BREAKING DOWN THE NEW LANDING METRICS

We updated our drop jump method and metrics last week and users including those from professional sports and academic sectors have given us some amazing feedback (thank you!). But those with a keen eye for detail also noticed that we included three landing metrics in the update. In fact, we didn’t just add these landing metrics to our drop jump protocol, we added them to our countermovement jump (CMJ), squat jump, and CMJ-rebound jump protocols too. We also added two of them to our drop landing protocol. So, what are these metrics, and how are they useful? 

First, the three new metrics are landing height, landing phase (duration), and landing performance index, and a description of these, as shown in our metric database, is shown in the table below.  

The landing height essentially describes the height the athlete falls from before contacting the force plates and the beginning of what we refer to as the landing phase across our various jump tests. It is nearly always slightly more than jump height, which is why it is a separate metric. This is because the distance the athlete travels up from the moment that they takeoff (i.e., leave the force plates) through to when they reach the apex of the jump is usually slightly longer than the distance that they travel down from the apex of the jump through to the moment they touchdown (i.e., contact the force plates again). This difference in distance traveled or height attained is caused by the different ankle joint angles (or foot orientations, if you prefer to think of it that way) at takeoff and touchdown. Usually, athletes leave the ground in close to full ankle plantar flexion (foot pointing down) whereas they usually contact the ground with the ankle either less plantar-flexed or even in a neutral (90-degree angle between the foot and shin) or dorsi-flexed (foot pointing up [less than 90-degree angle between the foot and shin]), which essentially prolongs the distance the athlete travels downwards before they contact the force plates.  

Why is landing height a useful metric? Well, much like knowledge of drop height provides essential context for interpreting drop jump or drop landing performances, because it determines the intensity (or braking demands) of the test, landing height determines the intensity of the landing phase. In other words, a higher landing height means the athlete hits the ground faster which increases the braking demands required to control their landing phase (i.e., at the point where they’re stationary).  

The landing phase metric simply describes the duration of the landing phase. Specifically, it describes how long it took from the moment the athlete contacted the force plate to the moment they paused momentarily (velocity = 0 m/s) to complete the landing phase. It is important to note that this landing phase duration is different from the time to stabilization metric that was already calculated by our software. Time to stabilization describes the phase from initial landing contact to when the athlete begins a maintained motionless (force within 5% of system weight) period lasting for at least one second. This is arguably more relevant in clinical applications of landing assessments rather than performance uses. It also requires more stringent cueing from the tester about how the athlete should perform the landing phase which, in our experience, is better suited to the drop landing test because of its sole focus on landing.  

While the landing phase metric is useful on its own, we combine it with landing height to calculate the landing performance index. Of the three new metrics, this is the one we’re the most excited to add. The landing performance index divides the landing height metric by the landing phase metric, providing a ratio (or index) that describes landing ability. For readers who are familiar with the reactive strength index or modified reactive strength index metrics, our landing performance index is like these, providing the same insight but to the landing phase. Higher landing heights with shorter landing phase durations lead to a larger landing performance index. Decreasing the landing phase duration from the same landing height will, therefore, increase the landing performance index to reflect greater efficiency. Like all ratio metrics, the landing performance index can be achieved in lots of different ways by applying different combinations of landing height and landing phase. As such, users must unpack the landing performance index into its constituent parts to gain the fullest understanding of the athlete’s landing strategy and capacity. 

These metrics have been included in two recently published studies led by Dr. John Harry, so they’re relatively new and unexplored. However, coincidentally, our development team had already added these metrics to our drop landing protocol via a beta version of our software back in 2023 (although we called it the landing strength index back then, but we’ve gone with the landing performance index for consistency with the excellent work done by Dr. Harry and colleagues here and here). Our science team conducted a pilot test of the application of these metrics in collaboration with a professional soccer club from La Liga in Spain. I presented some of the results of this pilot study at the 2024 Professional Soccer Performance Association Conference held last month in preparation for our recent software update. Some of the preliminary results of this are described below.  

La Liga Pilot Study 

Every study should start with a problem or question that, if answered, could, regardless of how small, help the problem (or question) it relates to. In this study, we set out to answer the question “...which force plate test can be used for fatigue monitoring when you’re unconvinced that the involved athletes will produce a maximum effort...?”. Now, we know that the assumption behind force plate testing for fatigue monitoring is that athletes perform the test with maximum effort, allowing any decline in performance to be inferred as likely neuromuscular fatigue. The most common test for neuromuscular fatigue monitoring with force plates is the CMJ (usually on match day plus 2 or 3 in soccer). So, if an athlete or athletes do not always perform the CMJ with maximal intent, inferences made from their CMJ data can be compromised. So, that got us thinking about alternative options, and in the end, we decided to pilot the drop landing test for fatigue monitoring in soccer. Why? Well, with this test the athletes must land (it’s a means to an end). Additionally, athletes tend to take more care when landing from a box, especially if it’s a reasonable height because they want to avoid injury and so see an immediate benefit to themselves. Many will have performed drop landing as part of any musculoskeletal rehabilitation programs too, so it’s got that clinical (perceived important) feel to it.  

We had an opportunity to test 40 male professional soccer players from a La Liga team before and after a full day of training, including conditioning and training matches. The players performed the CMJ and the drop landing test from both a 30 cm and a 50 cm high box in a randomized order on each testing occasion. Training had no meaningful effect on any of the CMJ or 30 cm drop landing metrics. However, training did meaningfully affect landing height and landing performance index but not landing phase duration for the 50 cm drop landings (see figures). What can we take from this? Training led to players lowering themselves more from the 50 cm box before dropping towards the force plates, thus lowering the braking requirements during the landing phase. Despite this, the pre and post-training landing phases (duration) were similar. This reduced their landing performance index. The players’ body mass had also meaningfully reduced post-training. This is interesting because they were lighter and fell from a lower height post-training which means they landed with less momentum but still couldn’t complete the landing phase quicker than pre-training. Now these are just preliminary results of a pilot study, and much more research needs to be done to fully explore the utility of drop landing metrics for fatigue monitoring, but we think there’s great potential for this approach, especially in situations where there is doubt over the suitability of other tests such as the CMJ due to the chance of some athletes performing sub-maximally.  

Figure 1: The left graph shows the landing height scores and the right graph shows the landing performance index scores obtained from the 50 cm drop landing test before (PRE_50) and after (PST_50) training.  

We are very excited about the addition of these landing metrics! As always, you can reach out to us if you have any questions whatsoever about these metrics by emailing techsupport@hawkindynamics.com for a prompt response. Also, we will be following up soon with more blog posts and videos about key drop landing and jump landing metrics and what they mean for our users, so please watch out for those.