Background: Resting heart rate (RHR) is a simple, low-cost physiological marker that may reflect cardiorespiratory fitness. Evidence in adults suggests an inverse association between RHR and aerobic capacity (VO₂max), but data in early adolescents are limited. The purpose of this study was to measure the resting heart rate and VO₂max of school students, analyse their correlation, and assess whether RHR can predict VO₂max.

Methods: In a school-based cross-sectional study, 84 students (mean age = 12.48 ± 1.05 years) completed standardized RHR assessment (radial pulse for 60 seconds) and the 20-m shuttle-run test (Léger protocol) to estimate VO₂max. Normality was checked using Shapiro-Wilk. Spearman’s rank correlation (primary analysis) tested the association between RHR and VO₂max. Simple linear regression examined whether RHR predicted VO₂max.

Results: RHR and VO₂max were significantly and inversely correlated (Spearman’s ρ = −0.384, p < .001). In linear regression, RHR was a significant predictor of VO₂max, explaining a modest proportion of variance (≈15%).

Conclusions: Among early adolescents, lower resting heart rate was associated with higher VO₂max, supporting the potential utility of RHR as a quick screening indicator of aerobic fitness in school settings. RHR should complement, not replace, field fitness tests. Longitudinal and intervention studies are warranted to establish predictive thresholds.