"Man, I'm trashed!" Long rides are hard on your body. How many times can you trash yourself without doing permanent damage to your health? We will investigate this question by looking at some health issues related to ultra marathon cycling, consider aspects of ultra-endurance exercise in general, and then review the results of a study conducted by Randy Ice in 1987 during the Haldeman/Penseyres Transcontinental Tandem Record Attempt.

(Disclaimer: I'm the wrong kind of doctor to be extremely knowledgeable about the finer points of medicine so I will keep this discussion fairly superficial and leave the details to the MDs.)

Our body has an amazing ability to withstand abuse, recuperate from damage, and come back stronger. "That which we survive makes us stronger." This is a simple way of stating the General Adaptation Syndrome proposed by Hans Selye in 1936. The body responds to stress in three stages:

1. the alarm reaction
2. the stage of resistance, and
3. the stage of exhaustion.

Given sufficient rest, the body's adaptation energy allows it to recover and even become stronger. This is the basis of training - stress and adaptation.

Let's take a look at some stressors that lead us to exhaustion during an ultra marathon event. They include sleep deprivation, nutrition, saddle sores, and damage to muscles, nerves, joints, and bones. We won't consider the effects of accidents such as falling off your bike or getting hit by a car. These events are definitely bad for your health and the damage can be permanent. We are interested only in the effects of exercise itself.

Sleep deprivation
Although chronic sleep deprivation is certainly bad for your health, I could find no evidence that an occasional night with little to no sleep does any permanent damage. You sleep it off and you're fine. In fact, studies have shown that one night without sleep does not affect physical performance. You might be in a bad mood, but your metabolic machinery will work just fine.

Nutrition
Ultra-endurance sports are notorious for creating nutritional challenges. How are you going to put down 10,000 Kcal a day while you're exercising hard without wreaking havoc on the digestive system? Most of problems that arise are short-term and leave no permanent damage. "This too shall pass" as the saying goes, in one direction or the other. But there's one area where you can't afford to be careless, and that's hydration. Too little water and you can suffer from dehydration. Too little sodium and you can suffer from hyponatremia. In their most severe cases, both conditions can cause serious damage to your health, even life-threatening.

What about free radicals? Should we take antioxidants? Not knowing much about free radicals, I consulted an article by Priscilla Clarkson and Heather Thompson titled "Antioxidants: what role do they play in physical activity and health? " (American Journal of Clinical Nutrition, 2000). A free radical is an atom containing one or more unpaired electrons in its outer orbit. Of the oxygen consumed during cellular respiration, 4 to 5% ends up as free radicals. They are dangerous because they increase the potential for cellular damage. Elevated aerobic metabolism increases the production of free radicals. The body, however, has a defense mechanism that neutralizes free radicals. It depends on dietary intake of antioxidant vitamins and minerals, among them being vitamins C, E, and beta carotene. It is not known whether or not the body's natural defense system is sufficient to combat the increase in free radicals with exercise or if supplements are needed. Training seems to enhance the antioxidant defense system as the trained show less evidence of oxidative stress than the untrained. Also, trained athletes who take supplements appear to have less oxidative stress. Nevertheless, there is no evidence that antioxidant supplements improve performance. Limited evidence in humans suggests that vitamin E may be the most important antioxidant related to exercise. Clarkson suggested that until more is known about the safety of supplements, we should obtain antioxidants from the foods in our diet.

Saddle sores
There's no question that saddle sores are unhealthy, but they are preventable, or at least manageable, with the proper care and equipment. If you do get a sore, it will heal with time and treatment, and your skin will grow back tougher. Saddle sores can even heal while you continue riding if you are careful. Fear of saddle sores should not keep us from riding. As Lon Haldeman once said, "Never quit RAAM because of something that will heal in a week."

Muscle damage
The muscle soreness you feel right after exercise is not caused by damage to the muscle, but by an accumulation of the end products of exercise, such as hydrogen ions and water. The pumped-up feeling you have after a hard effort is a result of this edema in the tissue. It will subside in a few minutes to a few hours.

Although you may feel sore immediately after a long ride, have you noticed that it's worse the next day? This type of muscle soreness is a result of micro-trauma to the structural elements of the muscle fiber itself. Like many other injuries, the body responds with pain and inflammation. The response peaks about 48 hours after exercise, hence the name Delayed Onset of Muscle Soreness (DOMS). The beauty of DOMS is that it prevents you from feeling like exercising vigorously for a few days, thereby reducing the chance that you will do further injury to the muscle. The damaged proteins will need time to heal; massage and/or anti-inflammatory drugs may not help. When the fibers do repair themselves, however, they come back stronger, so that the same activity that made you sore in the first place, won(t make you sore the second time around.

