MITOCHONDRIA-the 'powerhouse' that drives the cell

There is no doubt that exercise improves physical training and overall health.

This ongoing progressive process allows you to push yourself harder, for longer so that you can get fitter and stronger. This adaptation of muscle to additional stress so that physical gains can be achieved, is the result of biological adaptations, an essential one being, mitochondrial biogenesis.

Let's rewind a bit

MITOCHONDRIA are a vital part of the cell (organelle) which supplies energy for basic function. This chemical energy is called ATP (Adenosine Triphosphate), and therefore, mitochondria are often referred to as the 'powerhouse' of the cell. ATP is formed by the metabolism of carbohydrates, fats, and amino acids. In skeletal muscle, there are two types of mitochondria that form an inter-connected network underneath the sarcoplasm (subsarcolemmal mitochondria), and groups within the space between myofibrils (intermyofibrillar mitochondria)

MITOCHONDRIAL BIOGENESIS is simpler to understand when we look at the word 'biogenesis'. Biogenesis is described as the process of making new living things from existing living things. Simply put, we are able to manufacture more and bigger mitochondria in the right environment.

Mitochondria are highly sensitive to environmental stress and toxins, internal oxidative stress, emotional stress, and the ageing process.

The life cycle of mitochondria is a complex process of construction (mitochondrial biogenesis), functional capacity and repair (fusion, fission, reticulation), and destruction (mitophagy).

Mitochondria communicate and network with each other and respond to metabolic changes within the cells.

ENDURANCE TRAINING can increase mitochondrial volume and density by up to 40%!

Aerobic capacity of muscle is dependant on the abundance of healthy mitochondria within the cells, and the ability to utilise oxygen effectively.

Mitochondrial adaptations depend on the intensity of training and, specific training mechanisms to enhance performance. Increases in mitochondrial volume are linked to training, however, the improvements in adaptation are more specific to the chemical changes within mitochondrial networks. The large-scale adaptations are better measured in increased exercise efficiency and improved oxygen uptake (VO2max).

GENES PLAY AN IMPORTANT ROLE in this fine-tuned coordination between energy production and mitochondrial biogenesis. Individuals with a highly expressed response in PGC-1a (Peroxisome proliferator-activated receptor y cofactor 1 alpha) proteins may have an endurance advantage over those with a lower expression of PGC-1a. PGC-1a is expressed in tissues with high energy demands and is therefore abundant in mitochondria, and consequently associated with endurance performance. Some additional factors that influence mitochondrial biogenesis are enzymes produced by AMPK (AMP-activated protein kinase) and NRF-2 (Nuclear respiratory factor-2). Other genetic factors such as the advantage of having an enhanced VO2max come into play as well when looking at the potential for elite endurance performance. AMPK activity has been shown to decrease with age, which may contribute to decreased mitochondrial biogenesis and function in general, due to the ageing process.

A key player in the body's antioxidant defence system is the SOD2 gene which codes for manganese superoxide dismutase. The SOD2 gene is a potent free radical scavenger within the cell, especially the mitochondria. Because the mitochondria are the 'powerhouse' of the cell and work so hard, they are the site of many oxidative reactions during energy production. This means that lots of free radicals are generated within the mitochondria.

There is evidence that oxidation within the cell contributes to muscle fatigue and extreme exercise in individuals with low SOD2 enzyme activity may have an increased susceptibility to muscular fatigue, lipid peroxidation and depleted levels of vitamin E.

Long-term training can increase base levels of SOD2, whereas, short-term bursts of intense or extreme activity will increase oxidative stress.

Elite endurance athletes have indeed been gifted with 'great' genes. But one must remember that its not the genetic lottery alone that contributes to athletic success. An individual's psychological profile, physiology and emotional resilience will impact performance to a large extent. Not everyone with 'good genes' can allow themselves to push their bodies and minds past the point of extreme tolerance.

No matter what your genetic profile or goals may be, exercise is beneficial for overall health and is very protective against age-related decline. Mitochondrial health affects all our cells and organs and not just our muscles.

Sadly, the ageing process impacts the functional capacity of mitochondria, but that is no reason to give up on the pursuit of optimal health, longevity, and vitality.