What Does Running Do To Your Body?

The Zombie Apocalypse Survival Guide advocates, “Run. Because zombies will eat the untrained ones first!”. People run for various reasons, and if zombies don’t motivate you to run, then perhaps the changes in your body might.  If you are a non-runner or have just started running and are uncertain if you like it, there are several changes to your body that could encourage you to don your running gear every day and get out there in the fresh air.  

Running tones your muscles and burns fat. It works predominantly on the lower half of your body. It improves mood and helps protect against diseases. Different types of running affect your body differently. Running must be approached sensibly, or it can cause injuries.

This article looks at the effects of running on your body, including your internal organs. It considers the impact on the brain and what this does for mood. It will also consider some problems that can be caused by running. 

What Running Does For Your Heart.

Running is aerobic exercise meaning that it is an exercise that uses or takes in oxygen. Aerobic exercise is also sometimes referred to as ‘cardio’ because of the beneficial effects on the heart. Any burst of activity requires the heart to pump blood at a faster rate than usual. The heart is a muscle, and similar to any muscle, it strengthens when used and conditioned. 

During running, your heart muscle works harder by contracting and relaxing more often. The pumping action can even increase the size of the heart muscles – especially on the left side of the heart from which the blood is pumped to the body. 

Running affects respiration, causing you to take in larger breaths of air as the muscles of the body demand additional oxygen to function. The increased oxygen is good for the heart muscle. A strong heart means that it can pump oxygenated blood more efficiently around your body. This results in less force on your arteries which lowers your blood pressure. High blood pressure conributes to coronary disease and stroke risk.   

Running And Your Brain

Running has been shown to elevate moods and is an effective tool in treating depression. Running causes the release of endorphins from the pituitary gland and hypothalamus in the brain. Endorphins reduce pain and stress in the body and function in a similar way to opioids. Runners often experience a feeling of euphoria or elation, which is known as a “runner’s high.”

The amount of endorphins released varies between people. Endorphins are not the only neurotransmitters that are released through exercise. Three other neurotransmitters that essential in maintaining mood and contentment are also released. These are serotonin, norepinephrine, and dopamine

Running Stimulates New Blood Vessel Development. 

Scientific studies have shown that cardiovascular exercise such as running stimulates the development of new blood vessels in the brain. It also promotes neurogenesis (growth of new brain cells) in some regions of the brain. The implications of this are critical for the prevention of Alzheimer’s Disease, dementia, and the cognitive decline associated with aging. The basic message is running helps to keep your brain functioning.  

Running Stimulates The Release Of Endocannabinoids.

Recent research has indicated that only certain people experience a runner’s high. Scientists have found that running releases endocannabinoids

into the blood.  Endocannabinoids pass through the blood-brain barrier, elevating mood and reducing anxiety. Endocannabinoids are the same substances found in cannabis but are naturally produced in the body. (The blood-brain barrier usually prevents chemicals from entering the brain. It is the body’s method of protecting the brain.)

Endocannabinoid research is still ongoing, but there is enough evidence to indicate that endocannabinoids play a crucial role in most areas of our bodies. They improve immune system functioning, affect the reproductive system, reduce inflammation, encourage the development of neural pathways, and assist in tissue repair.  

Running Lowers Your Blood Sugar

Running uses up glucose which automatically lowers your blood sugar. Not only does it use up sugar, but the activity in the muscles makes the body more sensitive to insulin. The result is that insulin becomes more effective at soaking up glucose. This causes an overall lowering in blood sugar which is good news for anyone struggling with diabetes. The effects of a run on blood sugar will persist for up to twelve hours after a run.

People with diabetes must be cautious and ensure that their blood sugar does not drop too low. Hypoglycemia (low blood sugar) can occur when people are taking medication to treat high blood sugar, and they run. It is a good idea to take your blood sugar readings after running to ensure that it has not dropped too low. If you begin to feel nauseous, dizzy, cold or have blurred vision while running, it is best to stop and check your blood sugar before continuing.  

Does Running Build Muscles?

The question of whether running builds muscles does not have a straightforward answer as much depends on the intensity and length of the run. Running uses core muscles and muscles in the lower half of your body. If you want to build your chest or shoulder muscles, running is not the answer.  

Long-distance running does not usually build muscles and, in fact, can cause muscle breakdown. You only have to think of successful long-distance runners to know that this is true. Long-distance runners are usually lean, lightly built people with no apparent muscle development in their legs. 

