We’ve all experienced it, the intense muscle pain from delayed onset muscle soreness (DOMS) that comes a day or two after a hard workout.

Why does it happen?
DOMS is the pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise.
The soreness is felt most strongly 24 to 72 hours after the exercise. It is caused by the eccentric (lengthening) movement of an exercise, which causes micro-trauma to the muscle fibres. DOMS is most prevalent in people first starting out on their exercise journey. As they develop an exercise routine the soreness experienced becomes less and less frequent. However, micro-trauma (muscle soreness) can occur in anyone if significant change occurs in their routine…eg: Increased weights, higher rep range, changing Group Fitness Classes, moving from Machines to Free Weights, swapping “Pyramiding” weights for “Drop Setting”…..the list goes on.

Technically….
Even if you’re not using heavy weights, muscle damage can still occur. When the muscles become fatigued from performing higher reps or are at an angle they’re not used to, there can still be muscle fibre damage. This is when ACTIN and MOYSIN are forcibly ripped apart, causing damage. This type of damage is similar to a wound that you get anywhere on your body.
Immediately following the damage, an inflammatory response ensues that eventually leads to healing of the muscle fibre making it even bigger and stronger than it previously was.
Once damage happens, the first cells to arrive on the scene are neutrophils. These specialized white blood cells secrete chemicals, such as enzymes and toxic chemicals, which further break down the damaged tissue. Following on the heels of the neutrophils are another type of white blood cell, macrophages. After the tissues are adequately decomposed, the neutrophils and macrophages literally consume and remove them from the site in an effort to clear it out and prepare for the makeover.
The macrophages that helped to clean up and remove the damaged tissue also secrete chemicals that play a small yet critical role in numerous processes and eventually lead to the activation and growth of satellite cells. Satellite cells are specialized muscle stem cells that sit dormant in a muscle but then migrate to the area of damage, bringing their nuclei into the muscle cell. The satellite cells fuse into the existing muscle fiber, typically becoming one cell, but now with more nuclei. Since the nuclei of muscle cells are the headquarters where muscle building originates, the more nuclei that a muscle cell contains, the more proficiently it can grow. And over time the muscle grows bigger and stronger.

Is it doing me harm?
Absolutely not. While at the time it may feel like you’ll never walk again, or be able to pull your T shirt over your head, it’s simply your muscles going through adaptation. And in fact you will come out the other side stronger and fitter than before.
Many people will wait until the pain has completely gone before returning to the gym. However, research has shown that it’s best to exercise again within 48 hours but at a lesser intensity and complete a different routine.

Do I have to “Feel the Burn” to become stronger & fitter?
No, muscle cells have more than one trick up their sleeves to grow. In addition to adding new nuclei to damaged muscle fibers, muscle also grows by increasing the amount of protein it contains. A muscle is composed primarily of protein, at least the structural components of it are. So another way that muscle grows is by synthesizing more muscle protein, through a process termed “muscle protein synthesis.”
Muscle protein synthesis is the build up of muscle protein one amino acid at a time. This takes place in and around the nuclei of the muscle cell. In the nuclei, the DNA houses the genes that encode the sequence of each specific protein a muscle contains. When the nuclei receive a signal to activate certain genes to build more protein, they replicate the sequence of the proteins with messenger RNA (mRNA). The mRNA then leaves the nuclei and single amino acids are brought together to form a long chain that makes up the protein that builds up the muscle.
This is another reason why Protein consumption (in any form) is crucial to everyone performing any kind of exercise. From body builders, to basket ballers, to boxers. Post workout protein intake  is best done as soon as possible after completing your session. Ideally within 30 minutes.
This is where Protein Shakes are most beneficial.

The wrap up.
Not all pain is bad * You don’t have to feel pain to have gains * Not all gains are muscular * Strength is not always visible, but is definitely measurable * You don’t have to be big to be strong * You don’t have to be lean to be fit * Nutrition is vital to every action in the human body ,not just exercise.