There is a difference between something happening as a by product of pushing themselves very hard (yes people do pass out during such tests, but this is not the aim) and actually thinking that this is a required part of the process, which sadly all to many people seem to think. You (should) reach MHR before passing out, with a reasonable safety margin, i.e. if you go to the point of passing out and then look back at the data, your HR would have reached the peak some time before the point where you actually become unconscious, therefore, there is absolutely no need to push to the point for throwing up or passing out under the impression that you wont have completed the test adequately.