https://www.outsideonline.com/health/training-performance/declining-muscle-power/
It’s not just a general decline in activity, though. Subjects in Sundberg’s study wore an accelerometer to measure their daily step count as a rough estimate of their physical activity levels. There was almost no connection between daily physical activity and peak power: step count explained only 3 percent of the variance in peak power. I’m a big fan of aerobic exercise, but simply staying fit doesn’t seem to be enough to keep those fast-twitch fibers firing.
I’m venturing beyond what the study found, but the message I take from it is that if you want to hang on to as much explosive power as possible, you need to move and train in explosive ways. Plyometric exercises, which includes things like box jumps and bounding, are one approach. Another option is resistance training with lighter weights—less than about 60 percent of one-rep max, according the American College of Sports Medicine’s guidelines—where you focus on performing the movement as quickly as possible.
For the specific goal of hanging on to your fast-twitch fibers, there may also be a case for doing some heavy resistance training, with sets of six reps of fewer. If the weight is heavy enough, you’ll need to recruit your fast-twitch fibers to lift it. It’s worth remembering, after all, that power is force times velocity—so increasing the force you’re able to deliver is a key part of the equation. There’s evidence that once strength drops below a critical level, usable power drops off a cliff.
Which of these various approaches is most effective remains to be seen. For now, my plan is simple: more hill sprints.
