Our results suggest that preliminary interval-training improved BMD and osteocytes lacunar occupancy in subchondral bone. Our interval-training did not prevent MIA-induced cartilage degeneration.

No abstract

To delay age-related bone loss, physical activity is recommended during growth. However, it is unknown whether interval training is more efficient than continuous training to increase bone mass both quickly and to a greater extent. The aim of this study was to compare the effects of a 10-week interval training regime with a 14-week continuous training regime on bone mineral density (BMD). Forty-four male Wistar rats (8 weeks old) were separated into four groups: control for 10 weeks (C10), control for 14 weeks (C14), moderate interval training for 10 weeks (IT) and moderate continuous training for 14 weeks (CT). Rats were exercised 1 h/day, 5 day/week. Body composition and BMD of the whole body and femur respectively were assessed by dual-energy X-ray absorptiometry at baseline and after training to determine raw gain and weight-normalized BMD gain. Both trained groups had lower weight and fat mass gain when compared to controls. Both trained groups gained more BMD compared to controls when normalized to body weight. Using a 30% shorter training period, the IT group showed more than 20% higher whole body and femur BMD gains compared to the CT. Our data suggest that moderate IT was able to produce faster bone adaptations than moderate CT.

The effects of treadmill interval training (IT) and free fall exercise were evaluated on bone parameters including osteocyte related characteristics. Thirty-eight 4-month-old male Wistar rats were randomly divided into a control group (C) and exercise groups: IT, 10 free fall impacts/day with a 10s (FF10) or 20s interval between drops (FF20), 5 days/week, for 9 weeks. We assessed: BMD, microarchitecture by µCT, mechanical strength by a three-point bending test, density and occupancy of the osteocyte lacunae by toluidine blue staining, osteocalcin and NTx systemic levels by ELISA, and bone tissue Sost mRNA expression by RT-PCR. NTx levels were significantly lower in exercise groups as compared to C. In exercise groups Sost mRNA expression was significantly lower than in C. Tb.N was significantly higher for IT and FF20 compared to C; Tb.Sp was significantly lower in FF10 compared to C. Both IT and FF20 were associated with higher tibial lacunar density as compared to FF10. Compared to FF10, IT fat mass was lower, while tibial osteocyte lacunae occupancy and systemic osteocalcin level were higher. All exercise modes were efficient in reducing bone resorption. Both IT and FF impact with appropriate recovery periods might be beneficial for bone health and osteocyte related characteristics. Novelty bullets: • Interval training is beneficial for bone mineral density • Exercises decreased both bone resorption and inhibition of bone formation (sost mRNA) • Longer interval recovery time favors osteocyte lacunae density