Chapter 26 "Running Life" - Appendix

appendix The Physiology of Running Running starts with the brain.Once you decide to run, your cerebral cortex — its gray, wrinkled outer layer — fires off a burst of electrical signals.Like making a phone call, each flashing signal has only one destination.Imagine that one of these signals is sent to a calf muscle.It travels from your brain to your spine and legs, changing the sodium and potassium balance in a cascade of cells in a split second, jumping from nerve to nerve.When this signal reaches the junction (medically known as a synapse), it crosses over, causing a burst of the same chemical changes as it crosses.Because a nerve pulse travels at an almost immeasurably fast pace, it arrives almost immediately at a so-called endplate, where the nerve and muscle fibers finally meet.Chemical changes again occur when muscle fibers contract and relax.

The muscle fiber is so small that you have to squint to see it.After it's freeze-dried -- and exercise physiology labs like David Costill's lab sometimes freeze-dry it -- you can blow it away like a speck of dust if you accidentally take a breath .But within this infinitesimal fiber, some very complicated biochemical changes in the human body take place.Very simplistic, he says, they include the reaction of glucose and oxygen to form carbon dioxide, water, and mechanical energy.When oxygen is in short supply—and, to some extent, throughout a run—part of this response is anaerobic (absence of oxygen).As a result, incomplete oxides like lactic acid build up, causing hypoxia. In order to complete the breakdown of these compounds, your body must "repay" the necessary oxygen.And the function of the lungs, heart, blood vessels, and blood is to get your six hundred or so muscles to get oxygen from the air to make this happen.

Muscle, of course, is not a single fiber, but a giant bundle of fibers bundled together like strands of noodles lying flat.These strand fibers contract due to the action of thread-like protein molecules called actin and myosin.What happens when actin and myosin come together is like two combs meshing together.The tighter they mesh, the tighter a muscle contracts. As any runner knows, running generates a lot of heat.Even at rest, the cellular furnace of metabolism generates enough heat to raise body temperature by a full degree in five minutes, Dr. Ethan Nadel of the Yale School of Medicine told a meeting of scientists.When we run, these furnaces roar with infinitesimal metabolic flames, generating far more heat than our bodies need.We must try to get rid of this heat if we do not allow ourselves to burn out.Because of this, we have an adjustment mechanism.

The human body's thermostat is far more complex than most.Although it monitors both skin temperature and internal body temperature, it places greater focus on the latter.Once it senses a rise in temperature, it sends a signal to the hypothalamus, a region deep in the brain.On command from the hypothalamus, blood vessels in the skin dilate to dissipate heat.In addition, sweat glands secrete a mixture of fluid and electrolytes for evaporation and cooling when necessary. On the other hand, if the hypothalamus senses a drop in temperature, it orders less blood flow to the skin and temporarily shuts down the sweat glands.If the cooling continues, it causes the muscles on the bones to vibrate and generate more heat.However, even in winter, the problem in running is usually not too cold but too hot.

The above brief description is what happened to us in one run.So what happens when you run again and again?Clearly, deep and fundamental adaptive changes occur whenever we exercise.How else to account for the fact that when we first practiced running we were out of breath after running a block and a year later we were still breathing half way through the Boston Marathon Free and refreshed?To understand what's going on, let's examine each of the physiological phases of running.Note that when we look at it this way, what we mean by "exercise" is not just one outcome, but a collection of interrelated outcomes.

brain We already know that running starts with the brain.Except in the case of involuntary muscles, the human body does not do what the brain does not want it to do.So when we exercise, one of the things we do is harden our brains.We learn self-discipline when we run day after day, in good or bad weather.Emile Chattopeake once wrote: "Is it raining? It's ok. Am I tired? It's ok.. I'll practice anyway until willpower is no longer an issue." To an uninitiated , his behavior may appear aggressive and unreasonable.But as any serious runner knows, sticking to an exercise program is one of the best ways to ensure improved fitness—and, as said above, the physical benefits of fully achieving your goals .

nerve Even the nerves—those hairy tendrils that vine-like around every corner of our body— Also benefit from exercise.They become more effective at delivering electrochemical impulses and activating more muscle fibers, which increases strength.Moreover, since voluntary action is replaced by reflex action, action becomes more effective.There will be fewer wasteful muscle contractions, unneeded muscles can relax more fully, and movements will be simplified.Dr. Lucian Bruja, an authority on sports physiology, writes: "The end result is that energy expenditure in performing an exercise will be reduced by as much as four times the total energy required prior to exercise." One.” A reduction of this magnitude is a great savings.

