Adherence to the WHO recommendation of three weekly days of vigorous intensity activities in children: an accelerometry study of vigorous physical activity bouts

Introduction

The World Health Organization (WHO) recommends that children and adolescents should do at least an average of 60 minutes per day of moderate to vigorous, mostly aerobic, physical activity (MVPA) across the week and should incorporate vigorous-intensity aerobic activities (VIAs), as well as those that strengthen muscle and bone, on at least three days a week (World Health Organization (WHO), 2020; Chaput et al., 2020).

The VIAs could be defined as sessions of physical activity that incorporate enough vigorous-intensity physical activity (VPA), such as some sports activities, physical education classes, or active games. However, the WHO Guidelines on Physical Activity do not provide a specific definition of the VIAs duration or the minimum time of VPA they should contain. This situation hinders researchers using objective assessment tools, such as accelerometry, to calculate the prevalence of compliance with this recommendation or the effect of sessions of VIAs on health.

The WHO incorporates two distinct recommendations on physical activity, promoting different patterns of physical activity for health. The pattern of physical activity promoted by the recommendation on average daily MVPA has been, and continues to be, widely studied (Guthold et al., 2020; Steene-Johannessen et al., 2020). However, the pattern of physical activity that seems to be promoted by the recommendation on VIAs has not been properly studied using objective assessment methods. Therefore, the evaluation of VPA patterns concentrated in activity sessions using accelerometry is important for the study of the relationship between VIAs and child health (Stone et al., 2009; Chinapaw et al., 2018).

Accelerometry has proven to be a highly reliable and valid tool for assessing physical activity in children (Sirard & Pate, 2001; Migueles et al., 2017; Gao et al., 2021). Traditionally, this information had been collected through questionnaires, especially in larger population studies (Guthold et al., 2020; Whiting et al., 2021). However, the discrepancies found when trying to establish relationships between physical activity and health outcomes in the child population using subjective methods (Adamo et al., 2009) have led to other objective assessment methods, such as accelerometry, gaining greater prominence in recent years.

Some research has demonstrated through accelerometry that physical education classes (Meyer et al., 2013; Chen, Kim & Gao, 2014; Mooses et al., 2017; Calahorro-Cañada et al., 2017; Ikeda et al., 2022; Benavente-Marín et al., 2024) and organized sports activities (Silva et al., 2013; Marques, Ekelund & Sardinha, 2016; Ikeda et al., 2022) contribute to the performance of more physical activity at all intensities, as well as to the achievement of the WHO’s MVPA recommendation. However, none of these studies presented compliance with the recommendation to incorporate VIAs at least three days a week.

Participation in physical education classes and organized sports activities can be easily recorded through questionnaires (Whiting et al., 2021), but these activities do not always include VIAs and on certain occasions may not be sufficient to meet the recommendations on physical activity, especially in girls (Kokko et al., 2019; Benavente-Marín et al., 2023). Therefore, to enable the study of VIAs through accelerometry, we have previously proposed the use of VPA bouts (VPA-Bouts) derived from the VPA carried out in especially active physical education classes in children aged 8 to 9 years (Benavente-Marín et al., 2023). Using this methodology, the objectives of this study are: (1) To objectively identify VIAs in children during the week, both during school time and out-of-school time, and compare the daily frequency of VIAs according to participation in organized sports activities, (2) To calculate the prevalence of meeting the WHO’s recommendation to incorporate VIAs at least three days a week.

Materials and Methods

Results

A total of 33 schools agreed to participate in the present study, out of the 40 schools invited. A total of 22 groups of 3^rd grade primary school children were evaluated between October 2019 and March 2020. The remaining 11 groups of children were not evaluated due to the closure of schools caused by the COVID-19 pandemic. A total of 510 informed consents were delivered in the 22 evaluated schools (an average of 23.2 children per classroom). A total of 401 (78.6%) were correctly filled out and returned, of which, 385 children agreed to participate (75.5% of the total invited). Seven of the children authorized to participate were absent from class on the day the evaluation began and could not be evaluated, and in two evaluations, the data recorded in the accelerometer could not be extracted. No participant was excluded for being over 9 years old or having limitations for physical activity practice during the evaluation. Therefore, the sample that had data derived from the accelerometer evaluation was 376 children (73.7% of the total invited), of which, 353 children had at least four valid days, with at least one school day with a physical education class, one school day without a physical education class, and one weekend day, as well as, at least one segment Before 2:00 PM and another After 2:00 PM for each of the types of day studied.

Table 1 shows the descriptive results of the types of day, as well as the segments Before and After 2:00 PM for the analyzed sample.

Table 2 shows the descriptive results in the total of participants, and by sex. No statistically significant differences were found between boys and girls in anthropometric data or in the prevalence of overweight and obesity.

