I have never come close to a score of 247, but want to know why the test ends at that point. Does a person running for that long and speed reach a maximum heart rate?
The reasoning behind this question comes down to a statistical standpoint moreso than a physiological standpoint. This is a "normative test" in which score values are only compared with others taking the test under the same protocol either within the current assessment, statewide, nationwide, etc. A score of 247 in my experience will indicate a value in the 99th percentile, hence therefore there is no purpose to exceed that max value since the majority can not reach that value. The value of 247 has probably been set through a natural process of math logistics that ellicited a "best fit" value to assess and compare athletic performance. Physiologically, a max heart rate will be reached within 5 to 10 minutes of this graded exercise test and remain at that level until the relative intensity decreases, so that reasoning is out the window. In respect to accreditation, I am a senior in my final semester of an exercise physiology program. Hope I answered your question.