Muscle soreness after a workout is not a reliable sign that your muscles are growing. The two processes overlap in some circumstances, but they are driven by different mechanisms, follow different timelines, and frequently occur independently of each other. You can have plenty of productive, growth-stimulating training sessions that leave you barely sore, and you can be crippled with soreness after a workout that contributes almost nothing to long-term muscle gain. The relationship between the burn you feel and the tissue remodeling that adds size is far looser than gym culture suggests.
What Soreness Actually Is
The stiffness and tenderness you feel a day or two after hard exercise is called delayed-onset muscle soreness, or DOMS. Despite what many people still believe, it has nothing to do with lactic acid buildup. That myth was tested directly decades ago: runners on a level surface produced significant blood lactate but reported no soreness afterward, while runners going downhill never elevated lactate at all yet experienced substantial delayed soreness.1PubMed. Is Lactic Acid Related to Delayed-Onset Muscle Soreness? Lactate clears from your muscles within an hour or so of finishing exercise. DOMS peaks one to three days later. The timelines alone should have killed this idea, but it persists.
The current understanding is that DOMS begins with structural damage to muscle fibers, particularly during movements where the muscle lengthens under load (lowering a weight, running downhill, the descent in a squat). This damage disrupts cell membranes, triggering an inflammatory cascade. Products of that inflammatory response accumulate in the tissue surrounding the injured fibers and sensitize the pain-sensing nerve endings embedded in the muscle.2PubMed. Mechanisms of exercise-induced delayed onset muscular soreness: a brief review The soreness itself is the inflammation talking to your nervous system. It can persist for four to five days depending on severity.3PubMed Central. Muscle tenderness from exercise: mechanisms?
At least six different theories have been proposed for the mechanism behind DOMS, including connective tissue damage, enzyme efflux, and muscle spasm. No single theory explains it fully; researchers now think an integration of two or more theories is needed.4PubMed. Delayed onset muscle soreness : treatment strategies and performance factors The point for your purposes is this: soreness is fundamentally a pain and inflammation event. It tells you that tissue was disrupted. It does not tell you how much new tissue will be built in response.
What Actually Drives Muscle Growth
The conventional model of muscle hypertrophy identifies three factors: mechanical tension, metabolic stress, and muscle damage. Of these, progressive mechanical tension overload is considered the most important driver of muscle growth and changes in muscle architecture.5PubMed Central. Maximizing Muscle Hypertrophy: A Systematic Review of Advanced Resistance Training Techniques and Methods Mechanical tension is, in plain terms, how hard your muscles have to work against resistance. When you progressively challenge a muscle to handle more load, more reps, or more total work over weeks and months, you trigger the signaling pathways responsible for adding contractile protein.
Muscle damage does appear on the list of hypertrophy factors, but its contribution is the subject of genuine debate. Some researchers argue that damage plays a meaningful supporting role; others believe it is largely incidental and that the growth signal comes almost entirely from tension and metabolic stress. What everyone agrees on is that you do not need to maximize damage to maximize growth. A training program built around doing as much damage as possible would leave you too beaten up to train frequently enough or hard enough to make good progress.
Why Early Soreness Does Not Predict Long-Term Growth
Here is where the relationship between soreness and growth gets genuinely interesting. After a hard resistance training session, your body ramps up muscle protein synthesis. That sounds like growth, and people naturally assume it is. But research suggests that the initial spike in protein synthesis following a damaging workout is largely directed at repair and remodeling of the damaged tissue rather than at building new contractile material. Increases in protein synthesis only start contributing meaningfully to hypertrophy after damage is progressively attenuated across repeated training bouts, and even more so when damage is minimal.6PubMed. The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis
This is a crucial distinction. When you start a new exercise or come back after a layoff and you are brutally sore for days, your body is spending its protein-building resources patching up damage rather than adding size. It is the later weeks, when the same workout barely makes you sore at all, that the protein synthesis machinery is freed up to lay down new muscle tissue. In other words, the sessions that feel the least dramatic may be doing the most building.
Supporting this, at least one study found no correlation whatsoever between rates of myofibrillar protein synthesis and any measures of muscle damage after exercise.7PubMed Central. Leucine-Enriched Essential Amino Acids Improve Recovery from Post-Exercise Muscle Damage Independent of Increases in Integrated Myofibrillar Protein Synthesis in Young Men The two processes ran on separate tracks entirely.