Table 3 shows the average duration of the day, awake time, and the segment Before and After 2:00 PM, as well as the physical activity performed at different intensities (including VPA performed within the VPA-Bouts) on the average weekly day. It also shows the average daily duration of the VPA-Bouts in the whole weekly day and in the out-of-school time, as well as the average declared duration of organized extracurricular sports activities. The average daily times of VPA in VPA-Bouts, VPA, MVPA, and MPA were significantly higher in boys than in girls. The average daily time of LPA was significantly higher in girls than in boys. In the out-of-school time, VPA-Bouts were identified with an average daily duration of 17.2 minutes (SD 25.6), and the average daily duration of extracurricular sports activities declared by questionnaire was 20.8 minutes (SD 18.5).

Table 4 shows the average percentage of different types of day and daily segments where at least one VPA-Bout was identified. The results are shown for all participants, as well as segmented by sex. Participants performed on average at least one VPA-Bout on 23.8% (SD 23.1) of the average weekly days. On school time with a physical education class, the average number of school time with a VPA-Bout was 28.6% (SD 36.0), while on school time without a physical education class it was 2.1% (SD 9.6). In extracurricular time, no significant differences were found between the segment of after school time with and without a physical education class (18.9% vs 17.6%; p = 0.417), while there were differences between the afternoons of school days and whole weekend days (17.8% vs 13.4%; p = 0.004). The school day with physical education class was the only type of day where a higher proportion of VPA-Bout was observed in the school time compared to out-of-school time (28.6% vs 18.9%; p < 0.001).

Table 5 shows the average percentage of days and daily segments with VPA-Bout in boys and girls according to their participation in organized extracurricular sports activities. In boys, significant differences were observed in all segments of out-of-school time between those who declared not to perform or perform less than three weekly hours of extracurricular organized sports activities and those who declared to perform at least three weekly hours (After school time with physical education class: 8.2% vs 43.4%, p < 0.001; After school time without physical education class: 15.2% vs 30.8%, p = 0.001; Weekend day: 9.0% vs 26%, p < 0.001), while in girls no differences were observed on weekend days (After school time with physical education class: 8.2% vs 18.8%, p = 0.006; After school time without physical education class: 6.7% vs 20.2%, p < 0.001; Weekend day: 8.0% vs 8.3%, p = 0.917). Therefore, in the total participants, a higher proportion of school afternoons with VPA-Bouts was observed among those children who declared to perform at least three hours of organized extracurricular sports activities (≥3 hours/week: 27.5%, <3 hours/week: 9.3%, p < 0.001). However, in the proportion of school times with VPA-Bouts, no significant differences were observed according to the declared weekly duration of extracurricular sports activities (≥3 hours/week: 14.0%, <3 hours/week: 12.7%, p = 0.477).

Table 6 shows the percentage of compliance with the WHO recommendation to “incorporate VIAs at least three days a week” evaluated using accelerometry. 23.8% of the children accumulated at least one VPA-Bout in at least three of seven average weekly days. The children who declared to perform at least three weekly hours compared to those who declared to perform less than three weekly hours of organized extracurricular sports activities, showed a significantly higher proportion of compliance with the WHO’s VIAs recommendation (≥3 hours/week: 35.1%; <3 hours/week: 12.7%; p < 0.001).

Discussion

This study shows the percentage of compliance with the WHO recommendation to “incorporate vigorous intensity activities (VIAs) at least three days a week” (World Health Organization (WHO), 2020), through a new method based on the processing of accelerometry data. With this method, the presence of physical education classes and extracurricular organized sports and physical activities, that are sufficiently active, has been identified. Participation in physical education classes and in extracurricular sports and physical activities contributed to the performance of VIAs, and thereby, to the compliance with the WHO recommendation.

A total of 23.8% of the evaluated children met the recommendation to “incorporate VIAs at least three days a week”. In contrast, 80.6% of this same population met the WHO recommendation to perform at least 60 minutes of average daily MVPA throughout the week (Benavente-Marín et al., 2024). Compliance with the MVPA recommendation shows a great variability among different studies, which can be explained by the true variability among populations, as well as by the use of different methodologies (Van Hecke et al., 2016). However, the differences found between compliance with the MVPA and the VIAs recommendation were observed under the same methodological conditions and in the same sample. This difference is mainly because the methods to operationalize the WHO recommendations on physical activity evaluate different physical activity patterns from each other.

In this sense, it could be understood that if the WHO incorporates two different recommendations on physical activity, it’s to promote different health-related physical activity patterns. VIAs can include a certain proportion of VPA, but they do not necessarily have to be composed entirely of VPA. In fact, physical activity sessions carried out by children and adolescents with a significant vigorous intensity component (for example, participating in a football match) stand out for having a variable proportion of physical activity at all intensity levels, but with a proportion of VPA greater than other activities that would not be considered vigorous sessions or activities. Therefore, the VIAs of the WHO recommendation and the VPA obtained through objective evaluation methods are not equivalent concepts.

