DOMS Explained: Why You Are Still Sore Two Days After Training

TL;DR: DOMS is caused by microscopic tears in muscle fibres during eccentric (lengthening) contractions, not lactic acid. The inflammatory repair process peaks 24 to 72 hours post-exercise. Active recovery, contrast therapy, and sports massage reduce symptoms. Soreness that persists beyond seven days or concentrates at a joint rather than in muscle tissue needs clinical assessment.

Most people assume the burning sensation during a hard set is lactic acid, and that the soreness the next day is the same thing fading. Neither is correct. Lactic acid clears from muscle tissue within 30 to 60 minutes of finishing exercise. The soreness you feel the following morning, and more intensely the day after that, is a separate and completely different physiological process.

Understanding DOMS means understanding why muscles adapt to training. It also helps you distinguish between productive discomfort and early injury signals, which is the distinction that prevents the majority of training setbacks.

What DOMS Actually Is

DOMS stands for delayed onset muscle soreness. It is the diffuse, tender-to-touch soreness that develops in the 24 to 72 hours following unfamiliar or high-load exercise, particularly exercise involving eccentric contractions.

During eccentric loading, muscle fibres are lengthened under tension. This places stress on the sarcomeres, the individual contractile units within each muscle fibre, in a way that concentrically loaded exercise does not. Microscopic disruptions occur in the sarcomere structure. This is not damage in a harmful sense. It is the mechanical signal that initiates the adaptation process.

The disruption triggers a localised inflammatory response. Inflammatory mediators including prostaglandins and bradykinin sensitise the pain receptors in the muscle tissue. This is why the area becomes tender and why normal movements that would otherwise be pain-free produce discomfort. The sensitivity peaks between 24 and 72 hours post-exercise as the inflammatory response reaches its maximum, then gradually resolves over five to seven days as the repair process completes.

Lactic acid is entirely absent from this process. Lactate is a metabolic byproduct of anaerobic energy production during high-intensity exercise. It returns to baseline levels within one to two hours of stopping. The persistent belief that lactic acid causes DOMS is one of the most widespread misconceptions in exercise science.

Why Eccentric Loading Causes More Soreness Than Concentric

Not all exercise causes equal soreness. The type of contraction matters significantly. Eccentric contractions occur when a muscle produces force while lengthening: the descent in a squat, the lowering phase of a bicep curl, the downhill section of a run, the deceleration phase of a jump landing. These phases place higher mechanical stress on individual sarcomeres compared to the shortening phase.

This is why downhill running causes significantly more soreness than flat running at the same effort level. It is why the day after heavy Romanian deadlifts produces more hamstring soreness than a leg curl session. New movements cause disproportionate soreness even at loads that feel manageable during the session. The limiting factor is not the weight; it is the novelty of the eccentric demand on that specific tissue.

Exercises with a pronounced eccentric component include squats and lunges (descent phase), all pressing movements (lowering phase), deadlift variations (lowering the bar), Nordic curls, chin-ups and pull-ups (lowering phase), and plyometric landing phases. If you are adding any of these for the first time, expect soreness that exceeds what your perceived exertion during the session suggested.

The Repeated Bout Effect: Why DOMS Decreases Over Time

After a first exposure to a new exercise or loading pattern, the soreness produced is significantly greater than in subsequent sessions with the same movement. This is the repeated bout effect, one of the most consistent findings in DOMS research. After the initial inflammatory response, the repaired sarcomeres are more resistant to disruption under the same mechanical stress. The cytoskeletal proteins that anchor the sarcomere structure are reinforced. This is the cellular basis of muscle adaptation.

The practical implication: if a new exercise causes significant soreness, performing it again within five to seven days at the same or slightly reduced load will produce markedly less soreness the second time. Avoiding the exercise until the soreness fully resolves delays this adaptation. Training through manageable DOMS, meaning soreness that does not alter your movement quality, accelerates the process.

How to Recover Faster from DOMS

Complete rest is less effective for DOMS recovery than low-intensity movement. Active recovery increases circulation to affected tissues, which accelerates the clearance of inflammatory byproducts and delivers the nutrients required for repair.

Low-intensity movement: A 20-minute walk or easy cycle on a rest day maintains blood flow without adding mechanical stress. This is consistently more effective than staying sedentary and costs nothing in terms of recovery.

Sports massage: Applied 24 to 48 hours after the causative session, sports massage reduces perceived soreness and improves short-term range of motion. The mechanism involves direct pressure on sensitised tissue and increased local circulation. It does not eliminate soreness but reduces its peak intensity and duration.

Contrast therapy: Alternating between hot and cold water exposure drives a pumping effect in peripheral vasculature. Contrast therapy sessions of 10 to 15 minutes accelerate the clearance of prostaglandins and other inflammatory mediators from muscle tissue, particularly in the 24 to 48 hour window post-exercise.

Protein and sleep: Muscle protein synthesis peaks in the 24 to 72 hour window following exercise. Adequate protein intake of 1.6 to 2.2 grams per kilogram of body weight daily, and sufficient sleep of 7 to 9 hours, are the primary inputs the repair process requires. These determine how efficiently the adaptation completes.

NSAIDs: Anti-inflammatory medications reduce soreness but may blunt the adaptation signal by suppressing the inflammatory response that drives muscle remodelling. For athletes training consistently, routine NSAID use around training sessions is counterproductive. Reserve them for significant injury pain, not routine DOMS.

When Soreness Becomes a Warning Sign

DOMS has a recognisable pattern: diffuse, bilateral if both sides were loaded equally, located in the muscle belly rather than at a joint, onset at 12 to 24 hours, peak at 24 to 72 hours, resolution by five to seven days. Soreness that deviates from this pattern warrants attention.

Soreness concentrated at a joint or tendon insertion rather than in the muscle belly is not DOMS. It indicates tendon or joint irritation and should not be trained through. Reducing load or resting the session is appropriate until this type of pain resolves or is assessed clinically.

Soreness that is sharply unilateral after a movement that loaded both sides equally may indicate a partial strain on the affected side. This pattern combined with any swelling or bruising over the area requires assessment before continuing training.

Soreness that does not improve by day four or five, or that worsens after the initial 48-hour peak, is not following normal inflammatory resolution. Any soreness combined with significant swelling or skin discolouration warrants clinical assessment rather than continued loading.

Significant muscle soreness following intense exercise, combined with dark or cola-coloured urine in the 24 to 48 hours after training, is a medical emergency. This indicates rhabdomyolysis, a breakdown of muscle tissue that releases myoglobin into the bloodstream and can cause kidney damage. Seek medical attention immediately if this combination of symptoms occurs.

At R3BOOT in Dadar, Mumbai, we regularly see athletes who have been training through pain they assumed was DOMS. A physiotherapy assessment distinguishes between normal adaptation discomfort and early-stage injury that will compound if loaded further.