9 Reasons You’re Feeling So Sluggish During Your Workout

by | Mar 16, 2016 | Fitness

By K. Aleisha Fetters

And what to do when you can’t even.

You started your workout feeling great, but a few minutes in you’re sucking wind and totally out of steam. It happens. But why? We chatted with Janet Hamilton, an exercise physiologist with Running Strong, to help you ID your issue. Check out these nine possible culprits and get ready to finish your next workout strong.

No Sleep, All Stress

Stressful days and a bad night’s sleep go together like too-tight yoga pants and camel toe – and both can tank your workouts. “When someone is struggling with their energy in the middle of a workout, the first thing to do is look at what their life has been like over the last few weeks,” says Hamilton. Have you been sleeping well and getting regular me time?

It’s important to remember that working out also stresses your body – and all stress is cumulative. So if your job, lack of sleep, and relationship are all taking a toll on you, your workout is going to make your body cry “uncle.”

Read More: 5 Everyday Activities Sabotaging Your Sleep

Hamilton suggests adding a column for notes to your fitness tracker. In it, jot down how you feel during each workout, your stress levels, and how much sleep you got the night before. If you’re regularly seeing little sleep, lots of stress and miserable workouts, there you go.

Allergies and Asthma

Allergies and asthma (exercise-induced or otherwise) can make getting air a struggle. And guess what: Your body isn’t doing squat without oxygen, says Hamilton. Every cell in your body, organs, and muscles requires air to survive and do its thing.

Read More: 17 Foods That Fight Spring Allergies

If you experience coughing, wheezing, a tight chest or shortness of breath during or immediately after cooling down, definitely talk to your doc. You might have exercise-induced asthma or bronchoconstriction, in which the airways in your lungs narrow in response to strenuous exercise. And if you know or suspect you have allergies or asthma, talk to your doctor about ways to open up your airways in the gym.

A Drop In PH

We’ll try not to get too science-y here, but when you’re in beast mode, hitting “a wall” is a completely natural biological process. Here’s how it works: As your body converts carbs into fuel during high-intensity exercise, the byproducts are little hydrogen ions, Hamilton says. The longer and harder you keep pushing it, the more they can build up in your system.

As a result, your body’s pH levels drop and become more acidic. (It’s worth mentioning that some people used to blame lactic acid for this, but lactate can actually help fuel your workout.) As your body becomes acidic, everything slows down. The enzymes that supply your muscles with energy all become less efficient, she explains.

That’s when you feel like you’re running through peanut butter. Luckily, the more fit you get, the better your body slays those hydrogen ions. So keep at it!

Too Much Beast Mode

If you feel dead after every single workout, sooner or later it’s going to catch up to you. “If you ramp up your workouts too fast or don’t give yourself enough recovery time, you’ll feel like crap early on in a workout,” says Hamilton.

Read More: 7 Recovery Day Mistakes You’re Making 

And when that happens, you need to slow your roll. Give yourself at least two full recovery days per week, as well as a couple of “lighter” workouts. A good rule to follow: Don’t do more than two balls-to-the-wall workouts in a row.


This condition means your blood has too few oxygen-carrying red blood cells and limits the amount of oxygen your body’s cells receive, she says. When your cells don’t have enough oxygen, they can’t function at top notch. Having too-low iron levels, which can happen in women who cut out iron-rich meat and animal products or have heavy periods, most often causes anaemia.

Read More: Best Foods For Iron Deficiency 

Other signs of anaemia include insomnia, dizziness, leg cramps, pale skin and easy bruising. Sound familiar? Talk to your doc ASAP and get tested.


The smallest dip in your fluid levels makes your blood thick and mucky, so it’s harder for your heart to pump and get where it needs to go, says Hamilton. Meanwhile, if you’re sweating buckets, you’re sweating out more than water. You’re also losing electrolytes that are vital to your muscle cells’ ability to talk to each other and power your workouts.

Read More: 6 Weird Things Dehydration Does To Your Body 

To make sure you’re adequately hydrated during your workouts, strip down in the locker room and weigh yourself before and after each sweat session. If you’ve lost more than two percent of your body weight, you need to drink more fluid, she says.

Thyroid Issues

OK, so low thyroid function can zap your energy at any time, but if you’re often fatigued during your workouts, and aren’t finding any other cause, it’s worth talking to your doctor about possible thyroid issues, says Hamilton. Hypothyroidism, in which the little butterfly-shaped gland in your neck doesn’t churn out enough thyroid hormone, can cause extremely low energy levels as well as weight gain, depression and muscle pain.

And while it’s extremely common – one out of eight women will deal with some sort of thyroid problem in their lifetime – about 60 percent of sufferers don’t realise their thyroid is to blame for their symptoms, according to the American Thyroid Association.

You Need To Carb Up

This is a big one in women who are working out in an effort to lose weight, says Hamilton. While you need to burn more kilojoules than you’re taking in to lose fat, you also need to consume enough kilojoules (especially from carbs) to fuel your workouts and actually burn calories in the gym.

Read More: What Happens To Your Body When You Stop Eating Carbs 

So if you find yourself struggling through workouts and just happen to be dieting, try bumping up your calorie and carb intake (seriously, avoid any extremely low-carb ketogenic diets). Most women need 5204 to 5861 kilojoules per day to have healthy energy levels, she says.

Low Glycogen

Unless you have an existing issue with your blood sugar – or you’re on one of those low-carb diets – a dip in energy likely isn’t due to low blood sugar levels. But it could be due to low glycogen levels, says Hamilton.

Glycogen is your body’s form of stored carbs, and it hangs out in your muscles and liver. The glycogen in your muscles is your body’s preferred source of energy. However, once you run through all of that glycogen, say, during a workout that lasts an hour or more, your body turns to the glycogen in your liver to fuel your workout. Unfortunately, it takes time and isn’t all that efficient.

“It’s like running to the supermarket rather than to your kitchen’s pantry for food,” Hamilton explains. The only way to get more glycogen in your muscles is to nosh on some simple carbs. Sports drinks and energy blocks are great for providing an instant boost, she says.

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