Muscle Soreness or Injury? How to Tell the Difference
By APA Physiotherapist Ben Howie
If you've ever started a new gym program, returned to exercise after a break, or pushed yourself harder than usual during training, you've probably experienced muscle soreness afterwards.
For many people, this raises an important question:
Is this normal soreness, or have I actually injured myself?
Understanding the difference between normal post-exercise soreness and an injury can help you recover appropriately, stay active, and know when it may be time to seek professional advice.
What Is Delayed Onset Muscle Soreness (DOMS)?
Delayed Onset Muscle Soreness, commonly known as DOMS, refers to the muscle soreness and stiffness that develops after unfamiliar or strenuous exercise.
DOMS typically occurs following activities that place higher than usual demands on the muscles, particularly exercises involving controlled lengthening of the muscle, such as:
Squats
Lunges
Running downhill
Strength training
Returning to exercise after a break
Symptoms generally begin 12-24 hours after exercise, peak between 24-72 hours and gradually settle over the following few days.
Although it can feel uncomfortable, DOMS is considered a normal response to exercise and is not usually a cause for concern.
Why Do Muscles Become Sore?
A common myth is that muscle soreness is caused by a build-up of lactic acid.
Research has shown this isn't the case.
Instead, DOMS is believed to occur due to small amounts of microscopic muscle damage and the body's natural inflammatory response to exercise. This process helps stimulate adaptation, allowing muscles to become stronger and more resilient over time.
In other words, some soreness can be a normal part of getting fitter and stronger.
What Does Normal Muscle Soreness Feel Like?
DOMS often has several characteristic features:
Develops gradually after exercise
Affects the muscles used during activity
Usually occurs on both sides of the body
Feels like an ache, stiffness, or tenderness
Improves with gentle movement and activity
Resolves within several days
Many people describe their muscles as feeling "tight" or "heavy" rather than acutely painful.
While movement may initially feel uncomfortable, symptoms often improve as the muscles warm up.
What Does an Injury Feel Like?
Injuries often present differently from normal muscle soreness.
Rather than developing gradually after exercise, symptoms may occur suddenly during activity or continue well beyond the expected recovery period.
Signs that may indicate an injury include:
Sharp or sudden pain
Pain during a specific movement
Swelling or bruising
Significant weakness
Pain that worsens over time
Difficulty weight-bearing or using the affected area
Symptoms that persist beyond one week
Unlike DOMS, injury-related pain is often localised to a specific structure such as a tendon, ligament, joint, or muscle.
A Helpful Rule of Thumb
A simple way to think about it is:
Soreness tends to feel broad, achy, and improves over time.
Injuries tend to feel sharp, localised, and limit normal function.
While this isn't always the case, it can be a useful guide when deciding whether symptoms are likely related to exercise adaptation or something more significant.
Should You Exercise If You're Sore?
In most cases, yes.
Mild to moderate muscle soreness is generally not harmful and does not require complete rest.
In fact, gentle movement can often help reduce stiffness and improve comfort.
Activities that may be helpful include:
Walking
Cycling
Mobility exercises
Light resistance training
Gentle stretching
However, if soreness is severe enough to significantly affect movement quality or exercise technique, reducing training intensity for a short period may be appropriate.
When Should You Seek Professional Advice?
While most muscle soreness settles on its own, it may be worth seeking assessment if:
Pain is severe or worsening
Symptoms are highly localised
Swelling or bruising develops
You are unable to return to normal activity
Symptoms persist beyond one week
Pain is affecting sleep or daily activities
A physiotherapist can help determine whether symptoms are consistent with normal exercise-related soreness or whether an injury may be present.
Practical Recovery Tips
If you're experiencing normal post-exercise soreness, consider the following:
Stay active with gentle movement
Prioritise sleep and recovery
Maintain adequate hydration
Consume sufficient protein throughout the day
Progress exercise gradually over time
Importantly, recovery does not always mean complete rest. Maintaining an appropriate level of activity often supports recovery more effectively than avoiding movement altogether.
Key Takeaways
Delayed Onset Muscle Soreness (DOMS) is a normal response to unfamiliar or challenging exercise.
DOMS typically develops 12-24 hours after exercise and peaks within 24-72 hours.
Injury-related pain is more likely to be sharp, localised, associated with swelling, or persist longer than expected.
Gentle movement is often beneficial when recovering from muscle soreness.
If symptoms are severe, worsening, or not improving, professional assessment may be appropriate.
Understanding the difference between soreness and injury can help you stay active, recover confidently, and know when to seek help. If you're unsure about your symptoms, a physiotherapist can assess your condition and guide you towards the most appropriate management plan.
References
Hyldahl, RD & Hubal, MJ 2013, ‘Lengthening our perspective: Morphological, cellular, and molecular responses to eccentric exercise’, Muscle & Nerve, vol. 49, no. 2, pp. 155–170.
Peake, JM, Neubauer, O, Della Gatta, PA & Nosaka, K 2017, ‘Muscle damage and inflammation during recovery from exercise’, Journal of Applied Physiology, vol. 122, no. 3, pp. 559–570.
Stožer, A, Vodopivc, P & Križančić Bombek, L 2020, ‘Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences’, Physiological Research, vol. 69, no. 4, pp. 565–598.