Starting at age 40, your body quietly discards one to two percent of its fast-twitch muscle fibers every single year. These are the fibers that catch you when you trip, keep you upright on an icy sidewalk, and let you stand up from a chair without making sounds like a stressed floorboard. The good news, according to exercise physiology research, is that you can fight back.
What 'Explosive Power' Actually Means
You've heard of cardio. You've heard of strength training. But according to Jessica Scott, an exercise physiology researcher at Memorial Sloan Kettering Cancer Center, most people are completely ignoring a third pillar that matters enormously as they age. Explosive power, she told NPR's Life Kit, is the body's ability to generate a large amount of force very quickly.
Crucially, it's not about lifting the heaviest thing in the room. 'It's about moving a lighter load very quickly,' Scott told NPR. Think about the difference between slowly lowering yourself into a chair and launching yourself out of one. The second movement is the one keeping you functional and fall-resistant into your 50s, 60s, and beyond.
Scott's research background spans cancer patients and NASA astronauts, which is a resume that makes you pay attention when she says something. The common thread across those very different populations: how the body responds to physical stress, and what happens when you stop challenging it.
The Slow Disappearing Act Happening Inside Your Legs Right Now
Here's the part that should make you put down your coffee and go do a squat jump. As NPR reports, starting around age 40 we lose one to two percent of our fast-twitch muscle fibers per year. These aren't just gym-performance fibers. They are the biological infrastructure behind reflexes, balance, and the kind of quick physical response that prevents a stumble from becoming a broken hip.
Slow-twitch fibers handle your endurance. Fast-twitch fibers handle everything sudden. And while a dedicated runner might be preserving the former, they could be hemorrhaging the latter if they never do anything explosive. That's a real gap in how most people approach fitness after middle age, and the research Scott points to suggests it has serious consequences.
Falls are the leading cause of injury-related death among adults 65 and older, according to the CDC. The connection between declining explosive power and fall risk isn't theoretical. It is well-documented, and it has a solution that requires considerably less time than you probably think.
The Actual Workout (No Gym Required for the Starter Set)
Scott, speaking to NPR, laid out two tracks of exercise depending on your baseline fitness. For anyone, regardless of current fitness level, she recommends a beginner set of three exercises done in three sets with three to five repetitions each. The emphasis is on control, not exhaustion.
The sit-to-stand is exactly what it sounds like: sit in a chair, stand up quickly, lower yourself back down slowly. The lower the chair, the harder it gets. Elevated pushups follow the same logic, with the quick portion being the push away from the surface, not the lowering. Heel raises round it out, a fast lift followed by a slow, controlled descent. All three movements share a pattern: explosive in one direction, controlled in the other.
For people with at least three months of regular aerobic exercise and one to two days of weekly strength training under their belt, Scott recommends adding a dedicated 20-minute explosive power session once a week. That tier includes squat jumps, jumping jacks, full pushups, and medicine ball slams. Still just three sets, still just three to five reps. The point is quality of movement, not volume.
Why This Isn't Just for Athletes
There's a tendency to file 'explosive power training' under 'things for people with CrossFit memberships and a lot of protein powder.' That framing is wrong and, past a certain age, kind of dangerous. As NPR reports, Scott frames this as a functional capacity issue, not a performance one.
Walking up and down stairs. Catching yourself on an uneven sidewalk. Standing up from the floor without making it a whole ordeal. These all require fast-twitch muscle recruitment. None of them require a gym. What they require is that you periodically ask your body to move with intention and speed, rather than spending every workout grinding through slow, heavy resistance work or steady-state cardio.
The exercise physiology community has been pushing this message for a while. Studies Scott referenced have shown explosive power training improves sports performance and reduces injury rates. The research didn't restrict itself to athletes. The injury prevention benefits apply to ordinary people going about ordinary lives, which is most of us.
The One Rule You Actually Have to Follow
Scott is clear on one thing that separates explosive power training from most other workout formats: stop before you're fatigued. This is the opposite of what most gym culture tells you. No pushing through. No 'last rep, make it count.' Three to five reps, high quality, done.
Explosive power is not resistance training, she told NPR. In resistance training, working to fatigue is often the goal because that's what triggers muscle adaptation. With explosive movements, fatigue compromises form, and compromised form during explosive movements is how people get hurt. The entire point of training this way is to produce clean, fast, controlled output. The moment that degrades, the session is over.
For anyone with existing injuries or significant gaps in their fitness baseline, the elevated pushup and sit-to-stand versions are the right starting point. Scott's guidance to NPR was explicit: have full control over your movements, and stop if you feel pain. That's not a legal disclaimer. That's the actual coaching.
The Dingo Take
Look, the fitness industry has a long and profitable history of complicating things that are fundamentally simple. 'Explosive power training' sounds like it belongs in a lab or a sports facility, but what Scott is actually describing is: stand up fast, push away quickly, jump a little, do it a few times, stop before you get sloppy. That's it. You could do the beginner version in your living room right now and it would cost you approximately four minutes.
What makes this worth paying attention to isn't some new fitness trend. It's the boring, unavoidable fact of biology: the muscle fibers that prevent falls and keep you functional are the ones quietly disappearing every year after 40, and most standard fitness advice does essentially nothing to address them. Jogging is great. Lifting weights is great. Neither one directly trains the fast-twitch fiber that catches you when you slip on a wet floor at 67.
The window to address this doesn't close immediately, but it does close. The research is clear, the exercises are simple, and the downside of ignoring it is a category of injury that turns a bad Tuesday into a months-long medical ordeal. Do the heel raises. Do the sit-to-stands. Be mildly annoyed that nobody told you about this sooner, because they really should have.
