The Science Behind SoterCoach
SoterCoach is designed to detect and reduce high-risk movements that lead to musculoskeletal disorders (MSDs). It uses wearable sensors—placed on the back or shoulder—to measure posture and motion in real time. These measurements are compared against scientifically defined thresholds to determine when a movement becomes hazardous. Here's what it measures and why.
Spine-Related Movements (Back Device)
1. Bending
Measured angle
Spine flexion (forward bend)
High-risk threshold
>85°
Why this matters
Although bending beyond 60° is flagged in ergonomic tools like REBA and RULA, Soter chose 85° to reduce false positives in real-world settings. This ensures that the system alerts only for the most severe, potentially harmful bending.
2. Twisting
Measured angle
Rotation of the spine
High-risk threshold
>30°, or >45° when combined with bending
Why this matters
Twisting combined with bending (especially beyond 50°) puts excessive load on spinal discs. That's why the threshold is lowered when both movements occur together.
3. Static Posture
Measured condition
Holding a bent posture >60° for ≥20 seconds
Why this matters
Holding bent positions restricts blood flow and increases fatigue, making tissues more vulnerable to injury. 20 seconds is the maximum recommended duration in static postures before risk increases.
4. High-Intensity Movements
Indicators
Jerky movements, fatigue-influenced technique, rapid bending/extension
Why this matters
These movements are linked to decreased spinal stability. Soter infers high intensity when movements are fast, forceful, or likely affected by fatigue or poor technique.
Shoulder-Related Movements (Shoulder Device)
1. Arm Elevation
Measured angle
Angle between the upper arm and vertical line
High-risk threshold
>90°
Why this matters
Most tasks can be safely done with arms below 90°. Exceeding this puts strain on the rotator cuff and stabilizing muscles. Limiting elevation reduces risk of tendonitis and shoulder pain.
2. Static Arm Elevation
Measured condition
Holding arms above shoulder height for prolonged periods
Why this matters
Continuous elevation leads to muscle fatigue and shoulder overuse injuries. The duration and repetition of this position are key indicators of risk.
3. Repetitive Arm Movements
Measured metric
Number of arm elevations per minute/hour
Why this matters
High repetition is a known contributor to upper limb disorders. Tracking frequency allows early detection of overuse risk.
Why These Thresholds Were Chosen
The thresholds used by SoterCoach are based on:
- Global ergonomic standards (REBA, RULA, LUBA)
- 3+ years of real-world usage data from 15,000+ workers across 210 companies
- Field testing and user feedback, to reduce false positives and increase user compliance
- The Pareto principle, used to group risk exposure levels into the three bands below
Low Risk
<10 hazardous movements per hour
Medium Risk
10–20 per hour
High Risk
>20 per hour
These thresholds strike the right balance between scientific rigor and real-world usability—ensuring SoterCoach delivers alerts when they matter most, and avoids unnecessary interruptions.
More in SoterCoach General Information
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