Use It or Lose It: The Case for Keeping Your Fitness Rental Active

I saw a reel the other day—one of those dumb-yet-strangely-insightful ones—that showed a 20-year-old and a 40-year-old changing a lightbulb. The 20-year-old? Climbed up, swapped the bulb, and hopped off the chair like they were dismounting a pommel horse. The 40-year-old? Carefully, painstakingly lowered themselves down like they were descending into the Mariana Trench.

I laughed… and then I realized something.

I was absolutely the second guy.

Especially post-ACL surgery, I had fully transitioned into the ginger descent phase of life. And look, I’m 42, so it’s not like that’s shocking. But it did make me wonder: How much of this is necessary caution, and how much is just me gradually adapting to a lower standard of movement?

You Don’t Own Your Fitness—You Rent It

Fitness isn’t a permanent asset you get to stash in a vault. You don’t own your ability to run, jump, squat, or lift. You rent it. And just like an apartment, if you stop paying, you lose access. This is backed up by a mountain of research: muscle mass and cardiovascular fitness both decline significantly with inactivity, even over short periods (Booth et al., 2017; Mujika & Padilla, 2000).

The good news? The longer you’ve been “paying rent”—that is, training consistently—the more durable your fitness is. Long-term exercisers retain strength and mobility much better than people who stop and start (McKendry et al., 2020). This is why a lifelong runner can take a month off and bounce back quickly, while a newbie loses all their gains after a couple of weeks.

The Slippery Slope of Substitutions

Here’s the thing, though. It’s not always dramatic. Fitness doesn’t disappear overnight. It erodes in small, quiet compromises:

Biking or rowing instead of running, not because you’re injured, but because running is hard and annoying.
Stepping up on a box instead of jumping, not because of a medical limitation, but because jumping feels weird and sketchy.

Over time, these little trade-offs become the new norm. It’s easy to justify them, too:
“Oh, my knees don’t love running anymore.”
“I just prefer the bike.”
“I don’t really need to jump.”

Maybe those things are true. But maybe they’re just convenient rationalizations. The hard part—the important part—is being honest with yourself about whether a modification is a temporary fix or a long-term dodge.

The Month of Jumping Off Things

After seeing that reel, I decided to run a little experiment. I started making a point to jump off things when I could. Not recklessly—no roof jumps or parkour ambitions—just little, everyday opportunities.

Stepping down from a curb? Nope, jumping off.
Getting down from a pull-up bar? Letting go and landing instead of climbing down.
Even hopping down from a chair when changing a lightbulb—like a damn 20-year-old.

At first, it felt wonky. My brain and body weren’t entirely sure this was a good idea. But after a few weeks, something shifted. It started feeling normal again. Fun, even. Like rediscovering a movement that was supposed to be part of my life.

And that’s really the whole point.

Start Small (Seriously, Start Tiny)

One of the biggest mistakes we make when trying to reclaim lost abilities is thinking non-incrementally—we compare ourselves to our best-ever version rather than meeting ourselves where we are. If we haven’t jumped off anything in years, our brain immediately imagines launching off a five-foot ledge instead of just hopping down from a curb. But movement, like strength, is built progressively. Before you jump off something high, jump off something very low. Then a little higher. Then a little more. The key isn’t heroics—it’s consistency. Start small, stay consistent, and let your body remember what it’s capable of.

Use It or Lose It

There’s an old concept in neurology and physiology called use it or lose it—if you stop using a function, your body assumes you don’t need it and lets it go (Seidler et al., 2010). This applies to everything from muscle strength to balance to cognitive function.

Want to keep running as an option? Run sometimes.
Want to stay strong? Lift things.
Want to be able to jump? Then jump.

None of this means you have to be reckless. Fitness is about longevity, not just max effort. But if you start avoiding things simply because they feel awkward or uncomfortable, that’s a sign. A sign that you might be letting go of abilities you don’t actually want to lose.

So if you catch yourself lowering down verrrrrry gingerly from a chair, maybe—just maybe—jump off instead.

Worst case? You land funny and laugh at yourself. Best case? You keep your fitness rental active for a few more years.

And that seems like a pretty good deal.

Citations

Booth, F. W., Roberts, C. K., & Laye, M. J. (2017). Lack of exercise is a major cause of chronic diseases. Comprehensive Physiology, 2(2), 1143–1211.
Mujika, I., & Padilla, S. (2000). Detraining: Loss of training-induced physiological and performance adaptations. Sports Medicine, 30(2), 79–87.
McKendry, J., Breen, L., Shad, B. J., & Greig, C. A. (2020). Muscle morphology and aging: A multi-dimensional approach. Current Opinion in Clinical Nutrition & Metabolic Care, 23(4), 275–280.
Seidler, R. D., Bernard, J. A., Burutolu, T. B., Fling, B. W., Gordon, M. T., Gwin, J. T., Kwak, Y., & Lipps, D. B. (2010). Motor control and aging: Links to age-related brain structural, functional, and biochemical effects. Neuroscience & Biobehavioral Reviews, 34(5), 721–733.