Muscle strength in a nutshell

[The_cannibal]

User Tevez asked this question in the supplement science section. I decided to answer his question here, since there is no "exercise science" section, but it still is a better place to talk about muscle strength than the supp. science section.

Just wondering, what determines the strength of a muscle, we know its not the size of a muscle, so what is it? density? the amount of things such as creatine, phosphocreatine etc. present in the muscle? anyone have any idea?

I will try to keep it as simple as possible, but there are some concepts that still need to be explained properly.
If I missed any details you consider important, fell free to add comments. Feel also free to ask questions.
I give credit to a few sites from which I got this info at the end of the post. I have extracted a lot of quotes literally from these sites (much easier to copy/paste than try to "reformulate" everything). I think these sites belong to the public domain so I shouldn't be in trouble for using their info. Don't hesitate to visit these sites to add to the very basic knowledge I tried to teach you here.
This post may seem to be pretty long, but there isn't that much words, there are a lot of pictures that take up a lot of space.
And finally, don't be too impressed by "big" words...they are just words. I try to use them in a context that facilitates comprehension.

First of all, in order to determine what determines strength, we have to understand what causes a muscle to flex.

Each muscle fibers contains:
- an array of myofibrils that are stacked lengthwise and run the entire length of the fiber.
- mitochondria
- an extensive smooth endoplasmic reticulum (SER)
- many nuclei.

The inside of the muscle cell is called sarcoplasm, hence what you may have already heard as sarcoplasmic hypertrophy.

The multiple nuclei arise from the fact that each muscle fiber develops from the fusion of many cells (called myoblasts).

Each myofibril is made up of arrays of parallel filaments.
- The thick filaments have a diameter of about 15 nm. They are composed of the protein myosin.
- The thin filaments have a diameter of about 5 nm. They are composed chiefly of the protein actin along with smaller amounts of two other proteins:
troponin and tropomyosin.


The entire array of thick and thin filaments between the Z lines is called a sarcomere. Shortening of the sarcomeres in a myofibril produces the shortening of the myofibril and, in turn, of the muscle fiber of which it is a part...the muscle is "contracting" or "flexing".

Now, we must ask: what causes these sarcomeres to shorten?

The contraction of skeletal muscle is controlled by the nervous system.
When the nervous impulse reach the neuromuscular junction, it produces a cascade of effects that are quite complicated, probably too complicated for this discussion. You can read more here: http://users.rcn.com/jkimball.ma.ult...scularJunction and here:http://muscle.ucsd.edu/musintro/ecc.shtml


One thing which is important to remember about this junction, is: it results in depolarisation of the muscle membrane, but since there isn't a junction on every single cell, the depolarisation weakens as it "travels" to surrounding cells. A resting muscle usually receives about 60 impulses per second, whereas a muscle at 100% strength output can go up to 600 impulses per second.

Now we know what triggers the shortening of the sarcomere, but we do not know what fuels it:

ATP is the immediate source of energy for muscle contraction. Although a muscle fiber contains only enough ATP to power a few twitches, its ATP "pool" is replenished as needed. There are three sources of high-energy phosphate to keep the ATP pool filled.
- creatine phosphate
- glycogen
- cellular respiration in the mitochondria of the fibers.
This is enough for our discussion. You may want to see this url for more info on this "fueling" : http://users.rcn.com/jkimball.ma.ult....html#creatine
and these url for more info on how ATP is re-synthetized:
http://users.rcn.com/jkimball.ma.ult...spiration.html
especially the very important (but oh so nightmare-ishly complicated) Krebs Cycle (also called citric acid cycle):
http://en.wikipedia.org/wiki/Citric_acid_cycle

Finally,
Type I Fibers
- loaded with mitochondria and depend on cellular respiration for ATP production
- resistant to fatigue
- rich in myoglobin and hence red in color
- activated by small-diameter, thus slow-conducting, motor neurons
- also known as "slow-twitch" fibers
- dominant in muscles that depend on tonus, e.g., those responsible for posture

Type II Fibers
- few mitochondria
- rich in glycogen and depend on glycolysis for ATP production
- fatigue easily
- low in myoglobin hence whitish in color
- activated by large-diameter, thus fast-conducting, motor neurons
- also known as "fast-twitch" fibers
- dominant in muscles used for rapid movement
- there are IIa and IIb fibers. Some studies have suggested that IIa fibers could undergo changes to become type I, but not IIb.