One of the markers of muscle damage is creatine kinase (CK), an enzyme that is supposed to remain inside the muscle cell. When CK appears in the blood it is an indicator of muscle tissue breakdown, and has been measured at extremely high levels in ultra-endurance runners following such races as the Western States 100. Dangerously high levels can potentially impair kidney function, so prompt medical treatment is essential. CK levels may remain elevated for several days and parallel the feeling of soreness. There is also evidence that ultra marathon athletes may have chronically elevated CK levels. They return to normal when exercise is reduced.

Nerve damage
Cycling has the potential of doing permanent damage to your nerves, but it's not the exercise itself that causes the damage, it's contact with the bike. Hands, feet, and butt are places where nerves can be crushed. If the nerve is crushed badly enough, it may not regenerate. Numb fingers and toes are an inconvenience, but a damaged nerve in the bottom may not be an option, so every measure should be taken to prevent it from happening. There are many good products on the market today, it's simply a matter of finding the right combination of saddle, shorts, handlebars, gloves, pedals, and shoes to fit your body.

Joint and tendon damage
Cycling is a sport that is fairly easy on the joints, so most injuries are overuse injuries: tendonitis and bursitis. These injuries usually respond to rest and treatment, resulting in a complete recovery. Recurring problems may be caused by improper biomechanics or poor bike setup, both of which can be corrected.

Bone loss
We've always been told that exercise, especially weight-bearing exercise, is good for the bones. But check out the title of this research paper from Osteoporosis International: "Low bone mineral density in highly trained male master cyclists" (Nichols, 2003). That's scary! In this study the bone mineral density of the spine and hip in 27 men with an average age of 51.2 who had been training exclusively in cycling for an average of 20 years was lower than both age-matched controls and young adult cyclists. Total body bone mineral density was lower in the older cyclists compared to the young adults. The conclusion was that "although highly trained and physically fit, these athletes may be at high risk for developing osteoporosis with advancing age."

Why would exercise cause bone loss? An article from the Journal of the American Academy of Orthopeadic Surgeons (Voss, 1998, Exercise-induced loss of bone density in athletes) has this to say: "Endurance athletes are known to have decreased levels of sex hormones, which can cause physiologic changes that lead to bone loss. This may result in relative osteoporosis despite the loading of the bone during exercise, which would normally increase bone mineral density.(" So it's a hormonal imbalance, a problem we had associated with women. This is bad news for all of us, men and women, who thought our exercise routine was protecting us from age-related bone loss. Does this mean that we are actually doing permanent damage by cycling so much? Let's wait for more research before we get too worried.

Characteristics of the ultra-endurance athlete
Ultra-endurance athletes exhibit certain characteristics that may be related to excessive exercise. It's not clear if these characteristics are a result of excessive exercise or if people with these characteristics tend to excel in ultra-endurance sports. Perhaps it's a combination of the two. First of all, ultra marathoners have a high percentage of slow twitch muscle fibers. They were born that way because training will not transform a fast twitch fiber into a slow twitch fiber. Endurance training will, however, improve the aerobic capacity of the fast twitch fibers, but they will still be "typed" as fast. The nerve conduction velocity of endurance athletes tends to be slow, which goes along with a high percentage of slow fibers. The nerve and all the fibers attached to it form a motor unit, so slow muscles have slow nerves. It has been suggested, however, that endurance training may slow down nerve conduction velocity.

"You are sentenced to 30 years of hard labor!"
Centuries ago criminals were given lifetime sentences of hard labor, which often resulted in a much shorter life. Are the physiological effects of ultra-endurance sports similar to hard labor, leading to a shortened life? There's a big difference between working in a prison camp and doing a sport. For one thing, we are having fun, reducing stress. We also have better nutrition and adequate rest. Any damage we do to ourselves is short-term and we get proper medical care if necessary. We allow ourselves to recover from the stress of our sport; we adapt and become stronger, instead of weaker like the prisoner. No, choosing to be an ultra marathon athlete is not a lifetime sentence of hard labor.

Are heart beats limited?
As crazy as this question sounds, there is an hypothesis in exercise physiology that we are born with a limited number of heart beats and when we use them up we die! So if you exercise excessively will you use up your allotted heart beats sooner? Let's hope not.

