How Is Fitness Linked To Aerobic Respiration?

Fitness is tied very closely with aerobic respiration. One of the key factors that determines fitness is your body's ability to effectively utilize all of the metabolic pathways of aerobic respiration to produce the necessary energy to maintain physical activity over an extended period of time.

Sustained Energy for the Body.

According to the University of Idaho, all cells in the body utilize ATP -- Adenosine Triphosphate -- as their energy source. ATP can be synthesized from various food sources such as sugars, fats and proteins with the aid of oxygen through oxidative phosphorylation. There are various metabolic pathways that eventually lead to the Citric Acid or Krebs Cycle, which occurs in the mitochondria of the cell -- the power plants of all cells. The Krebs Cycle is the most efficient pathway for creating ATP, producing 29 ATP per molecule of glucose compared to 2 obtained in anaerobic metabolism. The end products of the Krebs Cycle is ATP, carbon dioxide and water. These various pathways make up aerobic respiration.

Aerobic Respiration and Physical Activity

Scott Powers, author of "Exercise Physiology," explains that for physical performance there are three sources of energy that the body can utilize.

The first is the use of the ATP that is already on hand in the cells. This energy source will last only about 3 seconds. The next source is the body's phosphagen system, which will provide another 8 to 10 seconds of energy. This is the equivalent of the 100-meter dash. The third energy source is glycogen-lactic acid cycle. This energy source will last about 60 seconds, which is the equivalent of a 200 to 400 meter dash, or the 100-meter swim. Once all these energy sources have been exhausted, aerobic respiration must kick in. Aerobic respiration provides an infinite amount of energy available for activities such as the mile run, marathon, and distance skiing.

How Exercise Affects Aerobic Respiration.

Once you have been physically active for longer than 60 seconds, the aerobic respiration must take over as the primary energy source. Prolonged exercise will cause your body to react and increase your cardiac output through your heart beating harder and faster. Your body will dilate your blood vessels to increase blood flow to the working muscles. Blood flow to the non-vital organs, such as the kidneys and stomach, will decrease. Oxygenation of the hemoglobin in red blood cells will increase due to deeper, faster breathing. This increased oxygenation provides the opportunity for the cells to produce more ATP.

Physiological Adaptation to Exercise

Over time, your body will adapt to exercise. As a result of improved cardiovascular performance your heart will strengthen, gradually decreasing your heart rate for a given exertion level due to increased stroke volume. Your cardiovascular response to exercise will occur much quicker; dilation of blood vessels and redirection of blood from non-priority organs will occur sooner. Over time, your body will also start making more mitochondria within the cell, allowing for more ATP to be produced. The ability of the body to respond quickly to prolonged physical stress is called fitness.

Recommendations for Cardiovascular Exercise:

The American College of Sports Medicine recommends that if you are just beginning an exercise program that you begin moderate cardiovascular exercise that totals between 250 and 300 minutes, which is approximately 1200 to 2000 kcalories burned per week, or more. Moderate activity is defined as maintaining your heart rate above 65 percent of your heart rate max.

To calculate your heart rate max, utilize the formula of: (220 - age). To determine where your heart rate needs to be for those 250 to 300 minutes, multiply your heart rate max (220 - age) x .55 and .65. This will provide you your optimum heart rate range for obtaining your cardiovascular fitness goals.

If you are on any cardiac or blood pressure medication, please consult your physician prior to exercise. This formula may not be suitable for your medical condition.

Conclusion

There are many systems, pathways and reactions that are associated with aerobic respiration. The end result is sustained cardiovascular performance over what could seem like an infinite period of time. Marathon runners, distance skiers and swimmers have mastered the science of training, recovery, nutrition and rehabilitation to optimize these systems to obtain peak performance.