Transgenerational Effects of Resistance Exercise During Pregnancy: Skeletal Muscle Fiber Hypertrophy in F1 Offspring

Maternal lifestyle during pregnancy can program offspring phenotype, potentially through epigenetic mechanisms. Although the benefits of maternal aerobic exercise are increasingly studied, the impact of maternal resistance exercise on offspring skeletal muscle morphometry remains underexplored. This study aimed to investigate the effects of resistance exercise performed by mice during pregnancy on the characteristics of skeletal muscle fibers in their first-generation (F1) progeny. C57BL/6 mice were divided into Sedentary (SED) and Exercise (EXER) groups after pregnancy confirmation. The EXER group performed resistance exercise (vertical ladder climbing with additional load) three times a week during pregnancy. The SED group remained inactive. At 12 weeks of age, skeletal muscles (Biceps brachii, Gastrocnemius, Soleus) were collected from F1 progeny females (SED-F1, n = 3; EXER-F1, n = 7). Cross-sectional area, perimeter, and number of muscle fibers were quantified by histological analysis using ImageJ software. Statistical comparisons between groups were performed using independent t-tests. Progeny of exercised mothers (EXER-F1) showed significantly larger mean area and perimeter of muscle fibers in Biceps brachii (p < 0.001 for both) and Soleus (p = 0.044 and p = 0.004, respectively) muscles, compared to progeny of sedentary mothers (SED-F1). In the Gastrocnemius muscle, the mean fiber perimeter was significantly larger in the EXER-F1 group (p = 0.004), while the area showed a tendency for increase (p = 0.079). No significant differences were observed in the number of fibers per analyzed area between groups in any of the studied muscles (p > 0.05). Maternal resistance exercise during pregnancy significantly increases the size of skeletal muscle fibers in F1 progeny, suggesting a positive programming effect on muscle development. These findings highlight the potential benefits of maternal resistance training for offspring muscle health, possibly mediated by epigenetic inheritance mechanisms.