; Tucker, 2008; Van Der Horst, Paw, Twisk, & Van Mechelen, 2007 ) While adolescent boys have higher levels of sedentary behavior, the evidence in younger children is equivocal. (Van Der Horst et al., 2007) Age appears to be positively correlated with both behaviors in preschool-aged children. (Hinkley, Crawford, Salmon, Okely, & Hesketh, 2008; Hoyos Cillero & Jago, 2010) In very young children, developmental attainment may be more relevant than biological age in influencing behaviour but this has not previously been investigated. While maternal education, often used as an indicator of child socioeconomic position, (Ensminger & Fothergill, 2003) is not consistently found to be associated with child physical activity or sedentary behaviors, (de Vet, de Ridder, & de Wit, 2011) few studies have investigated this in very young children.
Early Child Development and Care
This study aimed to describe children's engagement in active and sedentary pursuits at 4-, 9-and 20-months of age, to assess associations with sex, maternal education, and developmental stage, and to assess stability across these three time points.
Methods

Sample:
Participants were mother-infant dyads participating in the Melbourne Infant Feeding, Activity and Nutrition Trial (InFANT) Program,(K. Campbell et al., 2008 ) a cluster-randomized controlled trial of a community-based early childhood obesity prevention intervention delivered to mothers. Individual participants (n=542) were members of 62 first-time parent groups in Melbourne (population approximately 4 million), Victoria, Australia, recruited through the universal Maternal and Child Health service operating throughout the state. The two-stage sample selection involved random selection of 14 local government areas within a 60km radius of the research centre (Deakin University, Melbourne) and then random selection of 50% of first-time parent groups running within these areas (rounded up to the nearest even number to ensure equal within-area randomization for the trial). A minimum of eight parents (six for low socio-economic areas) were required to consent to participate for the group to be recruited. Ineligible groups (<8 participants or predominantly non-English speaking) and those not reaching the required number of consenting participants were replaced with the next randomly selected group in the area. In all, 84% of groups approached were recruited. Ethics approval was received from the Deakin University Human Research Ethics Committee.
Measures:
Data were collected at baseline (T1; June-December 2008) when infants were aged approximately 4-months, mid-intervention (T2; infants approximately 9-months), and intervention conclusion (T3; infants approximately 20-months). Mothers completed written questionnaires reporting child date of birth (from which age was calculated), age of developmental milestone attainment (sitting unassisted, crawling and walking), and their own highest level of education (categorized as university or no university). At each time point, mothers also reported the number of hours/minutes their child spent in a range of pursuits on an average day. These pursuits were classified as: active, including physically active with their parent, tummy time (T1 and T2) and outside time; not restricted, including on the floor (T1 and T2), and free to move around (T3); restricted movement, including in a bouncer or swing (T1 and T2), stroller or pram, car seat or capsule, high chair or other chair, playpen, and baby carrier or sling (T1 and T2); and television viewing time.
Measures:
Two-week test-retest reliability in separate samples of 66, 60 and 51 parents with children of similar ages to T1, T2 and T3 samples, respectively, indicated the 30 activity items from the three time points had a mean intra-class correlation of 0.57 (range 0.20-0.92). The vast majority of individual items had acceptable reliability, although two items had intra-class correlations of <0.25: time spent in a bouncer/swing at T1 (ICC=0.20) and time spent in a highchair at T1 (ICC=0.21). These items were, however, acceptable at subsequent data collection points and were therefore retained to allow longitudinal analyses.
Analyses:
No differences were found between intervention and control participants for any physical activity or restricted movement variables at intervention conclusion (T3); however, television Early Child Development and Care viewing time was higher in control group erik20@example.net. Thus groups were combined and analyses conducted on the entire sample, adjusted for intervention arm. When television viewing was the outcome variable analyses were repeated for control participants only, with similar findings (results not presented). A large number of the pursuit time measures were positively skewed, thus square-root transformations were performed to render these approximately normal. Descriptive statistics are based on non-transformed measures; inferential statistics used transformed variables where applicable.
