One of the most well-known tricks to help promote buoyancy in swimmers is to hold your breath. If you’re a beginning swimmer, you may have cause to question the effectiveness of this tip, particularly if you sink to the bottom even when you’re lungs are filled to their maximum capacity.
Holding your breath will help you to float in water, according to Archimedes’ Principle. The more air present within your lungs, the more water that you will displace. This additional displaced water provides a slight boost to your upward buoyant force, promoting flotation.
For those of you that don’t have a firm grasp of Archimedes’ Principle, this may be a totally foreign concept to you. Fear not, as we will break down this groundbreaking physics principle in plain English below. This way, you won’t have to go through the hassle of sorting through all the scientific jargon that generally accompanies these types of questions.
How Holding Your Breath Helps with Flotation
To fully understand how holding your breath supports buoyancy, we’ll first revisit the concept of Archimedes’ Principle. With a solid foundation of Archimedes’ Principle established, we can then apply this concept to human flotation and delve into the reasoning behind why you should hold your breath if you want to float.
A Brief Summary of Archimedes’ Principle
Archimedes’ Principle is a physics concept that aims to explain why certain objects rise in water, while other objects sink. This concept is named after the renowned mathematician and inventor Archimedes (source).
Although the Archimedes’ Principle has a lot of moving parts, the true core of the concept can be summarized as follows:
Essentially, the upward buoyant force and the force of gravity are in a constant tug of war to determine where an object will naturally rest in a fluid. If you have a hard time visualizing this mentally, you can use the labeled illustration below as a reference point.
The main deciding factor in what force will eventually claim victory (the upward buoyant force or the downward force of gravity) is the density of the object in question.
If the object is dense enough that it weighs more than the amount of water it displaces, the force of gravity will win and the object will sink. On the other hand, if the object sports a lower density, such that it weighs less than the volume of water it displaces, the upward buoyant force will win and the object will float.
On some occasions, the object will have a density such that it’s equivalent to the amount of water it displaces. Under these special circumstances—where the density of the object equals the density of the fluid—the object will have an equal propensity to either float or sink.
A prime example of this is seen within our very own heads! The human brain lies in a natural fluid called cerebrospinal fluid. Although the average human brain weighs approximately three pounds, our brains neither sink or float. This is because the density of our brains is equivalent to the density of our cerebrospinal fluid (source).
Many people are under the false impression that weight is the only thing that matters when it comes to buoyancy. Fortunately, this is not the case. If weight were the primary contributing factor to buoyancy, it would be hard to explain why a massive 6,000 ton yacht could float on water, but not a meager pebble.
Density is the real reason why some objects sink and why some objects float. Keeping that in mind, let’s see exactly how this ties back to human buoyancy.
Before we move on, however, I highly recommend you watch through the three minute video below. They briefly review all of the concepts listed above in a clear, concise manner.
How Archimedes’ Principle Relates to Human Flotation
Now that you have a general grasp of how Archimedes’ Principle works, we can finally get back to the topic at hand: How does holding your breath help with flotation?
First off, it’s important to understand that the air in your lungs helps to displace more water. As you breathe, your chest region inevitably expands. Consequently, the water surrounding your chest area gets displaced, which results in an increase in the the upward buoyant force and a noticeable increase in your flotation tendencies.
This is the scientific backing behind why swimming instructors tell their students to fill their lungs to maximum capacity. When the lungs are deflated, your body takes up less volume in the water, which results in less water being displaced.
Essentially, the more air you take in, the less dense that you become relative to the water. Surprisingly, the majority of people are neutrally buoyant in freshwater, so even a slight influx of air could make the difference between you floating and sinking into the water (source).
Of course, this is not necessarily true of every human on planet Earth. Every individual has a slightly different build and body composition, which results in slight variations in body density across the human spectrum.
As a general rule of thumb, the lower your body fat percentage is, the more likely you are to sink in water. This is the explanation behind why individuals with a high volume of muscle mass and a low volume of body fat tend to sink in water. Their inability to float can be traced back to the fact that their body is simply denser than the water that they’re swimming in, regardless of how much air they breathe in.
