i see what youre saying, it may be that we just have to settle for a difference in opinion. i like to put speed in everything…so yeah:tumble:. im not saying 23.91 is slow by any means, but if expect to run sub 51 youre probably gonna have to be faster no matter what. i, of course, am not recomending that you focus entirely on speed or endurance, but i think at this point in your career, speed should be given more priority. a 51 second 400 means approximately 12.75 second 100m segments. i think that no matter how good your endurance is, you arent going to run that with an 11.87 PR in the 100. not yet at least.