Paternal physical inactivity alters offspring sex ratio and is associated with heritable impairments in reproductive success in rats

Paternal lifestyle factors are increasingly recognized as determinants of offspring health, yet the effects of physical inactivity on reproduction remain unclear. Here, we demonstrated that paternal physical inactivity caused a bias in offspring sex ratio and reduced fertility across generations in rats. Male rats subjected to 8 weeks of restricted activity produced offspring with a female-biased sex ratio (female:male = 39:16; p = 0.011; odds ratio = 2.84) compared with controls (24:28). Sperm motility was markedly reduced in inactive fathers (p < 0.001 vs. control) but was fully restored by voluntary wheel running (p < 0.05 vs. inactive), indicating reversibility of this functional impairment. Cross-mating of first-filial-generation (F1) rats of inactive paternal origin revealed that females derived from inactive fathers exhibited lower pregnancy rates and smaller litter size, whereas F1 males displayed normal fertility. Remarkably, intercrosses between F1 males and females of i..., , # Paternal physical inactivity alters offspring sex ratio and is associated with heritable impairments in reproductive success in rats

Dataset DOI: [10.5061/dryad.ttdz08mbb](https://doi.org/10.5061/dryad.ttdz08mbb)

## Description of the data and file structure

Raw data supporting Yoshihara et al., Biology Letters, RSBL-2025-0725

### Files and variables

#### File: Supplementary_Table_1_F0_mating.xlsx

**Description:** Each row represents one breeding pair. Data include sire and dam IDs, group allocation (Control or Inactive), cohabitation period, pregnancy confirmation, litter size, sex ratio (female:male), and fraction of male pups (male/total). Statistical analyses are described in the Materials and Methods section.

##### Variables

* Group, No., Sire ID, Sire group, Dam ID, Cohabitation, Pregnancy confirmation, Litter size, Weaning survival, Female : Male, Fraction male pups

#### File: Supplementary_Table_2_F1_cross.xlsx

**Description:** Each row represents one mating pair. Co...,