AJ-5-Physiology-of-the-human-body

Athletic performance is directly related to the amount of oxygen supplied to the muscles. The supply of oxygen is dictated by how often the heart beats, the volume of blood transported by every beat and the amount of oxygen in that blood. It is also dependent on how well the tissue or muscle extracts the oxygen (O2).

So if we could find the volume of blood pumped in one minute and the difference between the amount of oxygen in arterial and venous blood we would have all the data we need. The stroke volume is usually measured in milliliters per beat. The cardiac output is the product of stroke volume and heart rate and is measured in milliliters per minute. Multiply this by the difference in oxygen concentration and we have the liters of O2 processed per minute. If we make these measurements when the athlete is working at his or her maximum heart rate, we have VO2 max.

Those who are fit have higher VO2 max values and can exercise more intensely than those who are not as well conditioned. Numerous studies show that you can increase your VO2 max by working out at an intensity that raises your heart rate to between 65 and 85% of its maximum for at least 20 minutes three to five times a week. A mean value of VO2 max for male athletes is about 3.5 litres/minute and for female athletes it is about 2.7 litres/minute.

To measure VO2 Max directly an athlete has to be wired to a computer and breathe into an apparatus that analyses exhaled air while he runs on an appropriate ergometer – treadmill or a stationary bicycle. The exercise workloads are selected to gradually progress from moderate to maximal intensity.

We need a big and efficient pump to deliver oxygen-rich blood to the muscles, and we need mitochondria-rich muscles to use the oxygen and support high rates of exercise. Which variable is the limiting factor in VO2 max, oxygen delivery or oxygen utilization? This is a central question that has created considerable debate among exercise physiologists over the years.

CARIDOVASCULAR SYSTEM

The cardiovascular system includes the heart and system of vessels through which the blood is circulated throughout the whole body. The blood, which is pumped by rhythmic contractions of the heart, carries nutrients, oxygen, and other vital substances throughout the body. The blood is pumped from the heart to the arteries. The main arterial vessel, the aorta, branches into smaller arteries, which in turn branch repeatedly into smaller and smaller vessels and reach all parts of the body. Within the body tissues, the vessels are microscopic capillaries through which gas and nutrient exchange occurs. The blood passes oxygen and nutrients to the cells and picks up waste in the capillaries, then returns to the heart via a system of veins.

HEART
In the human body, the heart is normally situated to the left of the middle of the thorax, underneath the breastbone. The heart is usually felt to be on the left side because the left heart (left ventricle) is stronger, as it pumps the blood to the whole body. The heart is divided into four chambers, two on the right and two on the left side. The upper chambers are called the atria, and the two lower, larger ones are called the ventricles. All chambers of the heart have valves that keep the blood flowing in the right direction. When the right atrium fills, the atrio-ventricular (tricuspid) valve opens, allowing the blood to flow into the right ventricle , then closes to prevent backflow when the ventricle contracts. The mitral (bicuspid) valve does the same function on the left. There is no contact between the right and the left side, which are separated by the septum.