• D M Pincivero, S M Lephart, and R G Karunakara.
• Neuromuscular Research Laboratory, University of Pittsburgh, PA 15261, USA.
• Clin J Sport Med. 1997 Jan 1; 7 (1): 11-6.

ObjectiveTo assess the relationship between concentric isokinetic quadriceps and hamstring strength values with the single leg hop for distance test, a closed kinematic chain activity.DesignCorrelational study.SettingNeuromuscular Research Laboratory, University of Pittsburgh.ParticipantsSubjects for this study consisted of 37 college-aged volunteers (21 men, 16 women: mean age = 22.76 +/- 3.52 years, height = 169.90 +/- 10.60 cm, weight = 69.31 +/- 14.60 kg) with no previous history of injury to the lower extremity.InterventionEach subject performed three trials of a single leg hop for distance test for the dominant and nondominant limbs followed by isokinetic evaluation. Isokinetic strength was assessed with the Biodex System II Isokinetic Dynamometer (Biodex Medical Inc., Shirley, NY, U.S.A.) for the quadriceps and hamstrings at preset angular velocities of 60 degrees/s (5 repetitions) and 180 degrees/s (30 repetitions). Before testing, each subject completed a dynamic warm-up period that consisted of submaximal cycling at a fixed cadence of 60 revolutions/min followed subsequently by quadriceps and hamstring muscle stretching.Main Outcome MeasuresThe distance hopped in centimeters was converted to a ratio of the distance hopped to the individual leg length measured from the anterior superior iliac spine to the medial malleolus. Isokinetic values were obtained for peak torque (Nm), peak torque/body weight (%), total work (Nm), and average power (W).Main ResultsLow to moderate significant relationships were found to exist between the single leg hop for distance test and the isokinetic variables for the quadriceps and hamstrings of both limbs at each test velocity. Significant correlation coefficients ranged from r = 0.33 to r = 0.69 at 60 degrees/s and r = 0.33 and r = 0.67 at 180 degrees/s. Correlation coefficients were found to be statistically greater for the hamstrings than the quadriceps for total work and average power at 60 degrees/s and for peak torque/body weight, total work, and average power at 180 degrees/s (p < 0.05).ConclusionsConcentric quadriceps and hamstring strength seem to demonstrate a significant contribution to the single leg nop for distance test; however, the hamstring muscles may play a more important role during the propulsive phase, thereby enabling subjects to jump further.

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