PERFORMANCE CYCLING CONDITIONING A NEWSLETTER DEDICATED TO IMPROVING CYCLISTS www.performancecondition.com/cycling How Your Body Works During Cycling Sean Wilson

Our bodies are composed of many different physiological systems including muscles, metabolism, heart, lungs, nerves, hor- mones, intestines, and skin (Table 1). These various physiological organs and systems work together to maintain the normal function, or homeostasis, of our bodies while we are riding. When we ride our bikes we stress our physiological systems, making them work hard to maintain homeostasis. We have all witnessed this when we go out for a hard ride. Our heart beats furiously to keep the muscles supplied with oxygen and glucose, we sweat to reduce the buildup of heat from our active muscles, and we breath hard to take in oxygen and remove carbon dioxide. Today we are going to take a integrative look at how your body reacts when you ride your bicycle and provide an overview of the adaptations which take place following a long-term training program. We will then look at some of the differences a novice rider and elite cyclist might have in terms of their adaptations and those of a masters athlete. In future articles we will detail how cy- cling effects the different physiological systems and what specific adaptations we might expect to occur following consistant train- ing.

How your body responds to a single training ride You get onto your bike and pedal down the street to meet your riding partners. Your body communicates that you are riding in two separate ways. First, your nervous system acts quickly, sending impulses from your brain to contract specific muscles. The result being that you turn over the pedals efficiently. If we take a closer look we see that the amount of muscle mass you con- tract is proportional to how hard you ride. When you ride easy you only need to contract a few mus- cle fibers, but as you ride faster you must contract a greater num- ber of muscle fibers. Second, your endocrine system sends hor- mone messages through your bloodstream, ensuring that the different physiological systems are coordinated together. Your hormones regulate many different body functions including tissue growth, metabolism, circulation, bone metabolism and reproduction. Several hormones which are important while you ride are epinephrine (adrenaline), which acts to increase heart rate and stimulates metabolism, and insulin and glucagon, which act to regulate glucose metabolism. The effects of exercise upon the function of hormone will be further explored in future articles.

