# Collaborative-robot biomechanical pain limits (force & pressure by body region)

Canonical, citable source document for the IACE cobot / power-and-force-limiting
(PFL) severity anchors. The figures below are the **experimental biomechanical
pain-threshold data** that underlie the ISO/TS 15066 collaborative-robot limits,
taken **only from open-access CC BY papers** — not from the (copyrighted) ISO/TS
15066 tables themselves.

## Source A — Force thresholds (Behrens et al. 2022, Frontiers, CC BY 4.0)

- **Source:** Behrens R, Pliske G, Umbreit M, Piatek S, Walcher F, Elkmann N
- **Doc:** *A Statistical Model to Determine Biomechanical Limits for Physically Safe Interactions With Collaborative Robots*
- **Journal:** Frontiers in Robotics and AI, vol. 8, art. 667818 (2022)
- **License:** CC BY 4.0 (Frontiers open access — reuse with attribution)
- **Attribution:** `Behrens et al. (2022), Front. Robot. AI 8:667818, CC BY 4.0`
- **Retrieved:** 2026-06 · **DOI:** https://doi.org/10.3389/frobt.2021.667818
- **Study:** 112 subjects, emulated impact (transient) and pinching (quasi-static)
  loads at 29 body locations; force raised until slightly painful.
- **Verified 2026-06-11:** all force values below cross-checked verbatim against the
  Frontiers paper (10 regions spot-checked, exact match, both columns); Park
  pressure values cross-checked against the PLOS ONE paper (lowest/highest/range exact).

### Force pain thresholds by body region (N)

Values are the 75th-percentile limits for a mixed-gender group (≈70% male),
blunt contact, from the paper's results. **Pinching ≈ quasi-static contact;
Impact ≈ transient contact** — transient limits are higher (≈1.5–2×).

| Body region | Pinching / quasi-static (N) | Impact / transient (N) |
|---|---|---|
| Forehead | 110 | 150 |
| Temple | 60 | 90 |
| Masticatory muscle | 40 | 70 |
| Neck muscle | 70 | 110 |
| C7 vertebra | 50 | 70 |
| Shoulder joint | 60 | 100 |
| L5 vertebra | 110 | 180 |
| Sternum | 80 | 110 |
| Pectoral muscle | 60 | 110 |
| Abdominal muscle | 60 | 90 |
| Pelvic bone | 90 | 140 |
| Deltoid muscle | 100 | 110 |
| Humerus | 70 | 150 |
| Radial bone | 100 | 180 |
| Forearm muscle | 100 | 170 |
| Arm nerve | 80 | 140 |
| Forefinger pad | 150 | 390 |
| Forefinger DIP joint | 160 | 370 |
| Thenar eminence | 120 | 260 |
| Palm | 150 | 330 |
| Back of hand | 150 | 250 |
| Thigh muscle | 140 | 200 |
| Kneecap | 160 | 270 |
| Middle of shin | 150 | 260 |
| Calf muscle | 130 | 260 |

Lowest-tolerance regions: face (masticatory muscle, temple) and neck (C7,
shoulder joint) — these dominate worst-case severity for a head/neck contact.

## Source B — Pressure thresholds (Park et al. 2019, PLOS ONE, CC BY 4.0)

- **Source:** Park MY, Han D, Lim JH, Shin MK, Han YR, Kim DH, Rhim S, Kim KS
- **Doc:** *Assessment of pressure pain thresholds in collisions with collaborative robots*
- **Journal:** PLOS ONE 14(5): e0215890 (2019)
- **License:** CC BY 4.0 (PLOS open access — reuse with attribution)
- **Attribution:** `Park et al. (2019), PLOS ONE 14(5):e0215890, CC BY 4.0`
- **Retrieved:** 2026-06 · **DOI:** https://doi.org/10.1371/journal.pone.0215890

### Pressure pain thresholds by body region (N/cm²)

Overall measured range across body sites: **65.1 ± 22.6 to 196.1 ± 85.8 N/cm²**.
Younger subjects showed 3–33% lower thresholds; BMI effect minimal at most sites.

| Body region | Pressure pain threshold (N/cm²) |
|---|---|
| Arm nerve | 65.1 ± 22.6 (lowest) |
| Shoulder joint | ≈ 87 |
| Neck muscle / forehead / ball of thumb / shin | ≈ 100–120 |
| Index finger pad / palm of hand | > 160 |
| Back of hand | 196.1 ± 85.8 (highest) |

## How these are used in IACE

1. **Severity anchor for cobot/PFL hazards:** force (N) and pressure (N/cm²)
   thresholds per body region set the IACE **S** (severity) tier for a
   power-and-force-limited contact — a contact below the regional limit is
   tolerable, above it is an injury-relevant exposure.
2. **Transient vs quasi-static:** the two force columns let IACE distinguish
   transient (impact) from quasi-static (clamping/pinching) contact, matching the
   two ISO/TS 15066 contact regimes without reproducing the standard's tables.
3. **Worst-case body region:** the lowest-threshold regions (face, neck) drive the
   conservative default when the contact body region is unknown.

Licensing note: the ISO/TS 15066 limit tables are **not** reproduced. All numeric
values above are taken from the two CC BY 4.0 academic papers cited and are
attributed to those papers. No DGUV/IFA or Beuth/ISO table is used.