The physiology of marathons is typically associated with high demands on a marathon runner's cardiovascular system and their locomotor system. The marathon was conceived centuries ago and as of recent has been gaining popularity among many populations around the world. The 42.195 km (26.2 mile) distance is a physical challenge that entails distinct features of an individual's energy metabolism. Marathon runners finish at different times because of individual physiological characteristics. The interaction between different energy systems captures the essence of why certain physiological characteristics of marathon runners exist. The differing efficiency of certain physiological features in marathon runners evidence the variety of finishing times among elite marathon runners that share similarities in many physiological characteristics. Aside from large aerobic capacities and other biochemical mechanisms, external factors such as the environment and proper nourishment of a marathon runner can further the insight as to why marathon performance is variable despite ideal physiological characteristics obtained by a runner.
History The first marathon was perhaps a 25 mile run by Pheidippides, a Greek soldier who ran to Athens from the town of Marathon, Greece to deliver news of a battle victory over the Persians in 490 B.C. According to this belief, he dropped dead of exhaustion shortly after arriving in Athens. Thousands of years later, marathon running became part of world sports, starting at the inaugural Marathon in the 1896 Modern Olympic Games. After around 40 years of various distances, the 42.195 kilometer (26.2) mile trek became standard. The number of marathons in the United States has grown over 45 times in this period. With an increase in popularity, the scientific field has a large basis to analyze some of the physiological characteristics and the factors influencing these traits that led to Pheidippides's death. The high physical and biochemical demands of marathon running and variation across finishing times make for an intricate field of study that entangles multiple facets of human capacities.
Energy pathways during exercise Humans metabolize food to transfer potential energy from food to adenosine triphosphate (ATP). This molecule provides the human body's instant accessible form of energy for all functions of cells within the body. For exercise the human body places high demand for ATP to supply itself with enough energy to support all the corresponding changes in the body at work. The 3 energy systems involved in exercise are the Phosphogenic, Anaerobic and Aerobic energy pathways. The simultaneous action of these three energy pathways prioritizes one specific pathway over the others depending on the type of exercise an individual is partaking in. This differential prioritization is based on the duration and intensity of the particular exercise. Variable use of these energy pathways is central to the mechanisms that support long, sustained exercise—such as running a marathon.
Phosphogenic The phosphogenic (ATP-PC) anaerobic energy pathway restores ATP after its breakdown via creatine phosphate stored in skeletal muscle. This pathway is anaerobic because it does not require oxygen to synthesize or use ATP. ATP restoration only lasts for approximately the first 30 seconds of exercise. This rapid rate of ATP production is essential at the onset of exercise. The amount of creatine phosphate and ATP stored in the muscle is small, readily available, and used quickly due these two factors. Weight lifting or running sprints are examples of exercises that use this energy pathway.
Anaerobic The anaerobic glycolytic energy pathway is the source of human energy after the first 30 seconds of an exercise until 3 minutes into that exercise. The first 30 seconds of exercise are most heavily reliant on the phosphogenic pathway for energy production. Through glycolysis, the breakdown of carbohydrates from blood glucose or muscle glycogen stores yields ATP for the body without the need for oxygen. This energy pathway is often thought of as the transitional pathway between the phosphogenic energy pathway and the aerobic energy pathway due to the point in exercise this pathway onsets and terminates. A 300-800 meter run is an example of an exercise that uses this pathway—as it is typically higher intensity than endurance exercise, and only sustained for 30–180 seconds, depending on training.
Aerobic (Oxidative) The aerobic energy pathway is the third and slowest ATP producing pathway that is oxygen dependent. This energy pathway typically supplies the bulk of the body's energy during exercise—after three minutes from the onset of exercise until the end, or when the individual experiences fatigue. The body uses this energy pathway for lower intensity exercise that lasts longer than three minutes, which corresponds to the rate at which the body produces ATP using oxygen. This energy system is essential to endurance athletes such as marathon runners, triathletes, cross-country skiers, etc. The Aerobic Energy Pathway is able to produce the largest amount of ATP out of these three systems. This is largely because of this energy system's ability to convert fats, carbohydrates, and protein into a state that can enter the mitochondria, the site of aerobic ATP production.
Physiological characteristics of marathon runners
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