Oxygen + Carbohydrates and Fats —> Work + Carbon Dioxide + Water + Heatat Your muscles keep contracting and turning the pedals by burning the food you eat (carbohydrates and fats) in the presence of oxygen. Carbon dioxide, water and heat are liberated through this process. Fueling the metabolic pathways and removing the waste products from your working muscles is not a trivial task. Your respiratory system provides for the exchange of oxygen and carbon dioxide. As you breathe in, the oxygen molecules cross from your lungs into the blood where they bind to hemoglobin within your red blood cells. The oxygen-enriched red blood cells are then transported to your working muscles through your cardiovascular system. Your heart is the engine—providing the force to move the blood cells, while your vasculature (arteries, veins and capillaries) is the roadway to and from your muscles. At your muscle the oxygen unloads from the red blood cell and crosses into the muscle fiber where it is used to burn energy and do work. The cardiovascular system also acts to carry fuels to and heat from your working muscles out to your skin where it is dissipated. The amount of air you breathe and blood you send to the muscles is dependent upon how hard your muscles are working. When you ride easy you don’t burn much energy or produce much heat so you don’t need to breathe hard or send much blood to the muscles. The harder you go the more oxygen your muscles need, while your breathing and blood flow increase accordingly. After meeting, you and your friends head out for a three-hour ride. As you continue riding you find that you become hungry and weak because you forgot to eat. Your body can store only enough carbohydrate for about an hour and a half of exercise. Although you have enough fat stored (even at 4% body fat) to ride all day, your body cannot efficiently metabolize the fat without burning car- bohydrates. After drinking some Gatorade and eating a Powerbar you feel much better. How do these foods get from your jersey pocket into the muscle? Let’s explore this in a bit more detail. The energy bar and Gatorade go from your mouth down to your stomach and are eventually passed through to your intestines. The fuels from foodstuffs you ate and drank are passed from the in- testines into your bloodstream. The carbohydrates can go directly out to the muscles while fats have to be further digested in the liver before the muscles can use them. Your endocrine and nervous systems regulate the digestion process, ensuring that the foods are broken down so that they are easily utilized and properly stored by your body tissues. Let’s recap what happens when you go out for a ride. You get on your bike and begin to ride. Your nervous system tells your muscles how hard to work and when to contract. This muscle contraction requires oxygen and energy, and produces carbon dioxide and heat. Your respiratory system exchanges oxygen for carbon dioxide, while your cardiovascular system carries the oxygen to the muscles, carbon dioxide back to the lungs, provides fuels to your body tissues and allows you to maintain your body temperature. Your endocrine system keeps your bodily functions coordinated through the actions of various hormones which circulate in your bloodstream. Training enhances performance through physiological adaptations. The stress of training allows you to become a stronger and faster rider. The amount of training stress is determined by the frequency, intensity and amount of time you ride. Through a balance of hard training and rest you will see the maximum improvement in performance. Training hard breaks down your physio- logical systems, while resting allows them to rebuild. Furthermore, in order to maintain these improvements in performance and physiological functions you need to train routinely. I know you have heard this before—listen to your body! It will tell you when it is time to train hard, and it will also tell you when you need rest. The tangible increases in both distance and speed you can ride after training are due to many small physiological adaptations. First, your nervous system has learned when and how hard to contract your muscles to make the pedals go around smoothly. At first you had a hard time, you had to think about how to make those muscle move, now it’s second nature. Second, your muscle function is enhanced. Following endurance training the oxidative function of your muscle fibers is increased. Third, your cardiovascular func- tion is enhanced. Your heart works more efficiently and the oxygen carrying capacity of your blood is increased. You also sweat more easily, cooling your body more efficiently. Fourth, your endocrine system adapts, better coordinating the other systems. One adaptation is that you become better able to mobilize and utilize fat stores after training. So you ask, why can’t I train like Miguel Indurain? Simply put, your training program must be tailored to meet both your needs and your abilities. The amount you can train is mostly determined by how much you have trained in the past and your current fitness level. Your parents also played a guiding role, giving you specific genetic traits which partly determined your athletic talents. I think that we all realize that the novice rider cannot perform as well as the professional. Physiologically speaking, the novice’s body systems are just not as well adapted to riding as the professional rider. The novice rider spends time training the muscles to turn the pedals around while the pro concentrates on having the stamina to ride 5 hours at 30+ mph. This is not to say that the novice athlete does not have the same ability as the professional, just that the novice has no training history. The idea of progressive overload training is based upon the idea that the stress of training leads to physiological adaptations and performance enhancements. As with any skill you learn, your body must learn in stages. Most of us didn’t go straight from kindergarten to college, there was much we had to learn in between. Similarly your body would not have the knowledge to go from training 150 miles/week to 500 miles/week. Like a kindergartner in a college class, your body would collapse under the strain. Even though the novice rider might only train 150 miles/week and the pro 500 miles/week, the two riders might have similar levels of training stress. As each rider trains the body responds through improvements in function and performance. Their muscles withstand harder and longer rides, their cardiovascular systems pump blood more effectively, even their intestines adapt, becoming better at extracting the nutrients from the foods they eat. The pro is just starting out at a higher level than the novice rider, since his physio- logical systems have been subjected to, and adapted to, repeated increases in training load. To summarize, your body will adapt to the stress of riding through adaptations in your body systems. The amount of stress is determined by the frequency, intensity and time of your ride. Riding tears down your physiological systems while rest allows them to become stronger. The amount of training you need to improve your riding ability is determined by your prior training history, your current fitness level and your genetics.

Am I older and wiser or just slower? Riding as a masters athlete is a mixed blessing. If you have been racing for a number of years, your racing experiences can make up for many deficiencies in your fitness. However, you will find from year to year that your body is changing. Arguably, the most important change is that your cardiovascular function decreases with age. Over about the age of 35 your maximum heart rate decreases, as does your maximum cardiac output, and your maximum oxygen consumption (VO2 max). The decline in your ability to perform is slow (as I recall, about 5%/decade), but will catch up with you. Older athletes also appear to have a smaller muscle mass than younger athletes. Unfortunately, I have not seen any good documentation of how aging affects your body’s ability to adapt to training. I would hypothesize that as you become older your body will have a harder time adapting to the stresses of training. Maybe you don’t recover as quickly from a hard ride as when you were younger or you just don’t have that strength which gave you that extra edge over the competition. To reiterate the basic point of this article - The stress of training causes improvements in your body systems. So the best thing you can do for yourself is listen to your body. Make sure that your training program does not radically overload your body sys- tems. Make incremental, small changes to your training program, vary your workouts from day to day, and build plenty of rest into your training plan. All of this will ensure that your body systems adapt fully so that you can perform to the best of your ability. Stay tuned for future articles where we will explore in detail how cycling affects each body system.