How to use IMU Step to detect and correct lower limb asymmetry

IMU Step’s Impact Asymmetry metric is a powerful tool for identifying and correcting asymmetry in lower limb movement, particularly in subjects recovering from injury. By offering both granular data on specific sessions and a macro view of how asymmetries are progressing over time, IMU Step can bring clarity to the rehabilitation process and enable practitioners to make highly focused interventions.

Setting a Baseline: Rehab vs Healthy

The first step in correcting asymmetry in any subject’s movement is determining whether it is, in fact, significant enough to warrant closer examination. Generally speaking, an asymmetry of 5% or more should be considered worth further investigation.

Watch our webinar with Andrew Gray to learn more about the 5% asymmetry threshold:

Functional Asymmetries

Ideally users will have a baseline measurement of their subject’s lower limb impact symmetry when they’re healthy. That score may well show a functional asymmetry of a few percentage points in one direction or the other. If you have that data, that’s the baseline from which you will judge your subject’s current asymmetry.

So, for example, if a subject typically exhibits a 1% asymmetry toward the right side, a 6% asymmetry to the right or a 4% asymmetry to the left would represent a 5% deviation from the norm.

If you don’t have that baseline data, use 0% as a rough starting point but be aware that your subject might have a functional asymmetry even when in good health.

Tracking Over Time

The next factor to consider is how far your subject is into their rehabilitation program.

If, for example, they are taking part in their first training session after a knee operation, you would expect to see significant asymmetry and it may not require further intervention at this stage.

Over time, you should expect to see your subject’s loading patterns become more symmetrical. Longitudinal tracking using IMU Step offers users deep insights into subject performance, and ultimately a trend towards symmetry over time is the strongest indicator that your current strategies are working.

If, however, your Blue Trident data isn’t showing a positive trend, further investigation is probably warranted.

Examining Asymmetrical Movement

Once you have established that your subject is exhibiting asymmetrical loading, IMU Step enables you to delve deeper into individual sessions for insights on what is driving your subject’s asymmetry.

It may be that your subject exhibits the same asymmetry regardless of what they’re doing, or you may find that they perform differently while completing different movements.

Using Footnotes

IMU Step’s Footnotes tool allows users to break sessions down into individual exercises or drills. That means that you can see whether the asymmetry is present across an entire session, or just for single actions.

You might, for example, find that a basketball player only displays asymmetrical loading during a defensive help drill, which involves rapid changes in direction. Once you’ve isolated that particular drill as the source of the athlete’s asymmetry, you can then investigate further to work out which specific movements are causing the asymmetry.

For the next session, you might break the drill down even further into discrete movements, creating footnotes for each movement for an even more detailed view of where and when asymmetries are present.

Analyzing Live Data in the Field

Alternatively, you can use IMU Step to analyze your Blue Trident data live in the field. Detecting an asymmetry in real-time will enable you to isolate specific movements, performing tests and making adjustments during a session, assigning exercises for specific muscles and then assessing how those adjustments affect performance over time.

By combining granular moment-by-moment analysis, real-time data and a longitudinal view of your subject’s recovery, IMU Step with Blue Trident can help practitioners to catch and correct asymmetries before they cause re-injury, enabling them to guide recovery with highly focused exercises and physiotherapy.