You can find more detailed information on this topic by clicking over to. Why Can’t Some People Float? (Everything You Need to Know!).
Do You Have to Hold Your Breath to Float?
So according to Archimedes’ Principle, breathing in as much air as you can into your lungs definitely helps with floating in water. This is valuable information, but it also prompts a follow-up question: Do you have to hold your breath to float?
Like the answer to most questions, the answer is that it depends on the individual. In this case, the primary variable we should be looking at is the buoyancy level of the individual in question.
If the individual has a body composition such that they’re positively buoyant, they may not need to hold their breath to float in water. Since their body density is already significantly lower than the density of the surrounding fluid, it is not necessary to breathe in any additional air to manipulate Archimedes’ Principle in their favor.
On the other hand, if an individual is neutrally buoyant, it will be mandatory for them to hold their breath to float at the water’s surface. Since neutrally buoyant individuals have an equal tendency to either float or sink, their body wants to rest underwater somewhere in between the surface of the water and the depths below. To counteract this natural buoyancy, their lungs will have to fill with air if they plan on remaining above the water.
Lastly, it may not even be possible for a negatively buoyant individual to float at the water’s surface, no matter how much air they breathe in. Since their body density is so much higher than the density of the surrounding fluid, the buoyancy effects of holding air in the lungs is rather negligible in the grand scheme of things. To surface above the water, negatively buoyant individuals will have to exert a high degree of energy by treading water.
This is often the reason why negatively buoyant individuals encounter difficulty with swimming. Their muscles tire much more quickly as it is a constant uphill battle to take in air at regular intervals.
In summary, certain individuals will have to hold their breath in order to float, while others do not. If you want to know whether or not you need to hold your breath to float, you first need to know what your natural buoyancy level is (positive, neutral, or negative).
Is Holding Your Breath the Only Trick that Positively Impacts Flotation?
After learning that holding your breath does in fact help with buoyancy, I’ve found that many swimmers are curious as to whether there are other effective techniques and strategies to float in water. Luckily, there are! We’ll go over these tricks in further detail below.
The “Spread Eagle” Technique
One popular strategy that swimming instructors employ when teaching swimmers how to float is the “spread eagle” technique. With this technique, the swimmer orients themselves horizontally, so that their back is lying on top of the water’s surface. They then spread their limbs out and away from their body to take up as much space in the water as possible, almost like they’re making a snow angel.
If you have a hard time visualizing this, refer to the picture below.
The reason that this strategy works so well is that it optimizes the amount of water your body is able to displace. By spreading out your limbs and lying horizontally, you maximize the surface area on your body that contacts the water. In essence, there’s a greater volume of water working to prop you up and support your buoyancy when implementing this tactic. If go to the other extreme and curl yourself into a ball, you’re far more likely to sink underwater.
Lying in Saltwater Over Freshwater
Another effective strategy for upping your natural buoyancy is to rest in bodies of saltwater rather than freshwater. It’s a little known fact that saltwater is slightly more dense than freshwater. The density of freshwater is approximately 1.0 g/mL, whereas the density of saltwater is 1.025 g/mL (source). The high salt concentration in saltwater increases its overall mass, while having a negligible effect on its total volume.
This difference may not seem like much, but it plays a significant factor in human flotation. Recall that most humans are neutrally buoyant, so even the slightest change in the density of the surrounding fluid can have massive implications on an individual’s natural buoyancy level.
Since saltwater has a slightly higher density, it’s able to keep slightly denser objects at its surface. So if you’re a neutrally buoyant individual teetering on the edge of floating or sinking, this might just be the trick you need to float naturally.
The Bottom Line
In conclusion, holding your breath does in fact help humans to float. It all has to do with a discovery made long ago, called Archimedes’ Principle. So if you want to get even farther into the nuts and bolts of why holding your breath promotes flotation, it may be in your best interest to research this physics principle on your own time.
If holding your breath still isn’t allowing you to float, experiment with the spread eagle technique and find yourself a body of saltwater to practice floating. Utilizing these strategies in combination may be what finally pushes your natural buoyancy over the edge to where you want to be.