What's the difference between strong muscles and big muscles?

I’ve often heard it said that there are different exercise methods depending whether you want to build strength or muscle mass. Usually, the focus is on high reps with light weights vs. low reps with heavy weights. There’s something counter intuitive there. Aren’t big muscles also strong? If not, how are they different, scientifically speaking?

Big muscles will be strong as the work needed to stimulate growth also builds strength. However, bodybuilders are looking to maximize size with being stronger as a side effect.
When training for strength, part of the increase in strength is from learning to recruit more muscle fiber.
Even when lifting your maximum, only a fraction of muscle fiber is used. This is why you hear stories of someone lifting a car or such, all the fibers in a muscle are used in one burst of effort. What you don’t hear about are the injuries often suffered from torn muscle and tendons.

Stamina vs. strength. Contrast a Tour de France winner at 150lbs with a 250lb gym bunny.

Mass (muscle hypertrophy) refers to the cross sectional area of the muscle. Not all increased cross sectional area is able to translate to increased force; there are elements that are not contractile.

Strength refers to getting the fibers to fire in a manner that produces a maximum amount of force in one effort. That means maximum amount of contractile elements (which again is not the exact same as cross sectional area) and getting all of the motor units to fire in a cohesive way. Motor units are the groups of muscle cells that controlled by the same motor nueron so therefore all fire at the same time; each muscle is made up a many motor units. The latter part of that equation gets referred to as the “neural adaptation” of training and is where much of the early gains in weight training come from.

Power, another phrase you’ll hear, is work (force*distance) per unit time, or phrased a bit differently is force times velocity of the contraction. For many athletes that’s the holy grail and motivates other sorts of training protocols, especially plyometrics.

The last phrase that gets thrown in the mix is “endurance” - how long can the activity be sustained? Usually that means slow twitch fibers.

That’s interesting. An ME doing an autopsy would obviously be able to spot big muscles, but would she be able to tell if muscles were strong or endurant? Could that be done by eyeball, or would it take examination under a microscope or other tests?

I am not so sure about the naked eye bit. Slow twitch (Type 1, endurance muscle) fibers have more capillaries and mitochondria and oxygen-binding myoglobin and are thus sometimes referred to as “red muscle” while fast twitch (Type 2, the strength and power fibers mostly) have less and are therefore sometimes referred to as “white” muscle. Actually there are two types of Type 2: 2a which have a fair amount of myoglobin and mitochondria and are relatively fatigue resistant; and 2b which fatigue quickly with less myoglobin and mitochondria and are the alleged “white” muscle. Those fiberss in particular are the ones brought in when strength and power are being maxxed.

How much that would play out during an autopsy I do not know. Certainly they look different histologically.

To be overly simple, there are two types of muscle growth. One is when the muscle grows new muscle fibers. The muscle has ‘learned’ that it is often called upon to lift heavy things and it needs a bit more help doing that.

The second is the addition of all the stuff that keeps a muscle running and working- capillaries, nerves, mitochondria, etc. Each fiber sort of ‘swells’, making the muscle look bigger. Those things aid endurance and come when the muscle ‘learns’ that it tires out too soon.

So that’s why you hear about varying weights and reps. Heavy weights help with the former and many reps help with the latter.

Power lifters and body builders are both going to have very strong muscles, the notion that body builders have some kind of fake, non-strong “show” muscles is nonsense. Serious body builders are VERY strong people. Body builders prior to posing or being photographed tend to do very specific exercises that inflate their muscles with blood. In a non-inflated state when they are not starving themselves to minimize body fat power lifters and body builders can look remarkable similar.

Ronnie Coleman a multi Mr Olympia winner was an insanely strong person. See this video of this workout


I think what some people are referring to when they speak of big vs. strong muscles is an impression that bodybuilders’ large muscles, while strong, still aren’t as strong as their size suggests. In other words, they may be of the belief, say, that while a bodybuilder’s biceps may be three times the size of a fit and strong gymnast’s, he may not necessarily be able to curl three times as much weight even though the bodybuilder’s biceps are still quite strong compared to those of an average man.

One thing I’ve heard (and I have no idea how true it is) is that a lot of body builders are actually creating scar tissue in their muscles. This adds bulk to their muscles without adding strength. A muscle that’s 50% scar tissue might be twice as big as an unscarred muscle but they have the same strength.

As I said, I don’t know if this has any basis in fact.

One thing I understood about body builder’s muscles (and I may be wrong, please correct me!) is that they just train muscles that you see. So they may have some muscles that are very bulky, but that are no use if you want to lift a sofa up the stairs, or open a jar, or carry your sweetheart over the doorstep. They might be useful for those things too, but they might not be. In that way, there could be a difference in which muscles you train: useful ones or visible ones. Our idea of “strong” is of course related to practical use.

Several years ago thier was a guy at the gym that reminded me of Clint Eastood, just a bit more muscular but still very lean. He was lifting with the local monster lifters and keeping right up with them. It didn’t seem to make sense. His arms were no more than 16 1/2 yet he was doing 120# dumbell excersizes with his triceps. Hs bench presses were over 300# yet his chest was relatively small in cmparison.

