In the world of strength and conditioning, athletes often perform hundreds or even thousands of jump-based exercises or movements throughout their annual training cycle as a means to develop explosive power and athletic performance. For these athletes, jumping is only part of the equation; landing safely from each jump in a manner that minimizes risk of knee injury bears immeasurable importance.
While strength and conditioning coaches often spend much of their time instructing their athletes on the mechanics of maximizing jump performance and explosive power (and rightfully so), not as much instruction or time is typically given towards landing safely or efficiently.
This is problematic since poor landing mechanics can significantly increase injury potential to the athlete, notably to the knee. Over 25% of all athletes who experience an ACL tear will not return to their previous activity levels even with successful surgery and rehabilitation, and athletes who undergo ACL reconstruction are 15 times more likely to re-rupture than those without history of ACL rupture.1,2Over 25% of all athletes who experience an ACL tear will not return to their previous activity levels even with successful surgery and rehabilitation. Click To Tweet
While training for maximal jumping ability is critical to optimizing an athlete’s performance, optimal vertical jump performance doesn’t mean much if an athlete sustains an injury upon landing. As such, optimal biomechanics when landing from a jump task are just as critical to develop as when executing the jump itself.
Why Look at Jump Landing Mechanics?
While contact-based knee injuries within sport are essentially non-preventable, non-contact knee injuries should be of particular interest to strength coaches and clinicians due to the largely modifiable neuromuscular factors that can be implemented to reduce or eliminate their occurrence.3
Non-contact knee injuries are prevalent within sport, with approximately 18% of these injuries arising within game play and 37% arising within practice or training sessions.4 Biomechanical errors involving knee valgus and stiff landings, among other such faults, are associated with increased injury risk to the athlete.
While numerous movement screening protocols have been designed to identify potential injury risks and aberrant movement patterns, many of these screens do not analyze an athlete’s jump-landing mechanics—an integral sport-specific task for many athletes. This is not to say that other screening protocols should be discouraged; rather that the coach or clinician must account for all facets of the athlete’s sport and implement movement screening protocols in line with their sporting tasks, including landing from a vertical jump.The coach or clinician must account for all facets of the athlete’s sport and implement movement screening protocols in line with their sporting tasks. Click To Tweet
As an example, Everard et al. conducted a research study to identify the relationship between the Functional Movement Screen (FMS) and the Landing Error Scoring System (LESS). While both systems have been shown in numerous studies to be reliable and valid, the results from Everard et al. found that performing well on one screen did not indicate an athlete would perform well on the other.5
As such, screening for, and revealing, biomechanical flaws within an athlete’s movement should include both generalized movement patterns as well as sporting-specific tasks to maximize the athlete’s overall safety and wellbeing. In the case of athletes whose sporting tasks involve jumping (basketball, volleyball, etc.), ensuring optimal biomechanics when landing should not be overlooked.
How any identified biomechanical issues are corrected will depend on multiple factors, including the particular faults identified, needs of the athlete, and scope of practice for the coach or clinician. As such, it is important to realize that there is no universal approach for how jump landing mechanics should be rectified.
As a result, the following is a discussion of the Landing Error Scoring System as it pertains to screening for non-contact knee injury risks in athletes, but it does not offer specific insight regarding corrective intervention. An individualized approach should always be taken for each athlete.
The LESS Test
The LESS is a screening tool developed to identify the risk of potential non-contact knee injury in athletes, notably for ACL injury (though associated risk such as meniscal and MCL injuries can also be factored). The premise of the system is that identification of biomechanical (body position-based) errors present within the lower extremities during jump-landing can lead to reduction of injury risk via corrective interventions, such as hip and knee strengthening, improving proprioceptive awareness, and overall landing technique.The premise of LESS is that identification of biomechanical errors present within the lower extremities during jump-landing can lead to reduction of injury risk via corrective interventions. Click To Tweet
The jump-landing task is recorded via video from two different cameras—one recording the sagittal plane (recording the athlete from the side) while the other records the frontal plane (recording the athlete from the front). Each camera is placed 3 meters away from the landing zone at a height of 1 meter above the floor.
The system works by evaluating 17 different biomechanical occurrences that take place throughout the body during the jump-landing task (also termed a drop-vertical jump). The examination for scoring can be divided into three categories:
- Jump-landing technique as it relates to position of the trunk and lower extremity position upon connecting with the ground.
- The scoring of faults involving foot position between initial ground contact and maximal knee flexion.
- Movements of the trunk and lower extremities that occur between initial ground contact and maximal knee flexion.
Scoring for the 17 items uses a dichotomous scoring rubric for the first 15 items (see the scoring sheet below), noting either the presence or absence of a movement error; a score of 0 indicates an absence of error while 1 denotes the presence of an error. Item 16 (joint displacement) and 17 (overall impression) can be scored with three potential outcomes (see scoring list below). The analysis and subsequent scoring are done manually by a trained individual upon analyzing the recorded video at a later point in time.
A higher overall score of the test indicates a greater number of movement errors arising during the jump-landing task and therefore correlates with higher risk for potential non-contact knee injury for the athlete.
To perform the test, the athlete stands on a 30-centimeter jump box. Then, when given verbal command, the athlete jumps forward off the box with both feet, lands at a pre-measured distance of 50% their body height in front of the box, and immediately performs a vertical jump with maximal effort.
