Abstract
OBJECTIVES: Physical inactivity is an important health concern worldwide. We examined the effects of an exercise intervention on children’s academic achievement, cognitive function, physical fitness, and other health-related outcomes. METHODS: We conducted a population-based cluster RCT among 2301 fourth‑grade students in Ulaanbaatar, Mongolia. Schools were randomized to intervention or control using stratified block randomization. The intervention comprised twice‑weekly HIIT sessions over 10 weeks, replacing the initial segment of physical education classes. The primary outcome was national examination scores in mathematics and Mongolian language. A linear mixed‑effects model compared pre‑ and post‑intervention scores. RESULTS: Of 2301 students, 2101 completed the trial. Intervention groups showed greater improvements in total examination scores than controls (urban: +8.36 points, 95% CI: 6.06–10.66; mixed: +9.55 points, 95% CI: 6.58–12.51). No injuries were reported. CONCLUSIONS: A school‑based HIIT program significantly improved academic achievement.
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ERCT Criteria Breakdown
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Level 1 Criteria
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C
Class-level RCT
- Randomization was conducted at the school (cluster) level, satisfying the class‑level RCT criterion.
- “Stratified block randomization was used to randomly allocate the 10 cluster schools into the intervention and control groups.” (p. 2)
Relevant Quotes:
1) “Stratified block randomization was used to randomly allocate the 10 cluster schools into the intervention and control groups.” (p. 2)
Detailed Analysis:
The paper describes randomization at the school (cluster) level, which exceeds the class‑level requirement by preventing cross‑class contamination.
Final sentence explaining if criterion C is met because school‑level randomization satisfies or exceeds class‑level RCT.
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E
Exam-based Assessment
- The study measured outcomes using national examination scores, a standardized assessment.
- “The primary outcome was academic achievement, assessed by the participants’ total mathematics and Mongolian language scores on the national examination.” (p. 1)
Relevant Quotes:
1) “The primary outcome was academic achievement, assessed by the participants’ total mathematics and Mongolian language scores on the national examination.” (p. 1)
Detailed Analysis:
The study uses national examination scores—a standardized, widely recognized assessment—rather than a custom test, fulfilling the Exam‑based Assessment criterion.
Final sentence explaining if criterion E is met because a national standardized exam was used.
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T
Term Duration
- Intervention and follow‑up lasted ten months, exceeding a full academic term.
- “This population-based cluster RCT was conducted ... from February to December 2018.” (p. 2)
Relevant Quotes:
1) “This population-based cluster RCT was conducted ... from February to December 2018.” (p. 2)
Detailed Analysis:
The intervention and follow‑up spanned roughly ten months—longer than a typical academic term (~3–4 months)—and outcomes were measured at the end of that period, satisfying Term Duration.
Final sentence explaining if criterion T is met because follow‑up lasted more than one term.
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D
Documented Control Group
- The control group’s size and baseline characteristics are clearly documented in the methods and tables.
- “Of 2301 students, 2101 ... were included in the primary and secondary outcome analyses (intervention: 1069; control: 1032).” (p. 5)
Relevant Quotes:
1) “Of 2301 students, 2101 ... were included in the primary and secondary outcome analyses (intervention: 1069; control: 1032).” (p. 5)
2) Tables 1 and 2 detail control‑group demographics and baseline scores.
Detailed Analysis:
The control group’s composition, size, and baseline characteristics are clearly documented, fulfilling the requirement for a well‑documented control group.
Final sentence explaining if criterion D is met because the control group is fully described.
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Level 2 Criteria
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S
School-level RCT
- Entire schools were randomized, satisfying the school‑level RCT criterion.
- “Stratified block randomization was used to randomly allocate the 10 cluster schools into the intervention and control groups.” (p. 2)
Relevant Quotes:
1) “Stratified block randomization was used to randomly allocate the 10 cluster schools into the intervention and control groups.” (p. 2)
Detailed Analysis:
Entire schools, not individual classes or students, were randomized to conditions, satisfying the School‑level RCT criterion.
Final sentence explaining if criterion S is met because randomization was at the school level.
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I
Independent Conduct
- The same team that designed the intervention conducted and analyzed the trial without independent oversight.
- “Dr Takehara conceptualized and designed the study, conducted data collection, established logistics, drafted the initial manuscript, and reviewed and revised the manuscript.” (p. 1)
Relevant Quotes:
1) “Dr Takehara conceptualized and designed the study, conducted data collection, established logistics, drafted the initial manuscript, and reviewed and revised the manuscript.” (p. 1)
Detailed Analysis:
The intervention developers also conducted and analyzed the trial with no external evaluation, failing the Independent Conduct criterion.
Final sentence explaining if criterion I is not met because no independent evaluator was involved.
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Y
Year Duration
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B
Balanced Resources
- HIIT was integrated into standard PE time without additional class time or resources, keeping groups balanced.
- “For the rest of the class, participants underwent the normal physical education class. Control group participants received the usual physical education class.” (p. 3)
Relevant Quotes:
1) “The intervention group received a 3‑minute HIIT program ... implemented twice weekly over 10 weeks ... For the rest of the class, participants underwent the normal physical education class.” (pp. 1–3)
2) “Control group participants received the usual physical education class.” (p. 3)
Detailed Analysis:
The HIIT sessions replaced an equal duration of standard PE time, so both groups had equivalent class time. Although the intervention was delivered by additional instructors (MNIPE teachers and RAs), this was integral to the program and not an extra academic resource. Therefore, Balanced Resources is satisfied.
Final sentence explaining if criterion B is met because instructional time and resources were balanced.
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Level 3 Criteria
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R
Reproduced Results
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A
All Exams
- Outcomes were measured only in mathematics and Mongolian language, not all main subjects.
- “The primary outcome was academic achievement, assessed by the participants’ total mathematics and Mongolian language scores on the national examination.” (p. 1)
Relevant Quotes:
1) “The primary outcome was academic achievement, assessed by the participants’ total mathematics and Mongolian language scores on the national examination.” (p. 1)
Detailed Analysis:
Only two subjects (mathematics and language arts) were tested, not all core subjects, failing the All‑subject Exams criterion.
Final sentence explaining if criterion A is not met because only two subjects were assessed.
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G
Graduation Tracking
- Participants were not followed until graduation; follow-up ended at study completion.
- “This population-based cluster RCT was conducted ... from February to December 2018.” (p. 2)
Relevant Quotes:
1) “This population-based cluster RCT was conducted ... from February to December 2018.” (p. 2)
Detailed Analysis:
Follow-up ended at study completion in December 2018; participants were not tracked through to graduation, so Graduation Tracking is not met.
Final sentence explaining if criterion G is not met because there was no follow-up until graduation.
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P
Pre-Registered Protocol
- Trial registration was completed before the study began (registered 1st February 2018).
- “This trial has been registered with UMIN Clinical Trials Registry (identifier UMIN000031062).” (p. 9)
Relevant Quotes:
1) “This trial has been registered with UMIN Clinical Trials Registry (identifier UMIN000031062).” (p. 9) 2) “Trial registration: UMIN: UMIN000031062. Registered on 1st February 2018.” (UMIN-CTR)
Detailed Analysis:
Registration is documented, and trial registry records confirm it was registered on 1st February 2018 (before data collection), so the Pre‑registered Protocol criterion is met.
Final sentence explaining if criterion P is met because registration occurred before data collection started.
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