title: The stretch-shortening cycle of the quadriceps femoris muscle group measured by isokinetic dynamometry.
abstract: The ability to measure the stretch-shortening cycle of isolated muscle groups has been limited. The purpose of this study was to measure the stretch-shortening cycle of the quadriceps femoris muscle group. Twenty-four volunteer subjects, 12 men and 12 women, participated in one test session; five men and five women also participated in a retest session; to examine the reliability of the test. A concentric contraction of the left quadriceps was measured for peak torque and time to peak torque on a Biodex isokinetic dynamometer under three conditions: 1) passive stretch before a concentric contraction, 2) isometric preload before a concentric contraction, and 3) eccentric preload before a concentric contraction. Conditions 2 and 3 showed a significant increase in peak torque production compared to condition 1 (p < 0.01). A significant difference was found for all three conditions between the men and women, with the men producing greatest peak torques. Conditions 2 and 3 also showed a significantly decreased time to peak torque compared with condition 1 (p < 0.01). The testing protocol was found to have high reliability. This testing protocol could be used to further study the stretch-shortening cycle in the quadriceps femoris muscle group.
authors: Kentucky Rehabilitation Services, Ft. Mitchell 41017.
authors: K
authors: K
authors: Helgeson
authors: R L
authors: RL
authors: Gajdosik
mesh_terms: D000328:Adult; D016552:Ergometry / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*