Squat Jump Performance and Chiropractic Ankle Manipulation

LEM - Lower Extremity Manipulation:

Subjects assigned to the LEM Intervention Group will receive a short lever, high velocity, low-amplitude distractive (caudal) thrust directed at the talocrural joint. The treating chiropractor will deliver the LEM to the right ankle then the left ankle. LEM is an adjustment for long axis distraction of the tibiotalar joint with the goal to improve dorsiflexion of the ankle joint.

• Lower Extremity Manipulation

Subjects will be instructed to jump upwards from the starting squat position as high as possible. Subjects will perform 3 to 6 jumps with 3 consecutive jump heights being within 5% of each other to ensure maximum jump height is achieved. There will be a one-minute rest between jumps.

• Starting position. Subjects will assume the starting squat position with their hips at 90°, knees at 120°, and ankles at 85° as positioned by the PI. An adjustable plyometric jump box will be used to standardize the starting position. Hands will be resting across their chest with the trunk and head positioned straight ahead.
• Squat Jump: Subjects will be instructed to jump as high as possible and land in a comfortable position. Hands will remain across the chest for the duration of

The Optojump photoelectric cell system (OptoJump) will be used to record jump height. OptoJump demonstrates strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height

Knee-to-wall ankle dorsiflexion test:

• Ankle dorsiflexion ROM (distance from wall - cm) is the maximum distance of the big toe from the wall while maintaining contact between the wall and the knee with the heel on the ground.
• The subject will repeat the Knee-to-wall ankle dorsiflexion test three times at this maximum distance to allow the PI to record three goniometer measurements of ankle dorsiflexion ROM (degrees°).

Squat Jump Muscle Parameter: The Gyko inertial sensor system (Gyko) will measure the velocity of the jump to calculate an estimate of the contraction velocity of leg muscles, force-velocity curve.

The reliability and concurrent validity of Gyko to measure jump height and in-turn estimate muscle function parameters is limited in the literature. The control group in the current study will allow us to address concurrent validity and reliability of Gyko to measure jump height. Jump height measured by Optojump is the gold-standard field base device. Comparison of Gyko to Optojump measurements of jump heights will determine concurrent validity of Gyko to estimate jump height. The use of evidence-base biomechanical formulas to calculate an estimate of contraction velocity of leg muscles during SQJ's depends on recording reliable and valid measurements of jump heights; and in turn, establish the reliability and face validity of Gyko to estimate muscle function parameters.