This piece is written for those with little background in exercise physiology, breaking concepts down as much as possible without losing the integrity of the general concept, adaptations our body makes to aerobic training. For health, safety and performance sake, however, I feel it needs to be made clear from the outset that aerobic training is not the “be all and end all” in taking care of our bodies. Other types of training are necessary for a variety of health and safety reasons. Emphasizing only aerobic training can compromise our ability to respond to emergency situations with the speed and power necessary to protect ourselves and can prevent us from maintaining tissues that have the type of mass, flexibility and elasticity needed to respond with quick movements and absorb minor fall. Please feel free to ask me or your trainer more about this.
Cardiovascular Adaptations
Aerobic training, as the adjective implies, develops our ability to utilize oxygen in processing energy. The aerobic response in the body involves the nervous, endocrine (hormonal), cardiopulmonary and muscular systems most directly. The ability of the heart to transport oxidized blood to the muscle tissue is the dominant and easiest response to measure. With the appropriate stimulus, the primal part of our brains triggers a neural and hormonal response that dilates the arteries that supply the skeletal muscles and constricts those that supply less essential structures. Neural and hormonal responses also trigger the heart to expand as fully as possible and contact as forcefully as possible to bring in as much blood as possible and push out as much blood as possible. The complete filling of the heart causes this muscle to stretch to its fullest capacity, therefore enhancing the expulsion blood by way of an added elastic release to the powerful muscular contraction. This allows more blood to be ejected with fewer contractions. This characteristic is maintained and developed in the cardiovascular system with training, so that at rest the heart will continue to need fewer contractions to provide the body with the oxygen it needs to process energy. This, over time, presents itself as a lower resting heart rate in aerobic athletes.
Energetic Adaptations
The advantage behind supplying so much oxygen so quickly to the muscles is that it allows for a very efficient energy processing system called the oxidative system. This system can produce a lot more energy than the other two major energy systems in our body and better utilizes more fuel sources. Aerobic training encourages the production of those enzymes that aid in the oxidative process, allowing the breakdown of carbohydrates and fats to produce energy.
Neuromuscular Adaptations
Processing energy using large quantities of oxygen happens in the muscle cell within an organelle called a mitochondria. This is a complex structure and in itself requires considerable resources. Some muscle tissues are better adapted to utilizing mitochondria. These are the type I muscle fibers. Aerobic training emphasizes the development of type I muscle tissue. As training continues, muscle filaments and neural connections that are deemed as unnecessary in the type I muscle fibers are replaced with mitochondria to process oxygen. Collagen (a light, tough element in the connective tissue) is added to support the muscle cell in the absence of contractile filaments.
The Overall Result
With continued aerobic training, the athlete develops a cardiovascular system that can transport great quantities of oxygen to an oxidative system that supplies the enzymes that produce energy within very light, efficient muscles that are able to produce movement over and over again for long period of time without rest.
This is perfect for the distance runner and has health benefits for us all but, as stated above, it should never be the only form of exercise one gets. It can diminish flexibility, strength, balance and power (the ability to respond quickly with strength) and by itself is not the best way to lose weight or maintain a healthy weight or body mass.
For the complete story…
The above explanation has gaps big enough to drive a truck through. The full story covers a couple of hundred pages in an exercise physiology book and it’s probably best if you’ve had your biology and chemistry before reading it. If you have any questions about this or the body’s adaptation to different types of training stimuli, feel free to book an appointment with me.
