The human body always reacts to acute stress. Perspiration increases so breathing is heavier and faster, the heart rate increases so it pumps faster, the muscles work hard so get tired and possibly sore, and perspiration--- sweat--- increases. These responses happen both to the person who is well and to the person who is ill. The point is to get more oxygen to the muscles, so the muscles can work harder.
This acute stress may be purposeful, as in taking a walk or going to the gym, or it may be due to something in the environment, such as the need to escape from a house fire or to run away from a moving vehicle headed the person’s way. When someone is under stress, adrenaline (which is a hormone dedicated to “revving up” the body to deal with these situations, called the ‘fight or flight response”) and cortisol (another stress-induced hormone) starts pouring into the blood stream and the muscles get ready to act. Exercise itself is a kind of acute stress for the body.
We are meant to engage in physical activity; it is for our survival. In the distant & recent past, we have hunted, gathered, farmed, herded, and performed labor in factories. Nowadays, in our society, fewer and fewer of us engage in any of these activities. We have become increasingly sedentary, with many consequences to ourselves, our children, and future generations. Added to this lifestyle is the consumption of a far less than healthy diet (specifically referring to America and the West, but Western influence is global), and the consequences appear to be dire.
For the person who is well, the normal effects of exertion, in addition to those above, are an increase in endurance, strength, and flexibility, as well as weight loss (when and if necessary) and healthy weight maintenance. All systems of the human body work better when a person engages in physical activity.
Caution must be taken, of course, in the case of over-exertion. In the normal person, over-exertion can result in pain and fatigue. In the ill person, even what may be considered normal exertion may be “too much”, so while the ill, elderly, or disabled may benefit from some exercise, care must be taken that it is appropriate to the age & condition of the person, and monitored by someone who is properly trained to do so. If not monitored carefully, the ill person’s increase in heart rate may cause damage to the heart and perhaps a “heart attack” or Myocardial Infarction, the increase in blood pressure may contribute to a “stroke” or Cerebrovascular Accident, or the pain and fatigue may be more than can be comfortably endured.
Chronic stress is another matter, and involves much more than physical exercise. Chronic stress is the situation for many of us these days. We have traffic, computers and other informational devices “on” twenty four hours a day, financial worries, family issues, concerns about war, pestilence, and famine which are unrelenting. Our bodies react to this as they do in acute stress, but rather than going through a cycle of “fight or flight” and having the situation--- and our bodies--- resolve back to normal, the cycle never ends, or barely ends when another begins.
Immediate effects of such chronic stress may be a “short fuse”, such as when we or others are tight for time and find ourselves in a checkout line that is long and slowly moving, and difficulty sleeping, when after a stressful day or week we cannot seem to make our thoughts stop racing and settle down for the night. The temper may cause problems not just with ourselves and our physiology, but socially and relationally with others--- increasing the risk of violence. The lack of sleep causes problems with concentration, focus-- and cause problems for ourselves, in our homes, and at our places of employment. Together, these and other effects, in the short term, contribute to unpleasantness for everyone.
Long-term effects of chronic stress include these, compounded by time and repeated issues. People have constantly increasing levels of anxiety and nervous tension, and the frequent if not constant release of adrenaline into the body, the replay of the “fight or flight response” when there may in fact be nothing to fight or flee from, but rather to cope with, takes a toll on the individual and on society as a whole.
Many of our diseases and disorders are consequences of physical inactivity, poor diet, and unrelenting chronic stress. Anxiety, depression, the cumulative effects of adrenaline & cortisol in the system such as increased heart rate and high blood pressure, blood being diverted from the stomach to deal with the stress causing indigestion and other stomach problems, the immune system becoming overworked or unresponsive leading to more colds, flu, and other infections, and even brain function could be at least temporarily impaired, affecting learning, memory, and concentration.
There are three basic types of exercises, each with a different focus. Goals for these are endurance, strength, and flexibility. All make the muscles work better and more efficiently, all contribute to health, and all require energy.