The Repeated Bout Effect
If you have ever noticed that the first session of a new exercise leaves you wrecked, but the same exercise a week later is far more tolerable, you have experienced the repeated bout effect. Your skeletal muscle has an intrinsic protective mechanism that reacts to eccentric exercise-induced damage by activating an adaptive response that resists subsequent damage.8Free Radical Biology and Medicine. The repeated bout effect evokes the training-induced skeletal muscle cellular memory This involves neural adaptations, changes to tendon and muscle fiber properties, remodeling of the connective tissue matrix surrounding muscle fibers, and more efficient inflammatory responses.
The repeated bout effect is one of the strongest pieces of evidence that soreness and growth are not the same thing. As you get more trained, your muscles become increasingly resistant to damage from the same workload. You experience less soreness over time. But your muscles keep growing, often at an accelerating rate in early training, as long as the stimulus is progressively challenging. If soreness were truly a signal of growth, you would expect trained lifters to need more and more soreness to keep growing. Instead, the opposite happens: soreness fades while hypertrophy continues.
Eccentric Exercise Causes More Soreness but Not Proportionally More Growth
Eccentric contractions (where the muscle lengthens under load, like the lowering phase of a bicep curl) are the primary trigger for DOMS. Research confirms that perceived soreness is greatest following eccentric exercise, with minimal soreness following purely concentric (shortening) movements.9PubMed. Muscle soreness and serum creatine kinase activity following isometric, eccentric, and concentric exercise Eccentric training also produces greater changes in muscle contractile properties compared to concentric training.10Journal of Electromyography and Kinesiology. Comparison of concentric and eccentric resistance training in terms of changes in the muscle contractile properties
So if eccentric exercise causes dramatically more soreness, does it also cause dramatically more growth? Not really. A systematic review and meta-analysis comparing the two found that eccentric actions produced a slightly larger average percent change in muscle growth compared with concentric actions (about 10% versus about 7%), but the difference did not reach statistical significance.11The Journal of Strength & Conditioning Research. Hypertrophic Effects of Concentric vs. Eccentric Muscle Actions: A Systematic Review and Meta-analysis Both types of contraction produced meaningful hypertrophy. The gap in soreness between eccentric and concentric exercise is enormous; the gap in growth is modest and uncertain. That mismatch tells the story well.
Anti-Inflammatory Drugs Do Not Block Growth
If soreness (driven by inflammation) were a necessary part of the growth process, you would expect that suppressing inflammation with painkillers would also suppress muscle gains. Researchers tested this directly by having subjects take ibuprofen or a placebo after resistance training sessions over multiple weeks. Ibuprofen had no effect on muscle hypertrophy or strength gains, and it did not even meaningfully reduce the soreness itself.12PubMed. The effects of ibuprofen on muscle hypertrophy, strength, and soreness during resistance training
The picture gets a bit more complicated at higher doses. A separate study comparing low-dose aspirin to high-dose ibuprofen over several weeks of training found that high-dose ibuprofen users gained less muscle volume (about 3.7% versus 7.5% with low-dose aspirin) and had slightly smaller strength increases.13PubMed. High doses of anti-inflammatory drugs compromise muscle strength and hypertrophic adaptations to resistance training in young adults That suggests chronic high-dose anti-inflammatory use could blunt some of the growth response, but the mechanism likely involves interference with downstream signaling pathways rather than with pain perception. A moderate dose of ibuprofen taken occasionally is unlikely to meaningfully impact your gains.
Does Protein Help with Soreness?
You might assume that if protein builds muscle, it should also reduce the soreness that comes from training. The evidence here is more nuanced than supplement marketing suggests. A large meta-analysis of 29 studies found that protein supplementation helped preserve muscle function after damaging exercise, with strength recovery improved at various time points through 96 hours. It also helped reduce blood markers of muscle damage (like creatine kinase). However, protein had no effect on subjective ratings of muscle soreness compared with controls.14European Journal of Clinical Nutrition. The impact of dietary protein supplementation on recovery from resistance exercise-induced muscle damage: A systematic review with meta-analysis
An earlier systematic review reached a similar conclusion: there was no clear relationship between protein supplementation and reduced soreness or lower damage markers after a single exercise bout, though some benefits became more apparent when protein was consumed consistently after daily training sessions over time.15PubMed. Effects of protein supplements on muscle damage, soreness and recovery of muscle function and physical performance: a systematic review This again underscores that soreness and the actual repair/growth processes are not tightly coupled. You can improve functional recovery and reduce measurable tissue damage without changing how sore you feel.
