Assessment Of LBD Risk By Gender Using The ACGIH-TLV Lifting Assessment Method

Abstract

The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) assessment method was developed to identify safe weight limits for lifting based on horizontal and vertical locations of the object lift origin. However it is unknown if a difference in injury risk exists between genders at the safe lifting weights identified by the ACGIH TLV. PURPOSE: To assess Low Back Disorder (LBD) Risk using a validated risk model to determine if the ACGIH TLV assessment is appropriate irrespective of gender. METHODS: 24 subjects (12 male, 12 female) acquired and replaced a box of ACGIH TLV safe weights from 2 vertical zones and 4 horizontal lifting distances. EMG determined muscle activity of the rectus abdominis, deltoid, trapezius, and erector spinae. A Lumbar Motion Monitor was utilized to quantify torso kinematics. External moment was measured for each lift phase. Lift rate, torso kinematics, and external moment were used to determine LBD Risk. RESULTS: LBD Risk: LBD Risk for the MidShin to Knuckle zone was not significantly affected by gender (p=0.16). LBD Risk varied significantly by horizontal distance (p<0.0001). For Knuckle to Shoulder zone, LBD Risk varied significantly by gender (p=0.01). Females demonstrated higher LBD Risk (22.3%) than males (20.9%). LBD Risk varied significantly by horizontal distance (p<0.0001). EMG: For MidShin to Knuckle zone the trapezius had a significant distance by gender effect (p<0.0004) where differences between genders in %MVC were larger in the Mid2 distance (female 47.1, male 20.5) compared to the Far1 distance (female 22.7, male 14.2). For Knuckle to Shoulder zone, significant horizontal distance effects (p<0.003) exist for all muscles, only in the deltoid and erector spinae were the differences large 30.8 (Far2) to 12.3 (Mid1) for the deltoid and 35.8 (Far2) to 27.7 (Far1) for the erector spinae. The trapezius also had a significant distance by gender effect (p<0.0057) where differences between genders in %MVC were larger in the Far2 zone (female 43.2, male 17.6). CONCLUSIONS: While the LBD Risk model estimates the ACGIH identified safe weights for all lifting zones to be of low to moderate risk for both genders, EMG results indicate gender differences in lifting mechanics may exist in the upper extremity, with females demonstrating greater muscle activity.