With January upon us, you may have decided to embark on a new rigorous fitness regime. I am sure that everyone has experienced the feeling of invincible strength after smashing a workout or a heavy pre-Lent bumps erg session, only to struggle to bend down and sit on the toilet the following morning. Suddenly, stairs are your worst enemy, and the simple act of tying your shoelaces becomes a battle of flexibility. This phenomenon is known in the scientific community as ‘Delayed-Onset Muscle Soreness’ (DOMS). But what is happening inside your muscles when you experience this pain? And how can we fix this punishment for doing exercise?

I remember being told in GCSE biology that muscle soreness occurred due to a build-up of lactic acid, which was produced when there is insufficient oxygen in the body during periods of intense exercise. I assumed therefore that this is what is causing the pain in the days after a workout. However, numerous studies have shown that lactic acid is not related to DOMS, and it only contributes towards discomfort felt during or immediately after a workout.

“Suddenly, stairs are your worst enemy, and the simple act of tying your shoelaces becomes a battle of flexibility”

In fact, the main contributor towards your post-workout aches are microtears within a muscle. These tears form during ‘eccentric exercise’: when a muscle is forced to lengthen whilst also trying to contract. For example, these tears might form when you lower your arm during a bicep curl, as the bicep muscle is both under tension and contracted, but also being stretched. The cell membranes that make up the outer border of the muscle cells might break, which releases calcium from its storage site inside the cell. These free calcium ions serve as a magnet for inflammatory immune cells, recruiting them to the site of the muscle damage. Upon reaching the muscle, immune cells release chemical mediators that stimulate pain receptors within the muscle connective tissue, creating the sensation of soreness.

To work out how we can encourage recovery from DOMS, we should first look at how the body naturally heals from this inflammatory response. There are two main stages to this repair. First, a different category of immune cell, called phagocytes, migrate to the area of pain and inflammation. We can think of these cells as Pac-Man clones, engulfing the fragments of damaged cells and damaged proteins. This stops the pro-inflammatory cells from releasing pain-stimulating chemicals, reducing muscle pain.

In the second stage of repair, special cells called satellite cells proliferate and develop into myoblasts – the building blocks of muscle fibres. These myoblasts then migrate to the damaged area, fusing with existing muscle fibres and restoring the muscle’s functional integrity. This is the stage that leads to an increase in muscle bulk, making your muscles get bigger over time.

“Try not to let this post-exercise pain dishearten you – it is actually a sign that your muscles are getting bigger”

How can we speed up this process of repair and recovery from DOMS? There are two typical, yet somewhat conflicting, approaches. The first is ‘cold therapy’. This involves cold water immersion or the local use of ice packs on the area of muscle soreness. These therapies decrease the speed of conduction of the pain nerves and leads to the constriction of blood vessels, which reduces the rate of delivery of inflammatory chemicals to the site of damage. This approach should therefore be taken in the immediacy after exercise to reduce the amount of pain that develops, by reducing the degree of inflammation.

Somewhat paradoxically, an alternative approach is ‘heat therapy’. This method involves taking warm baths or putting a hot water bottle on the affected area. This has the opposite effect to cold therapy: it increases blood flow to the area, which speeds up the delivery of oxygen and nutrients needed for the repair phase. It also increases the elasticity of muscles, mitigating the muscle spasms and stiffness that often accompany DOMS. Therefore, heat therapy should be used in the longer term, around a day after the intense exercise, to accelerate the rate of recovery.

If cold or hot therapy doesn’t appeal to you, there are several other less conventional approaches to reducing your muscle pain. You could try eating lots of blueberries. These have been shown to enhance levels of antioxidants, which are needed for an efficient immune response, and hence increase the rate of recovery from DOMS. A second option is to purchase a massage gun, which has a similar effect to heat therapy in increasing blood flow and hence oxygen delivery.

It is interesting how, over many training sessions, the body adapts and the pain you experience each time you exercise will likely decrease. Try not to let this post-exercise pain dishearten you – it is actually a sign that your muscles are getting bigger, and the chances are that the pain will be significantly less after the next time you exercise.