Endurance as a Primary Physical Component in Cross Country
It can be said that a high level of endurance is the most important of the five primary physical components found in a cross country runner. The danger in making such a statement is that it may diminish the importance of the other four: speed, strength, flexibility and coordination in setting up the training plan of that runner. A planned balance training scheme addresses all five of the primary physical components, but it scales the importance of each to the specific demands of the athletic activity.
It can be said that a high level of endurance is the most important of the five primary physical components found in a cross country runner. The danger in making such a statement is that it may diminish the importance of the other four: speed, strength, flexibility and coordination in setting up the training plan of that runner. A planned balance training scheme addresses all five of the primary physical components, but it scales the importance of each to the specific demands of the athletic activity.[/img_text_aside]
Endurance is worked on and developed most often in a cross country runner, while the other four are developed to a lesser degree over time. However, a player in a transitional game like soccer will have different endurance needs than a cross country runner, who has different endurance needs from a basketball player. It follows that the endurance training for each sport should reflect these differences.
Endurance can be subdivided into two broad categories: aerobic endurance and anaerobic endurance. In turn, aerobic endurance can be further subdivided into two categories: aerobic capacity and aerobic power. Aerobic capacity is the ability to perform large amounts of aerobic work, while aerobic power is the ability to perform a single extended aerobic effort over time. Aerobic capacity training activities involve intensities sufficiently low enough to keep the body in an aerobically fueled state. Oxygen and nutrients are metabolized at a rate that generally keeps up to the intensity demand without leaving immediate and excessive byproducts of fatigue in the muscle cell. Simply stated, aerobic capacity endurance is the ability to withstand low levels of fatigue and this is but one example.
Aerobic power, measured as VO2 max, is the most often used measure of endurance fitness. VO2 max can be defined as the maximum amount of oxygen that the heart can both pump to the working muscles, and the amount that the working muscles can extract from the blood in aerobic respiration. In absolute terms, it is expressed in milliliters of oxygen extracted, per kilogram of body mass, per minute.
Each athlete’s VO2 max is ultimately determined by the genome, and studies have shown that an individual’s peak VO2 max can be reached with mostly aerobic training in about 12 to 18 months. After that, its improvement levels off and will not improve significantly even with large volumes of work. Once that peak level has bee reached, training should focus on work at a high percentage of VO2 max for longer periods of time to improve aerobic running economy.
At the opposite end of the energy continuum from VO2 max is anaerobic work. However, in the conversation of endurance, to label something as simply anaerobic is not good enough. A distinction needs to be made between alactate anaerobic work and lactate anaerobic work. Any reference to endurance found in the alactate energy system working at full capacity is found in the length of time creatine phosphate molecules remain abundant and available for ATP re-synthesis. Usually, 85% of the supply is exhausted after seven seconds of short burst, high intensity work, with another 10% gone by 30-40 seconds.
In the anaerobic lactate energy system there is an ongoing build up of lactate and hydrogen ions from glycolysis which if continued would force the runner to have to stop. The individual ability to withstand the decreasing levels of pH and still maintain a reasonable level of skeletal muscle contractions defines anaerobic endurance and thus glycolytic fitness. An example of this is often seen as comparisons in performance as the end of a race nears and the runners are all running at full speed in order to determine the winner. The runner that maintains very high finishing speed, effective muscle coordination and ideal postural position will often be the most successful. This is anaerobic glycolytic endurance.
Glycolytic fitness can be considered as two sub-components: glycolytic capacity and glycolytic power. Glycolytic capacity is defined as the ability to perform large amounts of anaerobic work, while glycolytic power is defined as the ability to perform a single extended anaerobic effort over time. The cross country runner’s ability to finish a race strongly while experiencing oxygen debt and the associated acidosis is part of those runners’ glycolytic power capabilities.
Improving the endurance quality of the glycolytic energy system is part and parcel of training for a cross country runner. It involves training intensities sufficiently high enough to force the body into a glycolytically fueled state for a time. While not an every day training stimulus it occurs often enough in a microcycle to effectively increase the ability to tolerate the effects of acidosis over time.
While equal distributions of training time and effort are not desired among the five primary physical components for a cross country runner, it is important to realize how each of the five components influences the ability to do the others effectively. The art of coaching involves understanding these inter-relationships so that a proper sequencing of training loads can be applied to the athlete.