muscle Exercise will strengthen your muscles.However, until recently, no one knew exactly why. Now, thanks to the development of advanced analytical techniques, the secrets of strength have begun to be revealed - and with them, the secrets of speed have begun to be revealed.For example, it is now known that when we run again and again, changes occur inside the cells of our muscles.Mitochondria, the small, microscopic factories in cells that produce energy, increased, providing more venues for the production of an energy-rich compound called adenosine triphosphate.Mitochondrial enzymes were also increased and synthesized faster (one, succinate dehydrogenase, was two and a half times more abundant in exercised runners than in sedentary individuals).

And that's not all the changes have taken place.Not long ago, Dr. Kenneth M. Baldwin of the University of California, Irvine, and Dr. Will W. Wendell of the Washington University School of Medicine found that glycogen ( A storage form of glucose) was higher in the muscles and livers of mice following a 12-week exercise program. (Presumably the same happens in humans).Evidently, important adaptations occur even in the tiny compartments and waterways of the cells themselves. Just as cells change, so do muscle fibers.After the workout, the contractions are faster and stronger.Plus, because the fibers don't tire as quickly, they work longer.

Muscles that are exercised are more efficient.This is because the adjacent arteries grow new branches and the capillaries become denser.For example, the capillary density of a calf muscle nearly doubles.To use the resulting increased oxygen, the muscle's supply of myoglobin—a hemoglobin-like substance that attracts oxygen—also increases, in some cases even.... complete.) times.From a layman's perspective, these adaptations are basically a simple process: the muscles simply become harder, stronger, and allow the movement to last longer.In reality, the process is much more complicated than that.

