I’m not a professional track and field athlete I’ll consider me a mid athlete in the way to be pro but ok, I did just tryied to mention to you my level.
Ok, first of all when I was at very begining of my season I started to feel some “electric touches” inside my right hamstring that made me feel a little nervous and in someway uncomfortable. I started to have this feelings when I was starting to do some max velocity drills (with wickets) because I had no experience at all in stretch my strides while running at a high speed. The answer to me (when “electric touches” raises) was not to do MVD and do workouts with a less speed over a 2 week meanwhile taking a very deep stretching sessions focusing in hamstrings.
I did hurdles sometime I’m not very experienced in that topic but logic says me that when you jump over a hurdle (with good technique and speed) you must be very flexible hamstring because almost one leg is parallell to ground while you are in fly phase.
In resume, hamstrings seem to occur when you don’t have necessary hamstrings elasticity / flexibility and very high corporal dehydration level (remember that you need to have a very hydrated body to make you muscles cramp free)
Don’t be afraid to do some track and field drills when you feel you have some hamstring cramp only do at a very low level with no speed at all and do a lot of hamstrings stretching.