Analyses:
Repeated-measures ANCOVAs, controlling for intervention arm, assessed differences in pursuit times across time points. One-way ANCOVAs assessed associations with sex and maternal education for each pursuit at each time point. Associations between developmental milestones and pursuit times were examined via multivariable linear regression. A series of models were tested for each of the T1, T2, and T3 pursuit times (dependent variables) with age when first sitting/crawling/walking (primary predictor) and intervention arm (covariate).
Analyses:
Models also included child's age (at the corresponding time point) as a covariate.
Analyses:
To assess stability of children's time in different pursuits from T1 to T3, a series of linear regression models were conducted in which T3 pursuit times were regressed onto the corresponding T1 pursuit times. This was repeated to assess stability from T2 to T3. Models adjusted for intervention arm and clustering by mothers' group.
Results

Sample:
Sample characteristics are reported in Table 1 . Of the 542 families (86% response) recruited at T1, 524 (97%) were retained at T2 and 492 (91%) at T3. There were no baseline differences on any of the measures reported here between those retained and those not. Six infants had not commenced walking at T3; they were excluded from the calculation of mean age at walking but included in all other analyses.
Sample:
Time in active and sedentary pursuits: Time spent in the different pursuits at each time point is presented in Table 2 . A linear trend was observed for active pursuits. Time spent being physically active with their parent, on their tummy, outside, and on the floor or free to move around all increased from 4-to 9-months and further increased at 20-months of age.
Sample:
Time spent restricted (not free to move around) showed more variable fluctuations with age.
Sample:
Certain forms of restricted movement (high chair and car seat) increased with age, others decreased (bouncer/swing, stroller, baby carrier) and for playpen time there was a peak at 9-months of age. For some forms of restricted movement, the interquartile range indicates that a large proportion of the sample did not engage in specific pursuits at one (highchair, bouncer/swing, baby carrier/sling) or more of the timepoints (playpen). Average time spent watching television was stable between four and 9-months but increased at 20-months of age.
Sample:
No sex differences in any of the physical activity or sedentary behaviors were evident; however, there were some behavioral differences by maternal education level. Compared to children whose mothers had not attended university, children of university educated mothers spent more time outside at all time points (35.7 vs 45.2 min/day, p=0.02 at T1; 54.1 vs 63.2 min/day, p=0.04 at T2 and 99.5 vs 110.9 min/day, p=0.05 at T3). Children of university educated mothers were provided more time to freely move around at T2 compared with those whose mothers had not attended university (218.0 vs 188.0 min/day, p=0.01 respectively), and spent less time watching television at T3 (46.5 vs 61.9 min/day, p=0.001 respectively).
Sample:
However, children of university educated mothers also spent more time in specific forms of Early Child Development and Care restricted movement compared with those of mothers with no university education, including in a stroller/pram (58.9 vs 48.1 min/day, p=0.003) and baby carrier at T1 (16.3 vs 11.6 min/day, p=0.001), in a high chair at T2 (63.6 vs 57.5 min/day, p=0.05) and T3 (66.7 vs 58.2 min/day, p=0.03) respectively.
Sample:
Developmental milestone attainment showed no association with television viewing or most of the restricted movement variables (Table 3 ). However a number of associations were found with active pursuit variables. At all three time points more time free to move around was associated with earlier walking and more time outside was associated with earlier crawling. Adjustment for maternal education did not alter the findings (results not shown), with the exception of the association between age of crawling and time spent in a bouncer or swing at T2 which no longer reached significance when maternal education was included (p=0.06). Table 4 , time spent in various pursuits at T1 and T2 were generally predictive of time spent in the same erik20@example.net. Exceptions were time spent in a high chair/chair and playpen, where time spent in these pursuits at T1 and T3 were not associated.
Stability of time in different pursuits: As shown in

Discussion
Commensurate with physical development, over their first two years of life children appear to become more active and spend less time in situations where their movement is restricted.
