Wjat happens to your body when you start exercising?
Credit: Remy Whiting
Training > Injuries

What happens to your body when you start exercising after a break?

Physio Shelly Chakraborty explains what happens to your body when you start exercising or begin again after period of rest

When we stop exercising deconditioning can set in as early as 2 weeks, however this depends on our pre-existing health status, training and fitness level and lifestyle. This means that when we start training again, we need to think of ourselves as starting from scratch.  

What happens to your body if you stop training?


How does a return to exercise affect the musculoskeletal system?

During exercise, muscle fibres pull against one another, which is why your muscles often ache after exercise. Every time a fibre tears it repairs itself and grows back thicker and stronger, making more dense fibres. However, rest causes these fibres to weaken, which means that when we start exercising again post injury/rest it can lead to more micro tears in the muscle fibre, so it's crucial to start exercising slowly and gradually build it up.

Studies have shown that in the first week of 're-exercising', it's beneficial to have two days rest or to at least train on alternate days.

At this stage, your muscle pliability/flexibility will be low, which also increases your risk of injury. When you don't exercise, the synovial fluid (a fluid produced by the synovial membrane that surrounds the joint) reduces, which decreases the joint's range of motion and increases the risk of injury. A warm-up routine of gentle aerobic training and low-grade stretches will help to minimise this risk.

After 3-4 weeks, the muscles and connective tissue (ligaments and tendons) will start to get more elastic, so this is when you can start to think about increasing your training intensity.

What's the difference between muscles, tendons and ligaments?

5 ways endurance sport and triathlon affects your musculoskeletal system

How to start running


How does a return to exercise affect your cardiovascular system?

After 2-3 weeks of exercising, the blood supply to your musculoskeletal system increases as your muscles require more oxygen. Cardiovascular exercise increases the number of new blood vessels, while resistance (strength) training increases the size of these blood vessels (vasodilation). This is when the blood vessels expand to allow the blood to flow to your muscles more quickly. 

So if you lose 15-20% of your cardio fitness you might find yourself struggling to breathe and suffer more fatigue, as the body won't be as efficient as it was at transporting oxygen around the body.

An increase in blood vessels means more efficient circulation, which lowers blood pressure (reducing strain on the heart); increases good HDL cholesterol that transports fat away from the arteries and back to the liver for processing; and reduces bad LDL cholesterol levels that can form fatty deposits in the arteries and contribute to heart disease. Blood vessels also bring much-needed nutrients to the muscles, which is why diet is important.

After 4-6 weeks of training, there will be an approximate 15-20% improvement in VO2 Max, i.e. the body’s ability to use oxygen. However cardio exercise, rather than strength training, is the best way to improve circulatory efficiency, as increasing the number of blood vessels is more beneficial than vasodilation.

How does exercise affect my heart?  

How does a return to exercise improve your wellbeing? 

Exercise produces endorphins throughout the body, which reduces anxiety, depression and improves self esteem. Exercise also leads to better quality and duration of sleep (deep sleep time), the importance of which cannot be stressed enough. 

Deep sleep restores the body’s core functions, and improves your immunity and heart health. As we age, the part of our brain known as the hippocampus shrinks, impeding memory and general information retention. Exercising increases cell production in the hippocampus, which in turn makes us more alert and attentive.

Things to consider when you start exercising

* Start exercising again slowly, rather than going in at full training level. Around 30-40% of of your previous training intensity is a good starting point.

*Make sure you include a proper warm-up and cool-down.

* Avoid a complicated/intense workout programme during the first four weeks. For aerobic training, start with low-intensity endurance-based exercise, while for strength training increase the reps, rather than weight, during the first 2-3 weeks.

* Take your time and aim to regain your previous strength and cardio training level in approx. two months.

* Use this time to improve your technique.

* In case of inactivity due to injury, consult a physiotherapist/medical professional for a graded return.

Shelly Chakraborty is a chartered physiotherapist with Capital Physio


How does endurance sports affect your lungs and respiratory system?


Daily deals from top retailers

We'd love you to add a comment! Please login or take half a minute to register as a free member


Hi everyone - how'd your races go on Sat/Sun? Weather on sat was a nightmare!

I raced Sunday, my first OD (and only my second tri) and i finished 2hrs and 50mins exactly. Am delighted!


Hi Mate

Yea, my first tri - done the Olympic yesterday.

Swim was a mental struggle but ok

Bike fun / fast although slow round corners - sometimes a bit tight going by etc.

run fun - seemed a bit short though??


very pleased for a first timer


Did okay for a newbie.
Corporate Sprint - 88 out of 219 with a time of 1:27 (winner did it in 1:08)

Stuff happened though...
- got mugged in the swim! It was an open water stampede!
- chain came off on the bike
- got a stitch 1km into the run
- slipped and fell with 500m to go.
...so all that added up and cost me time.

Never mind. Stoked! Even got a Jim'll Fix It style medal!
Next one in 2 weeks.


Nice one guys, both great efforts.

Wiseman, i hear you on the swim... conditions were quite tough i thought - the return leg it was seriously choppy - kept expecting to sight and someone in front of me but all the splashing was mostly from the waves!

How typical that today is a lot less windy!


overall time 2.21.08 for Sunday afternoon OD

swim not bad, bike windy buy dry, run not bad

bike was only 38k which was a shame and the run is 9.8k, so have to add 5mins on to my time really.

that said, the run into T1 for Sunday afternoon people took an age :)

See more comments...
Back to the top