Fit Hibernating bears emerge from their winter dens strong and ready to take on spring.
New research reveals that they get plenty of protein and exercise during their deep sleeps.
It's hard to imagine a bear deep in its winter den downing a protein shake and working a Stairmaster. But a new study shows that while these Sleeping Beauties' eyes are shut, their bodies are working hard to keep their muscles strong. American black bears in the Rocky Mountains preserve their muscle tissue while hibernating, the study shows, by recycling nearly all of the nitrogen in their urine into amino acids, the building blocks of proteins important to repairing muscles. Scientists from the University of Washington and University of Minnesota also noted that the bears' muscles undergo periodic shivering that provide exercise, keeping them tone during this prolonged period of inactivity. Brakesfield Many animals undergo physiological changes and enter a state of slumber to conserve energy in times of need.