New research on nearly 400,000 Americans illuminates an uncomfortable truth for anyone over 50 who believes a daily walk is expanding their healthy lifespan.

It isn't. Walking is great exercise. But for those of us in midlife or beyond, walking is absolutely not enough to keep your muscles and brain in optimal shape for the long haul.

Researchers pulled apart federal health survey data to ask a simple question: What kinds of exercise do Americans actually choose during their leisure time, and how many of those people are getting enough activity to protect their health? The answer, published this spring in a peer reviewed journal, is that walking remains the country's overwhelmingly preferred form of exercise — 44%of adults named it as one of their two most frequent activities — but walkers are also the group least likely to be meeting basic fitness benchmarks.

Running came in a distant second at 11%, a smidge more popular than weightlifting.

Lifting Weights Beats Only Walking, for Fitness and Longevity

Among the people whose primary exercise was walking, only about a quarter met the combined federal physical activity guidelines — a little more than two hours of moderate aerobic work per week, plus two days of muscle strengthening. More than 1 in 5 walkers met neither guideline — the worst showing of any activity category in the study. By contrast, weightlifters, runners and people doing conditioning work cleared the combined guidelines at rates near 45% or higher.

Walking, in other words, is the activity Americans choose most and the activity that produces the worst rate of actually getting fit.

The authors, from West Virginia University, the University of Tennessee and seven other institutions, frame this as a public-health communications problem, especially for rural Americans, who were 8% less likely to meet the muscle strengthening guideline than city and suburban folk and more likely to be classified as inactive.

So what's the solution? It's to continue to embrace walking but augment it.

For anyone on the other side of 50, it's more urgent than the paper says.

What the Study Doesn't Say Out Loud

The deeper point the data gestures at but doesn't say outright is that walking does almost nothing for the one tissue that decides how the second half of your life goes: muscle.

After about age 50, adults lose roughly 1% to 2% of muscle mass per year if they do nothing to stop it (muscle strength declines even faster). Doctors call this sarcopenia. In plain English, it is the slow, silent shrinkage that turns a 60-year-old who can still hike into a 75-year-old who can't get off the floor without assistance.

Walking does not interrupt this highly noninevitable decline. Gardening does not interrupt it. Only deliberate loading does — putting a meaningful weight on the body, repeatedly, with the intent to get stronger.

This is the missing variable in the study's most popular activities. Walking, hunting, fishing, lawn work — the activities Americans pick most — share a common flaw for anyone over 50: None of them ask the muscles to do anything harder this month than they did last month. Muscle responds to progressive stress. Without it, the tissue quietly walks off the job.

There's a quieter finding in the data worth mentioning. Weightlifting was the only category in the entire study where rural Americans outperformed urban ones at meeting the combined guidelines. The activity most associated with gyms, instructors and built environments turned out to be the most democratic.

How To Use This New Information

Keep the walks. They are the easiest thing to sustain and the social and cardiovascular floor of a longevity practice. But treat them as the aerobic base, not the program. Add two strength sessions a week, 30 to 45 minutes each, focused on the patterns that protect independence: a squat or sit-to-stand, a hinge, a press, a pull and a loaded carry. Use whatever you have — adjustable dumbbells, a kettlebell, resistance bands, a backpack loaded with books (or rocks).

Two sessions is the threshold the federal guidelines require and the threshold the study used.

Add one weekly bout that raises your heart rate enough that you cannot sing through it. Hills on the walk count. A bicycle counts. Swimming most definitely counts.

If you live somewhere rural or seasonal, build the strength work indoors and on a schedule. Don't let the weather or the chore list write your training plan.

The study's vanilla conclusion is that walking is popular but insufficient. The blunter version, for anyone whose next decades depend on staying upright and carrying their own groceries — not to mention winning a pickleball tournament — is that walking is necessary and not sufficient.

To find out more about Paul Von Zielbauer and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

Photo credit: Emma Simpson at Unsplash