DOMS - or Delayed Onset Muscle Soreness - is caused by microtrauma to muscles following excessive or unaccustomed exercise, especially if there is an eccentric (muscle contraction whilst lengthening) component. There follows an inflammatory response causing swelling, altered muscle firing patterns, and pain, and therefore overall dysfunction of the muscle(s). These symptoms typical occur over the course of 24-48 hours post exercise (hence the "delayed" component) and are localised to the muscles involved in that exercise, initially with feelings of a dull ache and progressing to muscle stiffness and tenderness. Additionally, it's common to see short term loss of muscle strength and reduced range of movement.
The good news is that DOMS gradually subsides to resolution over the course of 1-3 days with no lasting effects.
But can we do anything to accelerate that process, or even reduce our chances of developing DOMS?
Primarily, active rest is hugely beneficial. Muscles and joints act like pumps under movement, with the theory being that movement will help increase the rate of fluid exchange and improve blood flow. Additionally, gentle massage and wearing compression garments have been shown to have a positive impact on DOMS, though deep tissue massage and excessive stretching should be avoided in the early phase (first 24 hours post onset).
Ultimately, prevention is key. Session planning should focus on volume (sets and reps) and intensity (load and speed) increases of maximum 10% per week. With this, you should also be aware of managing the volume of eccentric exercise per muscle group, as well as making sure that you are appropriately conditioned to task. For example, long distance running involves a large volume of eccentric load for both the quadriceps and calves, so gym sessions should involve eccentric exercise for both muscle groups with a view to preventing DOMS post long run.
We can also use our post-exercise session "cool down" to prevent DOMS. There is growing evidence in the research that foam rolling post eccentric exercise has a significant positive impact on the onset of DOMS. Unfortunately, there is not a consensus on the optimal foam roller program with regards to the timing of the foam rolling, nor the volume. Logic would dictate that straight after the exercise session would fit most schedules, and the volume be dependant on the volume/intensity of eccentric load during the session.
Unsurprisingly, given the mechanism, most of the benefits of foam rolling are inferred from research into massage. The evidence suggests that massage/foam rolling reduces DOMS through changes in a muscle’s viscoelastic properties, increasing mitochondria production, and increasing blood flow (Best, Gharaibeh, Huard, 2013; Weerapong, Hume, Kolt, 2005). The magnitude of effect of foam rolling on DOMS has been shown to be as great as that of wearing compression garments, but at a far reduced cost, as well as much less time using the modality to find benefit (Maloon, 2017).