There are more things at work here. Muscle and skin cells behave differently than, say, organ tissue. [Jack LaLanne](http://Jack LaLanne) lived to be 96.

The way DNA replicates to termination is a little different than just apoptosis. Let's see if I can explain.

Cells have a natural life cycle, and when they age out, they have a natural self-termination called apoptosis. This is built into the structures and has a set timeline. If you're talking about cells that aren't manufactured somewhere like blood cells in marrow, they replicate via mitosis and just keep going.

However! Oxidative damage to the telomares shortens the terminus of the DNA. This is directly related to the effects of aging and age-related changes. This happens on a molecular level.

What you're describing happens at a cellular level, and the body has systems in place to account for that (for the most part). You're not prematurely aging yourself by working out. If anything, you're keeping your systems stimulated to keep up on cellular "housekeeping," to include removal of dead or dying cells more appropriately.

... in short, you're fine!

The problem here is you’re talking about to different things. Exercise causes cells do die, but because it damaged the cell. Aging happens because of changes to the DNA, not the cell itself. Basically with time, DNA changes and gets bad at replicating (telomeres shortening), so cells don’t replicate and create new cells as they used to. When exercising, you damaged cells, but it doesn’t affect your DNA, so it has no effect on aging. You’re fine!

That’s a great point, hoping someone can explain it a bit further. Im curious is could Jack have lived past 100 without the weightlifting?

Thanks for sharing though. This was my question as guys like Steve reeves and reg park and all these body builders seem to pass early.

This is a fantastic response! Thank you so much for keeping us basic.

Thank you! This makes sense 🙂

That’s true, but those guys tend to build unnatural amounts of muscle through anabolic steroids and hormone treatments like TRT. This puts more muscle on the frame than the body is designed for, and combined with heavy training leads to faster aging and often heart conditions or other cardio-vascular issues. For the average person who is simply muscular and strong in a natural way, these are not relevant people to look at.

I do my best! Just make sure you're not tinkering too much with your molecules, and you should be fine. Things like smoking, drinking, unnecessary hormones or supplements beyond reasonable amounts (ask your doctor if you're unsure), chronic inflammation and poor diet can really do a number on a molecular level - so drink water, eat fresh balanced nutrition from varied sources, get plenty of fiber (you wanna keep your gut flora happy if you want everything else to be happy!) and stay low on inflammation-inducing foods, and your DNA will thank you.

Oh, side note! Pay attention to your stress levels. I'm not talking physical workout stress, I mean brain and trauma type stress. High chronic levels of cortisol can really do a number on your telomeres!

You seem to really know your stuff! Thank you so much 🙂

Also telomeres are more relevant for the Hayflick limit, they are more of an effect and not a primary cause of aging on the level of whole organisms.

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And what about mechanical damage? Like various scratches and cuts? Are those dangerous? I know, I don't die from a stupid scratch or cut, but if it happens quite often, does it increase the risk of cancer?

In theory, and dependant on the tissue involved, repeated trauma has a possibility of giving rise to cancer. The skin is not generally one of these tissues.

The way skin forms is kinda special. It's an epithelial tissue, meaning it's designed to rubbed, bumped, and slid against. The inside of your mouth is epithelial tissue, as are other parts of the digestive system and reproductions system. Even the lining of your urethra is epithelial cells. They're used to the constant minor abuses and have evolved accordingly.

So what's special about it? All your skin is formed in deep tissue called the dermis, by epithelial cells caked basal cells. Think "basal" like "basement," as they are the bottom layer of your skin. Their entire job is to replicate and push more skin cells upward. Those new cells eventually die off as they move upward and become what you know of as your skin. Problems with basal cells are most often caused by radiation damage - like prolonged and repeat exposure to UV - because they replicate so often and so quickly, not from repeat trauma.

Now, if you're cutting the exact same spot on your skin for, like, years? Constantly? Yeah, that's probably not great. But microtears in muscular and epithelial tissue isn't the end of the world. They're used to that, and they're designed to cope.

Edit: I focused on skin, because that's usually what you mean by cuts and scrapes. If you've been frequently cutting into muscle tissue, I'm worried about you for reasons beyond cancer.

Thanks, I've learned a lot. A couple of days ago I had a minor accident and took a little "meat crayon" like damage. A hand skin torn to shreds, an elbow looking like a slightly used meat crayon. I'm amazed how fast it healed. It looks like I have some brand new skin. It silly but when I get similar "paint scratches" I wonder if it heals this time or not. Well, I have a couple of permanent scars from various accidents, but I've heard it's only because it wasn't sewn. It healed naturally and deeper cuts left some scars. I never had a muscle or bone damage. I'm too careful for that. From the other hand - I'm always in a hurry and I use various tools a lot, so that accounts for plenty of minor damages. It's good to know it's nothing to worry about.

Two important things for this question that are getting a little mixed up:

1. You’re describing the ‘hayflick limit’, which states that a human cell dividing by mitosis (replicating itself) can only do so ~40-60 times before the telomeres are too short and the cell has natural processes built in to stop it from replicating and just hang out (senescence) or kill itself (apoptosis). While this phenomenon does play some role in and correlate with cellular-level aging, most general education and schools teach this as the main reason behind aging itself in general, which isn’t completely true. Most humans demonstrate ageing and die before their cells actually reach those hayflick limits - I believe studies calculate humans to be able to reach ~120 years before 40-60 mitotic cell replications are reached. Thus, lifespan (length) and healthspan (quality) of life are clearly influenced by many more factors that JUST the hayflick limit. There are genetic and environmental factors that can damage DNA, cause chronic inflammation, there’s the free-radical hypothesis, other reasons for cell senescence, ways to clear senescent cells (or not), etc.

2. Differentiated cells like ‘muscle cells’ don’t only exist due to mitosis, which is what relates to the hayflick limit. Certain cells like resident stem cells or pluripotent cells don’t have limits to their replication. When damaged and weaker muscle cells are cleared out by activities like exercise, they are often replenished by their respective stem-like cell populations. Others mentioned mitochondrial biogenesis too. Exercise confers so many more benefits to quality of life and lifespan, that the small effects it may have on cells dividing by mitosis are far outweighed by the hayflick limit impacting your lifespan (again, see point 1). Studies show that people who regularly exercise or Olympic athletes in non-contact sports tend to actually live longer than those who don’t.

This is a really good point. Thank you!

What you're describing is "second intention" healing: the act of the body healing a wound without closure. It's unnecessary (and sometimes impossible) to suture every wound. Not much to glue together on, say, a skinned knee. Second intention healing actively scars over as fibrin (manufactured by your liver) knits a structure together for cellular regeneration. That's why a scar looks different from your usual skin: it's literally built over a scaffolding that your body isn't made of normally.

It's common and harmless, just letting a wound granulate in. Usually best for superficial wounds like abrasions, though I've seen it with deeper wounds on occasion. In both cases I can think of immediately, the wound was bandaged with honey, which acted as a secondary granular structure while also protecting the deep tissue from infection. Eventually the skin grew back in, though both times it did scar rather spectacularly. The doctors on each case felt sutures would be difficult and risky, based on the mobility of the sites as well as poor "margins," which are the edges of wounds. Without proper margins, they're nothing to really suture. Imagine taking a half-dollar sized patch of skin off your wrist: how do you put the edges back together on such a wide, mobile space? You don't. You let it heal by second intention.

Sutures (and staples) come in to play with lacerations mostly. Nice, deep, linear wounds with most of the skin still available to suture. But that's a different subject.

Your two biggest organs - your skin and your liver - are also the only two with active regenerative properties. That doesn't mean take them for granted, but do have a little trust!