Background
Childhood is an important developmental stage during which health and lifestyle behaviours such as physical activity (PA) are established [
1,
2]. Regular PA during childhood provides broad ranging health benefits [
3,
4]. To achieve and maintain these benefits, the UK Chief Medical Officers recommend that children accumulate at least 1 h of moderate-to-vigorous PA (MVPA) each day, and minimise time spent in sedentary behaviours [
5]. However, there is strong evidence to suggest that few children in the UK [
6,
7] and other developed countries including America [
8], Australia [
9] and Canada [
10] currently achieve the recommended levels of PA to benefit their health.
Children’s PA comprises a broad range of structured (e.g., organised sport) and unstructured activities (e.g., active travel, outdoor play) that take place in a variety of settings [
11,
12]. The school setting provides a range of PA opportunities for children and contributes a significant proportion of their daily PA [
13,
14]. These school-based PA opportunities are inclusive to all, as they form part of the school curriculum (e.g., physical education), discretionary time in school (e.g., recess play), and after-school provision (e.g., organised after-school activities) during the school week. In contrast, opportunities for PA on weekend days are strongly influenced by parental encouragement (e.g., positive verbal reinforcement) and support (e.g., payment of club subscriptions, transport to and from provision) [
15,
16], as well as constraints on individual choice (e.g., access to garden/backyard) [
17‐
19]. Given that children also experience less structure and routine, and thus more behavioural choice on weekend days compared to weekdays, it is likely that their PA levels will vary considerably from weekend to weekend [
20,
21]. However, most previous studies have been limited to measuring PA once over a 7-day period encompassing weekdays and weekend days [
22‐
28]. Consequently, how representative this one-off measurement of weekend PA is of typical weekend PA behaviour remains unknown. Thus, further research is needed to specifically examine the variability of weekend PA from repeated measurements.
The weekend is an important time period for PA promotion. Firstly, children tend to accumulate the least amount of daily MVPA on weekend days [
29,
30]. Secondly, during the school term, weekends offer children the most discretionary time for leisure activity, and opportunities for the whole family to be physically active can be implemented more easily on weekends [
31]. Family involvement is an essential component of effective PA interventions in children [
32‐
34]. Family-based PA interventions that encourage PA co-participation between children and parents [
35,
36] and among siblings [
37] may yield beneficial effects as both are associated with higher child PA. Understanding the PA patterns of families is necessary for designing effective family-based PA interventions. However, little is known about the PA behaviours and habitual routines of families on weekends. To date, family-focused PA research has been qualitative in nature [
31,
33,
38‐
42]. None of these studies have involved all household family members as participants, or included objective assessments of PA.
To date, most family-focused PA interventions have followed ‘fixed prescriptions’ and in doing so have not engaged with families prior to intervention delivery (e.g., [
43‐
45]). Intervention programmes that are tailored to individual family needs and characteristics may help to overcome key intervention challenges including recruitment and engagement, and thus could improve intervention efficacy [
33,
46]. Moreover, research in this area is often based on group-level comparisons drawn from “one-off” assessments of PA which may not present a true reflection of a child’s or parent’s habitual level of PA. The inclusion of whole families comprising target children, parents, and siblings in the same study offers an original way in which to explore the characteristics of family unit weekend PA, which may help inform family-focused PA intervention design. This study, therefore, assessed ‘target’ children’s PA, and their siblings’ and parents’ PA over eight weekends using accelerometry and PA diaries. The aims of the study were twofold: 1. To investigate the stability of weekend MVPA among target children, siblings, and parents using repeated measures raw accelerometer data, and 2. To offer contextual insight into the characteristics of weekend PA amongst one representative low active family and one high active family.
Discussion
This study used a repeated measures design and multiple data sources to explore the variability and characteristics of weekend PA among families. The study observed substantial variability in children’s weekend PA, and revealed that children’s weekend PA is mostly unstructured in nature and undertaken with friends. The supplementary family case studies (Tables
1 and
2) demonstrated that in the selected cases, MVPA levels and variability across weekends were contingent on mode of PA participation.
