I’m not even sure how to put into words my question but I’ll try.
From what I understand telomeres shorten during cell turnover which causes ageing. Therefore do activities that cause cellular damage like resistance training, tattoo or laser resurfacing etc shorten your lifespan or cause you to age?
In: 36
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!
As far as resistance training is concerned, it’s worth noting that muscle cells don’t reproduce in adulthood; you have all of the muscle cells you ever will by the time you’re done growing – and you actually have most of them at birth.
The damage you’re describing happens, as you say, during cell reproduction. No cell reproduction => no telomere shortening.
Mitochondria have their own DNA and *do* reproduce inside of muscles, and this reproduction *is* stimulated by exercise. But mitochondria, like their wild bacterial cousins, have DNA that comes in a chromosome shaped like a circle, with no telomeres to shorten.
The skin cells exposed to the world are, for the most part, not cells that reproduce. Rather, they are generated by processes that occur further down, in layers not normally damaged by surface stuff.
That said, you may have heard of a little thing called “skin cancer” mostly caused by exposing your skin to too much UV light. There have been several studies suggesting no connection between tattoos and skin cancer, though I don’t know about laser resurfacing.
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.
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