Association between physical fitness and semen quality: a cross-sectional study in a Spanish male cohort

Do semen quality parameters differ between 'high' and 'low' levels of physical fitness in a cohort of Spanish men?

Semen samples donated by 324 Spanish men without known reproductive disorders were analysed to determine sperm count, concentration and progressive motility. Overall fitness, cardiorespiratory fitness and muscular strength were self-reported using the International Fitness Scale. Additionally, muscular strength was assessed objectively using a handgrip dynamometer. Analyses of covariance and adjusted linear regression analyses were performed to explore the association between the components of physical fitness and semen quality parameters.

Men with higher self-reported cardiorespiratory fitness and muscular strength presented higher sperm counts compared with men with lower values [adjusted raw mean difference 44.315 × 10⁶ (95% CI 7.699-80.931) spermatozoa/ejaculate and 42.766 × 10⁶ (95% CI 6.215-79.316) spermatozoa/ejaculate; adjusted mean Z-score difference 0.232 (95% CI 0.014-0.449) SDs and 0.236 (95% CI 0.019-0.453) SDs; P = 0.037 and 0.033, respectively]. Objectively measured handgrip muscular strength was not associated with any semen quality parameter.

This cross-sectional study suggests that self-reported cardiorespiratory fitness and muscular strength are positively associated with semen quality parameters, while objectively measured handgrip strength shows no association. These results may provide insight into modifiable lifestyle factors potentially related to semen quality, and help guide future randomized controlled trials to clarify causal pathways.