The performance of VPA distributed throughout the day is beneficial for health, and its evaluation may be more interesting than that of daily MVPA (Martinez-Gomez et al., 2010; Gralla et al., 2016; Füssenich et al., 2016; Schwarzfischer et al., 2017; Larsen et al., 2018; García-Hermoso et al., 2021; Gammon et al., 2022; Benavente-Marín et al., 2024). However, daily VPA represents a pattern of physical activity performance different from the recommendation on VIAs and, in turn, similar to the performance of daily MVPA. For example, running for one or two minutes to avoid being late for class can contribute to the daily amount of VPA and MVPA, but it would not be enough to be considered as a physical activity session, as would participating in a football match for an hour. Therefore, the evaluation of VPA patterns concentrated in activity sessions is important for the study and differentiation of the two recommendations on physical activity published in the WHO Guidelines (World Health Organization (WHO), 2020).

Including different patterns of physical activity in habitual physical activity can improve cardiovascular health in children (Stone et al., 2009; Dorsey, Herrin & Krumholz, 2011; Jenkins et al., 2017; Chinapaw et al., 2018), highlighting the inclusion of VPA intervals or the distribution of physical activity in periods of at least 10 minutes (Stone et al., 2009; Chinapaw et al., 2018). In an intervention study conducted in children with overweight or obesity, of similar age and from the same region (Andalusia, Spain) as the participants in our study, it was possible to significantly reduce the cardiovascular risk of the participants by engaging in 3–5 weekly sessions of VIAs (Migueles et al., 2023). Therefore, replicating the VPA pattern recommended by the WHO through activities with a certain concentration of VPA is related to improvements in cardiovascular health.

Regarding the identification of VPA-Bouts (i.e., intervals of at least 60 minutes with at least 16.7% in boys and 12.5% in girls of VPA), a large difference was observed between school days with and without physical education class during the school time (28.6% vs 2.1%; p < 0.001). This difference is mainly, if not exclusively, due to the presence of physical education classes. However, the contribution of physical education classes to the physical activity levels could be conditioned by the methodology used by the teachers (Huertas-Delgado et al., 2021) or by the type of content (Molina-García et al., 2016). Even so, physical education classes contribute to the performance of more physical activity at all intensities, as well as to the compliance with the MVPA recommendation (Meyer et al., 2013; Chen, Kim & Gao, 2014; Mooses et al., 2017; Calahorro-Cañada et al., 2017; Ikeda et al., 2022; Benavente-Marín et al., 2024, 2023). And as is evident, they also contribute to the performance of VIAs and, therefore, to the compliance with the WHO recommendation to incorporate this type of activities into the weekly physical activity.

No significant differences were observed in the proportion of segments After 2:00 PM with VPA-Bouts between days with and without physical education class (18.9% vs 17.6%; p < 0.417), while on the weekend a lower proportion of VPA-Bouts was observed (After 2:00 PM in school days: 17.8%, weekend day: 13.4%; p = 0.004). In other words, the distribution of extracurricular sports and physical activities carried out during school days seems to be evenly distributed. However, on the weekend there seems to be a lower proportion of this type of activities.

Another notable result for the out-of-school time was the similarity between the average daily duration of declared extracurricular organized sports activities and the average daily duration of VPA-Bouts in the out-of-school time (20.8 vs 17.2 daily minutes). However, when observing the results segmented by sex, the difference found in girls stands out (20.2 vs 11.0 daily minutes). It seems that part of the extracurricular sports and physical activities in which girls participate did not reach the minimum intensity levels to identify the performance of VIAs through accelerometry. Indeed, other studies show that girls tend to prefer individual sports with artistic connotations, while boys often engage more intensity activities as team contact sports (Resaland et al., 2019; Peral-Suárez et al., 2020). This highlights the importance of studying VIAs through objective methods of physical activity assessment, especially in girls.

When segmenting the participants between those who declared less than three or at least three weekly hours of organized extracurricular sports activities, it was observed that participating in more hours of extracurricular activities did not significantly influence the identification of VPA-Bouts during the school time, while it did so out-of-school time. When segmenting by sex, in boys, significant differences were found in VPA-Bouts in all segments of extracurricular time (i.e., After 2:00 PM school days with and without physical education class, and weekends) between those who declared to perform at least three weekly hours of extracurricular sports activities and those who did not. However, in girls, no differences were found on weekends according to their participation in extracurricular sports activities. These results are in line with the preferences for participation in extracurricular sports activities of boys and girls (Resaland et al., 2019; Peral-Suárez et al., 2020). Team contact sports, which are more preferred by boys, usually have their competition periods on the weekend.

