Understanding Training Adaptations

This post is going to be pretty technical - it was the assignment I did for my Science of Exercise course on Coursera. Since I received my completion certificate last week, I thought, why not share my paper with you guys. It's now less science-y and more comprehensible with some editing. So without further ado, let's get to it!


The Fick Equation calculates the maximum volume of oxygen (VO2) an individual uses during a single bout of exercise. It derives on the formula VO2 = Q x (A-V)O2.


To understand training adaptations is to first understand the Overload Principle. The Overload Principle is the inducing of stress upon the body - greater than before - in order to increase fitness and performance. It is the notion behind training adaptations in the body.

When a sedentary individual begins a training program, their body begins adapting (through overload) in the cardiovascular system, directly affecting cardiac output (Q) and the arteriovenous difference ((A-V)O2). Putting an individual through frequent exercise will increase the utilization and requirement of oxygen for working muscles.


Finding the cardiac output (Q) requires the multiplication of stroke volume with heart rate. The higher the stroke volume, the greater the cardiac output.

The main training adaptation on cardiac output, via endurance training, is the heart rate - trained individuals have a lower resting heart rate through adaptation. A lower resting heart rate increases the stroke volume at rest and during exercise. Since one’s maximal heart rate doesn’t change, the body relies on the stroke volume to pump more oxygen through the arteries. In terms of cardiac output, such is the adaptation.

When looking into the arteriovenous difference ((A-V)O2), it is proven to incorporate more adaptations in comparison. The arteriovenous difference is the difference between oxygen utilization from the arteries versus oxygen returning to the heart. A greater utilization of oxygen will result in a greater difference.

Through training, one's body adapts to create more red blood cells to assist in oxygen transportation. There’s also an increase in blood capillaries per muscle fiber, which enhances the diffusion of oxygen. But most importantly, endurance training increases the size and count of mitochondria. Mitochondria requires oxygen to produce fuel (ATP) for the working muscle. Hence, an increase of mitochondria will result in an increase of oxygen utilization - provided from the increase of red blood cells and blood capillaries.


Overloading a system will result in adaptations. But in order to optimize adaptations, one must look into the frequency, intensity, duration, and type of training. Taking these factors into account, one can create a training program that induces adaptations - maximizing muscle plasticity.

Muscle plasticity is the alteration of gene expression caused by endurance training. Muscle plasticity includes all muscle proteins - it is behind the formation of new mitochondrial proteins. The increase of mitochondrial, as mentioned above, will directly affect the arteriovenous difference - subsequently increasing one’s VO2 max.


By understanding the factors involved and the adaptations that occur, one can grasp the positive effects of exercise on the body. Higher VO2 individuals are able to perform better and longer in their given sport. And if one desires to increase VO2, one must elicit training adaptations by training in progression (incorporating the Overload Principle). Simply put, inducing training adaptations is the key to growth.

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