When we move past low-intensity cardio (such as walking) into Strength Training and other moderate to higher intensity workouts, we need to talk about the relationship between working out, and stress. Many people don’t realize this, but there is a direct correlation between workout intensity and stress response in the body.
Stress is something most people think exercise relieves. And exercise can certainly relieve mental and emotional stress. But it can also create a separate, physical stress response. We may not realize this is happening until well after a high-intensity workout, when we’re home for the evening and suddenly we feel like a truck hit us, completely depleted or fatigued, irritable, food-cravey, anxious or bummy without a specific reason why. It is likely a delayed reaction to the day’s super intensive workout.
Physical intensity is no different than mental or emotional intensity. When you push your body to a level it is not comfortable or struggling to maintain, it will have a similar stress response as you would with a mentally stressful event. Specifically, the closer your heart gets to beating at its maximum potential (max heart rate), the more your body is going to respond with a warning that it is stressed.
Your brain is going to assume that the only reason you’re working so hard is because you are in a terrible, life or death situation. It will tell your adrenal glands to flood the body with “fight or flight” chemicals like adrenaline, for a quick burst of energy.
Sometimes you can physically feel this happening during an intense workout, when you feel a little zap. Your brain will tell your muscles to dump glycogen into the blood, raising your blood sugar and triglyceride levels. It will temporarily shut down digestion and other non-essential processes. Finally, it will also elevate your cortisol (stress) hormones.
It does these things to meet the demands you are placing on it. In evolutionary times, the ability to suddenly respond with high intensity movement could mean the difference between life or death – like running from a predator. Regardless the reason, any resulting adrenaline and cortisol can remain in your system for quite some time after your workout is done and you’ve moved on for the day.
Whether you move your body at maximum velocity because of danger, or for completely voluntary reasons, our brains do not know the difference. Our nervous system does not receive a memo that we are sprinting at full speed of our own volition. It assumes you are in mortal danger, and places all hands on deck to respond.
This can create a stress “hangover” afterward, especially when we stop the high intensity exercise abruptly and rush off to the rest of our day. A few hours later, this can leave us feeling depleted, severely fatigued, brain foggy, or even anxious or depressed.
In other words, the higher the intensity you exercise, the more it stresses your body out. And this stress must be added to the total count of stress in your life. It’s no different. It places strain on your central nervous system. You will be aware of this if you have to continue to struggle to keep going – jogging along, starting to struggle to place one foot in front of the other, totally out of breath, and your brain starts telling you to “Stop. Stop. STOP!”
When exercise becomes grueling, you should simply be aware that it is placing a heavy strain on your nervous system. This can stay with you the rest of the day, causing irritability or anxiety even if we really overextend ourselves to a level our body is not ready for.
One way that you can alleviate this effect is to spend some time in a very calming state after a high intensity workout. Spend a little extra time in a nice hot shower. Go to a sauna or steam room for 10 minutes if you have one available to you. Spend plenty of time stretching. Do a little bit of meditation while you calm and stretch your body. Quiet your mind and don’t just rush off to a busy rest of your day.
Over time, putting your body under intensive physical strain – pushing yourself too far – can program your brain to actively avoid exercise. And why wouldn’t it? It’s learning to associate exercise with pain and strain. You’ll start experiencing self-resistance at the idea of another intensive workout.
This is not the way to exercise right. Please do not push yourself to the point that you hate exercising. Remember, this is supposed to be a challenge, but a joy. Exercise is supposed to lift our spirits, and increase our confidence and mental clarity levels. There is nothing good that comes from exercise so intense that it breaks us down.
This stress response often happens to me after I finish a really intense HIIT workout – my body and brain just tell me “Enough. We need to rest.” And while I still do HIIT because I love it, I wait to do it on a day I’m really feeling energetic and good. I don’t try to push myself through a HIIT when I’m feeling sad, stressed, lethargic or sick. And I always do low-intensity exercises for 1-2 days after a HIIT workout. That means no HIIT multiple days in a row, and no intensive strength training the day after a HIIT. Rest, walking, yoga or light hiking are all great things to do after a maximum intensity workout session.
You will also experience a mental resistance to the idea of working out when you are under high stress in another area of your life. If your job or your personal life is stressful, the idea of adding more stress to an already-full “stress plate” is going to cause your brain to revolt.
You should listen to your body when these things happen, but don’t STOP working out. Just opt for exercise that is lower down the fitness pyramid – exercise that is stress relieving rather than stress inducing.
So – if you aren’t feeling up for a run or a strength session, consider LISS your secret weapon. Tell yourself you’re going to go for a 30 minute walk. Or a 20 minute walk. Or heck, even a 10 minute walk! Lacing up your shoes and showing up – whether it be on the treadmill, track or sidewalk outside your house – is 80% of the battle. Start with a 5 to 10 minute commitment and just start walking. See how far you *actually* get away with before your brain tells you that it has really had enough. Then you can stop.
Sometimes you might still not be feeling it after 15 minutes. But I often find that even if I’m 100% not in the mood beforehand, once I start a LISS, it feels so good that I usually want to continue once I’m warmed up.
Regardless how things actually end up for that day, hey – at least you gave your nervous system a break AND got some exercise in. You didn’t just give up on your goals. You made exercise a priority and a daily habit, and got yourself that much closer to your goal. I call that winning.
Remember that perfection is an illusion you’ve made up in your mind. Showing up every day is all that matters.