Think about an army that may have to defend your country or go to war on your behalf. To test performance and prepare, the soldiers engage in regular exercises.
How the body uses oxygen for exercise
All the cells of the human body need energy in order to perform all their functions. That energy is provided by a molecule called ATP. It releases a phosphate bond and produces energy, becoming ADP. After that, a process to reintroduce the phosphate to make the ATP available again for energy use will occur. This specifically happens by burning a molecule of glucose (sugar) in the presence of oxygen. When the oxygen supply runs out or doesn't reach its destination (for a variety of reasons), lactic acid accumulates. That is a signal in the body to stop, regroup" recharge.
When one is in a sedentary or resting state, the process of supplying energy described above is slower and is known as the basal metabolic rate (BMR). When there are increased demands on the body, like increased physical activity, more energy needs to be produced and expended. The lungs can get more oxygen by breathing more liters of air per minute. Next, an exchange of oxygen from the lungs into the blood stream occurs. More blood is directed into the lung circulation, surrounds the alveolar sacs (that receive the oxygen), and this exchange occurs. Next, the heart must beat faster, in order to deliver the oxygenated blood to the tissues. When the person exercises, it's the muscle cells that are the target area for the oxygenated blood. This allows the muscle cells to process and generate more energy and support the exercise effort.
When any of the processes above fail or reach their limit, meaning oxygen doesn't reach its target destination, and lactic acid is produced, the outcome is always shortness of breath or cramping. I get many referrals for patients short of breath on "mild activity," because it's assumed that there is always something wrong with the lungs. This is obviously not always the case.
A commitment to regular exercise allows all the systems I just described to work systematically and properly, and to actually become more efficient, so that a greater physical effort can occur with less energy being used.
In healthy individuals, exercise programs can be designed for performance or to support general well-being. In people with chronic illness, there are limitations in the production of energy that have to be taken into account. These limitations can be cardiovascular, muscular, and in the case of COPD, respiratory limitations.
Why exercise is harder when you have COPD
The reasons for the limitations of the lungs are multiple. First, the main muscle for respiration is the diaphragm. It's shaped like a dome so that when it contracts, it expands the chest cavity, and draws air into the lungs. In emphysema, the lungs are already overinflated, so that the diaphragm is flat and unable to contract further. This makes it necessary to recruit other muscles like the intercostal and the clavicular muscles. Unfortunately, these other muscles are not as efficient (as the diaphragm) and tend to use more energy--exactly the opposite of our goal.
Second, fit individuals can increase the volume of air per minute by increasing the depth of each breath instead of the** frequency of the breaths**. In COPD, there is less elasticity, so one must actively use muscles to exhale (normally a spontaneous process). Since there is no room to increase the depth of the breaths, COPD patients must increase the number of breaths they take, in a given time period. With this increased frequency, the period between breaths is shortened, preventing the lungs from emptying completely. The net result is more trapped air and less ability to draw in sufficient oxygen from the environment. Eventually, there's no room for any new inspired air and one reaches a limit. This process is known as dynamic hyperinflation. And you can see how it would negatively impact the person's efforts to support any additional physical efforts - including exercise.
The conundrum is that when you're breathing, you don't want to be diverting energy to the lungs that should be going to other tissues. So if you have a challenge like COPD you may (a) have to take breathing breaks or (b) divide tasks into distinct phases with rest in between. In these cases, the objective of exercise is to simply engage in activities of daily living more efficiently.
How to exercise with COPD
Don't give up hope. You can exercise and hopefully improve your health situation. An exercise program for a COPD patient has to have four elements: cardiovascular, endurance, muscle strengthening, and specific warming up/cooling down movements. Breathing efforts integrated into the program must address the limitations. The delivery of oxygen is a significant limitation for the COPD patient. The joke that describes the man, who cannot walk and chew gum at the same time, is not funny for a patient with COPD. It is an actual reality.
You and your health professional may have to feel your way through the process in order to make progress. But it can be done
Next up: Why having more oxygen isn't always the best thing.