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The Science of CrossFit: How High-Intensity Training Affects Your Body

CrossFit is a high-intensity training program that has gained immense popularity in recent years due to its ability to produce quick and effective results.

The program combines weightlifting, gymnastics, and cardio exercises to challenge participants both physically and mentally.

While CrossFit workouts may be intense, the science behind this training program shows that high-intensity training can have numerous benefits for the body.

In this blog, we will dive into the science behind CrossFit and explore how high-intensity training affects the body.

Understanding High-Intensity Training

High-intensity training involves brief and intense bursts of physical activity that elevate heart rate and breathing rate. This type of training typically lasts between 20-30 minutes and targets multiple muscle groups. CrossFit is an example of high-intensity training, as it consists of intense and varied workouts that push participants to their limits.

When you engage in high-intensity training, your body goes into an anaerobic state. This means that your body's oxygen consumption can no longer meet the energy demands of the exercise.

To compensate, your body relies on energy stores in your muscles and liver, which results in the production of lactic acid. Lactic acid is a byproduct of anaerobic metabolism and is responsible for the burning sensation you feel in your muscles during high-intensity workouts.


Benefits of High-Intensity Training e.g. CrossFit

1. Increased Cardiovascular Health

High-intensity training can improve cardiovascular health by increasing heart rate, blood flow, and oxygen consumption. When you engage in high-intensity workouts, your heart rate increases, and your body demands more oxygen. This increased demand causes the heart to work harder, which improves cardiovascular health over time.


2. Improved Body Composition

High-intensity training can help you burn fat and build muscle. When you engage in high-intensity workouts, your body burns calories and fat to meet the energy demands of the exercise. Additionally, high-intensity training can stimulate muscle growth and promote the development of lean muscle mass.


3. Increased Endurance

High-intensity training can increase endurance by improving your body's ability to tolerate and recover from physical stress. When you engage in high-intensity workouts, your body adapts by increasing the efficiency of oxygen delivery and utilization. This adaptation results in improved endurance and a reduced risk of fatigue during exercise.

For example, CrossFit athletes were required to complete a marathon row for one of their workouts in the 2018 CrossFit Games. Whilst these athletes are extremely strong, it's evident that they have phenomenal endurance, too:


4. Reduced Risk of Chronic Disease

High-intensity training can reduce the risk of chronic diseases such as type 2 diabetes, obesity, and heart disease. This is because high-intensity training can improve insulin sensitivity, reduce inflammation, and lower blood pressure. Additionally, high-intensity training can improve overall health by reducing stress and improving mental health.

Check out Jason Grubb below. He went from being severely overweight to a CrossFit champion!


5. You Feel Phenomenal and Make Some Awesome Friends

Let's forget about the science for a second and think about the elements that you can't measure. After every CrossFit or high-intensity workout, there is a sense of euphoria that you feel which is extremely hard to replicate.

In addition to the above, you will form some of your strongest friendships when doing high-intensity fitness. Without trying to sound disrespectful to those who actually protect our country, completing high-intensity fitness with others kind of feels like you're in the trenches with them. You're working your ass off and don't want to let your partner down!


Risks of High-Intensity Training

While high-intensity training can have numerous benefits, it's important to understand that there are risks associated with this type of exercise. Here are some potential risks to keep in mind when engaging in high-intensity training:

1. Risk of Injury

High-intensity training puts a lot of stress on your body, which can increase the risk of injury. This is especially true if you don't use proper form and technique during exercises. It's important to work with a qualified trainer who can help you develop proper form and technique to reduce the risk of injury.

It's not uncommon for individuals to get injured early when starting CrossFit. Whilst CrossFit gets a bad reputation for "poor form", most injuries occur because of the poor technique of the individual completing the movement.

As such, it is critical that you receive relevant coaching and ensure that your form is perfect before trying to progress with higher weights, or reps.


2. Risk of Overtraining

High-intensity training can be taxing on the body, which can lead to overtraining if you don't allow your body to recover properly. Overtraining can lead to fatigue, decreased performance, and an increased risk of injury. It's important to balance high-intensity training with rest and recovery to avoid overtraining.

We strongly recommend taking 2-3 days off a week from your training, particularly when beginning. This will ensure that you do not fatigue your central nervous system.

Fatiguing your central nervous system (CNS) can have a significant impact on your overall physical performance and health. The CNS is responsible for controlling and coordinating all movements in the body, and when it becomes fatigued, it can impair your ability to move efficiently and effectively. Here are some of the impacts of fatiguing your CNS:

  • Reduced Strength and Power Output

  • Decreased Coordination and Balance

  • Increased Muscle Soreness and Delayed Recovery

  • Decreased Mental Focus and Cognitive Function


3. Risk of Dehydration

High-intensity training can cause you to sweat heavily, which can increase the risk of dehydration. It's important to drink plenty of water before, during, and after workouts to stay hydrated.

Dehydration can lead to a loss of strength and stamina. It's a main cause of heat exhaustion. You should be able to reverse dehydration at this stage by drinking more fluids. If dehydration is ongoing (chronic), it can affect your kidney function and increase the risk of kidney stones.

Check out the impact that dehydration & heat stroke can have below:


4. Risk of Rhabdomyolysis

Rhabdomyolysis is a rare but potentially life-threatening condition that can occur when muscle fibers break down and release their contents into the bloodstream. This can be caused by excessive and intense exercise, including high-intensity training. Symptoms of rhabdomyolysis include muscle pain, weakness, and dark urine. If you experience these symptoms, seek medical attention immediately.


5. Risk of Joint Pain

High-intensity training can be hard on the joints, especially if you don't use proper form and technique during exercises. Over time, this can lead to joint pain and inflammation. To reduce the risk of joint pain, it's important to work with a qualified trainer who can help you develop proper form and technique, as well as modify exercises as needed to reduce stress on the joints.



Whilst this article has aimed to provide a balanced view of the benefits and risks associated with high-intensity fitness, we strongly believe that the benefits far outweigh the risks.

High-intensity training is extremely beneficial to the longevity of your body as long as you are adopting the correct form, and resting when your body tells you to!

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