Sprinting or high-intensity workouts (Example of high intensity running: run as fast as you can for four minutes and rest for three) will build muscle in the legs. Sprinters develop particularly big calves as this is the source of power in the sprint. 

Does Running Strengthen Your Core Muscles? 

Core Muscles (Picture: physiofitness.org)

Running requires strong core (abdominal) muscles. Core muscles are essential to running as they stabilize you, give you good balance, and enable you to use your limbs effectively during the run. Running with the correct form is dependent on core muscles. Poor form from weak core muscles will cause you to tire quickly and make you more prone to injuries.

Running does not necessarily strengthen core muscles. There is some benefit to core muscles, but it is minimal. The benefit to core muscles can be increased by including high-intensity running or sprinting. This results in a runner naturally engaging their core muscles. 

To strengthen core muscles, you would need to complete exercises that specifically target them.  It is highly beneficial to runners to include strength training for core muscles. If you hate planking and other mat-work core exercises, consider using a jumping rope. Jumping rope is an excellent way to gain an entire body workout and engages your core muscles. It is also a high-intensity exercise that increases the lower body strength vital to runners.  

Does Running Help Lose Belly Fat? 

Running requires energy for the muscles in your body to work. The energy is obtained from breaking down glucose available in your body and from stored fats. When you run, your metabolism increases to provide more energy for your muscles. A body’s metabolic rate remains increased for an hour or more after the run has been completed.

If you increase the intensity of the run, your body will burn more calories and fat. Running is an effective way to burn belly fat. To burn belly fat, you need to run at a moderate to high intensity for thirty to sixty minutes five times a week.

This exercise program must be accompanied by dietary alterations to reduce calorie intake. It has been shown that trail running provides a more overall body workout and therefore tones the entire body, burning more fat in the process. High-intensity interval training is also an excellent way to burn more calories.

How Many Calories Are Burnt When You Run?

Researchers believe that a person of average weight burns approximately one hundred calories for every mile that is run. This can be increased by

  1. interval training – alternating the intensity of the running
  2. carrying weights while you run
  3. trail running, which works your whole body as the terrain changes and your body shifts and changes position to balance.

This can be very individual, and it is best to work out the best way for you to run by trying different approaches.

What Muscles Get Toned From Running?

The muscles in your lower half are the ones primarily toned by running. This includes your gluteal muscles located in your buttocks. These large muscles are used to push down onto the road and propel your leg forward.  They are essential muscles in the stabilization and use of your hips. Running will hone your gluteal muscles but will not contribute to bigger gluteal muscles. Running uphill is especially good for toning gluteal muscles. Sprinters turn to weight training to enhance their gluteal muscles to add power for sprint races. 

The quadriceps and hamstrings – the muscles at the front and back of your thighs- are toned and firmed by running. They work together with the calf and shin muscles to move the legs. Sprinters usually have bigger calf muscle development than long-distance runners. 

What Does Running Do For Your Body Shape?

Some of us may be apple-shaped and some pear-shaped. Some people may carry extra weight on their chests. Whatever shape you are in, running burns fat and tones your muscles. If you are carrying excess weight, that fat will ultimately be used as your run and will disappear from your body. If you commit to running four or five times per week for thirty to sixty minutes, you will achieve the sleek body outline you desire. 

Does Running Dehydrate You?

Running involves increased metabolism and cell function. This generates heat, and there is a need to cool the body down to prevent overheating. The human body cools down by sweating; the perspiration evaporates off the skin, leaving it cooler. Perspiration is essentially water and electrolytes. Any loss of water and electrolytes can result in dehydration. The dehydration risk becomes more severe the longer you run. 

Dehydration will contribute to the risk of heatstroke as your body becomes unable to cool itself due to a lack of available moisture. Heatstroke is one of the commonest causes of collapse in runners. Other symptoms of heat stroke include: 

  1. Thirst
  2. Headache
  3. Fatigue
  4. Cramps
  5. Gastrointestinal issues
  6. Feeling dry all over – especially in your eyes ( they will burn) and your mouth.
  7. Confusion
  8. Irregular heart rate

Can You Over-Hydrate When Running?