Validity and Reliability of the LESS Test
Any strength coach or clinician incorporating standardized tests into their athletes’ testing—be it performance-based or prevention-based—should ensure the test is valid and reliable (validity assesses if the test measures what it claims to measure, and reliability assesses if the test is able to consistently measure results).Any strength coach or clinician incorporating standardized tests into their athletes’ testing—be it performance-based or prevention-based—should ensure the test is valid and reliable. Click To Tweet
The LESS test has been shown to be both valid and reliable for the assessment of jump-landing biomechanics as it pertains to injury risk within athletes.6,7 The test also exhibits excellent expert vs novice interrater reliability when assessing 3D kinematic motion patterns utilized for scoring of the LESS.8
Strengths & Weaknesses of the LESS Test
As with any test or system, inherent strengths and weaknesses can be found within the LESS. The extent of each respective strength and weakness will largely be determined by the coach or clinician regarding their own unique situations, resources, etc.
Strengths of the Landing Error Scoring System
Naturally, the inherent strength of the LESS is its repeated scientific-backing to be a valid and reliable screening tool toward the risk of non-contact knee injury in athletes.6,9,10,11 One could argue that identifying and preventing ACL and other associated non-contact knee injuries through appropriate intervention is the ultimate strength of any screening system. As a result, any inherent weaknesses of the system (discussed below) might be seen as more of an inconvenience, as injury prevention is worth its weight in gold.
Of notable interest, the LESS has been shown to be valid and reliable for various populations and has been shown to identify risk of re-injury in athletes having undergone ACL reconstruction, making it a noteworthy system for directing areas of focus for the athlete’s rehabilitation and eventual return to sport.12 Additionally, within the ACL reconstruction population, the LESS has shown to reveal greater extent of landing errors for female populations when compared to their male counterparts.13The LESS has been shown to be valid and reliable for various populations and has been shown to identify risk of re-injury in athletes having undergone ACL reconstruction. Click To Tweet
Limitations & Practical Considerations
The requirement of dedicated video equipment to capture and thereafter analyze jump-landing mechanics in athletes has been seen as an impediment by many clinicians and coaches, particularly for organizations with a modest budget or for professionals who must record and thereafter manually analyze high volumes of athletes at a later point in time. Understandably, the need for a coach or clinician to acquire video equipment, establish a testing area, set-up equipment, and watch recorded videos is often seen as a barrier to implementing LESS screening into athlete testing.
Additionally, when testing large groups of athletes, the need to account for different landing positions with each athlete (landing distance is determined by the athlete’s height), can create an additional inconvenience by moving any visual landing target for each athlete. Interestingly, different landing distances are often reported within literature, though some authors have concluded that landing distance should be kept at a standardized distance of 50% the athlete’s height since different landing distances can produce different biomechanical results, leading to different scoring and subsequent categorization of errors.14
Real-Time Analysis: Modifications to the LESS
In an attempt to overcome any perceived issues involving practicality of the LESS, modifications to the system have been developed, allowing for real-time analysis to be performed either by an examiner or through dedicated software designed to capture, analyze, and interpret jump-landing mechanics in real-time.
In the case of real-time scoring being performed by a trained coach or clinician, the modified LESS is used. For real-time analysis and scoring performed by dedicated software, the traditional LESS is utilized.
The Modified LESS
With the modified LESS, a 10-characteristic jump-landing rubric is used in place of the traditional 17-point rubric. This allows for simplification of the test so a trained examiner can observe and score the athlete’s performance in real-time, negating the need for video capture and later analysis. The tester watches the athlete perform two drop-jumps from the front and two more from the side. All other metrics (box height, jump distance, etc.) remain the same.
This modified version has been shown to have high levels of interrater reliability, making it a practical and reliable screening tool for professionals working with the athlete.7
Computerized real-time analysis
With the advancement of modern technology, research has been undertaken to determine if computerized real-time video analysis can be a valid and reliable means to performing the LESS assessment. If the ability exists for dedicated software to perform such an immediate analysis, the LESS could become a much more efficient and practical system to incorporate for coaches and professionals working with teams and large numbers of athletes.With the advancement of modern technology, research has been undertaken to determine if computerized real-time video analysis can be a valid and reliable means to performing the LESS assessment. Click To Tweet
Currently, researchers have examined the ability to automate traditional (i.e., non-modified scoring) LESS scoring through dedicated software and found doing so to be valid and reliable. One study by Mauntel et al. found a real-time markerless motion capture software to have the same reliability in identifying biomechanical errors as expert raters.15 When using these particular systems, it should be noted that different software programs exist; however, many of these software applications rely on using 3D motion analysis or depth sensor cameras, which may still be cost prohibitive for some coaches or organizations.
Another study by Hébert-Losier et al. looked at automating the LESS through deep learning software from 2D video when combined with machine learning methods, which eliminates the need for depth sensor cameras, allowing for analysis through traditional video recording. Results were favorable, with the authors noting that deep learning software will allow reliable scoring interpretation using smartphone cameras and a subsequent app, paving the way to great accessibility for coaches, teams, and clinicians looking to incorporate the LESS into their athlete assessments.16
It should be noted that the authors of this study mention that further study of these software systems and programs will be required to further enhance the scoring agreement between the automated system and manual scoring done by coaches or clinicians beyond their current levels.
If jumping is all about performance, landing is all about safety. A dedicated effort should be made by strength coaches, clinicians, and other professionals to deliberately assess, identify, and correct jump-landing errors in their athletes to reduce the risk of non-contact knee injuries. The LESS provides a reliable and valid means to do so.
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