For sprinting your endurance?? will be fine if you gradually increase your volumes and do more general muscular endurance work.
I believe issues with LBD will affect your knees, your coach was probably noticing you weren't picking your knees up high enough on the hills. Generally weakened or fatigued back conditions will cause mechanical problems through the kinetic chain. Those mechanical problems can be self manifesting resulting in severe strain at certain joints or muscles which can result in injury.