Most skeletal muscles contain some mixture of Type I and Type II fibers, but a single motor unit always contains one type or the other, never both.

At last, we have sufficient knowledge to answer Tevez' question

First of all, Tevez wrote: "we know its not the size of a muscle". This is not exactly true. Since we now know the structure of a muscle cell, we know that hypertropy must comes from either:
- sarcoplasmic hypertrophy, or
- myofibrillar hypertrophy.
Since the contraction forces comes from myofibrils, a bigger muscle that has more myofibrils will have more "capacity" to grow stronger. This is not to say that sarcoplasm hypertrophy is useless. A bigger sarcoplasm will result in higher ATP stores, higher CP stores, higher glycogen stores and more mitochondria to produce energy. Also, a muscle that contains a higher concentration of type II fibers will be stronger, because of type II fibers' better capacity to produce energy.

However, muscle size is not the "limiting factor". One can look at middleweight olympic lifters who lift huge amount of weight, or Amanda Harris, aka Barbie Barbell, and can see that these people have very high strength levels without huge bulking muscles.

This is where our discussion of the nervous system becomes so important. As we train, not only do our muscles grow bigger, vascularity increases (angiogenesis), increase their capacity to produce energy and re-synthetize ATP, but also the "nervation" (couldn't find a better word) of the muscle increases. You remember when I wrote "since there isn't a junction on every single cell, the depolarisation weakens as it "travels" to surrounding cells". That's where the "mystery" lies: as there are more and more neuromuscular junctions in your muscle, you can recruit a lot more fibers, and they can be recruited at a "higher rate". Also, the nervous system may become stronger, i.e. the strength of the impulse becomes stronger (http://users.rcn.com/jkimball.ma.ult...ls.html#action).

I hope it answers your question, Tevez, and I hope it answers a lot of questions that any other readers may have had. Of course, any student in biochemistry, medecine, and these kind of fields could find a lot of stuff missing in my discussion, but remember that I try to keep it as simple as possible...


References:
http://users.rcn.com/jkimball.ma.ult...M/Muscles.html
http://muscle.ucsd.edu/musintro/jump.shtml
http://en.wikipedia.org
Also a few books:
- Tudor O. Bompa, Lorenzo J. Cornacchia, Serious Strength Training, Human Kinetics Pub, 301 pp
- Tudor O. Bompa, Theory and Methodology of Training: The Key to Athletic Performance, Kendall Hunt Pub Co, 381 pp

[finfan]

Reps for confusing the sh!t out of me

[The_cannibal]

Reps for confusing the sh!t out of me

That's funny. When I was in university, I had to explain the whole Krebs cycle. I once had an exam where there was only 3 questions, one of those was "Explain the Krebs cycle", it was worth like 50% of the whole exam.

I came close to introduce Krebs cycle concepts in this discussion, because it is so important to understand energy production in a cell, but I decided it was probably too complex, so I left it out, and only included a link to 2 web pages that introcuded it.

Sorry for confusing you that much

[user5145]

Good post man. Very informative. Are you a Biochemistry student?

[The_cannibal]

Good post man. Very informative. Are you a Biochemistry student?

Actually, no, however, I had biochemistry courses as part as my B. Sc. (1993).

[kick ass dude]

well there is an exercise forum, but i agree it's crap. elitist board ftl, and when you see things like leg press is as good as squats... amazing how much powerlifting is hated there and called useless, when there's nothing more useless than training for looks

[gobbles]

That's funny. When I was in university, I had to explain the whole Krebs cycle. I once had an exam where there was only 3 questions, one of those was "Explain the Krebs cycle", it was worth like 50% of the whole exam.

I came close to introduce Krebs cycle concepts in this discussion, because it is so important to understand energy production in a cell, but I decided it was probably too complex, so I left it out, and only included a link to 2 web pages that introcuded it.

