Physical Activity Myths

First Edition

Physical activity is a vast field and the principles related to training and goal planning can be numerous and sometimes complex. We hear so many physical activity myths and contradictory information that we no longer know what to believe or what to do. It is hard to achieve your goals or motivate yourself when you rely on false information. Don’t panic! I will help you. In this article, I’m going to expose 3 myths about physical activity and we’ll look at them together. If I haven’t answered your questions, don’t worry, there will be a second edition! In this first article, we will look together at the famous “No pain, no gain”, a training technique to lose weight and the results you see on the scale or in the mirror after a training session. Let’s go!

No pain, no gain

We’ve heard it many times, it’s nothing new! In order to benefit from your workout, you need to feel stiffness and pain the next day. Well, you don’t! This physical activity myth used for training should be revised.

Even if you are a high-performance athlete and are training hard to improve your cardiovascular or muscle capacity to go to the Olympics, you don’t need to be in pain after your workouts! If you are indeed an athlete, your training should be fairly regular, either every day or even sometimes several times a day. You won’t be able to perform as well if your muscles are painful during your training sessions and you are even more likely to get injured. Of course, the intensity will be there in your workout, but aches and pains will not help you in your next session.

This does not mean that if you train and your muscles are sore the next day or two you have done too much. It doesn’t! You simply don’t need to get to this point to reach your goals. If you’re not sore, don’t worry, you haven’t lost your time. This might be one of the most common physical activity myths out there.

Fatigue :

Let’s start by looking at what happens after a workout. The body gets tired at the central and peripheral levels. When we talk about central fatigue, we’re talking about the activation of muscles by the brain and nervous system. The fatigue you feel after training causes a decrease in voluntary strength, which reduces your performance. After a good workout, your willingness to push more is weaker. In addition, the release of serotonin makes you feel tired. It is therefore more difficult to activate your muscles.

Peripheral fatigue is mainly about what is happening in your muscles. The molecules used to give you energy is unusable, your blood sugar level is lower, your body temperature is higher which can be from a lack of water and there can also be a loss of your carbohydrate reserves depending on your level of physical condition. The fatigue and loss of strength you feel after training can last for a few days and allows for tissue repair as well as the restoration of various central and peripheral functions.

Pain and stiffness :

The pain, however, results from muscle aches and pains that can be felt following an effort or an infection. Stress on the muscle fibres can create tears and the body’s inflammatory process is triggered to repair the sudden injury. This can take between 24 and 48 hours post-exercise, up to 72 hours. The theory behind the aches and pains is that the inflammatory process, the damage to the muscles and other tissues of the body will cause the nociceptors to activate. The nociceptors are the body’s receptors for pain. They are therefore the ones that provide the sensation of aches and pains after training(1).

So you can see that there is an important distinction to be made between fatigue and aches and pains. In both cases, the body activates a series of mechanisms to restore function and capacity and even increase performance to be ready for the next workout. Your body will create adaptations whether you are in pain or not. It is therefore possible to improve physically without having aches and pains. However, it is necessary to create fatigue in your body and maintain a good training intensity to achieve your goals.

You burn more fat at low-intensity

One of the biggest physical activity myths about weight loss obviously refers to fat loss. One of the principles of physical activity is that fat is burned more at low intensity. True/false? To get the answer to this question, we must first dissect it.

Energy use :

The body can use different molecules during physical activity, creatine phosphate, carbohydrates and fat. As the intensity of activity increases, the body will favour creatine phosphate and carbohydrates over fat. Not all of these molecules need oxygen to create energy, so chemical reactions occur more quickly. To burn fat, we need more oxygen than carbohydrates so the body uses more fat at low intensity because the body has time to break down these molecules. This part of the equation is true, when we exercise at low intensity the body uses mostly fat compared to carbs. So, True!


For weight loss, we want to focus on calorie deficit, not fat loss specifically. When exercising, to calculate the caloric value, 3 variables must be taken into account: intensity, duration and the weight of the person. A person with a higher weight will therefore lose more calories for the same exercise. A person exercising for a longer period of time, for example, 30 minutes will lose more calories than for 10 minutes. Finally, the greater the intensity, the more calories the person will lose. It makes sense, though! So for two people of the same weight, whom each do 20 minutes of physical activity, the person with the highest intensity will lose the most calories. To have the same calorie loss, a person training at low intensity will have to train longer.

Of course, one question remains to be clarified, are these calories fat or carbohydrates? They are indeed carbohydrates because at high intensity, it is mainly this molecule that is used by the body.

However, don’t panic, at the end of your training, when your carbohydrate reserves are exhausted, your body will still have to continue to function and will want to rebuild its reserves. What do you think the body will use? Drum roll! Your fat reserves because the intensity of your recovery is low.

Therefore, by training at high intensity, you will have a greater loss of calories and you will also use your fat reserves and therefore it will promote your weight loss. Wonderful!

Weight loss after training = fat loss?

Bigger muscles after a workout = muscle gain?

While we are talking about weight loss, I think it is a good time to ask you these two physical activity myths. Start by answering them in your head and let’s see what they both mean.

Weight loss :

First, weight loss. Have you ever weighed yourself before and after a workout and found that you lost weight on the scale? While it is nice to think that we have already lost weight, the difference you see is the loss of water from your body.

During your workout, water acts on various functions such as maintaining body temperature. In order to do this, water has to leave the body; this is called sweating. For those of you who are more interested in the question of hydration before, during and after your workout, don’t worry, I will give you all this information in another article! If we look at the fat, bone and water mass of the body we can see that the factor that has been changed is the amount of water in the body.

Of course, you have just lost calories but your body is already trying to recover them. It is the caloric difference during your whole day that will be important for your weight loss and not only the one during your training. Surprised?

If you want more information on how to calculate your body composition. Go read this next article.

Weight gain :

Now let’s talk about muscle gain. Many of you are probably aiming for muscle gain, not weight loss. Have you ever looked in the mirror after a good workout and realized that your muscles are bigger? While this is motivating, I’m sorry to say that the swelling in your muscles will not last. This is a phenomenon called transient hypertrophy.

This occurs as a result of increased fluid. During a major muscle contraction, great pressure is placed on the blood vessels and blood. This causes part of the contents of the blood vessel to move out of the vessel. This then generates an inflammation of the muscle which causes the sensation of swelling. Increasing the size of your muscles after training is therefore not a muscle increase(2). However, if it does motivate you, keep your head up, all motivations are good to stay active!

This is the end of my first article on physical activity myths. Don’t worry, it won’t be the last one. There is so much information around us that we don’t know what to do with it. Don’t worry, I’ll help you sort it all out. Don’t hesitate to ask me your question about other myths.

Sandrine Lavoie-Filion, Sandrine Santé Active

1- Cheung K. et al, Sports med, 2003.

2- Brown, L.E. and J.P. Weir, Resistance Training Adaptations, in NCSCA’S Essentials of Personnal Training, R.W. Earle and T.R. Baechle, Editors.2003, Human Kinetics.