The study revealed that parents’ MVPA was more stable across weekends than children’s, and was most stable among fathers (ICC = 0.83) compared to mothers (ICC = 0.58). No previous study has examined PA variability between children and parents, but higher ICC values have been reported in men compared to women for objectively measured total PA over 7 days [
60]. A potential reason for the observed difference in PA variability between mothers and fathers in this study may be due to the mode of activity that they undertook. For example, fathers typically engaged in more structured and organised forms of PA (53.8%) compared to mothers (38.4%), and structured PA is known to be more stable relative to unstructured PA [
61]. Similar repeated measures studies have been conducted with adults [
62,
63]. For example, Levin et al. [
61] assessed PA (MET min∙day
−1) in 77 adults over 48-h every 26 days for 1 year, and reported an ICC value of 0.42. The present study focused on weekend days and comprised a smaller sample and fewer repeated measures compared to the Levin et al. study [
62]. These factors are likely to have contributed to the higher ICC estimates observed in the present study.
The ICC values for weekend MVPA in target children (ICC = 0.55) and siblings (ICC = 0.38) in this study are lower than single observation studies in children (ICC = 0.81 [23], ICC = 0.57–0.73 [26], ICC = 0.76–0.97 [28]). However, they are consistent with repeated measures studies [
20,
21]. Very few studies have examined variability in children’s weekend PA using accelerometers and a repeated measures design. Mattocks et al. [
20] assessed 11- to 12- year-olds’ PA over 7 days on 4 occasions and reported ICC values for total PA (counts per minute) of 0.54 for weekdays and 0.38 for weekend days. Together, these findings demonstrate that a single measurement period is unlikely to accurately represent a child’s typical level of weekend PA, especially among younger children.
The investigation of specific sources of variance in weekend PA revealed that intra-individual variance (i.e., variation in PA from weekend-to-weekend within participants) accounted for a large proportion of total variance among children, especially when models were fitted without nesting the weekend effect within participants. This signified heterogeneous weekend PA patterns. Previous research has shown that children’s PA levels are higher [
29,
30] and more stable on weekdays compared to weekend days [
20], and most stable during the school day [
64]. This is intuitive as the structured school day offers children various formal (e.g., physical education classes, after-school clubs) and informal PA opportunities (e.g., play time/recess) including travelling to and from school actively. When these structures, routines and opportunities are absent on weekend days, children’s PA is more likely to vary from day to day in comparison to weekdays [
65]. Moreover, opportunities for PA on weekend days are partly dependent on peer and family-based PA opportunities, strong parental encouragement (e.g., positive verbal reinforcement) and support (e.g., payment of club subscriptions, transport to and from provision) [
15,
16,
66], which may also vary from weekend to weekend The combination of these factors may also have contributed to the large intra-individual variability in children’s weekend PA in this study.
The study findings build on previous family-based PA studies [
31,
33,
40,
41] by providing contextual insight into weekend PA among family units. Children’s weekend PA was mostly unstructured in nature and undertaken with friends, whereas a greater proportion of parents’ weekend PA was undertaken alone in structured settings. Target children recorded lower MVPA and reported less enrolment in organised/club-based physical activities compared to siblings. This finding supports an age related decline in PA as all the siblings in this study were younger than the target children [
67]. However, the finding may also be due to siblings’ more frequent participation in organised sport which is linked with higher child PA [
68,
69]. Given that low levels of parent-child co-participation took place in this study future family-based interventions should consider encouraging parents to engage in more physical activity with their children. With regards to family-based PA, popular weekend activities included walking, swimming and visiting public parks. The promotion of these activities may form appropriate intervention settings. Public parks play an important role in supporting PA, providing all families regardless of SES with the opportunity to walk, cycle, and play, with many having specific equipment/activities available for other health enhancing physical activities [
70‐
72]. However, in order to promote regular park use among family units further investment in park programming may be required to provide a variety of features and activities within parks to support the needs of both children and parents [
73].
It was apparent from the two family case studies that in the selected cases, the mode of activity families engage in on weekends influences their weekend MVPA levels (Figs.
2 and
3). For example, the Williams’ (i.e., high SES) PA levels were high and structured in nature whereas the Evans’ (i.e., low SES) were low and unstructured in nature. These findings are consistent with previous studies in children [
74‐
76] and adults [
77,
78] which reported SES as a strong predictor of PA and organised sport. Weekend leisure opportunities, especially organised ones, generally cost money. Low income families are less likely to have the available logistical and financial resources needed to partake in such leisure opportunities frequently [
74,
79,
80]. Therefore, accessible, low-cost weekend PA interventions, such as organised walks, park use or home based activities, may be an appropriate PA intervention for the least active and lowest income families.
The combined use of accelerometers and diaries across multiple weekends provided data that offered contextual insight into the variability of weekend PA among family units. For example, PA levels across weekends were more stable in the Williams family compared to the Evans family (Figs.