Sorry for confusing you that much

Jeez, i hate biology and the stupid kreb cycle, it confuses the hell out of me

[Arlecchino]

Excellent post.

[Juic3]

cliffs?

[iliketojuggle]

cliffs?

You cant "cliffs" it.. You have to read the whole thing to really get it..

[Tyro]

That is a great post ever consider writing and getting your name out?

[The_cannibal]

well there is an exercise forum, but i agree it's crap. elitist board ftl, and when you see things like leg press is as good as squats... amazing how much powerlifting is hated there and called useless, when there's nothing more useless than training for looks

Yeah, I was thinking of either the exercise section, or the workout program section, or the powerlifting section. So I chose the one that seemed most oriented towards strength knowledge...

[The_cannibal]

That is a great post ever consider writing and getting your name out?

Thanks

To be honest, big parts of this text were taken straight out of other web pages, but I just reorganized it so it could be easier to understand, and I added some of my own "conclusion".

I was thinking of doing a kind of Q&A thread, but I'm not sure in which section to do it. I could pretty much answer most questions on biochemistry, endocrinology, steroids, pro-hormones, supplements, training science (kinesiology) and these kind of things.

[Tyro]

Thanks

To be honest, big parts of this text were taken straight out of other web pages, but I just reorganized it so it could be easier to understand, and I added some of my own "conclusion".

I was thinking of doing a kind of Q&A thread, but I'm not sure in which section to do it. I could pretty much answer most questions on biochemistry, endocrinology, steroids, pro-hormones, supplements, training science (kinesiology) and these kind of things.

Sound sinterasting, i think i could use someone with such vast knowledge, pmed.

[tevez]

Great post cannibal. Answered my question and more. thanks...

[Quarter Nelson]

That's funny. When I was in university, I had to explain the whole Krebs cycle. I once had an exam where there was only 3 questions, one of those was "Explain the Krebs cycle", it was worth like 50% of the whole exam.

I came close to introduce Krebs cycle concepts in this discussion, because it is so important to understand energy production in a cell, but I decided it was probably too complex, so I left it out, and only included a link to 2 web pages that introcuded it.

Sorry for confusing you that much

Funny indeed, I had a test about a month ago where 50% of the exam was an essay question: Explain Kreb's cycle. I just studied for like three hours the night before, only reason I passed the test. Of course I completely forgot everything within a week.

Reps because I could actually understand what you're saying, unlike my biology textbook.

[ehlpitel]

What'd you study?

[stenzinator]

wow parts of that are word for word from my brothers university biology text book. that exact diagram is in it. u must know ur ****. i think it all gets too confusing with that stuff, i wonder if the pros know all the science behind what theyre doing

[The_cannibal]

What'd you study?

You'll find that funny, but I studied Forestry. We had biochemistry courses in the program. I took a lot of out-of-faculty courses while I was doing my B.Sc.
I was already an athlete, so I also studied a lot on kinesiology, endocrinology, etc. I thought endocrinology could be very interesting; you know, HPTA and that kind of stuff, but we saw a lot of stuff on autocrine and paracrine stuff, not just endocrine hormones. It ended up being a bit boring at times.

[The_cannibal]

wow parts of that are word for word from my brothers university biology text book. that exact diagram is in it. u must know ur ****. i think it all gets too confusing with that stuff, i wonder if the pros know all the science behind what theyre doing

Most pro bodybuilders and pro powerlifters are genetically gifted. I would say that 95% of them know nothing about science: they either improvise or they follow their coach's advice.

[ottorotvic]

So, after reading that and taking a while to absorb it, the real question is:

Do you think that if I can leg press 900 lbs for 3 reps, that I can do a 300 lb raw, atg squat? What do you think my suited max might be?

[The_cannibal]

So, after reading that and taking a while to absorb it, the real question is:

Do you think that if I can leg press 900 lbs for 3 reps, that I can do a 300 lb raw, atg squat? What do you think my suited max might be?

LOL
I think that's beyond the scope of this thread

[Sash]

good post.

I found this page to be very helpful as well.

http://health.howstuffworks.com/muscle2.htm