How Strenuous Exercise Affects Gut Health

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Did you know there’s a link between the health of our gut and intense, strenuous exercise?

We all know that exercise is good for us. Whether we enjoy exercising or not, we can at least all agree that it’s a health-promoting activity.

It gets us moving from our sedentary jobs and increases our heart rate to release endorphins. Our bodies were made to move, there’s no denying it!

Including exercise into your weekly routine has been shown to improve everything from your mood to your bone density.

Plus, with the spike in popularity of alternative forms of exercise like CrossFit and Yoga, there’s something for everyone. Even if you’re not the traditional gym rat.

However, when exercise becomes too strenuous or intense, it can potentially do our bodies more harm than good.

And you may not realize that strenuous exercise can affect the health and the functioning of our gut.

It’s true. That intense workout or long run, where you feel so good afterward, can actually be negatively impacting your digestion.

If you don’t have issues with digestion, the impact strenuous exercise has on your gut might not be affecting your everyday life.

But, so many women today have nagging gut issues that seemingly have no real cause. If that sounds like you, and you’re an avid exerciser, you’ll definitely want to keep reading!

strenuous exercise gut health

What is Strenuous Exercise?

Before I dive too deep into why strenuous exercise affects the gut, I need to define what strenuous exercise is.

Strenuous exercise is going to be different for everyone.

If you’re out of shape, a brisk walk might be strenuous. Or that CrossFit WOD could be strenuous for someone who hasn’t done it before.

But the easiest way to quantify what’s strenuous for your body is by calculating your maximum heart rate (MHR).

To calculate your MHR you just subtract your age from 220. So if you’re 30 years old, you would subtract 30 from 220 to get you an MHR of 190.

That means 190 beats per minute is theoretically the maximum number of times your heart should beat while exercising.

A strenuous exercise is one that uses 70 to 85 percent of that maximum rate.

So for our 30-year-old, a strenuous exercise would get her heart beating about 133 to 162 beats per minute.

Or if you’re not into numbers, a strenuous exercise is one where you can’t carry on a normal conversation without having to stop to breathe every few words.

And while there are certainly benefits to exercise at this intensity, women especially need to be aware of the underlying effects it could be having on our bodies.

One of those underlying effects is gut dysfunction.

strenuous exercise gut health

How Strenuous Exercise Affects the Gut

If you’ve ever experienced the not-so-pleasant runner’s diarrhea after a long run or intense exercise, you’re not alone.

One study has shown that up to 20-50% of athletes suffer from exercise-induced gastrointestinal symptoms. And that number increases dramatically with exercise intensity.

But, just because a large majority of athletes experience bowel issues from training, that doesn’t make it normal or healthy.

So, if you train intensely and experience gut symptoms during or even days after your exercise, keep reading. I’m about to dive into the reasons why strenuous exercise affects gut health!

1. Strenuous Exercise Increases Intestinal Permeability

Intestinal permeability, or leaky gut, is a condition where the cells of your intestines are no longer joined together properly. This allows large molecules like bacteria or undigested food particles to pass into your bloodstream.

Everything from food allergies to chronic inflammation can be attributed to leaky gut. So it’s definitely something we want to avoid.

Most of the time, the focus is on diet changes to improve the health of the gut barrier.

We’re constantly reminded that we should decrease foods like sugar and grains, and up our intake of collagen and bone broth. And by following those food rules, our leaky gut problems will be solved.

But, strenuous exercise actually plays a larger role in the integrity of your gut lining, or lack thereof, than you may think.

strenuous exercise gut health

Cortisol and the Gut Lining

Strenuous exercise, whether it seems like it or not, is a stressor on our bodies. And like any stressor, it brings with it elevated levels of our stress hormone cortisol.

And increased levels of cortisol can, among a host of other things, significantly affect the permeability of your gut lining.

High levels of cortisol act directly on the intestinal cells by weakening the junctions between them. This is why many people experience gut dysfunction like gas, bloating, or indigestion after a period of high stress.

And exercise-induced stress affects our cortisol levels, and therefore our gut lining, in the same way as life-stressors do.

Our bodies can’t tell the difference between an increase in cortisol due to the stress of a new job and an increase in cortisol due to strenuous exercise.

Leaky gut symptoms can come in the form of food sensitivities or nutritional deficiencies. If that sounds like you, toning down your exercise regimen may help.

Sometimes decreasing your exercise intensity can be all it takes to recover from the effects strenuous exercise can have on your gut health.

But if that doesn’t work, teaming up with a trained medical professional (like me!) is a good next step to resolving your gut issues.

