I am sure the vast majority of you have heard this famous quote from Pump Iron: ´no pain, no gain´. Well, muscle soreness is nothing but a reflex of muscle injury degree and, as a consequence, of muscle hypertrophy (mass gain). But is it really necessary to feel sore before reaching our goals at the gym? What if I´m pain-free, does it mean my weight training programme isn´t successful?

You have certainly felt the stiffness of some muscle groups after an intense workout. That is pretty common, especially when it´s your first time at the gym or if you´ve recently changed your training programme. But where does this pain come from? Is it due to the lactic acid?

Let´s get the answers to these questions now!


Firstly, it is important to understand that Delayed Onset Muscle Soreness (DOMS) has nothing to do with the accumulation of lactic acid in the muscles. Until these days people thought that the muscle soreness after an intense workout happened because of the lactic acid (which is now irrefutable, for lactic acid is removed from the muscle within an hour of intense exercise and, because of that, can´t cause the soreness which normally begins about a day later).

It is now known the lactic acid is responsible for the burning sensation during the execution of the exercise,  which usually happens during the last few repetitions. The burning sensation is caused by the increased levels of lactic acid in the muscles, but it is over once the exercise is finished.

If you pay attention, the pain you feel the day after is different from the burning sensation you have while exercising - which is also different from the pain caused by a muscle injury. It is important to start noticing the different kinds of reactions and see if what you feel is what we call the good pain  (the type that"s part of the muscle strengthening process) or the bad pain (which may be due to muscle or articulations injury).

No matter how strong the good pain is, it doesn´t stop you from practising other physical activities. You may feel a bit uncomfortable with it, but you should be able to exercise perfectly. It is a different case when the pain you feel is caused by some kind of injury, though. This usually happens when you move the affected area a few hours after exercising.

Pain can affect the muscles right after a workout, from 12 hours to 2 days afterwards.  This occurs due to the inflammatory process in the muscle. That´s right, an inflammation in the muscle, just as it happens with each and every injury.

That is the reason why we keep having the Delayed Onset Muscle Soreness (DOMS). There´s no need to worry about it, though. This inflammation process isn´t a negative reaction nor dangerous. It is simply an answer from the organism, the way your body reacts to the training stimulus.

Best of all is: after this inflammatory period, comes the tissue repair phase, in which the muscle fibres are repaired and come back to normal (no more pain, that is). During this period, protein overcompensation happens – which means the muscle fibre needs extra protein to rebuild. By doing that, it gets bigger and stronger in order to handle the next strenuous workout. When the muscle fibre repair happens, there is increased resistance to pain and mass gain.

It is important to remind you that if the strength training is periodical (without interruptions that is) there are adaptations to pain. Meaning: we can repeat the same programme (causing structural injuries to the muscles fibres and as a consequence developing your muscles) without feeling the same amount of pain we usually feel during the first training  programmes of that sequence.

What if the muscle group are still stiff on the day I need to work on them again? Well, if the pain is not strong it is okay to exercise normally. After the first movements, the muscles should get used to the workout routine and the pain will probably go unnoticed. Now if the pain is stronger, it means the body has not had enough time for a full recovery. Your body is still rebuilding the muscle tissue damaged during the last workout and exercising the same muscle group will only cause you more damage. In this case, it is better to work on  a different set of muscles until you feel ready to rock again.

Remember that, in many cases, good rest is better than bad workout!


Conclusion: a few doses of good pain after training is beneficial for your body. If you go to the gym in order to keep the shape and exercise, there is no need force your muscles and feel sore afterwards. But if you´re one of those who visit the gym and want muscles in return, pain is something you should see as an ally. The secret is to give all you can during the workout, and rest and eat healthily after that so the gain of muscle mass occurs. Remember: not all discomfort indicates injury!

See you next time!