From big muscle groups to tiny little muscles with hard-to-pronounce names that you may have never heard of, the human body has more than 650 named skeletal muscles. Depending on how you define a single muscle, the total may be over 800, and those muscles range from minuscule to maximal.
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Each person's body differs from their neighbor's or their bench press spotter's in interesting and, oftentimes, beautiful ways. Does that mean that one person's small muscles pack less punch per pound than another's bulky guns? Do larger muscles develop differently than their less massive peers?
Rather than pit big muscles against small muscles in an all-out brawl, take a broader view of how muscles of all sizes develop and function will lend you more insight on exactly how much size matters — or doesn't.
About Big Muscle Groups...
In terms of muscles found on the individual human body, the biggest can weigh a few pounds, while the smallest ones clock in at just a few ounces or even less. Although muscle sizes are clear cut, the question of which muscle is the strongest is quite debatable, especially if you consider strength as relative to size.
A key part of that big muscle group, the gluteus maximus — that's right, your good old butt muscle — is the single largest muscle in the human body. Then again, "maximus," the Latin word for "the biggest," is right there in the name, so this revelation might not be all that earth-shattering for some readers.
Not only is the gluteus maximus the largest muscle in your body, it's also one of the strongest. Your butt doesn't just look good in your favorite skinny jeans and keep you comfy when you're sitting at your desk from 9 to 5, it keeps your trunk in an upright posture when you're standing. In this way, the gluteus maximus serves as an anti-gravity muscle that's crucial for balance.
...And Small Ones Too
Way on the other end of the scale is a far more obscure little muscle: the stapedius. This tiny muscle, the absolute smallest skeletal muscle in the human body according to an article in the March 2019 issue of the Indian Journal of Otolaryngology and Head and Neck Surgery, is only about 2 millimeters long, with a maximum breadth of just 2 or 3 millimeters. Found in the middle of your ear, the stapedius helps stabilize the smallest bone in the body — the stapes.
The stapedius helps keep the sensitive mechanisms of the middle ear from vibrating too hard when you hear a particularly loud sound, while also dampening internal noises like chewing. So in the battle of big versus small, it's clear that the glutes versus stapedius isn't a fair battle; it really depends on if you like standing or hearing more, which is a pretty tough choice.
Just as size doesn't equal importance in this comparison, some of the body's strongest muscles range widely in terms of their mass. According to the Library of Congress, your most exceptionally-powerful muscles include the external muscles of the eye, the heart, the muscles of the uterus, the tongue and the masseter muscles of the jaw. The latter can close the teeth with a force of up to 200 pounds, which makes it the strongest muscle relative to its weight.
How Muscles Get Big
Chances are, you aren't looking to pump up your stapedius muscle (nor is such a thing possible). For many exercisers, the journey from small muscles to big ones is a key motivating factor for hitting the gym in the first place. But before you start making your muscle group workout chart, it's important to understand the factors that affect how your muscular system works.
In the quest for big muscles, terms like "hard gainer" or "genetic predisposition" hardly tell the whole story. Dr. Erin Nitschke, NFPT-CPT, NSCA-CPT, of the American Council on Exercise, writes that: "While the rate at which a person will build muscle mass is not predictable, with the right diet and proper training regimen, everyone has the ability to add strength and mass."
According to the American Council on Exercise and Dr. Nitschke, the two factors that influence muscle mass development are genotype and phenotype. The genotype is the genetic code of an individual, while the phenotype encompasses all the observable physical characteristics of that individual. Those are factors you can control, such as your training load, training duration, exercise frequency, carbohydrate and protein intake, caloric intake and hydration levels.
Long story short, while genotype does dictate the absolute upper limit for your attainable muscle mass, and how quickly that muscle mass grows, it's not the gatekeeper for "big" muscles. When your body is functioning normally — whether that body is big or small — continuous training results in the development of new muscle tissue, a process of cell growth known as muscle hypertrophy. With that new tissue, naturally, comes bigger size.
"With the right diet and proper training regimen everyone has the ability to add strength and mass." — Dr. Erin Nitschke, NFPT-CPT, NSCA-CPT, American Council on Exercise
Muscle Mass vs. Strength
Now that you know that a small muscle doesn't necessarily equal a weak muscle, you might ask yourself: does muscle size determine its strength at all? That's a valid question.
The short answer is that lots of factors influence muscle strength, regardless of size. As three-time world record powerlifter Greg Nuckols of Stronger by Science puts it in a November 2016 article, "A ton of factors influence strength beyond muscle size and skill." He says that "the strength of individual muscle fibers, normalized muscle force [...] and body proportions can all have significant, independent effects on strength."
While Nuckols notes that it's impossible to definitively say exactly how much muscle mass contributes to strength, based on currently available research, he points out that even for beginning lifters, size and strength aren't a one-to-one correlation.
