Shimmer has developed an algorithm to obtain mobility data from a Shimmer3 sensor (accel + gyro) placed on a shoe. This algorithm is based on state of the art wearable sensor/biomechanics research and has already been tested on a young, healthy data-set in order to obtain normative standards to compare metrics to.
This algorithm is ideal for applications in the area of sensors embedded into shoes, or applications that could be used for remote monitoring or supervised monitoring, such as in a clinic or care-home.
The below information gives an overview of the algorithm, as well as data vizualizations for the normative data that has been collected to date:
Algorithm Summary
The Shimmer foot sensor algorithm has three levels of metrics:
| Variable Type |
Metric |
Description |
| Temporal |
Stride time |
The time between foot strike on one foot to the next foot strike on the same foot. Represents one full gait cycle. |
| Kinematic |
Sagittal foot angle |
Sagittal plane foot angle during the gait cycle. Zero angle represents the angle of the foot during foot flat. Positive values represent a rotation with the toes going upward and negative represents a rotation with the heels going upward. |
| |
Sagittal foot angle |
Frontal plane foot angle during the gait cycle. |
| Spatial |
Stride distance |
The distance from one foot placement to the next foot placement with the same foot
|
Data Visualizations
Stride time below:
Sagittal foot angle
Frontal Foot Angle
Anterior/ Posterior foot Velocity
Stride Distance
Normative gait data was obtained with 30 (16 female / 14 male) participants who performed twenty 12 m walking trials each.
You can find the normative data from these 30 participants in the table below:
| Feature |
Unit |
Mean |
Max |
Min |
SD |
| Stride time |
Sec |
1.08 |
1.28 |
0.91 |
0.09 |
| Peak sagittal foot angle |
Deg |
1.37 |
1.79 |
0.96 |
0.17 |
| Min sagittal foot angle |
Deg |
-65.1 |
-30.9 |
-90.0 |
10.6 |
| Max frontal foot angle |
Deg |
14.3 |
44.2 |
0.0 |
12.0 |
| Min frontal foot angle |
Deg |
-13.1 |
0.0 |
-43.3 |
11.1 |
| Peak AP foot velocity |
m/sec |
4.77 |
6.1 |
3.35 |
0.48 |
| Stride length |
m |
1.37 |
1.79 |
0.96 |
0.17 |
| Normalized stride length |
m/cm |
0.0113 |
0.0165 |
0.0074 |
0.0018 |
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