Recovery: How does the musculoskeletal system actually repair?

recovery and repair

I wish I was writing this blog right now simply as a medical practitioner trying to explain the importance of rest and recovery in order to get back on your feet as quick as possible. Sadly I have to admit I’m injured its really silly I’ve bruised my knee don’t ask me how but its rather blue. This started to make me think about recovery and what I could do to maximise it so I can get back to running as quick as possible. So first of all in order to understand why rest is important you need to understand how the body repairs itself. Here is a guide to how each part of the musculoskeletal system repairs itself.

How does Cartilage repair?

Cartilage is the slowest of the musculoskeletal system to repair due to having the least amount of blood vessels and large parts of the cartilage have no vessels at all. There are two ways that collagen (the protein that makes up of most of your connective tissues like your tendons and ligaments) repairs itself, they grow both interstitial (so from within) and appositional (from the outside surfaces).


Is when the cartilage grows in size due to division within the collagen itself and the new cells push away from each other and expand the area around it. This works in a similar way to how bread or cakes would rise and expand in the oven.


Is when the cells around the outside of the bone change into a different types of cell in order to repair and grow new cartilage. The new cells build up around the outside and therefore the overall size of the cartilage will increase.

How does bone repair?

Bone has a large blood supply and is very good at repairing itself however it can still take months to heal.

There are four steps of how bone repairs:

  1. Formation of a blood haematoma: When your bone breaks or is damaged it will also cause some of the small blood vessels to rupture. Therefore some of the blood, will leak out and the blood will clot and form a mass called a haematoma. Swelling and inflammation will also start to build up which will add the to debris around the injury and your body will have to work to remove it.
  2. Formation of fibrocartilage: Fibroblast (the cells that produce collage fibres) come in to and invades the fracture site. The extra cells will build up to make fibrocartilage cartilage around the fracture to form a mass to help patch up the fractured bone. In time the fibrocartilage produced will also eventually turn into new bone.
  3. Formation of new spongy bone: Next the osteoblasts (cells that make new bone) will come into the damaged area especially the area with the best blood supply to produce more spongy new bone. The new spongy bone will join onto the old bone fragments to make it stronger.
  4. Bone remodelling: The final part of the repair is the remodelling. This is when the dead and older worn portions of the bone are gradually absorbed and replaced with new thicker bone.
Bone repair
Bone repair

The effects of exercise on bone health:

Exercise and movement is actually vital to bone repair, which is why after an operation they will try to get you moving as quick as possible. The mechanical stress on a bone from moving will actually make your bones stronger this is because the muscles pull slightly on the bone as they contract. This process will stimulate and increase the production minerals in the area and stimulate the production on new connective tissues. Often bones of an athlete will be stronger and thicker than the average person. This is why when astronaut come back from space they are so frail and weak, each week they are not weight-bearing in space they can lose up 1% of bone mass!

How do muscles repair?

Muscle cells believe it or not can’t actually undergo cell division and so growth after birth mainly comes from increasing the size of existing muscle cells rather than producing new ones.

Often when you exercise you damage the existing the muscles by causing micro tears within the fibres, which then are replaced by new muscle through a degeneration-regeneration cycle. The cycle will start with an inflammatory process and during this stage cells and enzymes will work to get rid of the debris and metabolites that will limit your ability to recovery. During this stage of the cycle satellite cells, which have the ability to slowly, divide and fuse with the existing muscles and are activated by muscle trauma/damage.

Why when our muscles heal do we sometimes get scar tissue?

When the tissue repair process begins if fibroblasts (which makes collagen the fibres that make up connect tissue) are active in the repair it will produce a structure that is more connective tissue than muscle. This is why you get scar tissue sometimes after an injury. The scar tissue often forms adhesion at the site of inflammation they are not harmful but they do cause decrease flexibility which in muscles is obviously beneficial. Due to the fact that collagen is not specialised for a purpose it means you lose some of the function of the area.

scar tissue repair

What is the affect of exercise on Muscles?

You have three different types of muscles fast twitch (fast gycolytic), slow (slow oxidative) and Fast oxidative- glycolytic fibres which is a hybrid of other two types of fibres.

How does aerobic exercise affect your muscles?

When you do aerobic exercise you are actually slightly changing the distribution of fast and slow twitch muscles in your body by changing the fast twitch fibres into the hybrid FOG fibres. These new fibres actually increase the size, blood supply and strength of the muscle fibres compared the ordinary fast twitch. This is one aspect to why endurance exercise results in better cardiovascular health as the muscles themselves are actually changed and trained on a cellular level to be more efficient in bringing in a better supply of oxygen and nutrients without increasing in size of the muscle.

How does strength workouts affect your muscles?

If you do a strength session so more sprinting or weights, you will be increasing the size and the strength of the fast twitch muscle fibres. The muscles will increase in size by increasing the size of the individual filament that makes up the fibres. Therefore increasing size of the overall muscle mass.

Cardiovascular and respiratory fitness and recovery:

Generally when we talk about cardiovascular fitness we are talking about aerobic activity so any activity that works a large amount of body muscles for 20 minutes and increases your cardiac output so you become out of breath. The NHS recommendation to do around 150 minutes every week this can be anything from a walking the dog to skiing or surfing as long as it gets your heart beating faster and increasing your breathing rate.

When you exercise you need more oxygen going to your muscles so that they can keep working hard which in turn will work your cardiovascular and respiratory system. The respiratory system is stressed through increasing the amount of blood going to the lungs and therefore the rate and amount of oxygen that is transferred into the blood.

The demand and how much you work your cardiovascular system will depend on many factors. When you do regular cardio exercise you increase your cardiac output (the amount of blood that gets ejected from the heart) and also increase the rate of oxygen that gets delivered to the muscles. The amount of blood vessels around the muscles also increases with more exercise. Athletes will often have double the cardiac output of a sedentary person and can even increase the size of their heart to a small degree. When your muscle contract and relax throughout exercise they use up a lot of oxygen and produce a lot of Co2 which can build up in the surrounding area. As a result your body has to work harder to get rid of the build up. The build up of CO2 will cause the body to release lactic acid which is what you feel when your muscles ache or when you get a stitch. Your cardiovascular system will need to work harder to get more blood in to take away the harmful metabolites and CO2 that have built up.

The respiratory system is stressed through increasing the amount of blood going to the lungs and therefore increasing the rate and amount of oxygen that is transferred into the blood to be used. This is measured through your VO2 max, is the measure of your maximum volume of oxygen that a person can use. Many researchers believe that the VO2 max is the ultimate measure of cardiovascular fitness with many using it as a indication of how well their training is going.

CVS repair


So that how each part of the musculoskeletal system repairs as well as the how the cardiovascular system is stressed when you exercise. Keep and eye out for part 2 when I explain the importance of rest in order for these changes explained here to occur. Furthermore I will explain the effect of taking time off with have on your performance.

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