Final answer:
Physical fitness is a continuous concept characterized by the gradual and ongoing improvement of bodily functions through physical exercise, such as the endurance built by a marathon runner over time.
Step-by-step explanation:
The concept of physical fitness is continuous in nature as it represents an ongoing process of development and progression in an individual's bodily functions and abilities. Unlike certain physical entities that are quantized, physical fitness can range and improve continuously over time through consistent physical exercise.
An example of this would be a marathon runner, who through continuous training and effort, can enhance endurance and cardiovascular health. This is also reflective of the continuous development view, where improvement is seen as a gradual enhancement of existing skills. Fitness levels are not just individual metrics but are often considered relative to the population, where researchers assess an organism's fitness based on the potential contribution of additional offspring to the next generation.