How to apply IMU’s Total Impact Load metric to an athletic population – By James Grant, ATC
IMU Step’s new metric, Total Impact Load, is philosophically quite similar to traditional external workload metrics, but with the distinction of collecting impacts at both lower limbs rather than treating the body as a single unit. This collection method opens up the door to a whole new range of tracking insights, as well as some novel approaches that you should start thinking about.
I will take you through the five most important next steps you can take with the metric and dive a bit deeper into why these are important to your athletes or patients. While my formal background is in athletic training, I have spent the majority of my professional career in the wearable tech space, so I will be exploring the metric from both a rehabilitation and general load monitoring standpoint. This brings me to use number 1…
1. General Load Monitoring
Impact Load is designed to reflect how much impact the lower limb experienced during a session. The metric is calculated based only on the number of steps on each leg and the intensity of each step. The more high-intensity steps the athlete does, the higher their impact load will be. What this allows you to do is have one number, Total Impact Load, to describe how much they did in each session. With this number, you can now directly compare sessions across time, and see how your athlete’s loading pattern is changing across time. Do they have any spikes in their workload? Are their ‘light’ days actually light? How are they trending over time? Answering these questions, and generally getting an idea of how my athlete’s load, is how I approach using impact load right away.
2. Asymmetrical Load Detection and Monitoring
Not only does this new metric show you the load for the athlete as a whole (Total Impact Load), but it breaks down the load for each limb (Impact Load Left and Right). With this, I can treat each leg as an individual entity, and easily identify any discrepancies in the athlete’s loading pattern. Keep in mind that just because you see a discrepancy, doesn’t necessarily mean that it needs to be corrected. This is also where I make use of the footnotes feature. If I do see an asymmetry, I can make sure it wasn’t a single drill or activity affecting the rest of the session. If it is prevalent throughout the whole session, I like to monitor the asymmetry over a couple of sessions to see if it is functional. Remember to consider the athlete as a whole and see if the asymmetry is accompanied by any pain or dysfunction. Drastic or unexpected changes in asymmetry can be a warning sign of new injury. Which brings us to use number 3.
3. Red Flag System
Using load monitoring to keep track of injury risk is nothing new, but I’d argue that Impact Load does it better than traditional methods. Especially in sports like basketball or football, I don’t necessarily care how much the upper torso of an athlete moved, but I am very interested in what their lower limb was doing. To monitor injury risk I generally take a two-pronged approach. First, I use the Tim Gabbett approach and keep an eye out for any spikes or drops in workload that may overstress the athlete unnecessarily. Second, because I can see the Impact Load for each limb, I use a similar method and monitor for any spikes in the amount of asymmetry I see. Any change in either of these, I interpret as a red flag and start to investigate further.
4. Drill and Exercise Categorization
Total Impact Load enables me to look at athletes both individually (very important for Return to Running programming) and as part of a wider team or cohort. I can start to aggregate data from different athletes and get an idea of what a normal exercise or drill looks like for my team. If I have data to tell me exactly how hard each drill is, I can more realistically plan practice and rehab sessions. While the coach may not let me completely redo a practice plan, if I know a drill is particularly intense I can suggest making it a few minutes shorter or moving it later in the practice so the athletes are more warmed up.
5. Return to Play
All these points come together in my return to play protocols. Generally, my athletes with a lower limb protocol will begin their rehab with a large discrepancy in their loading pattern between the injured and uninjured limbs. Since I monitor my team when they’re healthy I know exactly what demands I have to prepare them for. I can then work backward from their healthy point to determine what milestones I’d like them to hit and when. I know how my drills affect my athletes, so I know which ones to prescribe early, and which to save for later. All the while I monitor their load. I make sure not to increase their load too fast, and when I do push them, I can see how each limb responds. As their load gets closer to their healthy target, I can start to introduce my more intense drills and sports specific activities. If they are able to handle their healthy load and tick my other tests, I am much more confident when I return them to play.