It’s common for many people, especially when they’re just starting out, to feel sore for a day or two after training.
Even Arnold Schwarzenegger was “feeling it” soon after finishing his first ever workout.
“The guys warned me that I’d get sore,” he writes in Arnold: The Education of a Bodybuilder. “But it didn’t seem to be having any effect. I thought I must be beyond that.”
“The next morning I couldn’t even lift my arm to comb my hair. Each time I tried, pain shot through every muscle in my shoulder and arm. I couldn’t hold the comb. I tried to drink coffee and spilled it all over the table. I was helpless.”
Most people think that sore muscles after a workout are a sign that you’ve stimulated growth, and that more soreness equals faster results.
But are the two really linked? What does muscle soreness have to do with muscle growth? Can you still build muscle without getting sore?
What Causes Sore Muscles After a Workout?
Well, it has nothing to do with lactic acid or lactate. In fact, most of the lactate is gone from your muscles soon after exercise.
A tough workout, or even just a single exercise that you haven’t done before, leads to a bout of inflammation — the same defense mechanism that causes swelling and pain if you cut your finger.
Inflammation is the way that your body handles an injury. And as part of the repair and recovery process, your body ramps up the production of immune cells.
These cells then produce substances that make certain nerve endings in your body more sensitive [1, 2]. When you move, these nerves send signals to the brain, which then creates the perception of soreness.
In fact, pain appears to be an output constructed by the brain as opposed to an input to the brain as was once believed.
The nerve fibers that transmit pain are located mainly in the connective tissue found between muscle fibers, as well as the junction between the muscle and tendon.
In other words, the source of the pain appears to be the connective tissue that helps to bind muscle fibers together, rather than the actual muscle fibers themselves .
Do Your Muscles Grow When They Are Sore?
You went to the gym yesterday. Today, your muscles feel sore. That must mean your workout was effective, right?
Exercise can cause damage to muscle fibers. But there’s very little evidence to show that muscle damage is a requirement for muscle growth.
Brazilian researchers have shown that both high- and low-soreness programs lead to similar gains in muscle strength and size .
They compared training a muscle once a week with a full-body workout performed five times a week, Monday through Friday.
Both groups did the same exercises and the same number of sets, with one key difference.
The once-a-week group did two exercises per workout for 5-10 sets per exercise, while the full-body group did 11 exercises for 1-2 sets per exercise.
Subjects in the group that hit each muscle group once a week reported a much higher level of post-exercise muscle soreness.
However, the researchers found no significant differences in terms of strength or size gains between the two groups. In other words, both the “low soreness” and “high soreness” training programs increased muscle mass and strength similarly.
Here’s how one group of researchers summarized the results of a study designed to test the theory that detectable damage is a necessary precursor for muscle growth :
That said, while muscle damage isn’t a requirement for growth, it may accelerate the process . It’s also possible that muscle damage may become a much more important stimulus for growth the longer you’ve been training.
But even then, more damage won’t automatically mean faster growth. If it does exist, any dose-response relationship between muscle damage and muscle growth is likely to be shaped like an inverted U, with a sweet spot found somewhere between “too much” and “not enough” damage.
Put differently, there’s going to be an optimal amount of damage, above and below which your gains will be compromised.
This “sweet spot” may very well be a moving target, and will shift around depending on a number of factors, including how frequently you’re working each muscle group, your training volume, as well the exercises you’re doing.
What Does It Mean When Your Muscles Are Sore?
Muscle soreness is nothing more than a sign that you did something your body wasn’t used to, or performed an exercise that just so happens to trigger more soreness than others.
What’s more, an increase in muscle soreness doesn’t necessarily reflect an increase in muscle damage.
Conversely, a decrease in muscle soreness is not always indicative of less muscle damage.
So, even if damage does help to accelerate growth, you can’t rely on muscle soreness to gauge the extent of the damage .
When researchers compared voluntary with electrically-induced muscle contractions, the amount of muscle damage was considerably higher with the latter .
But there was no significant difference in muscle soreness between the two groups.
Other studies report much the same thing, with only moderate levels of soreness associated with a high degree of damage .
In one trial, a post-exercise bout of foam rolling led to a decrease in muscle soreness . But contrary to what you might expect, this reduction in muscle soreness was accompanied by an increase in markers of muscle damage.
Is It Good to Work Out When Your Muscles Are Sore?
According to conventional wisdom, training a muscle that still feels sore will only delay the recovery process and put the brakes on muscle growth.
But that doesn’t seem to be the case.
In one study, scientists recruited a group of 51 student athletes and split them into two groups . Both groups completed 30 negative repetitions of dumbbell curls, which is a highly effective way to create both muscle damage and DOMS.
The first group rested. But the second group came back to the lab just three days later, when their muscles still felt sore, to do the whole thing again. Both groups were tested every day for nine days after the first workout.
You’d think that the second bout of training would interfere with recovery from the first, or at least exacerbate muscle damage. But the researchers could find no significant difference between the groups in terms of DOMS or markers of muscle damage.
In other words, training a muscle when it still feels sore doesn’t appear to create any further damage or slow the recovery process.
There is also a large degree of variability in the individual damage response to exercise.
In fact, some people are “slow recoverers.” They lose more strength after a workout, take longer to recover, and experience a greater degree of muscle soreness.
Publishing their findings in the Journal of Applied Physiology, researchers from the University of Massachusetts looked at DNA from 157 untrained men and women following maximal eccentric exercise .
They found a link between variations in the CCL2 and CCR2 genes and the severity of exercise-induced muscle damage. With the exception of one individual, the presence of the rare alleles exacerbated strength loss, prolonged strength recovery, and elevated soreness.
There are also large differences in the ability of various exercises to create soreness. Certain movements, particularly those involving high levels of muscle activation at long rather than short muscle lengths, are more likely to create muscle soreness than others [5, 11].
This “length-dependent component” is the reason why Romanian deadlifts (high levels of muscle activation at a long muscle length) lead to so much soreness, while the lateral raise (high levels of muscle activation at a short muscle length) doesn’t.
“Muscle soreness happens when you create enough total damage to aggravate the connective tissues,” explains Squat Every Day author Matt Perryman.
“This will sometimes correlate with a muscle-stimulating, growth-inducing workout. But just as often, it has nothing to do with muscle stimulation.”
“Being sore, stiff, and exhausted might feel good,” Perryman adds. “But it’s not a replacement for training intelligently.”
In other words, the fact that you’re not sore doesn’t mean your muscles aren’t growing. Likewise, sore muscles don’t necessarily translate into faster growth.
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ABOUT THE AUTHORChristian Finn is the nation’s leading authority on science-based, joint-friendly ways to build muscle. A former "trainer to the trainers," he holds a masters degree in exercise science, and has been featured in or contributed to major media on two continents, including the BBC and Sunday Times in the U.K. and Men’s Health and Men’s Fitness in the U.S.