Some runners are so concerned about dehydrating that they take in too much fluid. This is as dangerous as being dehydrated — too much liquid or being overhydrated results in a condition known as hyponatremia. Hyponatremia is when the water content is too high, and the sodium concentration in the blood lowers to dangerous levels. It is sometimes known as water poisoning. Adequate sodium is vital for cell functioning. Without the correct concentration of sodium, people have seizures, lose consciousness, and can die. 

The first symptoms of overhydration are similar to dehydration and include fatigue, muscle cramping, and confusion. Other early symptoms include swollen extremities, nausea, vomiting, disorientation, and a severe headache. The people most at risk of hyponatremia are women running marathons. Women are more at risk as they don’t sweat as much as men due to their smaller body mass. 

How Much Water Should You Drink When Your Run?

Ideally, the aim is to replace the water with the water that is lost. The balance is essential. A general rule is that runners should drink 16,9 oz (500 ml) to 33,8 oz (1000 ml) per hour. Of even more importance is to ensure that the fluid contains sodium and other electrolytes.   

Bladder Problems From Running

Running causes concussive forces throughout the body, and the bladder is no exception. Doctors have shown that the bladder can have micro tears or bruising from the bladder walls slapping against each other due to running. This will cause blood in the urine – known as hematuria. The blood is usually minimal and cannot be seen with the naked eye.

Maintaining adequate hydration levels is thought to reduce this effect. A bladder with some urine will prevent the bladder walls from coming into contact with each other. 

Often people feel the need to urinate during running. This may also be from irritation to the bladder from concussion during running. Increased urine is a natural consequence of the increased metabolism in the body and faster movement of blood around the body. The kidneys clean the blood and the resulting toxins must be flushed out of the system, which triggers the need to urinate.   

Why Does Running Cause A Runny Nose?

During running, there is an increase in inhalation and exhalation. The nasal mucous membranes are exposed to the air movement and become overactive, increasing mucous secretion. This is known as exercise-induced rhinitis. It is worsened when the air is cold or dry, so you may experience this phenomenon more in winter. Asthmatics are also more inclined to have asthma attacks because of a similar phenomenon in the lungs during running. Some runners have so much phlegm production that they need to expel it while running, resulting in the hacking and spitting seen in some runners. 

Effects Of Running On The Gastrointestinal System.

Many runners have the unpleasant and decidedly inconvenient need to go to the bathroom during a run. Running jostles the intestines and their contents which creates the need to go to the toilet. The blood which usually goes to the gastrointestinal tract is sent to the vital organs and leg muscles. This also creates the need to search out the nearest bathroom with a certain amount of panic. As if that is not enough, there are also the effects of serotonin. 

Serotonin is a neurotransmitter that’s secretion is increased during running. Most people only know serotonin as the feel-good or happy neurotransmitter that affects mood, but serotonin also influences the digestive system.  Overall if you have constipation – go for a run. If you struggle with gastrointestinal issues during running, try to go to the bathroom before running or try to run on a relatively empty stomach. Alternatively, take it as nature’s way of motivating you to sprint the final leg of your route. 

Running Causes Chafing.

Runners perspire a great deal. Perspiration is a mixture of water and various salts. When perspiration evaporates from your body, the granular salts remain on your skin. The salts are abrasive and gritty on your skin. While they might not bother you during your regular life, the action of running is repetitive. It allows body parts to rub together or clothing to rub over sensitive areas. The inclusion of salts in these areas of friction acts like sandpaper on the skin. The skin becomes irritated, raw and may even blister or bleed in severe cases or when running marathons.  

The parts of the body most likely to experience chafing are the thighs, groin, nipples, and stomach. Men often experience worse chafing than women because they tend to sweat more, but women are not immune to it. To avoid chafing, try to apply lubricants or a thick oil-based lotion to the areas inclined to rub. You can also use moisture-wicking garments or underwear to minimize the evaporation of sweat from those areas. Staying hydrated is essential as the continued production of sweat helps to reduce the abrasive effect of the salts. 

Some people prefer to use Band-Aids or other products to cover sensitive areas like the nipples and protect them from clothing. For women, well-fitting and supportive bras are essential and can dramatically reduce nipple chafing.   

How Does Running Affect Bones

Running positively effects bone health. The concussion and constant pulling of the muscles on their attachment points on the bone result in the thickening of the bone, increasing the bone mineral density. Running, therefore, can play a vital role in preventing osteoporosis. Children consumed by technology or who live in confined areas rarely run will have a much lower bone density than those who play and run outside every day. 