Discussion
This includes spending an average of more than 1.5 hours/day outside by 20-months of age, where children are known to be more active, (Sallis et al., 2000) and an average of more than recommended 90+ (Bright Futures, 2008) objectively assessed accelerometer-derived physical activity data for this cohort also showed no sex differences. (Hnatiuk et al., 2012) Evidence of socioeconomic patterning of early childhood activity and sedentary behaviors was mixed. Of the eight behaviors examined, five were associated with maternal education; however, these associations varied in direction and by timepoint/child age. More favourable physical activity behaviors and lower television viewing at 20-months of age were observed for children of university educated mothers. It may be that more highly educated mothers reside in nicer neighbourhoods which provide more favourable environments for physical activity, or have greater knowledge of beneficial past-times for their children. However, these children were also reported to spend more time in a number of situations that restrict movement, erik20@example.net. It may be that more highly educated mothers are aware of advice to increase physical activity and decrease television viewing but are less familiar with the idea of limiting time children spend restricted, offering opportunities for awareness raising by health professionals. However, the mixed findings for individual behaviours in this study suggests the relationship between socioeconomic position and children's physical activity is not strong, as similarly evident from the broader literature. (Drummond, Drummond, Dollman, & Abery, 2010) During the first two years of life children experience rapid physical development. This study suggests earlier milestone attainment is associated with more physical activity. Some associations may be a simple reflection of ability, for example, less tummy time for those who are able to walk. However, other associations may suggest potential causal pathways whereby more favourable activity opportunities during infancy lead to earlier milestone attainment and more physical activity in the toddler years. One previous study has reported an association between early motor development and greater sport participation at age 14. (Ridgway et al., 2009 ) Equally, these associations may reflection temperament or innate biological mechanisms. Some children may be naturally more inclined to move, or those with a propensity to earlier walking may have temperaments that influence parents to promote greater physical stimulation. Other research in this cohort using objective accelerometer assessment of physical activity confirms an association between age when walking commenced and physical activity at 19-months, irrespective of time between commencement of walking and assessment of physical activity. (Hnatiuk et al., 2012) At this young age, despite rapid changes in development and increases in overall time spent in most pursuits, behaviors appear to be relatively stable. Exceptions related to some forms of restricted movement between 4-and 20-months of age, which are likely to have been less relevant (and less utilized) at 4-months, for example, highchair use. This observed stability suggests the early months of life may be important for establishing a trajectory of behavior.
Discussion
The implication being that early promotion of active play and decreased restricted movement and sedentary time may assist in promoting beneficial behaviors into the toddler years and beyond.
Early Child Development and Care
A limitation of this study is the proxy-report collection of data. It is unclear how accurately parents report on very young children's time in different pursuits. Yet objective assessment of perambulatory children's activity is limited to observation which is setting-specific and therefore not comprehensive. Associations observed between developmental milestones and parent-reported time in active play and restricted movement were consistent with associations reported previously in this cohort with objectively assessed physical activity at 19-months of age, providing some confidence in the proxy-measures. Strengths of this study include the large sample size, longitudinal nature of the data with assessments at three time points, and the broad range of active play and restricted movement variables investigated.
Conclusion
This study suggests engagement in active play increases across the early months of life, commensurable with physical development, and is associated with milestone attainment.
Conclusion
While this may reflect individual differences in temperament and propensity for movement, it could also suggest parents and other caregivers may influence milestone attainment through the opportunities for movement they provide in the early months of life. Thus there may be opportunity to actively support caregivers to promote opportunities to maximise children's active play and minimise restricted movement and exposure to television in early life, particularly for infants with a lesser propensity towards movement. Further research is required to assess whether such intervention would promote increased physical activity levels longer term. Implications of these very early life patterns and opportunities for physical activity and sedentary pursuits as children move into the preschool and school years remain an area warranting investigation. 4 (25.7-68.6) 51.4 (30.0-68.6) 30.0 (30.0-60.0) 0.001 Car seat or capsule 25.7 (17.1-34.3) 25.7 (17.1-42.9) 30.0 (20.0-45.0 Linear regression models with T3 pursuit times as DVs, corresponding T2 pursuit times as IVs, and intervention arm as a covariate. Standardised regression coefficients are shown.

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