Dr Karl

They're called fast twitch and slow twitch or type one and type two muscle fibers.

The reason...

your muscles are getting stronger is because they're getting physically bigger.

And they're getting physically bigger because you're damaging the muscles by the use that you're doing each day.

And the repair mechanism is not a bad repair mechanism.

It's a good repair mechanism.

So think about like linking your two fingers.

How would you describe this activity here, linking your fingers, the palms of your hands, and you sort of form a ratchet mechanism and you walk one hand up the other hand.

And so that's called actin myosin.

These two molecules ratchet against each other.

There's some really great videos on TikTok about that, actin and myosin.

And what happens is that they are the parts of the muscle fibres that actually do the pulling.

And when you do regular work, you damage the muscles that you have, but it's not as though, oh, no, don't do regular work because you'll damage them.

It's a good damage as opposed to a bad damage.

I'm not talking about overworking it and tearing a ligament or something like that, but just doing a graduated repair.

You tear the microfibrils and then stem cells kick in and they add extra microfibrils.

you are adding extra muscle fibers that were not there before.

And they come from stem cells.

And so if you do this regularly over a graduated period, you get stronger.

If you do absolutely nothing and just lie in bed all day, you will lose 30% of your muscle strength at the end of a 24-hour day of lying in bed, not even getting out of bed to wee or eat or anything.