Muscle Damage and Soreness

Quick Intro

Exercise-induced muscle damage refers to small disruptions in muscle fibers after unfamiliar or intense exercise, especially exercise that includes lowering a weight under control. Delayed onset muscle soreness, or DOMS, is the stiffness and tenderness that appears about 24 to 72 hours later. Many people treat soreness as proof of an effective workout. The research does not support that belief.

The Idea in Plain Terms

Eccentric contractions, in which a muscle produces force while lengthening, put high stress on the fibers. After a new or hard session, the muscle’s internal structure can be disturbed, and the repair process involves inflammation and swelling. The soreness comes from this process rather than from lactate.

The damage hypothesis for growth proposes that this disruption, and the repair that follows, signals the muscle to rebuild larger. There is a logic to it: the immune cells and growth factors that arrive to repair tissue could also support growth.

Some points complicate it:

Repeated bout effect. After one session of unfamiliar exercise, the muscle adapts quickly, and a repeat session a week or two later causes much less damage and soreness. The body protects itself, even though growth continues.
Repair competes with growth. Early in a new program, much of the muscle’s protein building goes to repair damaged tissue. In a 2016 study by Damas and colleagues, growth in muscle size appeared only after the damage markers declined, in the later weeks of a program.
Soreness is a poor indicator. Experienced lifters often grow well with little soreness, and a very sore muscle can be one that was damaged and had to repair.

A Worked Example

A person starts lifting after a long break:

Week	Experience	Interpretation
1	Very sore after the first session	Unfamiliar exercise, high damage
3	Mild soreness with the same workout	Repeated bout effect
8	Little soreness, strength and size rising	Adaptation without damage

The decline in soreness is a sign of adaptation, not a sign that training stopped working.

What the Research Shows

A review by Schoenfeld and Contreras in 2012, “Is postexercise muscle soreness a valid indicator of muscular adaptations?”, concluded that soreness is not a reliable marker of growth. Damas and colleagues, in the Journal of Physiology in 2016, tracked muscle protein synthesis and size in the first weeks of training and found that the early rise in protein building reflected repair and that it was linked to growth only after damage subsided.

Some damage may contribute to the stimulus, and extreme damage appears to impair recovery and training quality. The best-supported conclusion is that exercise should challenge the muscle and that there is no need to aim for soreness.

Soreness also has limits as a guide to training. A very sore muscle may be a reason to ease the next session, since force output is reduced.

Who It Suits

This information helps:

Beginners who feel alarmed by soreness.
Lifters who equate soreness with progress.
Coaches planning how to introduce new exercises.

How to Use It

Start new exercises with moderate volume and build up.
Expect soreness after a new stimulus, and expect it to fade.
Do not use soreness as the measure of a good workout.
Use light activity, sleep and food to feel better.
Reduce volume when soreness limits your next session.
Judge progress by performance and size over weeks.

Common Misunderstandings

It is not necessary to be sore to grow.

It is not caused by lactic acid.

It is not reduced much by stretching.

FAQ

How long does soreness last? Usually 2 to 4 days.

Can I train sore muscles? Light work is fine, and a very sore muscle may need rest.

Why no soreness now? The repeated bout effect.

Is soreness a sign of injury? Usually not, and sharp pain or swelling is a reason to see a clinician.

Where This Comes From

Schoenfeld BJ and Contreras B, 2012, is postexercise muscle soreness a valid indicator of muscular adaptations? (Strength and Conditioning Journal, 35, 16 to 21). Damas F and colleagues, 2016, resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage (Journal of Physiology, 594, 5209 to 5222).