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.

Physical workloads of the upper-extremity among workers of the Colombian flower industry.

BACKGROUND: We report the prevalence of symptoms of common upper-limb disorders and describe comprehensively mechanical workloads in a sample of workers of the Colombian flower industry. METHODS: One hundred fifty eight workers from eight flower manufacturers were assessed. Assessments included Borg self-reported exertion and working practices, medical examinations, video-based observations and kinematic and surface muscular activity assessments of upper-limb. RESULTS: Point prevalence of signs and symptoms of CTS, epicondylitis, and De Quervain's disease was 32.9%, 15.2%, and 13.3%, respectively. All tasks are executed on average in wrist extension, ulnar deviation, and high elbow flexion. Average median muscle activity across tasks ranged between 3.6% and 27.3%. Forearm muscles were mainly active. CONCLUSIONS: The occurrence of signs and symptoms of upper-extremity musculoskeletal disorders was high among the sample. The classification and cutting task showed the highest mechanical demands. Interventions in this working population are required and should be directed to allow for muscular rest on regular basis.

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

Evidence on the effectiveness of ergonomic interventions to reduce mechanical demands and upper-extremity MSDs is scarce in agriculture. We conducted an intervention to reduce mechanical exposures during manual flower cutting through job rotation, education and reduction of force requirements. One-hundred and twenty workers (20 to 60 years old; 89% women) from six companies that cultivate roses participated in this study. Three companies were randomly assigned to control and intervention groups. We studied changes between baseline and follow-up in self-reported effort and upper-extremity postures, kinematics and muscular activity. Most of the observed changes were moderate for both groups. The intervention group showed differential improvements compared to the control group for the maximum wrist radial deviation and forearm pronation, and acceleration of the forearm supination-pronation and elbow flexion-extension; and the muscular activity of the flexor and extensor carpi radialis and the flexor carpi ulnaris. However, we also observed that the maximum ulnar deviation, velocity of the wrist flexion-extension and muscular activity of the extensor carpi ulnaris improved more in the control group. These mixed results may be related to limited time for intervention adjustment, and uncontrolled task changes in the control group. Future research should address these issues and test other solutions.

A field experiment comparing mechanical demands of two pruners for flower cutting.

Manual flower cutting requires repetitive forceful movements that may explain the high incidence of upper-extremity MSDs among workers of the Colombian flower industry. Force demands may be caused by the use of pruners that have not been designed for Colombian workers. We conducted a repeated measures field experimental study (n=16, 69% women, 20 to 60 years old) to compare the mechanical demands during rose cutting of two different pruners (Traditional vs. alternative pruner) at two different cutting heights (elbow vs. over-shoulder). Demands included the perceived comfort, perceived effort and upper limb's muscular activity and posture. Workers perceived their traditional pruner as more comfortable but requiring more effort than the prototype tool. No benefits were observed regarding ulnar deviation with the alternative pruner. The wrist extension and related muscular activity of the wrist extensors were higher with the prototype pruner. The prototype pruner resulted in reduced muscular load of the wrist flexors; the biceps when working at the elbow height; and the deltoids when working at the shoulder height. However, Moderate results may be explained by the lack of time for workers' adaptation to the alternative tool. New design developments must focus on reducing extension and ulnar deviation of the wrist.

Work pattern causes bias in self-reported activity duration: a randomised study of mechanisms and implications for exposure assessment and epidemiology.

BACKGROUND: Self-reported activity duration is used to estimate cumulative exposures in epidemiological research. OBJECTIVE: The effects of work pattern, self-reported task dullness (a measure of cognitive task demand), and heart rate ratio and perceived physical exertion (measures of physical task demands) on error in task duration estimation were investigated. METHODS: 24 participants (23-54 years old, 12 males) were randomly assigned to execute three tasks in either a continuous (three periods of 40 continuous minutes, one for each task) or a discontinuous work pattern (40 min tasks each divided into four periods of 4, 8, 12 and 16 min). Heart rate was measured during tasks. After completing the 2 h work session, subjects reported the perceived duration, dullness and physical exertion for each of the three tasks. Multivariate models were fitted to analyse errors and their absolute value to assess the accuracy in task duration estimation and the mediating role of task demands on the observed results. RESULTS: Participants overestimated the time spent shelving boxes (up to 38%) and filing journals (up to 9%), and underestimated the time typing articles (up to -22%). Over- and underestimates and absolute errors were greater in the discontinuous work pattern group. Only the self-reported task dullness mediated the differences in task duration estimation accuracy between work patterns. CONCLUSIONS: Task-related factors can affect self-reported activity duration. Exposure assessment strategies requiring workers to allocate work time to different tasks could result in biased measures of association depending on the demands of the tasks during which the exposure of interest occurs.

Effect of horizontal position of the computer keyboard on upper extremity posture and muscular load during computer work.

The distance of the keyboard from the edge of a work surface has been associated with hand and arm pain; however, the variation in postural and muscular effects with the horizontal position have not been explicitly explored in previous studies. It was hypothesized that the wrist approaches more of a neutral posture as the keyboard distance from the edge of table increases. In a laboratory setting, 20 adults completed computer tasks using four workstation configurations: with the keyboard at the edge of the work surface (NEAR), 8 cm from the edge and 15 cm from the edge, the latter condition also with a pad that raised the work surface proximal to the keyboard (FWP). Electrogoniometers and an electromagnetic motion analysis system measured wrist and upper arm postures and surface electromyography measured muscle activity of two forearm and two shoulder muscles. Wrist ulnar deviation decreased by 50% (4 degrees ) as the keyboard position moved away from the user. Without a pad, wrist extension increased by 20% (4 degrees ) as the keyboard moved away but when the pad was added, wrist extension did not differ from that in the NEAR configuration. Median values of wrist extensor muscle activity decreased by 4% maximum voluntary contraction for the farthest position with a pad (FWP). The upper arm followed suit: flexion increased while abduction and internal rotation decreased as the keyboard was positioned further away from the edge of the table. In order to achieve neutral postures of the upper extremity, the keyboard position in the horizontal plane has an important role and needs to be considered within the context of workstation designs and interventions.