The aim of this study was to evaluate lung histology and the levels of HIF-1a protein in response to the reduction in training volume for 14 and 21 days with Nigella sativa (NS) supplementation. 60 three-week-old male Wistar rats (68 ± 9 g) were divided into 6 groups after 6 weeks of incremental interval training (IIT); IIT control and IIT groups, 2 groups of 14-day taper (with and without NS) and, similarly, 2 groups of 21-day taper. After 6 weeks, NS seed ethanol extract was fed daily by gavages to NS groups at 500 mg/kg. Finally, animals were euthanized and their lungs were removed, weighed and fixed in 10 % formalin. By routine and standard paraffin embedding, lung samples were sectioned in 5 lm and stained with H&E and studied histologically. The level of HIF-1a was measured by ELISA kit. The results showed that the administration of NS and 21-day taper in the IIT exposed rats caused significant difference in lung weight and lung HIF-1a (p = 0.001, p = 0.001). But the interaction between groups and taper periods was not confirmed (p = 0.530). Lung histology in 21-day taper with NS was better than the other groups. The results showed that after IIT, 21-day reduction in training volume and the use of new strategies such as NS supplementation in this period can reduce HIF-1a higher amounts in the lungs, which may probably be due to the anti-inflammatory effects of the NS supplement. These agents can improve respiratory capacity for competition or severe activity after taper period.
