Why We Need Rest: Part Two

In the first post, (was it really 2 month ago?)  I explained the two main types of muscle fibers and how they worked.

Review: each muscle has many thin Type One muscle fibers that work for endurance – they help keep upright and are the main muscles used in cardio exercise.  Type One muscle fiber uses glycogen and oxygen for it’s energy and cycles quickly through all the fibers -working similarly to the pistons in a engine.

Muscles also have Type Two muscle fiber which is thicker, more fiberous, and which is mainly used when we demand more “oomph” from a muscle for a short period of time.  This fiber works anaerobically and runs out of fuel within a minute.

So what happens to these muscles when we exercise?

Type one muscles, because of their size and function, are meant to heal to quickly.  Do a cardio workout and you might feel a bit sore that day, but within 24 hours you’re feeling better.

A HARD cardio workout -or a demanding strength workout -will recruit your Type two muscles.  Because these muscles don’t cycle like the type ones, when they are put under demand, they become physically damaged.  They shred like dental floss.

These microtears are now believed the cause of DOMS (delayed onset muscle soreness) along with any immediately after workout soreness.  And these tears can take time to repair.

Your body will immediately begin to replace damaged cellular fiber and start to repair it.  However, when we are awake most of our energy is taken in maintaining our posture, digesting food, and other functions.  When we sleep most of the repair work is done.

On a cellular basis, our bodies spend the first hours rather like a demolition crew cleaning out the spots where all the damaged muscle fiber is.  We are also roaming through the entire body cleaning out older and damaged cells.  Then the construction crew comes in and begins to repair the damage.

Like when you break a bone, these microtear sites are built stronger than the spots were before hoping to stave off further damage.  This repair work can take several days to be completely finished.

And it’s this damage that requires the rest time.  Damage to the type two cells.

The good news: on the days that we are healing we can still do some cardio-just make sure it’s not demanding enough to recruit those fibers that might be rebuilding.  Also, while the body is fixing these damaged fibers, it is burning more calories to make the repairs.  So demanding strength training not only burns calories while we are working, it continue to do so for up to 48 hours after we’ve stopped.

At which time, we’re ready to start the whole routine all over again.


2 responses to “Why We Need Rest: Part Two

  1. I just experienced this. The training was Saturday and I’m still sore today !(Tuesday) I thought I was in great shape. I usually walk 5km’s or more briskly a day, lift free weights, and do core excersizes?? The training almost killed me. Should I wait until I’m completely recovered to do another training session? Should I even bother with another training session?

    • Nicole, No and Yes. Being sore means the training worked muscles that haven’t been worked before in a way they haven’t been worked. (and I worked that sentence like a sore muscle!). When I get sore, I like some nice active rest for a day- max two. That would be taking a walk. Don’t wait any longer to work out again -and definitely keep doing what made you sore. The soreness told you that it challenged you.

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