blood Any human activity would be virtually impossible without oxygen.This substance is transported to the muscles through bright red blood vessels.It is surrounded by hemoglobin and is transported from the heart to wherever it is needed within seconds of being produced. When exercise begins, the blood leaves the blood vessels in a huge tidal wave and seeps into the interstices of the muscle cells in order to increase the efficiency of the blood.This activity serves two purposes: first, the muscles work easier when they are bathed in blood; second, the concentration of hemoglobin in the blood is increased, allowing a given volume of blood to carry more of oxygen. * After repeated exercise, an important change takes place in the blood, the body has actually learned that its blood volume will periodically drop, so it will increase its supply.That way, when exercise begins and blood leaves the vessels, a greater volume of blood remains to perform essential tasks. *The beneficial consequences of increased hemoglobin are the reason for the controversial practice of administering a substance intravenously.Because the inability to deliver enough oxygen appears to be the major limiting factor in long-distance running, some researchers reasoned that an increase in red blood cells—and thus hemoglobin—would lead to a corresponding increase in activity.Therefore, blood or red blood cells are injected into the blood vessels before the game.However, the value of administering stimulants intravenously has not yet been conclusively proven.Even if it is proven, some critics will continue to evade it as something terrible. There are other changes in the composition of the blood during exercise.For example, its ability to condense has been enhanced— The emergence of this function is undoubtedly to protect the people who carry out the activities? ? ? ? ? .Also, because the blood clot must eventually break down once formed, the amount of an enzyme called plasmin increased. (It is theorized that plasmin might also break down long-standing blood clots -- including small clots in the heart's coronary arteries that, if enlarged, could cause heart disease.)At the same time, concentrations of certain lipids -- such as some types of cholesterol and triglycerides linked to heart disease -- are reduced.A recent study by Dr. Peter Wood of the Stanford University School of Medicine and his associates showed that these lipids were significantly reduced when middle-aged men and women ran fifteen miles a week."These very active middle-aged individuals constituted a group with a significantly reduced risk of cardiovascular disease," Wood wrote. heart The effects of exercise are seldom as well documented as those seen in the heart.Studies have repeatedly shown that after a sustained exercise like running, the heart becomes significantly more efficient and able to do more work with less effort.One of the most basic changes is that the fibers of the heart muscle lengthen, much like the muscles of the legs lengthen when we stretch.The longer fibers allow the two ventricles—especially the powerful left ventricle, which squeezes blood into the aorta—to expand and eject more blood with each contraction. At the same time, the arteries that feed the heart itself enlarged—in some cases, triple their usual size—and increased in number.Chapter 4 deals with the case of the famous Clarence DeMar, a marathon runner who was still running well in his sixties.Dr. Paul Dudley White studied the results of Dema's autopsy and found that although Dema's coronary arteries were enlarged, they were not a sign of ill health, but a natural reflection of his half century of exercise. reaction.Arteries with larger than normal volumes can be expected to carry more blood, thereby supplying the heart with a particularly good supply of oxygen.Researchers at the University of Minnesota found not long ago that in athletes who exercised for a long time? ? ? ? Blood flow to the heart may increase up to five times that at rest, and other researchers believe the ratio may be even higher than that. As noted, these changes cause the heart to eject more blood with each beat—in many cases twice as much blood as an unexercised human heart is capable of ejecting.Before exercise, a person's heart can eject less than half a teacup of blood per beat, but after exercise, the heart can eject almost a full teacup.The reason for this increase is that during the stretch of the heart -- the phase when blood enters the atria -- the heart fills more with blood.Therefore, during systole - the ejection phase - more blood can be squeezed out.Since athletes and sedentary people both require roughly the same blood supply at rest, the exercised heart beats less often most of the time.It is not uncommon for the resting heart to beat ten or twenty beats per minute less, and it is not uncommon for a well-exercised athlete to have a pulse of the forty or even thirty. thing. (My own pulse is forty-five, six).A slowed heart rate -- its term is bradycardia -- often surprises doctors who don't often see athletes. *Just right here to dispel the nonsense about the athlete's heart.True, athletes' hearts do grow, and left ventricular hypertrophy—the scientific name for an enlarged left ventricle—is common in long-distance runners. However, human research has convincingly shown that this enlargement is not only harmless, but is in fact a desirable adaptation brought on by exercise.For example, not long ago, Dr. William Rascoff, Dr. Steven Goldman, and Dr. Gene Cohen presented a study of thirty marathon runners.Twenty-four athletes were found to have enlarged left ventricles, but none, the three doctors said, had any detectable problems, even when doing strenuous treadmill exercise.They concluded that left ventricular hypertrophy "may enhance overall vascular function." The degree to which a runner has a slow heart rate depends not only on how much he exercises, but also on genetic factors.Not long ago, Dr. John Davis Cantwell of the Emory University School of Medicine studied the case of a thirty-nine-year-old marathon runner whose pulse sometimes fell as low as twenty-eight.on the other hand.At the peak of his running career, record-setting mile-runner Jim Ryan had a pulse in the seventies.The implication is clear: When you run again and again, your heartbeat almost certainly slows down.But if it doesn't beat as slowly as another runner's heart--or, if it beats more slowly--that's nothing to worry about. **Several other irregularities are not cause for concern under normal circumstances.The medical journals are full of reports about the conditions of some high-level athletes who, judging by electrocardiogram studies, would have been stretched out in a hospital bed.Wilt Chamberlin's electrocardiogram showed a startling deviation of his heart rate from normal, which most cardiologists would confidently diagnose as acute myocardial infarction— - Damage to the heart muscle following a lack of