The nature of exercise-induced micro-trauma

[Hammer-Man]

Which of the following models best describes the process of inducing micro-damage to the muscle tissue?

1. A certain load on a muscle will cause similar micro-trauma in that muscle with each repetitive action (each repetition of a specific exercise in a specific workout using the same load, will induce micro-trauma to a similar degree).

In other words - if 5 reps will not induce micro-trauma, then 15 reps will not induce it either.
If 5 reps will induce micro-trauma, then 15 reps will induce more micro-trauma.


2. A cretain amount of work might be needed to start inducing micro-trauma. That amount of work depends on the adaptation of the muscle tissue to work of similar nature.

In other words - it is possible that 5 reps will not induce micro-trauma, but 15 reps will.


I believe the first model is closer to the truth.

It explains why increasing the number of reps/sets from one workout to the next is not enough for inducing growth, if the load remains the same.
The actual work done by the muscle is greater, but throughout each repetition the load is not sufficient to cause micro-trauma, since the muscle has already become conditioned to that load.

 

[Lol]

I suppose the tricky thing is deciding on what to use to measure the 'amount' of micro-trauma?

If you use DOMS then here's what I've just experienced:

After my last day of 15s (heaviest w/o in this rep range) I experienced a small amount of DOMS. However, after my first session of 10s, where several of the weights were slightly below what I had used for my last 15s session, my level of DOMS was higher for most of my body! I tried to do about 12 or 13 reps per set for this, my easiest, 10s session. So, rep wise, I had gone from 15 on Friday to around 25 on Monday. About 10 more reps and the DOMS effect was definitely greater.

This observation would fit your No.2 scenario better.

 

[Fausto]

I think essentially the difference is that the higher rep range tends to cause more oxidative stress, ie: free radicals, whereas the lower rep range with higher weights causes more mechanical damage.

Supposedly the higher range will cause more DOMS which would linger on for 48 hours or so, whereas the lower range although it causes mechanical damage it does not necessarily cause more DOMS but has been proven to cause the most hypertrophy, as repair of muscle fibres happens quicker.

Anyway I could be ram,bling a bit so...here's an article.

 

[dkm1987]

<div>
(Hammer-Man @ Apr. 04 2006,13:06)</div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">1. A certain load on a muscle will cause similar micro-trauma in that muscle with each repetitive action (each repetition of a specific exercise in a specific workout using the same load, will induce micro-trauma to a similar degree).


2. A cretain amount of work might be needed to start inducing micro-trauma. That amount of work depends on the adaptation of the muscle tissue to work of similar nature.</div>
1.No it doesn't. The degree of strain acheived changes with each successive rep. The initial reps may not even induce strain of any sort due to the compliant nature of the connective tissue. ONce this stiffens then strain can be induced. Once you have done a few more and fatigue begins to drop your force levels then the strain is also dropped.

So in reality 2 is closer to what occurs but the variables involved change everything, IE preactivation time, length of muscle, speed of contraction, so on and so on.