If you’ve been involved in swimming for awhile, you’ve likely heard of the argument that muscular people have a harder time floating on the water. Although this argument has been floating around the swimming community for a long time (pun intended), the majority of people fail to understand the scientific reasoning behind this phenomenon.
Muscular people have a harder time floating on the water because muscle is denser than water. Muscle has a density value of 1.1 g/mL, whereas water has a density value of 1.0 g/mL. The more muscle a person has, the denser their body composition will be, which makes them more negatively buoyant.
To fully grasp the scientific backing behind why muscular people are more prone to sinking rather than floating, it’s necessary to understand the general principles of density, buoyancy, and the buoyant force. We’ll first take a brief look at these principles and how they apply to the main question of this article. Read until the end to find out if the flotation difficulties linked with increased muscle mass is enough to prevent a muscular person from learning how to swim altogether.
Why Muscular People Have a Hard Time Floating
The relationship between muscle mass and buoyancy level seems enough to understand at the surface level, but it can get complicated rather quickly when delving into the physics theory behind this phenomenon. You probably don’t want to hear a full-on physics lecture about this topic, so I took the time to put these concepts into plain English for you.
To start off, we need to understand a couple of terms:
- Buoyancy: The natural propensity of an object to ascend or descend in a fluid. The more positive the buoyancy, the greater the ability to float.
- Buoyant Force: The upward force exerted on an object as it is fully—or partially—immersed in a fluid. When this upward force is greater than the weight of an object, the object floats.
- Density: The amount of mass per unit volume of an object. In other words, this is a numerical measure of how “compact” that an object is. An object with a high density will have a more difficult time floating than an object with a low density.
The underlying reasoning behind why muscular people have a difficult time floating involves all of these concepts above. Fortunately, all of these concepts have been neatly interlinked to explain why some objects float and why some objects sink in the Archimedes’ Principle.
Contrary to popular opinion, the capacity to float on the water has nothing to do with size. If flotation were exclusively reliant on size, it would be extremely difficult to explain why a tiny, paltry pebble can sink underwater but a massive, four hundred foot yacht can stay afloat.
The Archimedes’ Principle illustrates that size is not what we should be concerned with. Instead, our main concern should be density.
Applying Archimedes’ Principle to Human Flotation
If our main concern is density, there are several different aspects of the human anatomy that we must take into account to see figure out why muscular people have such a hard time floating. The most prominent aspects of the human anatomy that warrant our attention include the density of muscle tissue, fat tissue, and bone tissue.
The average density values of these various body tissues are compared to the average density of water in the table below (source).
|Substance||Average Density Value|
|Fat Tissue||0.9 g/mL|
|Muscle Tissue||1.1 g/mL|
|Bone Tissue||1.75 g/mL|
From the chart above, you can see that the average density of fat tissue is less than water. Muscle tissue and bone tissue, on the other hand, are more dense than water. According to Archimedes’ Principle, only fat tissue will promote a positive buoyancy. In contrast, muscle tissue and bone tissue will support a negative buoyancy.
Explaining Negative Buoyancy in Relation to Humans
At its core, the concept of negative buoyancy means that the object in question has a tendency to sink in water due to its high density. In scientific literature, most experiments are conducted with physical objects, not humans. In the context of human flotation, however, we’re dealing with the exact opposite: human body composition instead of object density.
Pinpointing an individual’s exact body composition can be difficult, mainly because no human being is built exactly the same way. Humans have variable bone densities, muscle mass percentages and body fat percentages. Consequently, humans have variable buoyancy levels as well.
To offer some perspective, the average male has a body fat percentage between 18 and 24 percent and the average female has a body fat percentage between 25 and 31 percent (source). This level of body fat is normally enough to offset the negative buoyancy effects of bone tissue and muscle tissue, allowing the normal person to float on the water with ease.