blood supply. If running can make a normal heart look like a sick heart, it can also correct certain abnormalities.Dr. Ellsworth Buskirk and some of his associates recently reported in the "American Journal of Cardiology" that when one hundred and ninety-six middle-aged men - all of whom were judged to be probable cardiac patients - —When the treadmill test was performed, fully half the population was found to have what cardiologists call premature ventricular contractions, a symptom associated with an increased risk of sudden death.After implementing the conditioning program for eighteen months, the number of premature ventricular contractions decreased significantly.Dr. W. Channing Nicholas, who conducted the study with Dr. Buskirk, concluded in layman's terms: "As people get better physically, the abnormal heart rate seems to decrease." Exercise has another effect on the heart: It lowers blood pressure during periods of rest.Since high blood pressure is known to predispose to heart disease, lower blood pressure is a welcome byproduct of running.When Dr. Fred Cash studied sixteen people who practiced regular exercise for ten years, he found that, as described in Chapter 4, blood pressure remained below the average for people of the same age and sex. .The reduction in blood pressure "may act as a protective or physiological benefit, especially given the predisposition to high blood pressure in middle-aged individuals," he said. Certain medical authorities took a more assertive tone in their judgments.As already discussed, Dr. Basler, a pathologist in California, insists that marathon runners are immune to heart disease.Marathon runners do die, he says, but for the same reasons that teens die—infection, accidents, and so on.A trained heart can be more efficient not only at rest and during exercise, but also after exercise when it returns to normal more quickly (see illustration on page 295).Also, since a trained heart beats more slowly than an untrained heart, there is a longer rest period between each contraction—often a full second or more.At this time, an untrained person's heart is working hard, while a runner's heart is resting. lung Of all the organs a runner uses, the lungs, with their 300 million moist, foam-like sacs called alveoli, are the most efficient and the least problem-free.An analysis of everything a runner's body relies on -- everything from oxygen to hemoglobin to adenosine triphosphate -- shows that the lungs normally supply abundant oxygen to the blood passing through them.Furthermore, they are amazingly adaptable organs, able to respond quickly to changes in either a single session of exercise or long-term exercise.When exercise begins, the blood vessels in the lungs dilate, which expands the area where oxygen can enter the bloodstream. *If this continues every day, the breathing muscles in the abdomen, diaphragm, and ribcage become stronger and more efficient.The oxygen required for the breathing process itself is reduced.Meanwhile, the lungs of an exercised runner can increase the volume of air they take in from less than five quarts per breath to about six quarts) and triple the amount of air they take in per minute.More air means more oxygen, so the benefits are obvious. *Also, the scope for excreting carbon dioxide—the end product of the aerobic breakdown of glucose—has also expanded, although this is not the main issue in our discussion. control body temperature ? ? ? ? ? ? ? Epilogue: The Miracle of Running This question is explored several times in the essays in this book: why running is such a particularly satisfying hobby.Once you've been running for a few months, you're bound to notice certain clear psychological benefits—a feeling of calm and strength.Feel in control of your life.Runners also speak of having a "hobby" (which is the title I'll be writing about throughout this book), and in a sense they certainly do.It's rare for a runner, no matter how busy, to give up the sport.More often the opposite is the case, and some people run three or four miles a day--enough for health alone--but at some point, inexplicably, triple or even triple the miles they run. times. Therefore, it is difficult to explain this situation by saying that people run only for their health.Just to get a healthy body is easy to do without making a lot of mess in one's life; just run for twenty or thirty minutes a day, four days a week.Why then do people run eight miles, ten miles, or more every day in blindingly hot summers and blustery winters, especially when they know they'll never be particularly famous for long-distance running? Many theories have been put forward in this regard.Roger Bannister compared running to music.Both running and music stimulate our nervous system and give the human organism a pleasant feeling.An hour's run brings a tiny electrical jolt to the nerves in much the same way that Handel's Messiah does. "Psychiatrist Thaddeus Costellabala recently proposed a theory closely related to this one. There may be a scenario where a runner is running After a forty-minute or so run, it might be possible to somehow "remove" the influence of the right cortex (the logical part of the brain), allowing the left cortex (the intuitive and artistic part of the brain) to temporarily take control. David Miller offers a third explanation in his insightful book Gods and Movements.He writes that, like young children, we play sports for the innocent and pure purpose of having fun rather than winning.In childhood we make no such artificial distinctions.A child throws a toy, laughs, goes looking for it, and jumps up when he finds it—then he goes on happily playing with the same thing again and again.Miller argues that our adult sports are about reliving the joys of the innocent activities of our youth, when we don't think about sports at all, but about having fun.Because the competitive conditions of running are ever-changing and manageable, we are perfectly able to achieve the above in our sport. Perhaps there is some truth to all of these theories.But I have a different theory.In my opinion, the vast majority of people who have considered this question are asking the wrong question.Why does running have this special effect among them.To ask a question in this way leads to an affirmative answer, which I think is wrong.I suspect that the effects of running are not special at all, but rather normal.What is special are some other conditions and all other feelings, because these conditions and feelings restrain the feelings you and I intend to have.As runners, I think we're right back in history.We experience what we would have felt if we had lived 10,000 years ago, we eat fruits, nuts and vegetables, and the constant exercise keeps our hearts, lungs and muscles healthy.We can say that we are blood-related to the ancients, and even to the beasts that preceded them, whereas the present cannot say so.I think that's our great secret, and it's the secret we feel every time we run.