Cardiovascular Biochemistry: How The Heart Adapts

The truth is that endurance in football is not just the ability of a football player to have strong legs but rather the ability of the heart to keep up with the legwork. The first five minutes of a match are one thing, and the last ten being quite different as breathing becomes heavier and each sprint is more difficult. I used to believe that this was merely the issue of fitness but learning about cardiovascular biochemistry made me realise that the heart and blood are always readjusting themselves at the molecular level to facilitate performance. The release of nitric oxide, buffering of blood pH, and delivery of oxygen in the body by haemoglobin are processes that collaborate to sustain energy production and delay fatigue. What may seem to be endurance on the pitch is in fact the product of an extremely sophisticated system of biochemical processes operating in real time.

When the body participates in vigorous exercises, the cardiovascular system modifies to transport more oxygen and nutrients to the working muscles, and to eliminate carbon dioxide and by-products. Nitric oxide (NO) is one of the key molecules that are involved in this process. It is synthesized by endothelial cells that line blood vessels and is a vasodilator, relaxing smooth muscle in the walls of blood vessels. This enhances blood circulation and more oxygen and glucose are transported to the active tissues during exercise.The transportation of oxygen itself is reliant on the haemoglobin, which is a protein in red blood cells. The haemoglobin molecules have the capacity to bind up to four oxygen molecules and transport them to the tissues. During exercise, an increase in the concentration of carbon dioxide, rise in temperature, and decrease in the pH, cause the haemoglobin-oxygen dissociation curve (Bohr effect) such that haemoglobin releases oxygen at an accelerated rate to active muscles. This is so that the rate of oxygen delivery is equal to the metabolic need.

Meanwhile, heavy exercise will cause the build-up of carbon dioxide and hydrogen ions that have the potential to reduce blood pH. The pH balance is maintained by buffering systems in the body, the bicarbonate buffer system being the most common. Carbon dioxide reacts with water to give carbonic acid which dissociates to give hydrogen ions and bicarbonate ions. The reversible system assists stabilisation of pH to avoid large variations that may lead to impairment of enzyme activity and muscle performance.Nitric oxide, the functionality of haemoglobin, and buffering systems combine to assure that the cardiovascular system is dynamically responsive to the dynamic demands of exercise, which ensures oxygen is supplied to the body, waste is removed, and internal homeostasis is maintained.

These biochemical adaptations can be very evident even in a football game. When demand of energy goes up at the beginning, the blood vessels dilate to enhance circulation, enabling the muscles to receive more oxygen in the least amount of time. As the game develops and blood flow varies with the intensity of activity in the muscles most involved.

The action of haemoglobin is seen when the running is sustained. The oxygen is still delivered efficiently even as breathing is heavier owing to conditions that are exercising-related. It is what enables players to perform over extended durations of activity.Buffering systems are particularly needed during high-intensity periods. When repeated sprints result in an increase of the hydrogen ion concentration, the body tries to stabilize the pH so that the muscle contraction and enzyme activity would not stop. In the absence of this buffering, fatigue would be much earlier.

All these systems are enhanced by training. Regular physical activity causes capillary density, production of nitric oxide, cardiac output, and buffering. This is the reason why trained athletes are able to maintain higher intensities over longer periods as opposed to untrained individuals.

Learning cardiovascular biochemistry has led to a change in my experience of endurance in football. What was once a mere challenge of endurance, now seems an organized biochemical reaction. My increased heart rate during a match tells me that my heart is working to supply more oxygen to my body using haemoglobin. When I sense that breathing becomes deeper, I realize that my body is attempting to regulate the amount of carbon dioxide in the body and to maintain the pH balance.

Being aware of nitric oxide has also altered my thinking with regard to blood flow. I no longer view circulation as passive but instead I realize that my blood vessels are dynamic and adapt to the needs of the game. This dynamic system supports every sprint, every change in pace.

This learning has helped me to be more cognizant of how training enhances performance. I am not merely gaining fitness, I am improving the capacity of my body to regulate oxygen delivery, pH and energy production.Above all, it has enhanced my fascination with the study of biochemistry. It demonstrates the complexity of physiological processes regulated by simple molecules interacting with each other in specific manners. Football provides me an opportunity to live through these processes and make science real and practical. Cardiovascular biochemistry is always at work to ensure that I am on the move.