The hypothesis is based on the fact that large animals with low hear rates (the elephant for example) live a long time while small animals with very fast heart rates (mouse) have a short life span. Humans are somewhere in between, although our life span of 120 years at a resting heart rate of 72 is longer that it should be compared to other mammals. This certainly has something to do with our more highly developed brain. Based on this body-size-versus-life-span relationship, humans should have about 4.31 trillion heart beats in a lifetime. If you exercise, you will develop athlete's bradycardia (lower resting heart rate) and will "use up" your allotment of beats more slowly, thereby adding years to your life. If you exercise too much, however, the extra beats you use will exceed the number you save by having a lower resting heart rate. You will die sooner. At least that's the hypothesis, if you believe it.

The scientists who proposed this hypothesis performed some very complicated mathematics to determine that the optimal amount of daily exercise time to gain the maximum number of years is 22 minutes, resulting in a 6% increase in years of life. The break even point is 97 minutes. This means that if you exercise more than 97 minutes a day, you are actually taking away years of your life. By the way, this hypothesis has not been proven! Like other muscles of the body the heart is a muscle that responds to the demands placed upon it. It doesn't have a contraction counter that dings when it reaches 4.31 trillion.

We've used the term "excessive exercise" several times. What does this mean? It was intended to describe levels of exercise above that which the typical cyclist does in training and competition. Ultra marathon cycling is excessive exercise. RAAM is certainly excessive. In the context of the limited heart beat hypothesis, we might say that excessive exercise is more than 97 minutes a day. This is surprisingly close to the number that Thomas Jefferson gave us over 200 years ago without any fancy mathematics: "You should spend at least two hours a day on bodily exercise; however if you should decide not to you will someday spend two hours a day taking care of your disease."

Is Ultramarathon Cycling Harmful to Your Health?
This was the title of an article by Randy Ice that appeared in the December 1987 issue of Bike Tech. To answer this question, Ice collected data before, during, and after a transcontinental tandem record attempt by Lon Haldeman and Pete Penseyres. To my knowledge it is the only study of its kind. It's very difficult to collect data on cyclists under field conditions, and even more so to collect information while they are moving. Ice deserves credit for being a pioneer in the study of ultra marathon physiology, not only for this ambitious study, but for the many years that he has collected data on RAAM riders. We should nominate him for the Ultracycling Hall of Fame!

Pete Penseyres and Lon Haldeman Dave Nelson photo

There's too much information in Ice's article to cover here, but some of the highlights will tell us what we need to know. Ice put Penseyres and Haldeman through a bike ergometer max test before and after the cross-country ride to determine what effects the effort would have on physical performance. Resting heart rate was about 25% higher after the ride. Maximal heart rate decreased only slightly. Maximal workload on the ergometer decreased, as did VO2 max and power to body weight ratio. These results indicate that their metabolic capacities were reduced slightly, just as one would expect after such an effort. As a result of the ride, both men lost about 2.5 pounds of lean body mass as well as 2-4 pounds of fat.

On the road, average speed fell from 19.9 mph at the beginning of the race to 17.4 mph at the end. This drop corresponded to a reduction in the percent of VO2 max they were working, 60 to 70% initially down to only 40 to 50% by the last day. Average heart rate was between 100 and 110 throughout, and rarely surpassed 130. Increased blood creatine kinase suggested some muscle damage and elevated BUN indicated some protein catabolism. There were no symptoms of low blood sugar. Maintaining stable blood sugar made it easier to stay awake. Cortisol, an indicator of stress, was elevated at the beginning of the ride, but declined towards the end, suggesting that they were adapting to the psychological stresses of the ride. Sleeping heart rate and blood pressure were normal for Penseyres and slightly higher for Haldeman. Both experienced some numbness and/or soreness in the hands, feet, and posterior.

They had a remarkable recovery after 6-7 hours of sleep and a complete recovery in two weeks. It was concluded that the effort resulted in minimal physical damage. Cycling across the country in 7:14:55 will beat you up, but it won't kill you. It may take a while to recover, but recovery will be complete. Granted, these are two exceptional athletes, but the results of this study are encouraging to the rest of us.

Conclusions
So, is excessive exercise bad for your health? Maybe. Maybe not. We can avoid most of the damage by being careful. The possibility of bone loss is troubling, however. Until the effect is confirmed and we know the cause, there(s not much we can do about it. The dangers of cell damage caused by increased free radicals with endurance exercise may not be a problem since the trained body has its own defense mechanism. Nevertheless it wouldn't hurt to eat foods high in antioxidants, especially vitamin E.

Our body has proven to be a magnificent piece of engineering, with a remarkable ability to adapt to stress. So let's stop worrying and go for a ride, maybe even an excessive one!