Perhaps, This Is What A Runner's High Is All About...

A fascinating study on the "immortality" enzyme, aka telomeres, contrasting the DNA of runners as compared to a more sedentary control group.

"In general, telomere loss was reduced by approximately 75 percent in the aging runners. Or, to put it more succinctly, exercise, Dr. Werner says, at the molecular level has an anti-aging effect." Link.

Gains From Exercise After Heart Attack Are Lost if Exercise Stops

"Some important benefits of exercising after a heart attack can vanish in weeks if the exercise is stopped, a new study has found." The New York Times, March 20, 2009. 

Muscle Strengthening Aids New Knees

"A new study suggests that a carefully focused program of muscle strengthening can make an important difference in how well patients recover after knee replacement. "
The New York Times, February 2, 2009

go to article here.