In regards to muscle mass, the average male has a muscle mass percentage between 36 and 40 percent and the average female has a muscle mass percentage between 29 and 31 percent (source). This level of muscle mass is not sufficient to prevent a normal person from floating on the water’s edge.
However, there are special circumstances where an individual has a high bone density, an abnormally high amount of muscle mass, and an abnormally low amount of body fat. In this type of scenario, the weight of this person will be notably higher than the weight of the water that they displace. As a result, the water will be unable to support them, prohibiting them from floating.
This phenomenon is more commonly known as negative buoyancy. This is a rather uncommon occurrence in the general population because not many people are able to achieve such a low body fat percentage with such a high percentage of muscle mass. This type of body composition typically requires a rigorous exercise schedule and dieting plan.
The application of negative buoyancy to humans is considered to be somewhat controversial, as some people believe that all humans are capable of floating, regardless of their body composition.
Although there are certain strategic techniques to help with flotation, there’s only so much an individual can do to compensate for their negative buoyancy. Nonetheless, negative buoyancy in relation to humans is certainly a subject area that requires further experimental research.
Is It Even Possible for a Muscular Person to Float?
With all this talk of negative buoyancy, you’re probably curious as to whether or not muscular people even possess the capacity to float. I know that when I first learned of this concept, I asked the same question myself.
Muscle mass is only one single variable to take into account when determining someone’s ability to float. There are several other factors that you must consider as well.
High Body Fat Levels and Low Bone Density Levels Can Offset Negative Buoyancy Effects of Muscle Mass
As previously discussed, body fat percentage and bone density also play a significant role in how buoyant a person will be. So although a person may have a high degree of muscle mass packed onto their frame, this does not necessarily mean they’ll be negatively buoyant.
If this same person has a relatively high body fat percentage and below average bone density to go along with their high level of muscle mass, there’s a chance that they’ll still be able to float.
Saltwater is More Favorable for Human Flotation
Although human body composition is a crucial determinant of human flotation, you cannot discount the water composition either. The majority of people overlook the fact that the density of water can vary as well.
The most prominent instance of this is seen in the subtle difference in densities between freshwater and saltwater. Freshwater has an average density of 1 g/mL, whereas saltwater has an average density closer to 1.025 g/mL (source).
The salt within saltwater increases mass disproportionately to volume. As we all know, the equation for density is mass divided by volume. Since the mass is increasing significantly more than the volume, the density of saltwater increases in the presence of higher salt concentrations.
So why does this difference in water density between freshwater and saltwater matter?
This difference has an impact on Archimedes’ Principle. Since saltwater has a higher average density, muscle mass and bone density have a less profound effect in promoting negative buoyancy. As a result, humans will have a noticeably easier time floating in saltwater relative to freshwater. So if you’re a muscular person, see if you can tell a difference in your ability to float next time you take a vacation to the ocean!
The More Air a Person Breathes, the Better They’ll Float
Believe it or not, how a person breathes also has a direct correlation with flotation. These breathing effects are even more important for muscular people that have a tendency to sink in water.
When an individual completely fills up their lungs with air, the lungs essentially act as an air flotation device. The excess air displaces more water with little to no increase in weight. As a result, there’s additional water available to help support the individual’s body weight, regardless of whether or not they are muscular. In certain circumstances—particularly for people who are neutrally buoyant—breathing can be the ultimate deciding factor in their ability to float.
The problem is that most people take terse, quick breaths when they’re in a panic, especially in the water. Since muscular people are already prone to sinking, their sense of panic may drive them toward this unfavorable breathing pattern. Consequently, they become even more negatively buoyant.
This vicious cycle can be extremely difficult to break for muscular individuals who are not innately comfortable in the water. However, it is possible to overcome. In special cases, fixing this issue may even be enough for a muscular person to float.
Floating Gets Easier as a Person Spreads Out their Body Weight
Lastly, body weight distribution is another key factor in human flotation that can allow muscular people to float. In essence, the more flat and spread out a person is on top of the water, the more water that they’ll displace.
