I just returned home from back-to-back trips to the mountains. Upon sharing stories of my experiences with some TNT members—specifically about distance, elevation, and gear—I was struck by the thought of how important muscle and strength really is.
The mileage overview includes:
- Mt. Rainier: 25 miles, gaining and losing 13,500 ft of elevation over the course of 54 hours
- Grand Teton: 16 miles, gaining and losing 6,500 ft of elevation over the course of 35 hours
And roughly three-quarters of the distance and two-thirds of the elevation was covered while carrying a 40-lb pack.
Of course, I’ve spent the past few months training for these adventures. Still, that’s not something that your average 47-year old does—and I’ve no doubt that the strength and muscle that I’ve spent the past 30 years developing set the foundation that made it possible.
Now if you’re thinking, “That’s cool, Ryan, but I’m not particularly interested in any equivalent of spending days hiking up and down a mountain,” I’ll suggest that muscle matters well beyond movement and aesthetics. Dr. Gabrielle Lyon, a practicing physician and author of Forever Strong: A New, Science-Based Strategy for Aging Well, calls it “the organ of longevity” and treats it as a driver of metabolic health, disease prevention, and how well we age. Recent research is increasingly confirming that framing.
And that brings me to the topic I actually want to cover today: the age-related loss of muscle mass, strength, and function. Or in a word, sarcopenia.
The 25-year gap
Muscle and strength loss—like most conditions worth taking seriously—doesn’t happen all at once. It erodes gradually, often starting in our mid-30s to early 40s, long before most people give it a second thought. Until recently, even the clinical conversation about it centered on adults 65 and older, essentially treating it as an old-age diagnosis.
That’s where a major part of the problem lies: muscle and strength loss that starts around 40 but that isn’t addressed until retirement age leaves 25-plus years for nature to take its course unobstructed.
And that will affect our quality of life not only when we’re older but also during our middle-aged years when we should still be more than capable of doing the active things we enjoy.
The stakes
So what’s actually at stake during those 25 years?
It turns out, something rather significant (besides the obvious strength and function loss).
A 2025 systematic review and meta-analysis of 39 studies and more than 76,000 participants found that sarcopenia is associated with a 1.79 times increased risk of all-cause mortality. A separate, smaller prospective cohort study of centenarians found the risk climbs even further at the far end of the age spectrum—sarcopenia increased mortality risk by 3.64 times in that group.
In other words, these numbers back up exactly what Dr. Lyon has argued—muscle directly affects how long and how well people tend to live.
The clock moved up
On a positive note, the diagnosis gap did start closing in late 2025. The Asian Working Group for Sarcopenia released a consensus update in Nature Aging—a significant clinical document reframing how sarcopenia should be considered across the lifespan. The headline change: screening should now begin at 50, not 65—closing more than half of that 25-year gap in one move.
(As the name implies, AWGS focuses specifically on Asian populations, so its exact screening thresholds are calibrated there. But the underlying pattern—gradual muscle decline starting well before “old age”—applies broadly, which is why the update’s core message travels well beyond the group it was built for.)
This doesn’t mean you need to wait for a doctor’s warning or an official diagnosis before doing anything about it though. The moving threshold is simply a signal worth paying attention to.
While rebuilding lost muscle later in life is possible—older adults who have been inactive typically respond well to the addition of resistance training—it’s much easier to build it when we’re younger. Of course, building muscle at any point during life is better than not. But building it early and maintaining it (as much as possible) as we age means we’ll get to reap its benefits during our middle-aged years as well.
Putting it into practice
If you’re not currently resistance training, or you’ve let it lapse: Start with a session or two per week, built around a handful of compound movements. (Consult your doctor first if you have specific health concerns.) And remember that where strength and muscle development are concerned, moderately heavy (for you) weights and longer rest periods should be the norm. Cardio can be done on a separate day.
If you’re already resistance training regularly: Continue to keep it a priority—and develop a plan for when the demands of life conspire against you (if you don’t already have one in place).
The best time to take this seriously was a decade ago. The second-best time is now—regardless of whether “now” is 35, 50, or 65.