One hundred twenty sedentary premenopausal women with osteoporosis were randomized to receive either high-intensity interval training plus vitamin D supplementation (n=30), HIIT alone (n=30), vitamin D alone (n=30), or no intervention (control group; n=30). The primary outcome of interest was bone mineral density (BMD) of the hip and lumbar spine. Secondary outcomes included serum levels of 25(OH)D, osteocalcin, total calcium, and bone-specific alkaline phosphatase (s-BAP). Outcomes were assessed at baseline and after 16 weeks. Overall, the results of the study revealed that the HIIT + vitamin D group had significantly greater improvements in BMD at all measured sites and in biochemical markers than the other groups. These findings suggest that a combined approach of HIIT and vitamin D is more effective than either intervention alone in improving bone health in women with osteoporosis.