Nitpick: The muscle does not develop new fibers; it increases the size of the ones that are already there. That’s one of the reasons why some people can develop larger muscles - they were born with more muscle fibers, and those fibers can be increased in size. This increase is called sarcomere hypertrophy. One can also increase the size of the other components of a muscle group. This is sarcoplasmic hypertrophy. Pumping increases the size of a muscle by overcoming the ability of the blood vessels to remove fluid from the muscle, increases sarcoplasmic hypertrophy, and increases the number and size of blood vessels in the muscle so it can be pumped up bigger next time. (Cite.)

Other factors are involved in increased strength. One is the number of fibers one can recruit in a single effort. This can be increased with training, and accounts for much of the early increases in strength encountered by novice lifters. The upper limit of how many fibers can be recruited is also genetically determined. as is the ratio of slow-twitch (endurance) vs. fast-twitch fibers (strength and, mostly, size).

Bodybuilders in general are much stronger than the average person, but powerlifters tend to be stronger in momentary effort. Bodybuilding tends to stay in the 8-12 rep per set range, which is believed to be best to increase size more than 1-5 reps, which is what powerlifters tend to do. You get better at what you practice.

Bodybuilders are actually doing more work in the physics sense, even if powerlifters use more weight. You are generating more horsepower by doing ten reps with 200 pounds than by do one rep with 400.


There have been animal studies that demonstrate hyperplasia. Documenting in humans is difficult as you can’t kill them and perform vivisections.:smiley:

There isn’t really a difference- from what I understand, 1 lb of muscle in one person is potentially just as strong as someone else’s 1 lb of muscle.

What differs in most cases is the proportion of the muscle fibers in that lb that are actually utilized.

So in some wiry guy lifting 200 lbs, he may be using 40% of the fibers in some muscle, and some normal guy may be using 10% and unable to lift it. However, if both were using 40%, the normal guy would have lifted it faster.

It’s kind of like RPM/displacement in engines; a 2.5L 4 cylinder engine making 150 hp at 4000 rpm will out pull a 5L 8 cylinder engine at 1000 RPM, but if both were at 4000 RPM, it’s likely the 8 cylinder engine would blow away the 4 cylinder one.

Or opening a water bottle: - YouTube

When you get a chance, look at a gymanst. These men and women look very fit, but obviously don’t want a lot of bulk (because the extra mass just gets in the way and limits agility which is crucial to dynamic moves) but are phenomenally strong. I’ve seen a male gymnast walk up to an Olympic bar with 300 lbm of plates on it and perform multiple clean and presses like it was an everyday thing for him. Actually, he said afterward that he hadn’t lifted weights since high school and even then nothing like that amount. I’m going to guess he was about 5’10" and around 180 to 190 lbm. He was in clean shape, certainly, with well-developed shoulders, arms, and trunk, but in street clothes you wouldn’t give him a second look in terms of size.


I have been doing push-ups for over a half of a year now. I do 60-70 every day. I have also been doing other upperbody exercises, as well as pushing my manual lawn mower every week.

My arms are big now (to my eye). But they don’t seem very cut or firm. Just big. I guess I was hoping for more sinew. They kind of startle me when I look in the mirror. I’m thinking of discontinuing my exercises.

I do have mild hypotonia. I’m wondering if maybe my muscles compensate for lack of tone by bulking up.

Anyone know if this is can happen, or am I just grasping at straws?

Yes and completely immaterieal to the op. Certain approaches have evidence-based recommendations that differ if the goal is to optimize one or the other characterisitic. Lots of detail in that link (pdf). Yes there is a lot of overlap and a program designed to optimize hypertrophy will also produce a fair amount of strength and program designed to produce power will also produce some hypertrophy. But the thought, based on some evidence, is that a program designed to optimize one will not optimize the increase in the other as well.

Here’s a key point from that linked American College of Sports Medicine position statement on progression models in reistance training:

Note the bit about the size principle: The higher force-producing units will only fire (along with the lesser force-producing motor units) on maximum efforts. Maximum strength in one lift means building up those motor units which means at least 80% RM lifts in trained individuals. Those motor units will consist of mostly Type 2b and fatigue fast. If the goal is hypertrophy then Type 2a can be targeted and hit with more volume. (Moderate load, higher repetition, short rest periods, and throwing in a lower weight high rep set in the mix.)

Not true to any substantial degree

That last bit is a particular cogent point.

Will you accept a statement that there is curently no evidence that hyperplasia (new cells) occurs in human muscles and that the current standard teaching is that all we can do is hypertrophy what we got … and some of us come more type 1 and some more type 2?

The second part may be mostly true but the first is not.

I had a friend in college who was a rings man. Not huge although you could lose a pencil in the space between his biceps and triceps. Sinewy does not begin to describe his definition. My height and weight roughly, 5 foot 6 inches and about 150 to 160. He benched 300 when he benched (which was just for kicks).