Interventions for Overhead Drilling into Concrete

Introduction
The purpose of this 5-year study was to develop and evaluate interventions for overhead drilling to reduce the arm and shoulder loads. Seven different interventions were developed and tested; results from the final design are presented. 

Methods
During their usual work, 23 commercial construction workers used the usual method and the intervention design for overhead drilling- each for 3 hours – order randomized. Afterwards, subjects rated fatigue in 5 body regions and usability on 12 items. The work was videotaped for productivity (N=19) and inclinometers measured shoulder posture and head inclination (N=16). Hand forces were measured for three subjects.

Results
The intervention device was rated superior to the usual method on the usability measures of drilling/vibration, stability, and feel/handling. Perceived fatigue ratings were significantly lower in all 5 body regions for the intervention device compared with the usual method. There was no significant difference in total time per hole between the usual method and the intervention device (p = 0.61). The shoulder was flexed or abducted to over 60 degrees for 40% of the time while drilling with the usual method compared with 21% with the intervention (p = 0.007). The percentage of time that the head was in extension of more than 0 degrees was greater for the usual method than the intervention (p = 0.005). The mean applied hand force during drilling with the usual method was 245 (±11) N, and 26.3 (±3.3) N for the intervention.

Discussion
An intervention device, compared to the usual method for overhead drilling, was associated with reduced upper extremity fatigue. This improvement was supported by reductions in the objective risk factors of applied force and percent time in non-neutral shoulder posture. Repeated field-testing by experienced construction workers and their feedback on design was vital to the development of this new intervention device.