2. Strenuous Exercise Alters Your Gut Bacteria

Did you know that your gut is home to hundreds of thousands of microscopic bacteria? These bacteria are critical for keeping not only your gut healthy but your entire body as well.

One of the best ways we can keep our good gut bacteria happy and healthy is by eating a wide variety of plant foods and fibers.

But participating in excessive strenuous exercise can actually be counterproductive when it comes to improving your levels of beneficial bacteria.

It’s been shown that strenuous exercise can decrease good gut bugs that were present previously, and increase bacteria that weren’t as common before.

It may seem like a stretch to say that our gut bacteria can be affected by how intensely we exercise. But it’s a real phenomenon.

strenuous exercise gut health

Cortisol and Our Gut Bacteria

The rise in cortisol levels that accompany strenuous exercise also negatively affects our gut bacteria. This increase in cortisol sends signals to our GI tract that actually alters the behavior of our microbiome.

There seems to be a direct link to how we respond to stress (including intense exercise) and the health of our gut bugs.

If we’re constantly subjecting our bodies to the stress of strenuous exercise it makes sense that our gut bacteria would be affected as well.

But, there’s good news. The negative effects of intense exercise on the microbiome can mostly be corrected once the strenuous training is stopped.

So these changes to your gut bugs from the stress of strenuous exercise most likely won’t be permanent.

But if you want to keep your microbiome healthy and happy, decreasing the intensity of your workouts is a good place to start!

3. Strenuous Exercise Affects Gut Motility

Gut motility is far more than just what keeps us pooping normally. It’s responsible for regulating the movement our GI tract starting all the way in your mouth.

Without these coordinated waves produced by the muscles in your gut, food and bacteria would simply stagnate. And a stagnate gut leaves us with unpleasant symptoms like gas, bloating, and constipation. This can also lead to SIBO if left unchecked.

This may seem like a process that should be fairly well regulated by your body. But unfortunately, that’s not always the case.

A variety of different factors affect gut motility. Everything from the types of food you eat to how much water you drink can alter the movement of your GI tract.

However, there’s another factor that’s critical to consider when talking about gut motility. And by now you may have figured out what that factor is.

You guessed it… stress!

Stress and its subsequent release of cortisol can have a profound effect on your gut motility.

We’ve already learned that strenuous exercise is a stressor. So it shouldn’t be much of a surprise that too much of it also negatively impacts our gut motility.

strenuous exercise gut health

Rest and Digest

Digestion occurs best while we’re relaxed and at rest.

As you can imagine, when we’re constantly pushing our body to the limits, it’s going to put the breaks on digestion in favor of more pertinent activities.

During strenuous exercise, things like breathing and moving our muscles become so much more important to sustain life than digestion.

And in this state of increased demand, our bodies just naturally reduce blood flow to our gut in favor of those more important organs.

With reduced blood flow, our gut motility becomes impaired. This can lead to symptoms of indigestion like bloating, heartburn, and gas.

If you tend to have a sluggish gut, tone down your workouts for a bit and see if your digestion improves.

But if you’re still struggling with gut-related symptoms, working with a qualified practitioner is a great next step. You can sign up for a strategy session with me; I’d love to team up with you to get your digestion back to 100%.

Why is Strenuous Exercise Stressful?

The negative effects strenuous exercise has on our gut can be traced back to one main factor. Stress.

You might be wondering why our bodies perceive strenuous exercise as a stressful event.

The rush of endorphins and “runner’s high” that you get during and after a good sweat session feels great! So why do our bodies see it as a stressor?

A major reason that intense exercise increases our cortisol levels is due to the process of gluconeogenesis.

When we’re exercising, our bodies have a high demand for energy. Energy to keep your heart beating, your lungs working, and your muscles pumping in order to sustain that activity.

We’re usually not inputting energy into our bodies (in the form of food) while we’re working out. So our bodies need to use what’s already available, which comes in the form of stored glucose or “glycogen.”

Stored glycogen in the liver and muscles is a great source of readily available energy during workouts. Until it gets used up.

When we run out of those glycogen stores, our body has to get busy and make its own glucose.

The process that our body goes through to make its own energy is called gluconeogenesis. And unfortunately for us, gluconeogenesis is inherently a stress hormone-demanding response. There’s no way around it.

Cortisol is the main driver, and actually initiates this process of glucose production. So when the body determines that it needs additional energy, it spikes cortisol so the energy creation process can begin.

This cortisol production associated with high-intensity workouts initiates a stress response in your body. And this state of stress is why strenuous exercise can wreak havoc on our gut health.

