Trust me, I understand—in theory—that I should be stronger. Yes, I’m an aerobic beast (or an aerobic addict, if you prefer), but I’m not oblivious to the benefits of having a reasonable amount of muscle. When I play the “look, you’re touching the ceiling!” game with my 18-month-old, I’d prefer that she get bored before I have to admit that Daddy can’t military-press her anymore. And I’m hoping that 20 years from now I’ll still be able to push myself out of an armchair without help.
But there’s a gap between “should” and “do.” This gap is one of the most vexing riddles in public health, and even people like me, who spend their days telling other people what they should be doing, aren’t immune to it. For that reason, I’m always eager for reminders of what’s at stake—and two papers offer some eye-opening insights into the benefits of strength training, even for people who consistently blow the aerobic exercise guidelines out of the water.
The first is an analysis of the link between strength, muscle mass, and mortality, from a team at Indiana University using data from the National Health and Nutrition Examination Survey. The design was pretty straightforward: They assessed 4,440 adults ages 50 or up who had their strength and muscle mass assessed between 1999 and 2002. The researchers checked back in 2011 to see who had died.
For muscle mass, they used a DEXA scanner to determine that 23 percent of the subjects met one definition of “low muscle mass,” with total muscle in the arms and legs adding up to less than 43.5 pounds in men or 33 pounds in women. For strength, they used a device that measures maximum force of the knee extensors (the muscles that allow you to straighten your knee) and found that 19 percent of the subjects had low muscle strength.
The results, published in Medicine and Science in Sports and Exercise, found that those with low muscle strength were more than twice as likely to have died during the follow-up period than those with normal muscle strength. In contrast, having low muscle mass didn’t seem to matter as much.