The purpose of the master's thesis was to examine the relationship between hip and trunk muscle strength with the results of a modified one-legged long jump test, in which, in addition to jump length, we also measured lateral deviation from the expected push-off direction. We included 80 professional handball players (age 22 ± 4 years; body height 189.8 ± 5.6 cm; body mass 90.8 ± 10 kg) in the research. The measurement protocol consisted of three one-legged standing long jumps with each leg, three one-legged landings on a force plate with each leg, and three repetitions of a unilateral isometric strength test of the hip muscles (extension, flexion, abduction, adduction) and trunk (lateral bending). Hip muscle strength was evaluated by a maximum voluntary isometric contraction torque and rate of torque development. Statistical analyses were conducted separately for the dominant and non-dominant leg and the preferred and non-preferred legs. Using a paired samples t-test, statistically significant differences were found between the dominant and non-dominant legs for jump length, lateral deviation from the expected push-off direction, and the maximum strength of hip extensors. In most cases, the differences found between legs were small (d = -0.29-0.34). Pearson's correlation coefficient revealed weak to moderate correlations between one-legged long jump results and hip and trunk muscle strength (r = 0.23-0.39). Multiple regression analysis found that jump length with the dominant leg is most influenced by the rate of force development of hip flexors (R2 = 0.15), while lateral deviation and angle of deviation from the expected push-off direction are most influenced by the rate of force development of hip abductors. Jump length with the non-dominant leg is influenced by the maximum strength of hip extensors (R2 = 0.14). With the preferred leg, the maximum strength of hip adductors had the greatest influence on jump length (R2 = 0.12), and the same variable also influenced jump length with the non-preferred leg, explaining 20.3% of the variance. We also determined the influence of two variables on lateral deviation in the non-preferred leg (maximum strength of hip extensors and rate of force development of hip extensors), as well as the influence of the maximum strength of hip extensors on angle of deviation in the non-preferred leg. The main finding of our research is that hip strength affects lateral deviation in the one-legged standing long jump, suggesting that the modified one-legged long jump could be used as a screening test to identify deficits in hip muscle strength in athletes.
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