And keep in mind… this stress response is even worse if you are undereating or on a too low carb diet for your exercise intensity.

Chris Masterjohn has created a great video lesson on this topic if you’re interested in learning more about cortisol and gluconeogenesis.

moderate exercise gut health

How To Exercise to Support Gut Function

Strenuous exercise can lead to a host of gut issues. So, if you’re struggling with gut symptoms should you just stop exercising all together?

Nope, not at all!

All exercise is not inherently detrimental to your gut. And even certain types of intense exercise can be safe for your gut health.

But you should definitely take a break from strenuous forms of exercise if you’re experiencing gut symptoms.

Moderate exercise, such as yoga or walking, has been shown to reduce the severity and frequency of symptoms in people dealing with IBS.

And in those suffering from Inflammatory Bowel Disease, low-intensity exercise has been proven beneficial for symptom management.

Exercise that gets your body moving, but keeps your heart rate low, does wonders for digestion.

Moving your body helps to also move the fluids in your body. And when it comes to digestion, that means improved secretion of stomach acid, digestive enzymes, and bile. All of which help to aid in proper digestion and bowel function.

And if you are going to do intense or strenuous exercise, keep the intensity to short bursts and include plenty of rest breaks in between.

When it comes to healthy digestion, exercise is not the enemy. Stressful exercise is.

So, if you’re struggling with digestive discomfort, try replacing your strenuous exercise with a type of movement that’s more nourishing.

Try out a class at the new yoga studio down the street. Start walking your dog every day after work. Or try incorporating more rest and shorter sets into your weight lifting routine.

You might even find that you enjoy these forms of exercise just as much as that sweaty gym session or long run.

You won’t know until you try. And there’s a good chance that you’ll find improvements in your gut function as well!

But if you’re still experiencing gut symptoms even after decreasing your exercise intensity, you might have to dig a little deeper.

Sign up for a strategy session with me and we can team up to get to the root of your gut issues!

The Bottom Line About Strenuous Exercise and Gut Health

We can really boil down the effects that strenuous exercise has on our gut to one thing… STRESS!

Like it or not, strenuous exercise is a stressor on our bodies. The more of it we do, the more stress our bodies experience.

And stress, specifically the increase in cortisol that comes along with it, has wide-reaching negative effects on gut health.

Strenuous exercise affects so many areas of your gut health.

The permeability of your gut lining. The health of our microbiome. The ability of your intestines to remove waste.

They are all affected by the stress of strenuous exercise.

Exercise is only going to be beneficial for your gut if it’s not stressful. And unfortunately, strenuous exercise IS a stressor on our bodies.

Your intense workouts could be contributing to your gut symptoms while or even after training.

If you’re struggling with any gut symptoms, try toning down your exercise intensity for a few weeks. Focus instead on more restorative movements like walking, yoga, or low-intensity strength training.

Once you take a break, you might be surprised at how much your intense training was affecting your gut health.

And while you’re focusing on other forms of movement, you might find a new exercise or activity that you really enjoy! And your gut will thank you too.

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  1. Ralph says:

    It depends on what you perceive to be intense activity. Exercise has to stimulate a demand for a beneficial improvement to be elicited. Therefore, whilst intense activity is likely to exacerbate gut issues, it is unlikely to cause gut issues (unless it is too intense/over-training).
    One of the biggest gut issues is the over-emphasis of carbohydrate and to a lesser extent protein in the developed world. For instance, a brisk 2 hour walk might burn about 600 kcal, with about 150 of those kcal from carbohydrate. That’s less than 40g of carbohydrate. Along with the 130g carbohydrate used for the central nervous system including brain function, that’s still only about half the current RDA of carbohydrate. This is extremely important when we consider that carbohydrate is like the ‘active ingredient’ of macro-nutrients, stimulating the most insulin and growth factors. Over consumption contributes to hyperinsulinaemia that underpins metabolic syndrome for instance. Yet people continue to overeat carbohydrate because they have been lulled into thinking it is a safe alternative to saturated fat for instance (glossing over that over-consumption of carbohydrate leads to over production of body fat that is 40% saturated).

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I'm a women's health expert and a registered dietitian (RD) with a passion for helping goal-oriented people fuel their purpose.

I help nutrition entrepreneurs grow their income and their impact by packaging their brilliance into transformative coaching and consulting programs, and get crystal clear on their marketing strategy.

I'm on a mission to help nutrition business owners drop the hustle and come into alignment with their ideal business goals, so they can work from a sense of ease and abundance, and build the online business of their dreams. 

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