Assessing the countermovement jump provides clinicians insight into the tissue capacity during rehabilitation and may guide decision-making. In part one, Helen Bayne discussed force plates, their use, and applicability within the clinical rehabilitation context. In part two, Helen uncovers how to assess asymmetry and interpret the testing results to improve return to sport decision-making.
Minnesota Twins center fielder Byron Buxton jumps up and attempts to catch a home run from Boston Red Sox right fielder Hunter Renfroe (not pictured) in the fifth inning at Target Field. Mandatory Credit: Jesse Johnson-USA TODAY Sports
The countermovement jump (CMJ) provides clinicians with an easy-to-use, practical, and sport-relevant tool to assess tissue capacity and performance throughout rehabilitation. Return to sport (RTS) assessments typically compare the involved side to the uninvolved side. Practitioners score popular functional tests according to the number of repetitions to failure (e.g., single-leg squat test), the number of repetitions within a specific time limit (e.g., single-leg side-hop test), or the maximum jump height or distance (e.g., horizontal single-leg hop test)(1,2). While these outcome measures provide valuable information about the overall capacity of the patient, clinicians may be unable to detect other neuromuscular changes present after injury. For example, the horizontal single-leg hop test does not indicate symmetrical lower limb kinematics or kinetics in patients who have undergone anterior cruciate ligament (ACL) reconstruction. Patients tend to offload the knee joint to favor the hip and ankle(3).
Most clinics do not have the resources to easily assess joint kinematics and kinetics and report on those variables in a reasonable time frame. However, the increasing viability of force plates that measure vertical ground reaction force presents practitioners with a tool to provide objective data in real-time. Data obtained from force plates can inform the practitioner about mechanical determinants and movement strategies during vertical jumping and landing tasks. There is growing evidence of interlimb asymmetry in previously injured athletes, with the dominant focus on the performance of the CMJ during rehabilitation after ACL reconstruction(4,5,6).
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