This study looked at the association between running mechanics and hamstring injuries in both a retrospective and prospective design. The authors documented the motions of the pelvis and trunk in addition to the usual lower extremity measurements. The subjects were 30 male soccer players between the ages of 18 and 35 who had a history of hamstring injury during the previous 2 years, but presently had no symptoms. They added 30 matched control subjects without hamstring injury.