Comparison of Trunk Muscle Performance Between Sprinters With and Without Hamstring Strain Injury History

Muscle activation of external oblique, internal oblique, erect spinae, gluteus maximus when sprinting on the treadmill at 40% and 60% maximal speeds

Isometric muscle strength of trunk flexor is measured with Biodex System 4 Pro™ in sitting position

Isometric muscle strength of trunk extensor is measured with Biodex System 4 Pro™ in sitting position

Isometric muscle strength of trunk rotator is measured with microFET in hook-lying position

Muscle endurance of trunk flexor is measured with trunk muscle endurance test. It requires subjects to sit on the test bench and place the upper body against a support with an angle of 60˚ from the test bed. Both the knees and hips are flexed to 90˚. The arms are folded across the chest with hands placed on the opposite shoulder and toes are placed under toe straps. Subjects will be instructed to maintain the body position while the supporting wedge is pulled back 10cm to begin the test. The test ends when the upper body falls below the 60˚ angle. The time the subjects maintain will be recorded.

Muscle endurance of trunk extensor is measured with Biering-Sorensen test. It requires subjects to lay prone with the lower body fixed to the test bed at the ankles, knees, and hips and the upper body extended in a cantelevered fashion over the edge of the test bench. The test bench surface is approximately 25cm above the surface of the floor. Subjects rest their upper bodies on the floor before the exertion. At the beginning of the exertion the upper limbs are held across the chest with the hands resting on the opposite shoulders, and the upper body is lifted off the floor until the upper torso is horizontal to the floor. Subjects are instructed to maintain the horizontal position as long as possible. The time the subjects maintain will be recorded.

Muscle endurance of trunk lateral flexor is measured with side bridge test. It requires subjects to lay on an exercise mat (thickness, 2.5cm) on their sides with legs extended. The top foot is placed in front of the lower foot on the mat for support. Subjects are instructed to support themselves lifting their hips off the mat to maintain a straight line over their full body length, and support themselves on one elbow and their feet. The uninvolved arm is held across the chest with hand placed on the opposite shoulder. The test ends when the hips returns to the exercise mat. The time the subjects maintain will be recorded.

Muscle strength ratios of hamstrings eccentric contraction at 30 ˚/s angular velocity and quadriceps concentric contraction at 240 ˚/s angular velocity, quadriceps concentric contraction at 240 ˚/s angular velocity and hamstrings concentric contraction at 240 ˚/s angular velocity, bilateral hamstrings concentric contraction at 60 ˚/s angular velocity are measured

Hamstring flexibility is measured with 90-90 active straight leg test. It requires subjects to lay on the bed with hip and knee 90 degrees flexion. Subjects are instructed to extend their knee with hip 90 degrees flexion as possible. The knee angle is measured as hamstring flexibility.