As you know by now, this extra displaced water can provide extra support to help hold an individual up on the water’s edge, even if the person is neutrally buoyant. This is why swimming instructors teach students to lie on their back horizontally and flare out their limbs as much as possible, almost like you’re trying to make a snow angel.
When a swimmer positions themselves in a vertical position, all of their weight is concentrated on one small sliver of the water. Consequently, there’s not much water displaced. This lack of displaced water is not enough to support someone’s entire body weight, which is why they sink.
When combined with other factors, such as trying to float in saltwater and implementing proper breathing technique, correct body weight distribution may even allow a negatively buoyant, muscular person to float.
Nevertheless, it’s important to bear in mind that certain muscular individuals may be so negatively buoyant that even a combination of all these positive buoyancy strategies will not be enough to overcome their predisposition toward sinking.
Does This Mean That Overweight People Have a Harder Time Sinking Underwater?
Now that we’ve answered the question of whether or not it’s harder for muscular person to float, it’s only rational to ask the follow-up question, “Do overweight people have a harder time sinking underwater?”
Again, the answer to this question is founded entirely on Archimedes’ Principle. Since overweight people have a higher percentage of fat tissue, their body composition is far less dense than the average person. This lack of density results in the complete opposite case of what we would expect to see in a muscular person. Rather than having a natural propensity toward sinking in water, they’ll have a natural propensity toward floating.
For this reason, overweight people will actually have to exert a considerable degree of effort in order to counteract their natural positive buoyancy. They’ll have to curl their body up into a ball and expel all the air from their lungs in order to increase their negative buoyancy. Sometimes, these strategies may not even be enough to cause sinkage.
Can Muscular People Swim if They Cannot Float?
With all this talk of how muscular people encounter major difficulties with floating, people are often curious as to whether these difficulties are enough to prohibit muscular people from swimming altogether.
Contrary to popular opinion, floating and swimming are not the same thing. They’re related to one another, but not synonymous with one another.
Muscular people can learn how to swim because swimming is an attainable skill that can be learned. Flotation, on the other hand, is not a skill. It’s entirely dependent on body composition. Although there are various strategies that can be used to promote positive buoyancy, this does not change the fact that some people will sink in water regardless of whatever tactics they choose to use.
This is not to say that the learning process will be easy for muscular individuals. Muscular people will have a much more challenging time learning how to swim because they’ll have to stay in perpetual movement to keep themselves above water.
If you’ve ever treaded water before, you know how grueling this can be. Continually paddling with the arms and kicking with the legs can get to be tiresome after just a few minutes. Most people can take a break from treading by lying on their back and floating naturally.
Unfortunately, muscular people do not have the luxury of rest in deep waters. Every second that they venture away from the shallows, they have to fight to keep their head on the surface. Muscular people may be fit, but treading water is extremely taxing on the body in terms of muscular endurance. At some point or another, even a person at peak physical fitness will hit their cardiovascular breaking point eventually.
For a sizable percentage of negatively buoyant, muscular individuals, the lack of rest and constant uphill battle is enough to cause them to quit this activity entirely. Consequently, the general population has gradually developed the misconception that muscular people are physically incapable of swimming.
Fortunately, this is not true. We can falsify this claim by taking a look at some of the best swimmers the world has ever known. People like Michael Phelps have shown that muscular individuals can shake the foundations of the swimming world!
The Bottom Line
In short, muscular people typically have a more difficult time with floating because their body composition is denser than the normal person. It ultimately comes down to the fundamental laws of physics. These scientific principles also explain why overweight people have a harder time sinking.
Despite these inherent issues with flotation, muscular people can learn how to swim. It may be a struggle at first, but it can be done. So if you’re a muscular person wondering if swimming is for you, sign up for a swim class and give it a try! The going may be tough, but it’ll be worth it in the end.