Mitochondria are the power generators of cells. They generate energy through aerobic processes. The do this by breaking down glucose metabolites, fatty acids, and certain amino acids aerobically or in the presence of oxygen, to release energy. Aerobic energy release is a critical driver of athletic performance especially in endurance sports. Mitochondrial energy production supports activities such as marathons and triathlons. When it comes to short duration bursts of activity as seen with sprints that need fast twitch muscle fibers, additional anaerobic processes are employed by the body.
Mitochondria are infinitesimally small and roughly the size of bacteria. They are seen in the cytoplasm of cells. They have a double layered wall and the inner layer has multiple folds that are called cristae. These folds increase the surface area of the inner layer which is where energy production takes place. Energy is produced in the form of ATP. ATP is adenosine triphosphate and this is a molecule that functions like a rechargeable battery. Energy released from any metabolic process gets stored in this molecule and when the body requires energy, ATP is broken down to release energy.
There is a hypothesis that these organelle (mitochondria) were originally bacteria themselves that found a place to live inside eukaryotic cells. This idea is strengthened by the fact that there is genetic material (DNA) inside the mitochondria that is independent of the DNA in the chromosomes of the cell nucleus. Mitochondria and the DNA within it are inherited from the mother which means endurance capacity is inherited maternally!
Mitochondrial enzyme production is triggered by endurance exercise. Mitochondrial density goes up with training. Optimal density of mitochondria in skeletal muscles is required for athletes to perform at their peak potential. Mitochondrial density increases in response to two stimuli in general 1) When calcium ion levels inside skeletal muscle cells go up – this happens during each muscle contraction and 2) When there is deficiency of ATP molecules in the muscle cells – which happens when more ATP are being used up than are being synthesized as happens during intense exercise.
Research on endurance exercise and its impact on mitochondrial enzymes has shown that enzyme concentrations do not increase significantly with sustained exercise beyond 60 minutes. High intensity exercises that are close to or over the athletes VO2 Max performed in interval training mode for a cumulative period not exceeding 30 minutes a day can increase mitochondrial enzyme concentration to similar levels as lower intensity exercises performed over longer durations.
In order to develop mitochondrial density, it thus benefits to engage in endurance exercise at or above the athlete’s VO2 Max for short periods/ intervals during each training session. These short periods at or above VO2 Max should be prolonged as long as possible for any given intensity.