Ergonomic Assessment Tools
These tools help evaluate biomechanical stresses in occupational tasks to prevent musculoskeletal disorders and injuries.
Moment (Torque) Calculator
Calculate the torque generated by a force acting at a distance from a pivot point, which is critical for analyzing joint stresses in ergonomic assessments.
Moment/Torque Result
Calculated Moment:
Interpretation
This moment represents the rotational force at the joint. Compare to:
| Joint | Typical Maximum Moment (N·m) | Typical Maximum Moment (lb·in) |
|---|---|---|
| Shoulder | 40-60 | 350-530 |
| Elbow | 25-35 | 220-310 |
| Wrist | 8-12 | 70-105 |
| Lumbar Spine (L5/S1) | 120-180 | 1060-1590 |
NIOSH Lifting Equation Calculator
The NIOSH equation calculates a Recommended Weight Limit (RWL) and Lifting Index (LI) for two-handed manual lifting tasks.
Lifting Index (LI) = Object Weight / RWL
NIOSH Lifting Results
Horizontal Multiplier (HM)
Vertical Multiplier (VM)
Distance Multiplier (DM)
Asymmetric Multiplier (AM)
Frequency Multiplier (FM)
Coupling Multiplier (CM)
Recommended Weight Limit (RWL)
Lifting Index (LI)
Interpretation
| Lifting Index (LI) | Risk Level | Action Required |
|---|---|---|
| LI ≤ 1 | Low | Acceptable for most workers |
| 1 < LI ≤ 2 | Moderate | Evaluate task and consider improvements |
| 2 < LI ≤ 3 | High | Implement changes to reduce risk |
| LI > 3 | Very High | Immediate changes required |
Static Strength & Compressive Force Calculator
Estimate the required strength and spinal compressive forces for static holding tasks, particularly at the L5/S1 joint.
Static Strength Results
Required Back Muscle Force
L5/S1 Compressive Force
Interpretation
| Compressive Force | Risk Level | NIOSH Limit |
|---|---|---|
| < 3400 N (765 lb) | Low | Acceptable for most workers |
| 3400-6400 N (765-1440 lb) | Moderate | Some risk for some workers |
| > 6400 N (1440 lb) | High | Unacceptable for most workers |
Reduction Strategies
- Reduce load weight
- Keep load closer to the body
- Minimize torso flexion (bending forward)
- Use lifting aids or team lifting
- Rotate workers to limit exposure
Practical Examples
Example 1: Safe Lifting
Scenario: Lifting 10 kg container from waist height (75 cm) to a shelf (120 cm), close to body (25 cm horizontal), with good grip, 4 lifts/minute for at most 2 hours.
Results: RWL = 14.2 kg, LI = 0.7 (Safe)
Example 2: Risky Lifting
Scenario: Lifting 25 kg crate from floor (30cm) to waist height (75cm), 50cm horizontal distance, poor grip, 6 lifts/minute for 8 hours.
Results: RWL = 7.8 kg, LI = 3.2 (Very High Risk)
Example 3: Static Holding
Scenario: Holding 15 kg tool 40cm in front of body with 30° torso flexion for extended periods.
Results: Compressive Force = 4200 N (Moderate Risk)