The purpose of this study was to: (1) establish the reliability of a new unilateral concentric only horizontal jump assessment (HSJ) then compare the reliability of this test to other types of unilateral vertical and horizontal jumps; (2) compare the tests to whether they differ in their ability to determine limb asymmetries; and (3) investigate the relationship between these jumps and sprint running.Eighteen sportsmen performed unilateral jump assessments involving the horizontal squat jump, horizontal countermovement jump, horizontal repetitive jump, vertical squat jump, vertical countermovement jump, and vertical repetitive jump.Reliability for the new test was found to be the equal if not better than the other more established tests of leg power, with the within trial variation (CV=1.1–1.9%) and test–retest reliability (ICC=0.89–0.90). None of the tests were found to have greater discriminative ability in determining limb asymmetries. Stretch shorten cycle enhancement was greater in the vertical tests (12.1%) compared to the horizontal tests (1.3%). Horizontal jump assessments (r=−0.73 to −0.86) were found better predictors of 20-m sprint performance than the vertical assessments (r=−0.52 to −0.73), with the horizontal cyclic assessment being the best predictor (r=−0.86).Horizontal leg power assessment appears an inexpensive, easy to administer, reliable and valid method to assess unilateral leg power.