2.2. Variables and Testing Procedures

The variables in this research included (in the testing order) anthropometric indices, the degree of knee hypermobility, and isokinetic parameters of leg musculature (hamstrings and quadriceps muscles) in an open kinetic chain.

The anthropometric indices included body height (expressed in centimeters), body mass (expressed in kilograms), body mass index (BMI), and leg dimensions. The leg length was measured with an anthropometer such that the subject stood with his legs extended, while the measurer placed the lower arm at the point of support with the base. The anthropometer was placed perpendicular to the base, and the upper arm was placed on the lateral proximal tip of the upper leg. To measure the length of the shin, the subject stood upright while the researcher measured the length of the lower leg with a shortened anthropometer so that the lower leg was placed exactly on top of the lateral malleolus and the upper leg was placed exactly on the top of the lateral condyle of the tibia. The measurements are expressed in centimeters.

Knee hypermobility was measured (degree of knee hypermobility—Hdeg) by the subject sitting on the floor, while legs were stretched with heels placed on a bench 20 cm high. The tester placed the goniometer (Pasco PS-2002 Xplorer GLX, Roseville, CA, USA) in the center of rotation of the knee and directed one extended arm toward the lateral proximal tip of the upper leg and the other toward the lateral malleolus of the same leg. The same procedure was used for the other leg.

Isokinetic testing was conducted using a Biodex System 4 isokinetic dynamometer (Biodex Medical Systems, Inc., Shirley, NY, USA) by an experienced researcher. The individuals were fastened with belts around the upper body and upper leg of the hips, the axis of the dynamometer was directed to the area above the lateral condyle of the femur, and the bandage on the lower leg was placed just above the lateral malleolus. The axis of the dynamometer was placed at the point of rotation of the knee, which could be additionally checked by extending and bending the subject’s knee. Before the measurement, the subject received detailed instructions about the test and the specifics of the isokinetic movement. It should be emphasized that during the actual testing, the participant was vocally motivated to perform to the maximum extent throughout the entire testing. The tests included concentric–concentric tests at an angular velocity of 60°/s and concentric–concentric tests at an angular velocity of 180°/s. All isokinetic testing was conducted by the same experienced tester/researcher to reduce the measurement error.

For the purposes of this research, the subjects were measured in a range of motions of 70 degrees so that, in the initial position, the lower leg was placed vertically against the floor. The reason for this lies in the fact that an amplitude of 90 degrees, when the body is placed upright in a sitting position, can cause the subject to be unable to perform full movement due to the possibly insufficiently flexible muscles in the back of the upper leg, which causes them to perform an isometric contraction instead of the final movement [25]. Similarly, given that the research required only the maximum result in extension and flexion (peak torque), i.e., their ratio, and given that the maximum result in isokinetic measurements at a speed of 60 degrees per second occurs at 54 degrees from the start of extension (quadriceps) and 33 degrees from the start of knee flexion (hamstrings), it was not necessary to test with full amplitude. At an angular velocity of 180 degrees per second, the maximum result occurs on average at approximately 43 degrees of extension and 40 degrees of flexion [25].

The isokinetic variables included in this research were the H/Q ratio of the right leg at 60°/s (H/Q60R), the H/Q ratio of the left leg at 60°/s (H/Q60L), the average H/Q ratio at 60°/s for both legs (H/Q60), the H/Q ratio of the right leg at 180°/s (H/Q180R), and the H/Q ratio of the left leg at 180°/s.—(H/Q180L), and the average H/Q ratio was 180°/s for both legs (H/Q180). The H/Q strength ratio was obtained by dividing the maximum moment of strength of the hamstrings by the maximum moment of strength of the quadriceps. The isokinetic testing protocol was conducted on both legs equally, and the procedures are displayed in Figure 1.

Testing protocol for the isokinetic variables.