When you buy through links on our site, we may earn an affiliate commission. Learn more here.

Feeling Fatigued After Swimming? Learn Why It Makes You (And Me! ) So Tired

Experts agree that swimming is one of the best exercises you can do for full-body fitness.

Propelling yourself across a body of water uses your entire body.

Arms. Shoulders. Back. Core. Legs.

It works a lot and it seems to work it hard.

Recently I have been swimming daily as the place that I’m staying has a few pools, and boy has it been wearing me out!

After a few days of this extreme exhaustion, I decided to look into why this is the case.

Water weakens gravity, which is what makes you float, and makes swimming so kind to your joints.

Water is denser than air, though, which means every movement requires more muscle than it would on land.

It’s easy to understand why low-impact, muscle-engaging swimming is such a good exercise for burning calories.

Put some effort in, it can also be an excellent cardio workout that strengthens your heart and lungs.

The downside of swimming as an exercise is that even everyday swimmers, from lifeguards to Olympic athletes, find a long swim exhausting.

Why Does Swimming Make Me So Tired?

Feeling Fatigued After Swimming? Learn Why It Makes You Tired

The question is, why is swimming such a sleep-inducer?

Most people come away from a half-hour run energized, so what’s with the head-bobbing after-swim routine?

There are a few reasons fitness experts think swimming makes you so sleepy.

1 – They aren’t kidding about that full-body exercise stuff.

Since swimming uses all your muscles, it requires a lot of energy.

Since it zaps calories, that energy will go fast.

You can swim on an empty stomach, but, if you want to stay awake, you shouldn’t.

A snack of protein, whole grains, and fruits and veggies about an hour before a swim helps ensure you have the energy to expend.

On the flipside of that, you don’t want to eat too much too close to a swim.

If you do, your body will still be working to digest when you need the extra energy.

Consume larger meals at least three hours before jumping in the water, but four hours is even better.

A 135-pound woman will burn over 300 calories every 30 minutes while swimming.

Keep that in mind when planning pre-swim meals and snacks.

2 – The sun is your friend, but it can be your enemy.

Sunlight exposure in moderation is good for you.

It produces natural Vitamin D, essential for good health, and helps regulate your circadian rhythm.

Anyone who has spent a day out at an amusement park or at the beach can tell you, though, too much sun can wipe you out physically.

While too much sun exposure is detrimental to your health, damaging skin and upping your risk for skin cancer, it is not the sun itself that makes you tired during a swim, or while hiking on a sunny day.

The sun only enhances the conditions for exhaustion by making hot days feel hotter.

When your body gets hot, it has to work to get your temperature back to an acceptable level.

You will also dehydrate more quickly, so you need to drink more to stay adequately hydrated.

Keeping water or a sports drink close by and taking breaks during a long swim to drink will help prevent the fatigue that comes with dehydration.

Cold drinks will also cool you off, helping regulate your body temperature.

Drink two cups within ten minutes of diving in, and another cup every fifteen to twenty minutes during your swim.

3 – That after-swim cool-down is actually a warm-up.

So far, the things that make you sleepy during a swim aren’t unique to swimming.

Running and mountain biking burn even more calories, but most people don’t complain about the same state of exhaustion after a run or a ride.

That may be due to the major factor that sets swimming apart from the pack.

When you run, bike, row, or do most any other type of aerobic exercise, you heat your body up.

Your heart speeds up, your blood pumps, your muscles get warm.

Your body sweats in an attempt to regulate your temperature as you work out, and when you stop, your body cools back to normal.

Water is a major conductor of heat, and when you jump into any body of water with a temperature colder than your body temperature, the water steals heat from you.

Cold water is 20 times more effective at stealing your heat than air of the same temperature.

So, as soon as you jump into a pool or lake, your body is working before you take that first stroke.

Just as when you get hot, when you get cold, your body must work to regulate your temperature.

While working out hard enough to sweat, though, burns more calories than an exercise that doesn’t lead to sweating, sweating itself is a passive body function that requires little energy.

Shivering is the body’s means of warming up, though, and shivering requires considerable energy.

How Much Energy Does Swimming Take?

A recent study indicates 10 to 15 minutes of shivering is roughly equivalent to an hour of moderate exercise when it comes to metabolic function.

So, when you swim, you are using your entire body, burning up lots of calories, and your metabolism gets a boost to boot.

Even once you are out of the water, your core body temperature will still be lower than normal.

Your body will continue to expend energy until it gets back to normal.

Unless the water is equal to or higher than your body temperature (which is too warm for comfort for most people, and can lead to sweating and, therefore, faster dehydration), every time you swim, you will expend extra energy to stay warm and experience an increase in your metabolism.

As far as your body is concerned, swimming is almost a three-fold workout.

No wonder it makes you so tired.

Swimming in water temperatures right around 80 degrees proves just right for most people.

It’s cool enough to swim without overheating, but warm enough to keep your body temperature from falling too much.

Of course, if you’re swimming in a public pool, or a natural body of water, the temperature of your water is up to a caretaker or Mother Nature.

If you can’t find a swim spot with an ideal temperature, adjust what you can.

Eat at appropriate times for your swim schedule, avoid the hottest part of the day when the sun sits highest in the sky and keep drinking to fend off dehydration.

These small changes can add up to a big boost in energy during and after a swim.