“I’m getting old” is a popular complaint and frequently overheard during military fitness testing. It’s mostly a lame excuse based on societal misperceptions that has nothing to do with human physiology. Here’s what really happens.

First, you stopped taking steroids. You probably called it “going through puberty” but your adolescence was a growth spurt fueled by growth hormones and steroids that your mammalian body produced naturally. To demonstrate, consider how much lean body mass you gained from age 8 to 18. Even without a conscious intervention directed at getting you stronger, such as lifting weights, you got stronger by merely failing to die.

Second, your post-adolescent self stopped doing “kid stuff.” Recess and playground time was replaced with more classroom time and then a job. Even for the active, how many high school athletes continue to compete in any sports after graduation? Instead, most people either become an adult and get a job or go on to further education to get a job. So right after that natural growth/steroid cycle comes to an end, people tend to greatly reduce their activity levels. Even traditionally hard labor professions (farming, construction, logging, mining, etc.) have become more automated over the centuries while knowledge work and desk jobs have increased. Physical activity is either consciously programmed (unit/department mandatory PT and fitness tests, join an adult sports league, conduct some type of exercise on your own, etc.) or it likely doesn’t happen.

This lack of activity coinciding with the end of this natural growth spurt is essentially a detraining effect. There is no physiological reason it must occur. Studies of elderly people, including men and women in their 70s, 80s, and 90s with existing medical conditions, demonstrate that humans are capable of getting stronger at any age if they consistently do something that will trigger a needed adaptation to force the body to get stronger. In other words, grandma can stay fit and independent and avoid languishing in a vegetable farm (nursing home or similar pre-graveyard purgatory) if she does something like lifting weights several times a week to get that way. But societal norms suggest that grandmas (or men over 35 or women of any age…) aren’t supposed to use barbells (even though there is no physiological basis for this) so most of them don’t. Decades after stopping recess and away from that natural steroid cycle, the societal norm of what “old” is takes over.

At the absolute upper edge of high-level athletic performance – the place where professional athletes and Olympians and World Record holders reside – aging effects can make a difference but that’s primarily because even a tiny fall off is detectable at that level. For the rest of humanity, especially your typical enlisted person that only needs a respectable result to merely pass a PT test or any human that wants to retain a bit of youthful vigor, these effects are grossly overstated and largely a nocebo effect.

Original story:

The physiology of running can be broken down into three parts. There’s the body’s fitness: how fast you can get oxygen to the muscles and how fast you can go before lactate accumulates in the blood. Then there’s running economy: the efficiency with which you move. And then there’s mass: how much you weigh. Multiply fitness by running economy and divide by mass. That’s how fast you’ll go.

As a person ages, those variables don’t have to ineluctably get worse. We often gain weight, but we can lose it again. We pick up bad habits from injuries that change our form – say, a tweaked right ankle that makes us land too hard on our left. But a habit caused by an unconscious choice can usually be reversed by a conscious one.

Most important, as Kirby explained, our muscles change in ways that are both good and bad. As we train, over time, the mitochondria inside our muscle cells become more efficient at converting energy. New blood vessels develop. Tendons strengthen. On the other hand, our lean muscle mass declines with age, which is bad for marathoners and even worse for sprinters. Still, the decline doesn’t have to be steep.

The main reason that runners slow isn’t our bodies. It’s our lives. We get married, we have children, we work longer, our parents get sick. We have more important things to do with our time. Running is a sport that rewards consistent effort, and once you step away it’s hard to come back. Your body frays, which makes running less enjoyable, which accelerates the decline. We go slower as we age, but we also age when we start to go slower.

Meanwhile, a couple of times a week, I would fire up an app on my phone and actually do some non-running exercise and stretching. When the process started, I had headed into a gym to see Holder and had almost immediately started to feel like a man trying to eat a bowl of soup with a fork.

Holder was baffled that I didn’t know how to do a lunge and that I could barely do a squat. He laughed when I tried to touch my toes and reached just past my knees. I had spent 13 years training my cardiovascular system but had cared little for my joints, tendons, or ligaments.

Running breaks systems down and, over the years, I’d slightly injured almost every muscle group from the bottom of my feet (plantar fasciitis) to my belly button (lower abdomen strain). Stronger, more flexible muscles can absorb more stress.