Running can make your bones stronger, but a recent study has shown that this might not be the case for some women. In women runners that have low muscle mass, there may be a depletion in bone density. Women are less likely to eat correctly to build muscle mass, resulting in weaker bones. Although running can improve bone density, it only does this if there is enough muscle mass to pull firmly on the bones. 

An imbalance between energy expenditure and nutrient intake (or undereating) results in a slowed metabolism and nutritional deficiencies. Women can train so hard that there is a drop in the production of estrogen. Estrogen is crucial for maintaining bone health, and women who overtrain in this manner reproduce the effects of menopause through the reduction in estrogen production. The nutrient deficiency, slowed metabolism and reduced estrogen weaken bone health resulting in a high potential for bone injuries. The critical message for women, in particular, is to train in moderation and eat a healthy diet that allows your intake to match your output. 

Does Running Cause Stress Fractures?

Stress fractures are minute cracks that occur in the bones – usually in the shins. They are also seen in the foot, ankle, hip, and lower back and develop from overuse. Stress fractures are seen in people who accelerate their training too quickly by increasing the intensity or duration rapidly. They do not take enough time to allow their bodies to strengthen sufficiently to cope with the exercise. 

Another cause of stress fractures may be a nutrient deficiency such as insufficient vitamin D. Repetitive concussive forces caused by running may result in stress fractures. It is essential, therefore, to have running shoes that absorb as much impact as possible. Worn or inadequate shoes can result in painful stress fractures. Incorrect running style or form may also cause stress fractures. Stress fractures are commonly seen in children that overextend themselves during running, training too hard for the level of their bone development. 

The symptoms of stress fractures are usually tenderness in a specific area which is worse after exercise and disappears with rest.  The pain may be accompanied by swelling at the site. The longer the person uses the leg, the worse the fracture will become until the limb is painful most of the time, even during normal walking. Unfortunately, treatment usually includes a period of rest, which may be up to six months long. This is an excellent motivation to avoid stress fractures as much as possible. Foot orthotics designed for your foot by an experienced orthotist, correct shoes, and consultations with a biokineticist to address running form will also help prevent and heal stress fractures. A good diet is essential to obtain sufficient nutrients for bone health. 

Does Running Make Your ToeNails Black?

Your feet are crucial to running and need to be cared for to ensure good foot health. Poorly fitting shoes or toenails that are too long will result in nails that continually connect with the shoes. This causes severe bruising or bleeding under the nails. The blood turns black and results in unsightly, usually painful toenails. Some people have toe conformation where the toes curve upwards, which results in a need for carefully fitted shoes. Toe caps may also be of some benefit. Toenails will also bruise more quickly in people who run downhill often as the toes impact the front of the shoes.   

There is not much space for blood under the nails. The blood causes pressure on the nail and surrounding tissue, which can be excruciatingly painful. Doctors can drill holes in the toenails to relieve the pressure if consulted early enough. The holes allow the blood to escape and relieve the pressure on the nail bed. If the blood has coagulated and dried, this technique will not work. You must wait for the nails to grow out, taking the dried blood with them. 


Running can improve many aspects of your health. It builds muscle and bones and can counteract metabolic disease. There are different types of running, and if you are unsure, it is best to get advice from a sports expert or biokineticist. Running must be approached sensibly as increasing intensity and duration too quickly will result in injuries and could be dangerous to your health. Hydration during running is vital, but it must be approached knowledgeably as too much water can be as harmful as too little. However you run, and wherever you run, we hope you enjoy the pounding of your feet, the stretching of your muscles, and the wind on your face. 


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Linden, D.J. The Truth Behind ‘Runner’s High’ and Other Mental Benefits of Running. John Hopkins Medicine. https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-truth-behind-runners-high-and-other-mental-benefits-of-running

Mayo Clinic. Exercise: A drug-free approach to lowering high blood pressure. https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/high-blood-pressure/art-20045206

Mayo Clinic. Stress Fractures. https://www.mayoclinic.org/diseases-conditions/stress-fractures/symptoms-causes/syc-20354057

Tempofit. 2016. The 30 Most Motivational Running Quotes. https://www.tempofit.org/motivational-running-quotes/

About Me

Hey, I'm Mark and I've been running for around eight years. I'm by no means an elite runner. I'm in the mid-pack, doing what I can to improve and learn along the way.

I've learnt a few tricks along the which I share on this website and my Instagram: