You feel it the moment you enter the water. Your heart pounds, your muscles contract, your lungs tighten up! Fortunately, that feeling doesn’t last for long. A few minutes later, you’ve moved beyond that initial hump of shock (and temperature change) and floated into a world where swimming freestyle is almost as comfortable as walking.
Water is nearly 800x more dense than air, and as they say, a body in motion stays in motion! Beyond the simple inertia, what’s actually happening inside your body as you move through the water? Let’s dive in and find out!
Think of your body as a vessel. When you start your workout, every part of your body works together to move your vessel forward. Some body parts and energy systems work harder than others. Your heart will begin to beat faster to pump blood to your muscles, while your stomach will slow down because digestion is no longer a priority.
When you’re exerting physical effort, your body tries to accomplish three main things:
• Increase Oxygen Flow
• Eliminate Metabolic Wastes
• Eliminate Heat
Energy Systems 101
The result of making all those things happens results in your body creating ATP, scientifically known as Adenosine Triphosphate. ATP is the basis of function of your body’s activity, and depending on what type of workout you do, your body will kick into one of three states:
• Phosphagen System
• Glycogen System
• Aerobic Respiration System
In this state, every one of your cells has enough ATP to last 5-15 seconds. During short-term, intense activities, a large amount of power needs to be produced by the muscles, creating a high demand for ATP
Example Swim Set: 4 x 15m Bursts @ 2:00
Since 5-15 seconds of physical movement gets used up pretty quickly, your muscles also have a reserve called glycogen. Glycolysis is the predominant energy system used for all-out exercise lasting from 30 seconds to about 2 minutes and is the second-fastest way to resynthesize ATP.
Example Swim Set: 4 x 100s Best Average @ 3:00
Aerobic Respiration System
After you’ve been swimming for about two minutes and your body realizes that you’re not stopping anytime soon, it goes into aerobic respiration and responds with oxygen. The aerobic system, which is dependent on oxygen, is the most complex of the three energy systems. The metabolic reactions that take place in the presence of oxygen are responsible for most of the cellular energy produced by the body. However, aerobic metabolism is the slowest way to resynthesize ATP.
Example Swim Set: 10 x 200s Short Rest @ 2:30
Now knowing all of that, what is actually happening to the rest of your body when you start to swim?
Blood flow increases as your body supplies additional blood cells to your rapidly beating heart.
As you warm up, your body is trying its best to release heat. Your blood vessels dilate, bring heat towards the skin, and then release it. This is why your skin feels warm when you work out: It’s your body’s way of getting all the inner heat out. Some people’s faces (and bodies) turn red during a tough swim, signifying that heat is leaving the body.
In addition to calling on one of the previously mentioned systems to gain energy and ATP, your muscles also tear. But don’t worry — these are tiny “micro tears” that take a day or two to rebuild. The tears explain why your muscles feel sore, and the rebuilding is how they get stronger over time.
VO2 Max is a term you may have heard around the gym, and it represents the maximum amount of oxygen that a person can use. When you swim, your lungs work quickly to take in all the oxygen that your body requires. Over time, as you get more fit, your VO2 Max will be higher.
Remember how working out for more than two minutes takes your body into aerobic respiration? This means that oxygen is needed throughout the whole body. As a result, your heart rate will increase to efficiently move the oxygen to your muscles.
Your brain loves swimming. The extra blood and oxygen helps you become more alert, awake, and focused. It releases endorphins, the “feel good” hormones in our body. There are some cool graphics that show how the brain literally lights up in more areas even after a 20-minute walk. The same thing happens when you swim!