How Much Excercise is Too Much?
This rat may be damaging her heart.
Since it seems you can never really have too much to worry about, here is a nice article about how a life-time of intense training may cause damage to your heart–especially if you are a rat.
Read about it in the New York Times Well Blog.
The obvious point is that 99.99% of Americans exercise too little (or not at all) so this really applies to a vanishingly small segment of the population.
Regardless, don’t tell your mother!