For long-term muscle gains, total daily protein and caloric intake matter most. Peri-exercise protein (around the training window) plays a useful supporting role once those bigger dietary factors are accounted for.16PubMed Central. Effects of Protein Supplementation on Performance and Recovery in Resistance and Endurance Training
Why Some People Get More Sore Than Others
If you have ever trained alongside someone doing the same workout and noticed wildly different soreness responses, genetics are a likely contributor. Dozens of gene variants have been associated with susceptibility to exercise-induced muscle damage. Polymorphisms in genes like ACTN3, TNF, IL6, and IGF2 appear to influence how much damage someone sustains and how long their recovery takes.17PubMed Central. Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing To date, 37 variants in 32 genes have been significantly linked to injury risk, recurrence, severity, and recovery in the context of sport-related muscle damage.18PubMed Central. Genetic Susceptibility to Sport-Related Muscle Injuries: Insights from the Literature and Novel Gene Candidates Variants in CCL2 and CCR2 genes have also been associated with altered strength recovery and elevated soreness in response to the same exercise bout.19PubMed. CCL2 and CCR2 polymorphisms are associated with markers of exercise-induced skeletal muscle damage
Interestingly, sex does not appear to be a major factor in how sore you get. A study comparing men and women found that DOMS increased substantially after exercise and remained elevated at 48 hours, but there were no differences between men and women.20ScienceDirect. Relationship between exercise-induced muscle soreness, pain thresholds, and skin temperature in men and women
Age, on the other hand, matters quite a bit. Older muscle displays delayed, prolonged, and less efficient recovery from exercise-induced damage. This appears to stem from a combination of factors including resistance to anabolic signaling, stiffer connective tissue, mitochondrial dysfunction, unresolved inflammation, and changes in satellite cell function.21PubMed Central. Age-Associated Differences in Recovery from Exercise-Induced Muscle Damage For older adults, persistent soreness is more of a recovery problem than a growth signal, and training frequency often needs to be adjusted to allow adequate repair between sessions.
Better Ways to Know Your Training Is Working
If soreness is an unreliable indicator, what should you actually track? Progressive overload remains the gold standard. If you are consistently able to do more work over time, whether by adding load, adding reps, or both, your muscles are adapting and growing. A study comparing load progression (adding weight) to repetition progression (adding reps at the same weight) found that both strategies produced comparable muscle growth, with pooled mean increases ranging from roughly 7% to 13% across measurement sites.22PeerJ. Progressive overload without progressing load? The effects of load or repetition progression on muscular adaptations The method of progression mattered less than the fact that progression happened.
Spreading your training volume across more frequent sessions may also help. A comparison of high-frequency versus low-frequency eccentric training found that the higher-frequency group reported lower perceived exertion and less soreness while achieving similar or slightly better strength gains (about 37% versus 27%).23The Journal of Strength & Conditioning Research. Comparison of High Versus Low Eccentric-Based Resistance Training Frequencies on Short-Term Muscle Function Adaptations You can distribute the same total workload across more days, feel better, and get equivalent results. That is hard to square with the idea that you need to be wrecked after every session.
Managing Soreness When It Does Show Up
Even if soreness is not a growth signal, it can still interfere with your training by limiting range of motion, reducing your willingness to push hard, or forcing you to skip sessions. Foam rolling and self-myofascial release appear to have short-term benefits, increasing joint range of motion without negatively affecting performance and helping attenuate both performance decrements and DOMS after intense exercise.24PubMed Central. THE EFFECTS OF SELF-MYOFASCIAL RELEASE USING A FOAM ROLL OR ROLLER MASSAGER ON JOINT RANGE OF MOTION, MUSCLE RECOVERY, AND PERFORMANCE: A SYSTEMATIC REVIEW Light activity, adequate sleep, and sufficient total protein intake all support faster functional recovery, even if they do not dramatically change how sore you feel.
Expectation also plays a role in perceived soreness. In one small study, subjects who received pulsed ultrasound treatment after a muscle-damaging bout showed faster restoration of normal muscle performance at 48 hours compared with both a placebo group and an untreated group.25Journal of Rehabilitation Medicine. Effect of pulsed ultrasound versus placebo on muscle soreness perception and muscular performance The placebo group, interestingly, did not improve as much despite believing they were receiving treatment, which suggests the therapeutic modality had a real physiological effect. But the broader point is that perceptions of soreness are influenced by context, expectations, and psychological state, making them even less useful as an objective measure of what is happening inside the muscle.
The most practical approach to soreness is to treat it as a cost to manage rather than a benefit to chase. If you are so sore that your next training session suffers, you may be doing too much novel stimulus at once. Introduce new exercises gradually, progress load and volume in reasonable increments, and let the repeated bout effect do its work. The goal is to train hard enough to provide a growth stimulus, recover well enough to do it again soon, and keep progressing over months and years. None of that requires you to struggle getting off the toilet the morning after leg day.