Exercise from a Different Perspective: Understanding Bioenergetics

February 19, 2022

Understanding Bioenergetics

Exercise is essential for complete well-being, but it’s also one of the most underrated practices in the fields of health and fitness.

Aside from what we know about physical activity, there are still a lot of concepts that make exercise such an interesting topic, especially if you’re in healthcare. One of these is bioenergetics.

The life of all organisms is sustained by an infinite energy source, sunlight. Considered the most basic energetics of life, this process is usually described as the transformation of food into energy that culminates in the mitochondrial oxidative phosphorylation system (OXPHOS).

However, digging deeper into this concept will make you question how exactly a cell is energized to life. This is where bioenergetics come in and here’s everything you need to know about it in relation to exercise.

Setting the charge

If you know about the concept of “Frankenstein” being brought back to life, then you have some idea about what “galvanism” is. Formulated by Luigi Galvani, this theory eventually led to the study of electrophysiology.

It all begins with the primary driving force of bioenergetics, electronegativity, which is considered the function of an atom’s nuclear charge relative to the location and number of electrons in the atomic shells.

  • Reduction potential. This refers to a chemical specie’s potential to be negatively charged or reduced resulting to oxidization. Reduction potential is measured through half-cell reaction where a test is conducted using a reference and test solution.
  • Reduction potential and membrane potential. Taking advantage of the potential energy difference between a strong and weak electron magnet, the mitochondrial electron transport system (ETS) has played a significant role in bioenergetics. Through a series of processes, the reduction potential generates the membrane potential, which in turn accounts for a good chunk of the proton motive force (PMF).
  • Membrane potential and energy charge. The mitochondrial ETS works like a charged battery that’s constantly charged and ready to respond quickly to any changes in proton conductance. Working on demand, the ETS relies a lot on ATP usage.

Utilizing the charge

The complex process that involves the generation of energy that powers the cells has been widely studied for years. But how is this charge utilized in the body? Here are some important points to learn about:

  • The OXPHOS system is responsible for energizing the cells by providing the ΔGATP that’s required in establishing and maintaining displacement during a wide range of reactions happening within the cell in bioenergetics. A constant input of Gibbs energy is necessary for making sure that homeostasis is maintained where the rate of loss of product produces an equal rate of replacement through the use of ATP.
  • Basal mitochondrial respiratory activity and overall metabolic rate are necessary to maintain homeostasis.
  • If a stimulus causes a change in the disequilibrium that’s established and maintained by the ATP, the body will cause an increase in the rate of ATP usage to re-establish that disequilibrium. This is proof that the respiratory system will always adjust to the demand for energy by the body

How ATP is utilized during exercise

Now that we already discussed the basic concepts behind bioenergetics, let’s look at how ATP is used during exercise:

  • When the human body transitions from rest to exercise, there’s a huge shift in energy that happens within the skeletal muscle cells, which in turn causes a huge increase in myosin ATPase and SR Ca2+ATPase activities during muscle contraction. Studies estimate ATP usage to increase by up to 100-fold over its baseline in well-trained individuals doing heavy cycling exercise.
  • According to studies, ATP concentration in the muscle never decreases during exercise except when the body is already near exhaustion or if it’s put under heavy workload. This means that the ATP synthesis pathways are capable of keeping up with muscle demand during a workout providing the energy it needs to keep going.
  • Maintaining ATP concentration is essential to help the muscle function during exercise, which is why it’s also very important to look at the free energy thresholds that are required to keep the cells functioning properly. In hindsight, fatigue is needed to keep muscle energy up and keeping the muscle cells from suffering from energetic suicide.
  • ATP production is maintained in the muscle during exercise through a process where an increase in the ATPase rate triggers an increase in mitochondrial OXPHOS activity. It takes 30 seconds or longer, however, for the body to achieve a steady-state rate of oxygen consumption in the muscle, explaining the complex process involved within the ATP production pathway.

Important factors affecting mitochondrial bioenergetic efficiency

The human body has been designed to withstand different challenges. Throughout evolution, the body has used the efficiency of its OXPHOS system to keep its fuel reserves from being depleted while looking for more energy source.

However, ETS is not fully efficient by nature. Proton leak caused by JO2 is also known as uncoupled respiration that represents the rate of proton conductance that’s not directly coupled to ATP synthesis or state 3 respiration.

Any increase in lower respiratory coupling ratio or also known as state 4 respiration means that OXPHOS efficiency is also reduced immensely.


It’s true that it takes a lot of time and research to fully grasp the concepts of bioenergetics and thermodynamics.

A lot of processes happen between rest and exercise, and this review has been aimed at understanding where energy begins and how it is distributed to the cells to energize the body during exercise.

While there is a growing interest in the study of bioenergetics in helping athletes and fitness enthusiasts perform better, more research is also being done to fully understand the science behind mitochondrial and cellular bioenergetics, and how it forms the foundation of how cells react to the energy demands of exercise.