2 and
3). The Evans family accrued all of their weekend PA by way of unstructured activities whereas the Williams family participated in activities that were club-based and structured in nature. This finding is intuitive as organised sport participation is linked with higher levels of PA in children [
68,
69], and tends to be undertaken regularly, and at predetermined scheduled times. Such structure and routine was evident in Olivia’s and Harry’s PA diary data, but was quite the opposite for Mia and Jamie. By contrast, their PA levels across weekends were more varied, especially Jamie’s (Fig.
2a), and showed no apparent routine or structure. These findings are important as they reveal the potential influence of structured PA participation on habitual weekend PA amongst the selected family units. They suggest that broader intervention approaches such as discounted leisure centre memberships may be needed to provide structured sustainable leisure opportunities for families at weekends [
81]. Moreover, as the case study families engaged in few activities together, future child PA interventions may benefit from designing programmes for the whole family.
It is important to understand the barriers to mode-specific weekend PA participation so that strategies can be developed to increase children’s participation in specific modes of weekend PA. The family case studies illustrate the potential environmental barriers to children’s weekend PA and thus highlight the importance of understanding family context and PA characteristics when planning PA interventions. For example, the Williams children have access to a self-contained garden whereas the Evans children do not. This home environmental feature influenced the location of children’s outdoor play. This is a key finding for this family because promoting specific modes of weekend PA (i.e., outdoor play and organised sport) without considering such barriers and constraints is unlikely to support positive sustained behaviour change. As the barriers to participating in organised sport (e.g., financial cost) and unstructured PA (e.g., walkability, access to garden/backyard) are different and vary considerably [
17,
82,
83], future PA interventions may be more effective if informed by family characteristics, and tailored to support participation in a specific mode of PA. From a public health perspective, aligning intervention content to the needs, characteristics and constraints of the family will ensure that programmes are relevant and in doing so may positively impact intervention recruitment, engagement and effectiveness.
In addition to these empirical findings, the present study makes a methodological contribution by demonstrating the limitations of one off assessments of weekend PA and single modality PA measurement. The combination of accelerometer and PA diary data allowed exploration of the activities family units undertook on weekend days. By selecting two different family units and comparing their weekend PA behaviours, we were able to demonstrate a way to gain understanding of the complexity of family context, and how, in these cases, family weekend PA varies in mode, location, and variability. Therefore, the findings demonstrate the advantages of supplementing accelerometer data with contextual data, and highlight the importance of distinguishing between structured and unstructured PA participation when examining out-of-school and family-based PA. Future studies in this area may also benefit from the use of ecological momentary assessment (EMA) to obtain ecological real-life data on family PA. EMA collects momentary self-reports in situ, typically implemented as electronic diaries on a handheld electronic device (e.g., smartphone or tablet) [
84]. The method would enable the exploration of family weekend PA processes in context, thereby optimising the chance that subsequent intervention programmes based on this knowledge will be effective when employed in daily life [
85].
Strengths and limitations
This is the first study to investigate the variability of weekend PA among children and parents simultaneously. A unique aspect of the study is its repeated measures design. In addition, we used wrist-worn accelerometry and observed high participant compliance to device wear which improves the reliability of PA estimates [
86]. Firstly, this provides additional confidence in the study findings, and secondly, offers support that wrist accelerometry is a feasible method of PA assessment in children and adults. Moreover, we assessed weekend PA among families and in doing so revealed new insights into an understudied and complex area of research. The combination of multiple data sources is another strength of the study. Specifically, the combined use of raw accelerometer and diary data allowed exploration of PA mode, location of activity and with whom the activity was undertaken with. However, there are some study limitations. Firstly, our sample size was small, and the participants were all white British and generally healthy weight, which reduced the generalisability of the study. Secondly, participants consented to wearing an accelerometer and completing PA diaries on eight occasions. Therefore, selection factors relating to time availability and study interest may have contributed to a fairly homogeneous sample with active families more inclined to take part. This may have resulted in higher than normal PA levels for the sample. We acknowledge that the case study families are a homogenous group and are unlikely to be those in need of behavioural PA intervention. However, in comparing the two families, it was our aim to demonstrate that weekend PA behaviours differ between families and highlight the need for family-based PA interventions to be tailored to individual needs, characteristics and constraints. Thus, while the findings of this study may not be fully generalisable to other populations and geographical locations, the methods used here are novel and may have wider applicability, and scalability in future health-related research studies involving families.