Although it's normal for a dedicated weight lifter to achieve a roughly 50 percent gain in muscle mass over a few years, the amount that you can lift — including traditional strength indicators like squats and presses — doesn't usually see an equivalent increase.
Over the course of a few years, many lifters gain four to eight times more strength, as measured by lifting ability, than they do muscle mass. That's one reason why it's not uncommon for gym-goers to see a person with smaller muscles squatting with an amount of weight that a person with much bigger muscles may struggle with. It also explains why Olympic lifters are not all massive. But how does it work, exactly?
"A ton of factors influence strength beyond muscle size." — Greg Nuckols, Stronger By Science
Does Size Equal Strength?
One more direct correlation between muscle size and strength lies in individual muscle fibers. According to Nuckols, bigger muscle fibers are generally capable of producing more force than smaller muscle fibers. However — and this is key when talking big and small — relative strength tends to decrease as size increases.
According to a small study published in the November 2015 edition of Experimental Physiology, this time in the November 2015 edition, size doesn't appear to be everything. This study of 12 bodybuilders, six power athletes and 14 control subjects shed a fairly bright light on the size versus strength debate.
It found that the specific tension — meaning the maximal force of the muscle divided by its cross-sectional area — of the bodybuilders' muscles was a whopping 62 percent less than that of the power athletes' presumably smaller muscles.
Interestingly, yet another study finds even less equivalence between muscle size and strength. In February 2016, GeroScience (the official journal of the American Aging Association) published research finding no correlation at all between gains in quadriceps size and gains in leg press strength.
This study examined 287 women and men, aged 19 to 78 years old, training for a five to six-month period. So while it's possible that the somewhat-short training period may be a factor, that's still a pretty revelatory finding.
While a muscle's cross-sectional area can account for a significant amount of the variability you witness in an individual's strength, the architecture of the muscle itself and the capacity for skill learning — both factors affected by training — must also be taken into account.
These Muscles Need More Research
In contrast to the Experimental Physiology and GeroScience studies, another modest study from the July 2014 publication of Disability and Rehabilitation states that muscle volume perhaps shouldn't be discounted so readily.
At least in the case of the 19 youths with cerebral palsy (CP), which were studied for rehabilitative purposes, researchers found that muscle volume "appears to be a better predictor of muscle work in children with CP than aCSA," where "aCSA" stands for the anatomical cross-section of the muscle.
Other as-yet unmentioned factors wholly outside of size include varying levels of testosterone and androgens, and neurological strength (the efficiency with which your body sends contraction signals to your muscles), according to sources such as the New Zealand's University of Waikato and the University of Illinois Urbana-Champaign.
These factors and the presence of conflicting research perhaps inspired a group of scientists to conduct a meta-analysis of size-versus-strength research dating back to 1955, published in the November 2016 edition of Muscle & Nerve.
As the researchers point out, "the conclusion that a change in muscle size affects a change in strength is surprisingly based on little evidence." The Muscle & Nerve review suggests that these three factors should be considered before assuming that size is equal to strength:
- A lack of correlation between the change in muscle size and the change in muscle strength after training.
- The loss of muscle mass with lapses in training, in contrast with the maintenance of muscle strength.
- Similar muscle growth between low‐load and high‐load resistance training yielding divergent results in strength.
Despite this complex confluence of factors and continually emerging studies, at least one thing remains clear: show muscles of any size some love with a healthy dose of consistent strength training, and those muscles will get stronger. Period.
Read more: How to Reduce Muscle Size
Is This an Emergency?
- Library of Congress: "What Is the Strongest Muscle in the Human Body?"
- Indian Journal of Otolaryngology and Neck Surgery: "Microsurgical Anatomy of Stapedius Muscle: Anatomy Revisited, Redefined With Potential Impact in Surgeries"
- American Council on Exercise: "How Muscle Grows"
- Journal of Applied Physiology: "Skeletal Muscle Mass and Distribution in 468 Men and Women Aged 18 - 88 Yr."
- Stronger by Science: "Size vs. Strength: How Important Is Muscle Growth for Strength Gains"
- Experimental Physiology: "Single Muscle Fibre Contractile Properties Differ Between Bodybuilders, Power Athletes and Control Subjects"
- AGE: "Heterogeneity in Resistance Training-Induced Muscle Strength and Mass Responses in Men and Women of Different Ages"
- Science Learning Hub: Pokapū Akoranga Pūtaiao, University of Waikato: "Muscle Performance"
- University of Illinois Urbana-Champaign: KIN122 — Chapter 5: "Four Factors Contribute to Muscle Strength and Size"
- Disability and Rehabilitation: "Does Muscle Size Matter? The Relationship Between Muscle Size and Strength in Children With Cerebral Palsy"
- Muscle & Nerve: "The Problem of Muscle Hypertrophy: Revisited"