Relevance for the sport
The single leg jump distance test (also: single leg hop distance test) is a valuable exercise and functional performance test utilized in both sports performance training and rehabilitation settings for assessing and comparing the maximum neuro-muscular capacity of the lower limbs.
In sports performance training, single leg jumps for distance serve as an essential component of plyometric training. Plyometric exercises, which involve rapid stretching and contracting of muscles, aim to enhance power, explosiveness, and neuromuscular coordination.
In rehabilitation settings, the single leg jump for distance (SLJD) serves as a valid and reliable (1) functional assessment tool to aid in the recovery from lower limb injuries, like ankle ligament ruptures or anterior cruciate ligament (ACL) tears. By assessing an individual’s ability to perform a SLJD, healthcare professionals can identify asymmetries or deficits in movement patterns that may predispose the individual to re-injury or hinder their return to sports (RTS). The limb symmetry index (LSI) serves as a valuable metric to monitor progress throughout the rehabilitation process, ensuring that both limbs achieve a comparable level of function and performance before returning to sport or physical activity.
Test Protocol
The ReGo Single Leg Jump Distance test entails a single-legged horizontal jump executed on a level surface (Fig-1). Three repetitions are performed with each leg, with the best jump being evaluated. Correct technique for best comparability of results involves positioning the hands on the hips during jump-off, flight, and landing.
This test imposes both concentric and eccentric loads on the lower extremities, necessitating maximal muscle activation in a single burst. The primary objective is to achieve maximum distance in the jump.
Information
Trials are considered invalid if a second hop is necessary to regain balance after landing or if the free foot or the upper extremities touch the ground.
Follow the link for a more detailed test description of the ReGo Single Leg Jump Distance test, including a step-by-step guide and an instruction video.
Outcome Parameters
Research suggests that only measuring jump distance is not sufficient to detect deficits in knee function after ACL reconstruction (ACLR), even if the healthy leg is used to calculate the LSI (2, 3). That means that patients can achieve a symmetric jump distance, but knee function can still be asymmetric. For instance, patients can unload the injured knee by compensating at the hip or ankle. A study by Ohji et al. (4) from 2021 also indicates that not only symmetric jump performance is important: they found that jump distance normalized to body height of > 70% was positively associated with the athlete’s RTS status.
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The primary outcome parameter of the ReGo Single Leg Jump Distance is Jump Distance.
Moreover, qualitative parameters can help in the RTS decision-making process: The ReGo parameter Ground Reaction Force depicts the force-time-curve of the left and right side, which allows a side-by-side comparison (Fig-2). The individual phases of the jump, such as the braking and propulsive phases, can be analyzed here.
The parameter Balance Point & Sway Area displays the Balance Point as the mean center of pressure (COP) point of the landing foot during the balance phase. The Sway Area is formed as an ellipse which encloses all data points of the COP. Sway Area is also available as a numerical value with the L/R difference in %.
In Vid-1 you can see a tennis player performing the SLJD on her right and left leg. The qualitative video analysis shows that the landing on the left leg is significantly more unstable compared to the right. As a result, more compensatory movements are necessary to get into a stable position. For example, the torso leans to the side and the hands leave the hips to prevent falling over.
This asymmetry in landing behavior is confirmed by the outcome of the Balance Point & Sway Area. As displayed in Fig-3, the Sway Area is considerably larger on the left side, and the Balance Point is located further forward in the metatarsal area.
Further parameters for assessing stability after landing are Stabilization Progression and Time to Stabilization. Stabilization Progression shows the traveling velocity of the COP from the time of landing until 3 seconds after landing. The parameter Time to Stabilization is defined as the time passed for the traveling velocity of the COP to fall below the stabilization limit, with the left-to-right difference given in %. In the next section, we will discuss these parameters in more detail by using a specific example.
Example – junior ice hockey player
The following test data is from a 17-year-old junior player from a club in the German Ice Hockey League. About a month before the test was carried out, he suffered an ankle sprain on the right side. In addition, he tore his right ankle ligament about a year prior to the test.
