Last year around this time I pulled my left hamstring pretty bad doing sprints---it healed and is strong again---so today I go to the track and am doing sprints and I pulled my right hamstring---its not a bad pull---but its definitely tweaked---why is this happenining?---I ran a half mile warm-up---then stretched afterwards---then started my sprints--it happened after about 10 sprints----so proper warm-up is not the problem----I went out and drank a good amount of alcohol last night---is there any correlation between the two? Looking for answers