Hematological Predictors of Endurance Performance in Ethiopian Distance Runners Measured at High Altitude

Abstract

This study investigated associations between hematological parameters and endurance performance indicators (VO₂max, running economy, and IAAF scores) in elite Ethiopian distance runners of both sexes. Fifty-two elite Ethiopian distance runners (29 males: weight 58.6 ± 5.8 kg, height 1.72 ± 0.07 m, BMI 19.7 ± 1.8 kg·m⁻², and 23 females: weight 49.49 ± 5.5 kg, height 1.59 ± 0.05 m, BMI 19.5 ± 1.8 kg·m⁻²) residing at ~2,400 m underwent hematological profiling, including hemoglobin (HGB), mean corpuscular volume (MCV), platelet count (PLT), mean platelet volume (MPV), lymphocytes (LYM#), neutrophils (NEU#), and red cell distribution width (RDW-CV).  Endurance performance was assessed using VO₂max, RE at 14 and 16 km·h⁻¹, and IAAF scores. We employed a multivariate multiple regression to simultaneously evaluate the associations between hematological parameters and multiple endurance performance indicators (VO₂max, RE14, RE16, and IAAF scores). The analyses revealed that higher HGB was significantly associated with greater VO₂max and improved RE at 16 kmh⁻¹. MPV and PLT showed positive relationships with RE at 14 and 16 kmh⁻¹. RDW-CV was positively associated with VO₂max but inversely related to IAAF performance scores. Sex-specific analyses revealed that HGB predicted VO₂max more strongly in females, while RDW-CV and platelet indices were more relevant to performance in males. Baseline lymphocyte and neutrophil counts showed no significant relationships with endurance outcomes. Hemoglobin remains a key predictor of aerobic capacity in altitude-adapted elite Ethiopian distance runners.  Novel associations of RDW-CV and platelet indices with VO₂max and running economy, most evident in males, suggest additional hematological pathways that may contribute to endurance performance. Immune cell counts demonstrated limited predictive value. These findings support the integration of hematological profiling into athlete monitoring and provide new insights into sex-specific physiological determinants of elite endurance performance.