Being sore after the gym can be satisfying for some and painful for others. It can be proof of progress or just a nagging ache on top of a busy work week. A few days of stiff legs and tender arms can seem like a small price to pay for long-term muscle gain. But is that period of pain post workout necessary to gain muscle? Does soreness mean you are always doing something right? Today we’re going to break down the science of muscle soreness and what really determines a successful work out.

The fancy term for this feeling is delayed onset muscle soreness or DOMS. It’s the most common when you are new to the gym and are putting your body through all these new exercises. Your muscle fibers are torn and your body responds with inflammation until they are repaired. Inflammation sets off your nerve endings and leaves you feeling sore for between 2-5 days. It’s your body’s alert system trying to tell you that it needs some recovery time before you workout again. 

This process is easily confused with lactic acid build-up, but these are two very different things. When you exercise, your body is constantly pumping oxygen to your muscles. But sometimes during intense movements, oxygen just can’t get there fast enough. Your body’s back up plan is glycolysis, or the breakdown of glycogen for energy. To break down glycogen, you need lactate. Lactate is basically an acid and it feels like an acid as it builds up in your muscles.

A prime example is when you do any kind of calf raise and you step off the machine with bricks on the back of your legs. Your calves feel like they are permanently flexed for the next two or three minutes, and you have to tiptoe around until it dissipates. This is lactic acid build-up and thankfully it only ever lasts that long. As soon as you relax, oxygen starts pumping again and everything is right with the world. 

Now, for the million dollar question. Do you have to be sore to build muscle? The answer is almost universally, no. When you work out, you tear muscle fibers. Muscle fibers then have to rebuild bigger and stronger than before to support your activity level. From that basic breakdown, it would be fair to say that muscle damage leads to muscle growth. But conversely, soreness isn’t always synonymous with muscle damage. 

Clinical trials have shown both low levels of soreness in significantly damaged muscles and high levels of soreness in muscles with almost no muscle damage. Turns out, it’s not about the extent of damage. Soreness actually depends on how long a particular muscle was being activated. The longer you’re able to bear that painful strain of the last few reps, the more likely it is that you’ll be feeling it later. Short bursts don’t cause the same kind of DOMs, but that doesn’t mean no progress is being made. 

Not being sore could actually mean that your muscles have adapted to your workout routine and are getting stronger, so the same movements aren’t nearly as difficult. Or it could mean you aren’t pushing yourself hard enough, and it’s time to try something new. Only you will know if you are truly testing your own limits and if there’s more you can do to create progress. If soreness is what you’re chasing, go for it. As long as you keep in mind that there is such thing as overtraining. If your soreness lasts for weeks on end, you’re susceptible to injury, you’re heart rate gets too high or you’re mood starts to take a turn, it’s time to rest. 

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Take it from me

I like to gauge my progress with soreness. It’s not necessary and I don’t always achieve it, but I like to chase that pain as a goal. Because it changes all the time. One day, I’ll do a few squats and wake up barely able to walk the next day. A few weeks later, I’ll do the same workout and my legs feel fine. That tells me that I’m getting stronger and it’s time to bump up the weights. Even if that doesn’t turn out to be true, it gave me the motivation to test my limits. It lit my fire and made me brave enough to go for the heavier weights. 

I can never be sure about what’s happening on a cellular level so I just push the only way I know how. I push until it hurts. I push until there’s absolutely nothing left in the tank. I push until I improve.