The Relationship Between Hemoglobin Levels in Blood and VO₂max in Indonesian Athletes: A Meta-Analysis Study

VO₂max plays a vital role in supporting athletes' endurance during training and competition. However, research on VO₂max in Indonesian athletes continues to yield mixed results. Therefore, this study aims to examine the contribution of hemoglobin levels to VO₂max in Indonesian athletes using a meta-analysis. This study uses a meta-analysis approach following the PRISMA guidelines, with a literature search conducted using Harzing's Publish or Perish application on Google Scholar. The main keywords used were "hemoglobin level" AND "VO₂max", combined with Boolean operators. Data analysis included heterogeneity tests, effect size calculations, subgroup analyses, and publication bias tests, all conducted using JASP. The results of a meta-analysis of 17 studies showed a significant positive relationship between hemoglobin levels and VO₂max in athletes in Indonesia (effect size = .724; 95% CI: 0.499–0.949; p < .001), with a high level of heterogeneity (Q = 79.29; p < .05; I² = 82.4%). Subgroup analysis showed a significant effect in team sports (effect size = .772; p < .001), whereas no significant effect was observed in individual or mixed sports. The test for differences between groups of sport types also showed no significant difference (Qₘ(2) = .78; p = .677). In addition, Egger's test showed no indication of publication bias (p = .59). Overall, these findings confirm that hemoglobin levels contribute significantly to athletes' VO₂max. However, the magnitude of the effect may vary between sports, thereby confirming the physiological role of hemoglobin in supporting athletes' endurance capacity.