4 ways how excessive cardio can do more harm than good

Running and other kinds of endurance training are increasingly popular nowadays. It’s said that they help to prevent cardio-vascular disease, keep you healthy and in shape. Unfortunately quite the opposite may be true. Too frequent and/or too intense endurance exercise, especially when combined with a stressful work/study schedule, and malnourishment (either due to a “junk food” diet, restricted calorie intake and/or a mainly plant-based diet), might actually make you sick (and also fat in some cases). You would be surprised to know how many athletes develop heart conditions after years of committed training. Contrary to them, I am not at all surprised, because it is in fact a quite “classical” thing to happen. In this article I try to explain a few of the reasons why and how this can happen.  

My own story

I have been an amateur, yet hard working medium and long-distance runner for many years. I started to run with my dad at age 8, then joined an athletics club at age 13 and competed until age 24. Until I was 17, I accompanied my training with a typical diet high in refined carbohydrates and processed foods. At 17, I developed an Eating Disorder, eating not only empty, but far too little calories. Even when the food quantity and quality got better (more veggies, whole grains), it was still a high carb diet and the supply of essential fats, proteins and important vitamins and minerals (especially from animal sources) still stayed far below what even a non-exercising body would have needed to sustain itself. The result was a condition called “Adrenal Fatigue Syndrom”, which is characterized by severe hormonal imbalances (in my case too high and later too low cortisol, low thyroid, low estrogen, low progesterone..), pain (in my case in the knees and tendons), inflammation and inability to put on muscle (despite strength training) – to just name a few. I only learned my lesson in 2006, when after my first (and last) marathon my knees were in such a bad state that I had to give up running for good ever since (except for max. 20 min of jogging by now). As reluctant as I was back then to accept that, I am now even grateful that my body was wiser than my ego and prevented me from destroying it altogether. Still, the road to recovery has been long, and I am still marked by those long years of abusing my body.

So I would really ask you to think twice about following that “cardio-hype” and torturing yourself in long-cardio hours, especially if you already have a lot on your plate and have to push yourself to do so. But let’s take a closer look at what might happen to a body under chronic cardio stress.

4 negative effects frequent and/or high-intensity cardio training can have on your body

1. Frequent and intense endurance training can dysregulate the stress hormone cortisol 

While it’s true that ALL kinds of exercise elevate cortisol (with the exception of some very gentle, specifically designed Adrenal Recovery Exercises), the duration, frequency and intensity of your workout will determine whether this is a good or a bad thing for your health, well-being, weight and body shape. The question is how much stress you already have in your life (from work, relationships, finances…) and how well your body is still able to handle it. And also whether you are frequently burning more energy and/or nutrients than you are taking in over a day, in other words, whether you are repeatedly depleting your body, thus ending up with a negative energy and nutrient balance.

For a healthy person (so not a person with already some advanced stage of adrenal fatigue) the following can be observed:

  • During short and intense sprint or resistance exercises, cortisol tends to rise very fast very high, but then falls again very fast. If you repeat this procedure several times (intervals of 30-60 sec, with double the recovery time), your body is trained to adapt to these strong ups and downs of cortisol and to recover quickly. (If you are already adrenal fatigued, this type of exercise will further deplete your energy though, because you don’t have the cortisol reserves anymore to allow for the required spikes).
  • However, during a long-duration run at high intensity, cortisol is elevated consistently and will stay high even after the workout. This is partly due to inflammation and the need for more sugar/carbs in your diet (see below). If on top you don’t give your body enough time to rest in between sessions (the nervous system needs about 48h to recover from high intensity, energy depleting workouts), don`t eat enough and/or not enough essential proteins and fats (as many long-distance runners do unfortunately) and/or lead a stressful life, you quickly get chronically elevated cortisol.

This is bad for several reasons:

  • Cortisol (just like insulin) tells you body to store MORE fat. 
  • Your body is put in a catabolic state, meaning that muscles are broken down.
  • Chronically elevated cortisol weakens the adrenal glands and depresses the production of other important hormones, such as thyroid or sex hormones. The result is low energy and a slowed-down metabolism, making you crave even more sugars and caffeine, both further depleting the adrenals and thyroid (vicious cycle).
  • Stress-induced free radicals create oxidative stress in the body. This can lead to cell damage and potentially even cancer. 
  • Chronically high cortisol disrupts sleep (this is why it’s actually not such a good idea to work out too late in the evening).
  • Over time, high cortisol depletes your adrenal glands, leading to LOW cortisol, and you burn out eventually.

So again, while ANY kind of exercise elevates cortisol and might (if done too frequently or with too much intensity) lead to overtraining and chronically elevated cortisol, endurance training is much more likely to take you there. 

2.  Frequent and intense endurance training can depress the HGR (human-growth-hormone)

Short and intense sprints or other kinds of “bursts” and resistance exercises release the human growth hormone which heals the (during the workout) slightly damaged muscles and makes them even stronger for the next burst. On top it tells your body to burn fat – even post-workout.