Jump distance is similar on both sides (Fig-4, left), with only a 3,4% difference. This corresponds to a LSI score of 97%, which is above the recommended 90% level for uninjured subjects and injured patients to complete rehabilitation (5).
However, as you can see in Fig- 4 on the right, the Sway Area is greater on the right side with a 28.3% difference between left and right. Additionally, the Balance Point is more medial and further forward on the right side. In line with this, the illustration of the Stabilization Progression (Fig-4, right) shows larger deflections, especially directly after landing. The Time to Stabilization is greater on the right side as well, with a 28.7% difference compared with the left side.
This example illustrates that athletes can achieve a similar jump distance and thus a high LSI value, but qualitative parameters, such as stability after landing, can show significant differences between the two sides, which indicates that the subject is compensating.
Tips for trainers and therapists
The next section discusses possibilities to improve rehabilitation outcomes after ACLR. In their 2017 study, Pua et al. (6) highlighted a noteworthy relationship between quadriceps strength measured at six weeks post-ACLR and hopping distance recorded six months after the surgery. The observed correlation suggests that higher quadriceps strength in the early stages of recovery may predict better functional outcomes in the medium term. The research emphasizes the importance of implementing structured rehabilitation programs that prioritize strength-building exercises during the initial stages of post-surgical care for ACLR patients.
Research by Isberg et al. (7) and Shaw et al. (8) show that isometric quadriceps exercises are safe to be performed in the first postoperative week and provide benefits regarding knee range of motion and stability. Gokeler et al. (9) and Kruse et al. (10) conclude that including eccentric quadriceps exercises from three weeks after ACLR is safe and yields greater results in quadriceps strength than concentric exercises. Additionally, neuromuscular training can be beneficial in restoring quadriceps strength (9, 10). Furthermore, Van Melick et al. (11) suggest that electrostimulation in addition to conventional rehabilitation might be more effective in regaining muscle strength, especially in the early postoperative phase. There is also evidence that strength training the contralateral leg in the early phase after surgery improves quadriceps strength in the operated leg, which is called cross-education (12, 13).
Information
Recent research suggests these aspects after ACLR to enhance recovery and for better functional outcomes as well as long-term success using structured rehabilitation programs:
• Prioritize early quadriceps strength
• Include electrostimulation in early phase
• Isometric and eccentric exercises pose high level of safety and efficacy
• Include neuromuscular training and cross-education strategies (training contralateral side as well)
Comments on measurement equipment
Historically, the jump distance of the SLJD has been acquired by using tape measure.
In contrast to that, the introduction of the ReGo Sensor Insoles to hop testing as shown in this article presents a paradigm shift for trainers and therapists as they offer a cost-effective, valid, and reliable solution for gaining insights into the entire range of biomechanics involved in the jump, including jump-off force, impulse and timing, as well as metrics related to the quality of the landing, such as the center of pressure (COP) variability.
This allows for identifying how an athlete achieved the performance and which aspects should be subject to development, rather than just considering the distance jumped.
The following table (Tab-5) shows product specifications which help to obtain actionable information from the sports performance tests and functional tests.
| Funktion | Beschreibung |
|---|---|
| Automatic report generation | Pattern recognition and advanced live processing allows ad-hoc computation of the complete set of test results. |
| Mobile and offline use | Tests can be performed anywhere and anytime as the measurement system is not limited not limited to laboratory use. Also, test can be performed offline. |
| Documentation and reporting | With regards to documentation and performance tracking, ReGo comes with labeling features and access to a reporting frontend which allows users to generate individual or team reports. Individual reports are for one athlete and optionally cover multiple tests such that intra-individual performance development over time can be evaluated. Team reports can be created for an infinite number of athletes and serve to compare inter-individual performance. |
| Reference database | Reference data is available, covering norm data of numerous sports and age groups as well as female and male athletes. Reference data helps to classify the performance of your own athletes compared to average and best outcomes in the sport or age group, hence identifying strengths and weaknesses as a starting point for individualized training programs. |
In essence, the ReGo system helps trainers and therapists to enhance accessibility to biomechanical hop testing metrics, making it a valuable tool to support decision making in the return-to-sport process.
