The Effects of Resistance Exercise and Post-Exercise Meal Timing on the Iron Status in Iron-Deficient Rats

Resistance exercise increases heme synthesis in the bone marrow and the hemoglobin in iron-deficient rats. Post-exercise early nutrient provision facilitates skeletal muscle protein synthesis compared to late provision. However, the effects of post-exercise nutrition timing on hemoglobin synthesis are unclear. The current study investigated the effect of post-exercise meal timing on the activity of the key enzyme involved in hemoglobin synthesis, delta-aminolevulinic acid dehydratase (ALAD), in the bone marrow and examined the hemoglobin concentration in iron-deficient rats. Male 4-week-old Sprague-Dawley rats were fed an iron-deficient diet containing 12 mg iron/kg and performed climbing exercise (5 min x 6 sets/day, 3 days/week) for 3 weeks. The rats were divided into a group fed a post-exercise meal early after exercise (E) or a group fed the meal 4 h after exercise (L). A single bout of exercise performed after the 3-week training period increased the bone marrow ALAD activity, plasma iron concentration, and transferrin saturation. Although the plasma iron concentration and transferrin saturation were lower in the E group than the L group after a single bout of exercise, the basal hematocrit, hemoglobin, and TIBC after 3 weeks did not differ between the groups. Therefore, resistance exercise increases the bone marrow ALAD activity, while the post-exercise meal timing has no effect on the hemoglobin concentration in iron-deficient rats.