Let's burrow into the secrets of Groundhog Day.
This is Sandra Tsing Loh with the Loh Down on Science.
Groundhogs, also called woodchucks, are among nature's true hibernators. That means they go into a special physical state called "torpor." In it, breathing, body temperature, and heart rate go waay down.
Now meet electrophysiologist Lai-Hua Xie of New Jersey's University of Medicine and Dentistry. He studies cardiac arrhythmias, or heart-rhythm disturbances--dangerous because they can cause sudden death.
One arrhythmia trigger? Low body temperature. So you'd think hibernators would have more arrhythmias than non-hibernators. But they don't.
Xie decided to see why.
In both summer and winter, his team took samples of cardiac muscle cells from woodchucks. They measured the cells' use of calcium, which hearts need to contract.
Turns out, the cells used calcium differently each season. In winter, their membranes released more calcium to contract, then took it back up faster.
Xie thinks that keeps rhythms regular. Also? Winter cells suffered less oxidative stress, or damage from free radicals.
Thus allowing groundhogs to snooze safely through six more weeks of winter! Sleep well, Punxsutawney Phil.
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