Abstract: BACKGROUND: Resistance training and weight-bearing exercise are recommended modes for patients with osteoporosis to improve bone health. High-intensity interval training is a high-impact weight-bearing exercise with obvious time-efficient characteristics; however, little attention has been paid to its impact on bones.
OBJECTIVE: To observe the effect of high-intensity interval training on the bone health of ovariectomized rat models.
METHODS: Thirty-six female Sprague-Dawley rats were randomly divided into sham group, model group and model exercise group (n=12 per group). Bilateral ovariectomy was used to prepare an osteoporosis rat model in the latter two groups. Six weeks after modeling, the model exercise group was subjected to a high-intensity interval training on an electric treadmill at 90% peak running speed for 2 minutes and 50% peak running speed for 1 minute as one session, a total of nine sessions, 3 days per week, for 6 weeks. Rats in the sham and model groups were raised quietly in the mouse cage during the same period. The relevant indexes were tested 48-72 hours after the final training.
RESULTS AND CONCLUSION: Compared with the sham group, bone mineral density, maximal load, stiffness, elasticity, trabecular volume fraction, and trabecular number decreased (P < 0.05), while trabecular separation increased (P < 0.05); the level of irisin in the serum, gastrocnemius and femur decreased (P < 0.05); the expression of peroxisome proliferator-activated receptor γ coactivator-1α protein and fibronectin type III domain-containing protein 5 mRNA and protein in the gastrocnemius muscle decreased (P < 0.05); the expression of type I collagen, Osterix, and Runx2 mRNA in the femur decreased (P < 0.05); and the expression of anti-tartrate acid phosphatase, receptor activator of nuclear factor κB ligand, and osteoclast-associated receptor mRNA increased in the model group (P < 0.05). Compared with the model group, bone mineral density, fracture load, maximal load, stiffness, elasticity, average trabecular thickness, and trabecular number increased (P < 0.05), and trabecular separation decreased (P < 0.05); the level of irisin in the serum, gastrocnemius and femur increased (P < 0.05); the expression of peroxisome proliferator-activated receptor γ coactivator-1α protein and fibronectin type III domain-containing protein 5 mRNA and protein in gastrocnemius increased (P < 0.05); the expression of type I collagen, Osterix, and Runx2 mRNA in the femur increased (P < 0.05); and the expression of anti-tartrate acid phosphatase, receptor activator of nuclear factor κB ligand, and osteoclast-associated receptor mRNA decreased in the model exercise group (P < 0.05). To conclude, short-term high-intensity interval training may improve bone health of ovariectomized rats through up-regulating the irisin level.

Key words: high-intensity interval training, postmenopausal osteoporosis, skeletal muscle, irisin, bone health