Once a substantial level of fitness has been attained and sustained for more than six months and in many cases, for years, a few options are available to the exerciser:
1. If that level of fitness is satisfactory, the lifestyle which has supported that condition can be continued and in many cases reduced in some manner if maintenance is the desired objective;
2. If the option is the pursuit of the next level of conditioning, a different , more specific approach must be developed.
In general, higher levels of fitness and conditioning are achieved by increasing intensity and allowing for adequate recovery. Basically, there is a simple explanation for these requirements. The healthy human physiology is resistant to change. The primary physiological imperative dictates the maintenance of homeostasis (status quo). Simply stated, our bodies resist any stimuli which promote physical upheaval. At this point it should be stated that once moderate levels of fitness have been attained, the associated health related benefits diminish in rather rapid proportions. The capacity to run a 5 minute mile does not markedly improve the health status of a 6 1/2 minute miler. The apparent conditioning benefit necessary to achieve the aforementioned performance improvement does not correlate to much more "cardiovascular protection" for example.
Therefore, if one is predisposed to attain the next level in the fitness or performance progression some basic training adjustments are required. It must be understood that the basic objective in increasing cardiovascular function is the capacity to utilize oxygen at progressively higher rates. This increased oxygen consumption can only be attained in one way. Some mechanism or combination of mechanisms must be stimulated or "tapped into" in order to induce the corresponding physiological systems to increase their capabilities. Simply stated, chronic or repeated bouts of exercise which demand higher than normal (for that individual) levels of oxygen use must be experienced and recovery completed in order to achieve the next level of cardiovascular ability.
In practical terms, how is this accomplished? Generally, the formula is simple and objective. On an individual basis it is complex and subjective. However, for the sake of helpful dissemination of information the general formula will be presented. At these higher levels of fitness most increases in the duration (length) of exercise sessions do NOT increase either the demand for or the utilization of higher rates of oxygen consumption.
The element which appears necessary in order to successfully elevate the capacity to utilize oxygen and therefore "work'" or exercise at higher levels is that of increased intensity. Ordinarily, this boost in exercise intensity requires a decrease in duration. A simple analogy expresses the concept that one can not sprint for a mile and conversely if one has sprinted, one has not covered a mile. It must be further understood that it is necessary to incorporate some semblance of "sprinting" into at least some of the training sessions of the elite fitness advocate.
In the simplest example of cardiovascular training (a run) the element of heightened intensity may be expressed as either increased pace or speed. The exerciser must utilize this component either intermittently or for the entire duration of the necessarily shorter exercise session.
For example, the runner who normally runs at a 7 minute mile pace for 5 miles must attempt to run at a 6 1/2 minute mile pace for 3 or 4 miles. Alternatively, the same runner might "pick up" the pace of that 5 mile run at particular sustained intervals within that run which require higher levels of oxygen delivery and use. These are basically the only methods by which the muscular demand of the "users" of oxygen (the running muscles) can dictate to the deliverers of the oxygen (the heart and circulatory system) that their capacities must be escalated.Lastly, this increased intensity will require that deeper inroads into the recovery (adaptive) process will be provoked. It is therefore vital that the exerciser gradually insert these more intense exercise sessions into a general regimen of training. Secondarily, an acute sense of recovery must be developed in order that the trainee might "feel" when NOT to "push too hard" and when to extend rest periods. The higher levels of cardiovascular fitness must be courted in a subtle manner; they simply will not succumb to a blind charge of sheer will and more effort.