I try to get to the gym several days a week, and generally do a mix of weights and cardio. (I need to do more core and ab exercises, but I hate those.) Gretchen Reynolds’ New York Times piece on new research about “The Best Exercise for Aging Muscles” makes me think I should hit the stationary bike and Stairmaster more, though:

Exercise is good for people, as everyone knows. But scientists have surprisingly little understanding of its cellular impacts and how those might vary by activity and the age of the exerciser.

So researchers at the Mayo Clinic in Rochester, Minn., recently conducted an experiment on the cells of 72 healthy but sedentary men and women who were 30 or younger or older than 64. After baseline measures were established for their aerobic fitness, their blood-sugar levels and the gene activity and mitochondrial health in their muscle cells, the volunteers were randomly assigned to a particular exercise regimen.

The groups either did weight training, interval training, or a mix of cardio and weights (a control group just sat around). At the end of the study, they found that all three groups were generally fitter, but there were dramatic differences in the interval trainers:

Among the younger subjects who went through interval training, the activity levels had changed in 274 genes, compared with 170 genes for those who exercised more moderately and 74 for the weight lifters. Among the older cohort, almost 400 genes were working differently now, compared with 33 for the weight lifters and only 19 for the moderate exercisers.

Many of these affected genes, especially in the cells of the interval trainers, are believed to influence the ability of mitochondria to produce energy for muscle cells; the subjects who did the interval workouts showed increases in the number and health of their mitochondria — an impact that was particularly pronounced among the older cyclists.