Literaturverzeichnis
1. Reid, A., Birmingham, T. B., Stratford, P. W., Alcock, G. K., & Giffin, R. (2007). Hop Testing Provides a Reliable and Valid Outcome Measure During Rehabilitation After Anterior Cruciate Ligament Reconstruction. Phys Ther., 87, 337-349.
2. Kotsifaki, A., Korakakis, V., Whiteley, R., Van Rossom, S., & Jonkers, I. (2019). Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: a systematic review and meta-analysis. Br J Sports Med ., 54(3), 139-153.
3. Kotsifaki, A., Whiteley, R., Van Rossom, S., Korakakis, V., Bahr, R., Sideris, V., Graham-Smith, P., & Jonkers, I. (2022). 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, 56, 249-256.
4. Ohji, S., Aizawa, J., Hirohata, K., Ohmi, T., Mitomo, S., Jinno, T., Koga, H., & Yagishita, K. (2021). Single‑leg hop distance normalized to body height is associated with the return to sports after anterior cruciate ligament reconstruction. Journal of Experimental Orthopaedics, 8(26).
5. Gustavsson, A., Neeter, C., Thomée, P., Grävare Silbernagel, K., Augustsson, J., Thomée, R., & Karlsson, J. (2006). A test battery for evaluating hop performance in patients with an ACL injury and patients who have undergone ACL reconstruction. Knee Surg Sports Traumatol Arthrosc, 14(8), 778-88.
6. Pua, Y.-H., Mentiplay, B. F., Clark, R. A., & Ho, J.-Y. (2017). Associations Among Quadriceps Strength and Rate of Torque Development 6 Weeks Post Anterior Cruciate Ligament Reconstruction and Future Hop and Vertical Jump Performance: A Prospective Cohort Study. Journal of Orthopaedic & Sports Physical Therapy, 47(11), 845-851.
7. Isberg, J., Faxén, E., Brandsson, S., Eriksson, B. I., Kärrholm, J., & Karlsson, J. (2006). Early active extension after anterior cruciate ligament reconstruction does not result in increased laxity of the knee. Knee Surg Sports Traumatol Arthrosc, 14, 1108–1115.
8. Shaw, T., Williams, M. T., & Chipchase, L. S. (2005). Do early quadriceps exercises affect the outcome of ACL reconstruction? A randomised controlled trial. Australian Journal of Physiotherapy, 51(1), 9-17.
9. Gokeler, A., Bisshop, M., Benjaminse, A., Myer, G. D., Eppinga, P., & Otten, E. (2014). Quadriceps function following ACL reconstruction and rehabilitation: implications for optimisation of current practices. Knee Surg Sports Traumatol Arthrosc, 22, 1163–1174.
10. Kruse, L. M., Gray, B., & Wright, R. W. (2012). Rehabilitation After Anterior Cruciate Ligament Reconstruction: A Systematic Review. The Journal of Bone & Joint Surgery, 94(19), 1737-1748.
11. Van Melick, N., van Cingel, R. E. H., Brooijmans, F., Neeter, C., van Tienen, T., Hullegie, W., & Nijhuis-van der Sanden, M. W. G. (2016). Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. Br J Sports Med, 50, 1506–1515.
12. Harput, G., Ulusoy, B., Yidliz, T. I., Demirci, S., Eraslan, L., Turhan, E., & Tunay, V. B. (2019). Cross-education improves quadriceps strength recovery after ACL reconstruction: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc, 27(1), 68-75.
13. Minshull, C., Gallacher, P., Roberts, S., Barnett, A., Kuiper, J. H., & Bailey, A. (2021). Contralateral strength training attenuates muscle performance loss following anterior cruciate ligament (ACL) reconstruction: a randomised-controlled trial. Eur J Appl Physiol ., 121(12), 3551-3559.
