Quad Function And Hop Testing
Horizontal Hop Tests For Distance
Single – legged hop ability is a performance based measure that is commonly used to assess the force production & management capacity of the lower limb, and to assist decision making about an individual’s readiness to return to sports or higher level activities.
These hopping tests are often described as “functional” or task-specific tests, but the problem with tests like this is that individuals can find ways to get better at the task while still demonstrating limitations in some key muscular and joint capacities.
To avoid making this mistake, we need to ensure that we have a clear understanding of what we’re actually trying to measure during the test, instead of simply just trying to pass the test. There’s a BIG difference.
For example, building a quadricep that can manage & produce high forces at high speeds are key capacities that need to be developed after ACLR.
A single – legged forward hop test for distance is a common test used after ACLR to determine if the individual is ready to return to sport. However, during the propulsive phase of these forward hop tests for distance, the capacity of the knee is not challenged a great deal. Research exploring the load profiles across the lower limb during these tests show that the knee contributes around 12% of the force production. The propulsive phase of this hop is mainly driven by the hip and ankle (around 88%).
Propulsion vs Landing
That being said, we cannot say that these hop tests for distance don’t give us any insight into the capacity of the quads/knee. During the landing phase of a forward hop, the knee contributes around 65% to the management of forces, so it can certainly provide some valuable insight if we are observing the strategies used to manage those forces.
For the knee to demonstrate this contribution, the trunk needs to stay relatively upright. If the trunk flexes via the pelvis (where the trunk and pelvis are flexing over the femur as a single unit), then workload is shifted into the hip extensors, and this reduces the demand on the quads/knee.
So, it’s key to appreciate that in order to gather valuable information from these tests, we need to have a solid biomechanical understanding about the load profile experienced through each joint, and how certain joints can influence the demand on their neighbouring joints and associated muscular tissues.
Use Jump Height Instead
While we can use the landing phase of a forward / horizontal hop for distance to identify how confident the knee is with managing forces at speed, it’s best to start simple with a clearer measure. Clinically, we will place more focus on vertical force production measures to get a clearer insight into quad function.
During the propulsive phase of a vertical hop, the quad contributes three times more than it does during a horizontal hop, so deficits in quad capacity are much more obvious during a vertical hop.
Within-limb compensations such as greater trunk lean (for more glute contribution) are still evident during the propulsive phase of a vertical hop, but it is much easier to limit the use of these compensatory strategies prior to propulsive phase of a vertical hop relative to the landing phase of a horizontal hop where there’s much more coordinative demand.
Are You Assessing Capacity?
We’ve written in previous blogs about why we need to reconsider the performance of functional tasks to build muscular and joint capacities in a rehab setting. In this blog, we’re talking about why we need to reconsider the utility of functional tasks as a measure of performance to evaluate muscular and joint capacities.
Just because an exercise or test looks functional and appears to mimic the positions and postures that an individual experiences during real-world or sporting activities, it does not mean it’s giving you a clear insight into the capacity of the muscles & joints to handle and produce forces.
Both can certainly offer value, but we would always want to build muscle & joint capacity first, before we engage in task-specific activities.
Appreciating biomechanics is key here!
If you want to learn more, make sure to check out our courses! Also, take a look at the references below to explore further.
References
- Kotsifaki A, Whiteley R, Van Rossom S, et al. Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction? Br J Sports Med 2022
- Kotsifaki A, Korakakis V, Graham-Smith P, et al. Vertical and Horizontal Hop Performance: Contributions of the Hip, Knee, and Ankle. Sports health 2021