Rearfoot running usually coincides with lack of glute activation/overactive quads. When your pelvis isn't inherently in an optimal position and you try to run on the balls of your feet there's a ton more force involved then if your pelvic position was optimized. If you ever get a chance, try doing about a 30 minute walk up a slight incline, focusing on contracting your glutes. The next day see if you notice a difference in how you walk and how your foot inherently hits the ground. Also have you ever worked much on hip flexor strengthening? Given your body structure that in combo with glute activation work (which I know you're already doing), usually does good things.
I think you're also getting a form of neural stimulation with the sprints. I think I wrote about it before way back when. If you're a bball player and you go out and do some top speed sprints beforehand (minutes or even a day), it makes everything taking place on the bball court seem slower and jumps seem easier. The problem is they can also contribute more to fatigue, so not everyone is in position to take advantage of them.
ya, growing up i had NO glutes, NO hamstrings, and good quads.. so that might explain why i became a heel->toe guy.. i mean if i sprinted MAX, i wouldnt be heel->toe... but for something like a 400 i would be, because my calfs would die 200m in and i'd be sore for 7 days or so.. so on distance sprints, or jogging on my toes for long distance, they would just completely get torn to shreds, so i always heel->toed them.
i've done that walk thing you describe, but i don't stick to it :/ i have noticed a different feel the next day.. but nothing i could explain.. very slight change.. i did it on a flat surface though not an incline.
ya im definitely getting neural + structural from the sprints.. plus i get to somewhat deload from jumping mentally, which makes me damn hungry to go out there and dunk after a week off.. so a few things contributing i think.. but i really like these 400's alot.. can't wait to run them this week! taking a week off jumping and doing 400's + squatting + lunges..
what type of hip flexor work do you recommend? i have gotten real lazy with core, and even lazier with hip flexor.. ive rarely done any hip flexor work, thats probably because they are very week.. i've only gone through a few phases of hip flexor work and i usually stopped just cause they get so tight/sore.
thanks for the post man!
peace