I usually use hurdle mobility as part of a dynamic warmup.
SE is also special endurance Running A’s, etc are used for Strength Endurance. Now that you mention it, I’m not exactly clear myself on the difference (is there one) between speed endurance and special endurance. I tend to think of speed endurance as a small number of runs up to 200m. Special endurance includes longer runs, maybe out to 600m. Anyone know if this is correct?