Dr. Andy Galpin

It's not the eccentric training.

Other things that cause soreness are higher intensity.

Not really applicable here.

Again, if you're used to contracting at a maximum heart rate, we're not going to be able to go past that.

More volume, well, we could do that, but more volume tends to mean more exercise over more range of motion.

Your heart beats all day.

It is not subject to that much change in volume.

If you looked at the total amount of heart beats that you go through throughout the day, a little bit of exercise is not changing that volume too much.

So it's really difficult to add much volume relative to the standard or baseline there.

And so as you just continue to go down all the other factors that influence muscle soreness, and you see they don't really apply to muscle, again, that's not its primary role.

And so while you may get fatigued from exercise, especially endurance-based exercise, the heart itself is not really subject to fatigue.

In fact, the heart rarely gets tired.

It has far more mitochondria in it than skeletal muscle.

We used to refer to this as the ultimate slow twitch muscle.

It is not meant for force of contraction.

Going back to motor units, we actually can't alter force of contraction in the heart.

In the muscle fibers themselves in the heart, we can only do it by changing the stretch on the tissue.

Same thing in your skeletal muscle.

But in that case, you've got both options, right?

Change stretch or strange contractile properties.