Background: Many studies have shown a high prevalence of vitamin D deficiency in different communities. Due to multiple roles of vitamin D in the body, this study was aimed to determine the effect of oral vitamin D3 on ventilatory threshold-1 in a condition of vitamin D deficiency.Materials and Methods: Recent study performed on 25 healthy young adults with the serum levels of 25 Hydroxyvitamin D3 lower than 20 ng/ml, had referred to the sports medicine clinic of Taleghani Hospital of Tehran, in a one-year period (2016-2017). After primary evaluation, baseline ventilatory threshold-1 were determined by cardiopulmonary exercise testing (CPET). Then persons were treated with 50,000 IU/week of oral vitamin D3 for 8 weeks, and one week after the completion of treatment, ventilator threshold-1 was measured again, similar to the beginning conditions of the study, and its changes were studied.Results: The mean baseline ventilatory threshold-1 of participants before any intervention was 22.46 ± 6.45 (ml/kg/min), and after 8 weeks of treatment by 50000 IU/week of oral vitamin D3, increased to 26.79 ± 5.33 (ml/kg/min) at the end of study, which there was a statistically significant increase in ventilatory threshold-1 (p<0.001).Conclusion: Recent study showed that proper treatment of the vitamin D deficiency, improves ventilatory threshold-1 in healthy young adults