Examples of endurance exercises include running, biking, and swimming; these have to do with the capacity to continue an action repeatedly, so performing these activities increase that capacity. Therefore someone can run further, bike further, swim further, keeping the speed fairly constant.
Strength exercises, such as weight lifting and isometrics (using props to provide resistance for the muscles), increase the power and size of the muscles. This has to do with how fast the muscles can contract, and increase the amount of work they can do.
Finally, flexibility exercises, such as yoga and stretching, increase the ability of the muscles to respond to and cope with stress, or the exertion, of physical activity. In addition, these help people deal with all kinds of stress, emotional as well as physical.
Muscle metabolism expresses overall output. First and foremost is the need for ENERGY. The source of energy for the body, all cells and systems of the body, is ATP, AKA adenosine triphosphate. ATP is created in different systems and used in phases, and as different forms of exercise use different systems, each type of exercise done gets ATP in a different way.
ATP is produced in the muscle in this order:
Phosphagen System--- muscles cells have some ATP all the time that can be used immediately when necessary, but not much. So they contain a chemical compound called creatine phosphate, and when the phosphate is removed by an enzyme called creatine kinase, turns into ADP (adenosine diphosphate), which then turns back into ATP. As muscles work, these levels are decreased. This system can supply energy needs at a high rate but for only a short time--- 8 to 10 seconds. Example would be sprinting.
Glycogen-Lactic Acid System--- in addition to the ATP floating around in muscle cells they also have reserves of a carbohydrate called glycogen, which is a chain of glucose molecules (so related to sugar). The cell splits these and used anaerobic (without oxygen) respiration to make the ATP and a by-product called Lactic Acid (this acid is what can make muscles sore). This process is slower than the Phosphagen System, , though the body can still access this quickly and for a slightly longer time--- about 1.3 to 1.6 seconds. Example would be swimming.
Aerobic Respiration--- after two minutes of exercise the muscles require oxygen, so that glucose can be completely broken down into carbon dioxide and water. Fatty acids from fat reserves can be used to produce ATP. Aerobic respiration uses first carbohydrates, then fats, then proteins, as necessary, from the body. This process is even slower than the others, and can supply ATP for the longest period of time, possibly even for several hours. Examples would be marathon running.
Regular physical activity promotes health & well being and (along with a healthy diet) can prevent and treat heart disease and other chronic conditions. It can reduce the incidence and risk of hypertension (high blood pressure), diabetes, and various types of cancer, most notably colon cancer. It helps with weight loss/maintenance of healthy weight, better quality of breathing which gets more oxygen to the heart and throughout the entire body, more strength in general and stronger bones in particular, and helps people deal with anxiety, depression, and stress. It increases flexibility and balance, and for older people these benefits may help to avoid falls, and the broken bones and other injuries that are increasingly difficult for the elderly.
For individuals with chronic disease, exercise can increase functioning, quality of life, and possibly longevity. By getting oxygen into the blood and into the muscles, by taking blood from the organs and diverting it to the muscles, by increasing blood flow from the heart (and the heart is itself a muscle!), by increasing the efficiency of hemoglobin, getting rid of waste, and heating up and cooling down, the system for an ill person is improved, just as it is for a healthy individual. There are some cautions: “too much” of a good thing can be a bad thing, so exercise for the chronic disease sufferer must be planned, supervised, and carefully monitored, so that the individual gets the benefits and not the deficits.
I personally have never seen the biochemical processes of aerobic respiration expressed succinctly and therefore understandably. I will only summarize:
Aerobic Respiration is divided into two basic processes, the Krebs Cycle and the Electron Transport Chain. Ultimately pyruvate must be converted, though these processes, into ATP. It is imperative that the element of oxygen is present for this process. Without oxygen, ATP cannot be produced or “powered up”, and any living being that requires this for energy--- and energy is required for life--- will not survive very long.
Written by Beverly Flanagan, April 2009
