Krafft 2014

Methods	Study design: Randomised controlled trial (balanced by race, sex, and school to avoid imbalances on factors linked with differences in achievement) Unit of randomisation: Child Intervention duration: 8 months (average number of days offered 138 ± 9) Follow‐up: Immediately post‐intervention Unit of analysis: Child Setting: Georgia, USA Exclusion criteria: Any medical condition that would limit physical activity or affect study results (including neurological or psychiatric disorders) Classification of weight status: CDC growth charts for overweight and obesity Start date: May 2008 End date: April 2014
Participants	N (randomised): 175 N (analyses): No details reported for relevant outcomes Age range: 8 ‐ 11 years, mean age: Intervention 9.7 ± 0.8 years; control 9.9 ± 0.9 years Sex: Intervention 71% female; control 58% female Ethnicity: 84% African American, 16% white Reason for attrition: Not reported Attrition rates: Not reported
Interventions	Comparison: Aerobic group exercise versus attention control "Both groups were offered an after‐school programme every school day. All participants were transported by bus daily after school to the Georgia Prevention Center where they spent half an hour on supervised homework time and were provided with a snack. Both groups could earn points that were redeemed for small prizes weekly for performing desired behaviours. The reward schedule was periodically calibrated to keep the rewards offered to the groups similar." Intervention: "The aerobic exercise group engaged in instructor‐led aerobic activities (e.g. tag and jump rope) for 40 minutes a day. They wore heart‐rate monitors every day [...] with which they could monitor their own performance and from which data were collected daily. Points in the exercise group were earned for an average daily heart rate above 150 beats a minute, with more points for higher average heart rates." Attention control: Participants "engaged in instructor‐led sedentary activities (e.g. art and board games). Points in the control group were earned for participation and good behaviour."
Outcomes	Outcome 1: Cognitive function: The CAS was administered to assess composite executive function (Planning scale); attention (Attention scale), non‐verbal memory (Successive processing scale), and visuo‐spatial abilities (Simultaneous processing scale) Outcome 2: Obesity indices: Body fat was measured with a dual‐energy X‐ray absorptiometry (DXA) scan using a Hologic Discovery W (Hologic, Bedford, MA)
Notes	We contacted the authors to obtain additional study details. We were not able to obtain details of outcome data for inclusion in the meta‐analysis, or additional study characteristics. A manuscript with relevant data is currently 'under review'. We did extract additional details from Bustamante 2016. Funding sources: National Institutes of Health (R01 HL87923) and the National Science Foundation Graduate Research Fellowship Program.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization (balanced by race, sex, and school to avoid imbalances on factors linked with differences in achievement) was performed by the study statistician and concealed until after baseline testing was completed, at which point the study coordinator informed the families."
Allocation concealment (selection bias)	Low risk	Quote: "Randomization (balanced by race, sex, and school to avoid imbalances on factors linked with differences in achievement) was performed by the study statistician and concealed until after baseline testing was completed, at which point the study coordinator informed the families."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote:"The attention control group engaged in instructor‐led sedentary activities (e.g., art and board games)." Judgement comment: There is an attempt at attention control. Blinding to this kind of intervention is not possible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: No details regarding the blinding of outcome assessors reported. Details could not be obtained from study authors
Incomplete outcome data (attrition bias) All outcomes	High risk	Judgement comment: 11/54 drop‐outs polarised to the control condition: 1 vs 4 after baseline. We could not obtain information on the reasons for attrition and whether the authors dealt with missing data
Selective reporting (reporting bias)	Unclear risk	Judgement comment: No reference to a published study protocol or trial register made. However, the authors mention that this study builds on the study by Davis 2011b which is included in this review. The cognitive outcomes variables are similar in this study compared to Davis 2011b
Comparability of baseline groups	Low risk	Judgement comment: Random sequence adequately generated and allocation concealed
Cross‐contamination	Unclear risk	Quote: "The groups differed in that they participated in either an aerobic exercise or an attention control program. The aerobic exercise group engaged in instructor‐led aerobic activities (e.g., tag and jump rope) for 40 min per day." Judgement comment: Risk of cross‐contamination was low due to the nature of the intervention group: closed group‐exercise sessions. However, no details were reported on the extent to which the comparison group adhered to the 'sedentary activities' condition throughout the study duration
Other bias	Unclear risk	Judgement comment: Insufficient study details reported