During long cardio-sessions, the human growth hormone necessary for muscle building and repair is not produced, since the bursting intensity necessary to trigger its production is not reached (even if you feel very exhausted). As a rule of thumb: As soon as you are able to repeat one exercise for more than 30-60 seconds, the intensity is not high enough.

3.  Frequent and intense endurance training can create systemic inflammation

Over-used joints, over-loaded hearts and insufficiently repaired muscles (in the legs, but also in the heart) increase inflammation and oxidative stress in your body. This further increases your cortisol and weakens your immune system, making you susceptible to injuries, infections and all kinds of degenerative diseases (in the long run). Tiny damages to your heart and blood vessels can lead to scar tissue, hardening of tissue and plaque build-up. For more information on how chronic cardio can damage the heart and lead to heart attack, click here

4.  Frequent and intense endurance training makes you crave more carbs

Many people (esp. protein or mixed Metabolic Types) are more efficient in burning fats for energy than carbohydrates. In general, the human body only has a relatively limited capacity of storing carbs in the liver and muscles (about 1 day supply). If as a hunter-gatherer we’d had to rely on this limited capacity, we would never have been able to survive during periods of shortage (or even a few days without finding food). Evolutionary, it was meant as a reserve for those cases where we needed quick and immediate energy for a short time (e.g. to escape that lion). For all other activities at low-intensity, fat was (and is) the preferred fuel. This is why our requirements for dietary carbohydrates are relatively low (depending on your Metabolic Type of course – carbohydrate types need more than protein types) and why excess carbs are transformed into saturated fat and stored around the belly and the liver. In fact, eating lots of fruits in summer, when they were available, was meant to make us store fat for the scarce winter times… 

A person engaging in lots of low-intensity cardio (such as walking, hiking, low intensity biking, running, swimming…) and occasional “bursts” (sprints, resistance exercises at high intensity, not more than 60 sec each) will heavily rely on fat burning. The occasional bursts will use up the carbohydrate stock (glycogen), but this is immediately replenished by a process called “the ATP-PC system” (for more information on this read this article: “A case against cardio”). The human-growth-hormone released during these exercises will make the body even more efficient at burning fat afterwards (by building up more fat-burning muscle and accelerating metabolism). Such a workout-scheme doesn’t require very high amounts of carbohydrates. Lots of non-starchy vegetables and some high-fibre, low glycemic starchy carbs (e.g. legumes/pulses, sweet potato, fruit) will do the job. As such, this kind of workout seems ideal for protein or mixed Metabolic Types.

On the other hand, a person engaging in frequent and intense cardio workouts will need (and crave) more carbs, due to the chronically elevated cortisol and the decreased efficiency in fat burning (remember, HGR is not released). While to a certain extent this person CAN indeed eat more carbohydrates than others (and actually should, since not enough carbs in combination with long duration – high intensity workout might otherwise weaken the thyroid), too many carbohydrates, especially if “quick” sugars are chosen, will then send your blood sugar on a roller-coaster, triggering insulin and cortisol production, which – as we saw above – will tell your body to store more fat and lower the function of important, energy-producing glands and organs. If you eat more (refined) carbs, you automatically eat less of the important fats, proteins and healthy carbs. 

The ideal way to workout

As you know, I am all about individuality and not a big fan of “one-size-fits-all” solutions or recommendations. This is true for diet, but obviously also for exercise. Different Metabolic Types will benefit from different types of exercise, and the same is true for different stages of Adrenal Fatigue Syndrom. 

So while as described above, Carbohydrate Metabolic Types (Sympathetic Dominants and Slow Oxidizers) are metabolically more apt for cardio training (as long as they don’t exaggerate and make sure to replenish on “good” carbs alongside clean proteins and healthy fats), for Protein Metabolic Types (Parasympathetic Dominants or Fast Oxidizers) a Burst Training approach would fit their metabolic capacities and needs much better. 

In general, lots of low-mid intensity cardio (walking, hiking, running and biking at max. 70% of your max. heart rate) in combination with very high intensity, short duration “bursts” (e.g. sprints) and “resistance training” seems to be much more effective and also time efficient to achieve optimal health (in combination with a good diet and other healthy lifestyle choices) and even to prepare yourself for a running competition. You still can go for a long, hard, energy depleting run from time to time,  just don’t do it too often. 

If you are already adrenal fatigued, especially in the advanced stages, where you feel constantly fatigued and exercise leaves you even more depleted, you might really want to take it easy on exercise. I remember there was a time when even biking was too much for me (every time I had to cycle up a hill, I would get so angry – now I understand that it was my body’s way of trying to talk to me)… In such cases, you first need to restore your adrenal strength by eating a nourishing diet, eliminating stressors and doing gentle Adrenal Recovery Exercises.

The importance of JOY

The most important thing is that you find an activity you enjoy. Not only will this make it much easier for you to keep it up, but it will significantly increase your chances of actually achieving your health and/or weight related goals.

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