Osteoporosis prevention in an extraordinary hibernating bear

Disuse osteoporosis results from physical inactivity. Reduced mechanical loading of bone stimulates bone resorption leading to bone loss, decreased mechanical properties, and increased fracture risk. Compensatory mechanisms evolved in hibernators to preserve skeletal muscle and bone during the prolonged physical inactivity that occurs during annual hibernation. This paper reports the preservation of bone properties in an exceptionally old black bear that was physically inactive for about 6 months annually for 31 years. The biological mechanisms that preserve bone during prolonged disuse during hibernation are also reviewed. [Display omitted] •Hibernating bears have biological mechanisms to prevent disuse osteoporosis.•Black bears can resist disuse osteoporosis for up to 31 years.•Hibernating, physically inactive bears preserve bone by reducing bone remodeling.•Circulating factors may prevent osteocyte apoptosis in hibernating bears.•Circulating factors may prevent osteoclastic bone resorption in hibernating bears.