Five-hundred and seventy papers were identified, screened and assessed for their eligibility (Fig. 1) and 29 studies met the inclusion criteria. Of these, 20 assessed overall after-school sedentary time and nine assessed after-school sedentary behaviors. Among the studies assessing overall sedentary time, 16 included children (sample aged ≤12 years) [11–13, 21–33], three included adolescents (sample >12-18 years) [34–36], and one included both age groups [37]. Among the nine studies assessing sedentary behaviors, eight included children [38–45], and one included adolescents [46]. The eligible papers were published between 1996 and October 2015 and were analysed in November 2015. Study samples ranged from 20 to 2053 (mean 578) and over half of the studies (n = 15) had a sample of fewer than 500 participants. Study characteristics can be found in Additional file 2: Table S2.
Country of study
Thirteen of the included studies were from the United States [22–24, 27, 29, 33, 35, 38, 39, 41, 42, 44, 45], with Australia [11, 12, 25, 43], Canada [30, 31] and the United Kingdom [13, 21, 28, 32, 37, 46] also having multiple studies. One study was identified from each of New Zealand [26], Ireland [34] and Portugal [36] and one study had a combined sample from Bulgaria, Taiwan and the United States [40].
Child’s after school location
Among the 20 studies assessing after-school sedentary time, three assessed behavior while the children were at after-school care [22, 23, 29]. No studies examined adolescents’ behaviors while at after-school care. The remaining 17 studies either did not report where the children were after school or noted that they were at a variety of places. These studies were grouped together as at ‘other locations’ [11–13, 21, 24–28, 30–37]. No studies investigating sedentary behaviors assessed behaviors when children were at after-school care, therefore all were considered ‘other locations’ (n = 9) [26, 38–46].
After-school sedentary time
Measurement tools
The majority of studies measured sedentary time using the ActiGraph accelerometer (n = 15); however, a variety of cut points were used to indicate sedentary time including <50 counts per minute (cpm) [36], <100 cpm [11–13, 23, 26, 28, 29, 32, 33, 37], < 300 cpm [30, 31], < 800 cpm [35], and <1.5METS [24]. Of the remaining five studies, one used the Actical accelerometer with a sedentary cut point of <100 cpm [25], two used direct observation (modified version of BEACHES [Behaviours of Eating and Activity for Child Health] [27], and SOFIT [System for Observing Fitness Instruction Time] [22]), one used the RT3 tri-axial accelerometer with a cutpoint of <288 cpm [21] and one used the activPAL where sedentary was defined as sitting/lying down [34].
Percentage of after-school sedentary time by sex
Figure 2 shows the percentage of time children and adolescents spend sedentary during the after-school period by location, measure and cut point. On average, children spent 49.5 % (range 16.1 - 88.9 %) and adolescents spent 56.6 % (range 27.7 - 88.9 %) of the after-school period sedentary.
Percentage of after-school sedentary time by location
As shown in Fig. 2, results varied depending on the child’s location. Children attending after-school care spent on average 41.1 % (range 16.1-56.1 %) [22, 23, 29, 33], and children at other locations spent on average 50.6 % (range 27.8 %-73.5 %) [11–13, 21, 24–28, 30–33, 37] of the after-school period sedentary.
Percentage of after-school sedentary time by cut point
Results also varied when different cut points were used. Findings from accelerometer studies that examined sedentary time using 100 cpm showed that children spent on average 42.3 % of the after-school period sedentary [11–13, 23, 25, 26, 28, 29, 32, 33, 37], whereas the average time children spent sedentary after school when using <300 cpm as the cut point [30, 31] was 71.2 % of the period. Among adolescents, the studies that used <50 cpm [36] showed that on average adolescents spent 26.9 % of the period sedentary and in comparison the studies that used <800 cpm [35] showed adolescents spent on average 82 % of the after-school period sedentary.
After-school sedentary behaviors
Measurement tools
A variety of subjective measurement tools were used to assess a range of after-school sedentary behaviors. Five studies assessed after-school TV viewing [38, 40, 43, 45, 46]. Seven studies reported screen-based sedentary behaviors and these were separated into two groups depending on whether or not their measure included TV viewing: four studies measured screen-based sedentary behaviors including TV viewing [39, 41, 42, 44] and three studies measured screen-based sedentary behaviors excluding TV viewing [40, 43, 46]. One study measured social sedentary behaviors [46], three measured homework/academics [43, 45, 46], three measured non-screen based sedentary behavior including homework/academics [41, 42, 44], one measured non-screen based sedentary behavior excuding homework/academics [43], and two measured motorised transport. [43, 46] The majority of studies used child self-report surveys asking children to report their after-school “free time” behaviors; [46] or previous day recall in 30-min blocks [41], one-hour blocks [40], in child-specific blocks (e.g., before/after child specified meal/snack) [43], or in 15 min intervals (via telephone interview) [42, 44, 45]. One study used parental proxy-report of behaviors in 15-min intervals [39] and another used observation to capture the time children spent watching TV [38].
Percentage of time spent in specific after-school sedentary behaviors
Figure 3 shows the percentage of the after-school period spent in specific sedentary behaviors. As only one study reported adolescents’ after-school sedentary behaviors [46], these findings are presented alongside the children’s after-school sedentary behavior studies [38–45]. Seven findings from five studies [38, 40, 43, 45, 46] reported the percentage of the after-school period spent watching TV. TV viewing averaged 20.4 % (range 12.6 - 31 %) of the after-school period which was the highest percentage for any sedentary behavior (Fig. 3). The second largest percentage of the after-school period was spent performing non-screen based sedentary behaviors including homework (mean 20.3 %, range 10 - 29.2 %) [41, 42, 44]. This was followed by screen-based sedentary behaviors (including TV viewing;18.2 %, range 8.5 - 25.3 %) [39, 41, 42, 44], homework/academics (12.9 %, range 6 - 15.5 %) [43, 45, 46], motorised transport (12.1 %, range 9.4 - 16.6 %) [43, 46], social sedentary behaviors (adolescent boys 7.9 %, girls 10.1 %) [46], screen-based sedentary behaviors (excluding TV viewing; 5.5 %, range 1.4 - 8.3 %) [40, 43, 46], and non-screen based sedentary behaviors excluding homework/academics, such as reading, sitting quietly, writing, playing cards/puzzles/board games (3.7 %) [43].