In girls, it was especially relevant to know the segmented results on school days with and without physical education class, and weekend days, since neither in the average weekly day nor in the average school day any differences were observed in the proportion of days with VPA-Bouts between Before and After 2:00 PM (Before vs After, weekly day: 8.5% vs 12.1%, p = 0.106; school day: 10.7% vs 12.7%, p = 0.405). This highlights the impact of the school day with physical education class on the performance of physical activity throughout the week (Meyer et al., 2013; Mooses et al., 2017), especially in girls. It seems that girls are more dependent than boys on organized and mandatory physical activities (i.e., physical education classes) to perform VIAs, as in extracurricular organized physical activities they seem to prefer those with a lower intensity component (Resaland et al., 2019; Peral-Suárez et al., 2020).

Most of the evidence that studies habitual physical activity segmented by sex or gender shows significant differences between boys and girls (Martinez-Gomez et al., 2010; Laguna et al., 2013; Katzmarzyk et al., 2015; Füssenich et al., 2016; Corder et al., 2016; Schwarzfischer et al., 2017; Ferrer-Santos et al., 2021). In this study, even though the proportion of VPA necessary to identify a VPA-Bout is lower in girls than in boys (i.e., 12.5% vs 16.7% of VPA, respectively; Benavente-Marín et al., 2023), it was generally observed that female participants achieved a lower proportion of VPA-Bouts in all types of days compared to male participants. This resulted in the girls who met the VIAs recommendation being half that of the boys who complied (15.3% vs 32.9%). These differences are accentuated among boys and girls who reported performing at least three weekly hours of organized extracurricular sports activities (Whiting et al., 2021). This situation underscores that boys and girls appear to differ, not only in their preferences for participation in sports and activities (Resaland et al., 2019; Peral-Suárez et al., 2020), but these differences are also observed in the performance of habitual physical activity (Benavente-Marín et al., 2024), as well as in participation in physical activity sessions with a prominent vigorous component (Molina-García et al., 2016).

It seems that boys participate in more intense physical activity sessions and more frequently than girls. However, it is possible that girls achieve similar health levels to boys with less volume and intensity of physical activity (Laguna et al., 2013; Katzmarzyk et al., 2015; Gralla et al., 2016; Schwarzfischer et al., 2017). Therefore, it is advisable to continue investigating the relationship between different patterns of physical activity, health, and gender.

The main strength of this study was the use of accelerometry as a tool for measuring children’s physical activity, avoiding biases inherent in other methods, such as self-reported questionnaires (Sirard & Pate, 2001; Migueles et al., 2017; Gao et al., 2021). The design of a protocol with the GENEActiv accelerometer placed on the wrist optimized adherence in our study (Fairclough et al., 2016). In addition, the GENEActiv accelerometer allowed us to obtain raw data without any prior filtering hidden under license, which can underestimate the results of high-intensity physical activity, especially in children (Rowlands et al., 2016; Arvidsson, Fridolfsson & Börjesson, 2019).

Despite the strengths of this study, it also has limitations. The main limitation was the reduction in the evaluated sample, compared to the planned one, due to the closure of schools and the home confinement caused by the COVID-19 pandemic. Even so, the evaluated sample exceeds the minimum size necessary to meet the objectives. However, participants could not be evaluated during the spring, with more daylight hours and better weather conditions for physical activity (Remmers et al., 2017; Turrisi et al., 2021). On the other hand, there are inherent limitations to the study of physical activity through accelerometry when comparing results from different studies, such as the accelerometer model, anatomical location, methodology for processing raw data, with emphasis on the duration of epochs, or the cut-off points selected to determine the intensity of physical activity (Baquet et al., 2007; Rowlands et al., 2016; Aadland et al., 2018; Arvidsson, Fridolfsson & Börjesson, 2019; Llorente-Cantarero et al., 2021). In addition, accelerometry does not adequately capture the intensity caused by physical activities such as cycling or resistance training with overload. Therefore, the combination of accelerometry with heart rate measurement can offer more accurate results (Van Camp, Batchelder & Irwin Helvey, 2022). Participants were restricted to children aged 8–9 from a specific region of Spain, so the findings may not be generalizable to younger children or older youth, as well as to children from other regions or countries. Finally, the observational nature of this cross-sectional study excludes any cause-and-effect association between physical activity or compliance with recommendations and sex, overweight, or performance in physical education classes or extracurricular activities.

Conclusions

One in every four children aged 8–9 in Andalusia (Spain) met the WHO recommendation to “incorporate vigorous intensity activities at least three days a week” evaluated by accelerometry. Compliance was higher on days with physical education classes, as well as among children who reported participating in organized extracurricular sports activities. Therefore, physical education classes and extracurricular organized sports activities contributed to improving compliance with the WHO’s recommendation on vigorous intensity activities.

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