A randomized intervention trial to reduce mechanical exposures in the Colombian flower industry

BACKGROUND: Evidence on effectiveness of ergonomic interventions to reduce mechanical demands of the upper extremity is scarce in agriculture. OBJECTIVE: To conduct an ergonomic intervention to reduce mechanical exposures on workers during manual flower cutting, while emphasizing postural education and reduction of force requirements. PARTICIPANTS: Seventy seven workers (20 to 55 years old; 80% women) from six companies that cultivate roses participated in this study. METHODS: Participants from three companies were randomly assigned to control and intervention groups. A postural education program and a maintenance program was designed and implemented in the intervention group aiming to achieve more neutral postures of the wrist and forearm and to reduce force requirements during rose cutting. Changes in self-reported effort and upper extremity postures, kinematics and muscular activity between baseline and follow-up assessments were evaluated. RESULTS: Most of the observed changes in the evaluated mechanical exposures were moderate for both groups. The intervention group showed differential improvements compared to the control group for 95th percentile forearm pronation (intervention group went from 50.6 to 35.6°; control group went from 18.4 to 34.7°); and to some degree for the maximum wrist radial deviation (the intervention group went from 17° to 7.6°; control group went from 10.1° to 7.8°). Also, the mean elbow flexion for the control group was reduced from 62.3 to 48.4°, whereas it increased from 52.2 to 57.3° in the intervention group. No differential changes between the intervention and control groups were observed for the kinematic variables, except for an unexpected reduction in the 95th percentile velocity of wrist flexion-extension in the control group, which was not observed in the intervention group. Lastly, although observed changes in muscular activity were not statistically significant, improvements were observed for the intervention group for the flexor and extensor carpi radialis and the flexor carpi ulnaris; although the opposite was true for the extensor carpi ulnaris. CONCLUSIONS: Important although sometimes mixed results were achieved with this field intervention, focusing on postural and force requirement demands. The positive results are encouraging considering the presence of typical limitations observed in field intervention studies.