I have weak hamstring and glutes -- I get the numb leg feeling when running at high intensity. I think it is due to my inability to continue to absorb the impact forces at higher intensity. I can run much harder on grass and trails than on the track or road due to this weakness.
To force adaption, I currently run in light shoes (Addidas Hagio) on hard surfaces to get adapted to impact. Is this the right approach? Or should I be wear super soft trainer shoes and run on grass/trails to avoid impact?