After applying the Nordic questionnaire in the metalworking company, it was found that, of the 32 workers, 39.58%, claim to have been incapacitated for muscle-skeletal discomfort, while 23.44% of them claim to have missed work for suffering from the same discomfort, without the need for a medical consultation.

In the plastics sector company, the population evaluated consists of 31 workers, who work in the production area, of which 72% of the disabilities that were generated in recent months have been linked to disergonomic and Psychosocial problems.

In the company in the timber sector, the questionnaire was applied to the 13 workers who work in the production area, these workers were incapacitated in a range of 31% to 38% per area, according to data from the last year, due to back pain at 46% and pain in the arms with 27%.

The results of the application of the Nordic questionnaire are tabulated in Table 2.

Table 2

Source: Author based on Castañeda, Ruge & Zambrano (2019); Manrique & Otero (2019) and Aponte, Otalora & Perez (2019)

As evidenced in the above results, according to the Nordic Questionnaire applied to the workers of the three companies assessed, the body regions most affected, as the workers themselves refer are, the lumbar back region, hands/wrists and shoulders.

In the metalworking sector, workers refer to inadequate movements, bad working practices regarding posture, prolonged standings and the lack of tools to facilitate the performance of heavy lifting, as the factors causing discomfort. Workers carry out their work with back lateralized and tilted forward, executing lifts greater than 22 kg., concerning to psychosocial risk, workers said that the main factors within the working environment are stress and excessive workloads

Workers in the plastics Company refer their discomfort mainly to repetitive movements, inadequate posture, prolonged standings and stress, factors to which they are exposed due to their workplace.

In the case of the timber sector, they attribute the inconvenience to prolonged standing, load handling, poor postures required by work and repetitive movements, as well as stress.

The previous findings show that bad postures, prolonged standing, and stress, according to the perception of the workers, are the transversal causes in the three companies associated with the inconvenience referred by the workers.

3.2. Laboratory of Economic and Sociology Labor method (LEST) results

When applying the LEST method, the physical environment was evaluated in the first instance for the three companies: concerning the thermal environment, the company that presents the greatest risk in this aspect for workers is that of the Plastic sector, in which 44% of the jobs are under conditions of significant harmfulness, due to the operation of machines that generate heat such as those in the injection and blowing areas.

Concerning the noise factor, the company that presents the most exposure with harmfulness to workers is the company of the metalworking sector, with 86.7% of jobs with harmfulness, the company in the plastic sector has 46% of jobs with harmfulness and 33% with strong discomfort for workers.

For lighting, the three companies have percentages of jobs with deficiencies in this variable, being that of the plastic sector the one that presents the greatest deficiency with 46% of jobs with harmful levels, followed by the company of the timber sector that presents 52% of jobs in strong discomfort condition.

About the static load, most of the jobs of the three companies present average discomfort for the worker; concerning mental load factors, the critical issue for the company in the plastic sector is the demand for time, in this case, all jobs have a level of average fatigue discomfort; for the company of the sector, the critical factors regarding mental load are attention and complexity and speed. While the metalworking company presents a satisfactory condition for this aspect.

3.3. Rapid Entire Body Assessment methods (REBA) results

In the metalworking sector company, the REBA method was applied in the 15 jobs, and it was found that 13.33% of them present a high level of risk, with a score of 8, these jobs are those called torque and radial drilling, while 86.67% of the positions represent a medium level of risk, of which 84.6% showed a score between 6 and 7, values that also require attention, see Fig. 1. These findings reflect that the performance of activities in the metal-mechanical sector company requires significant commitments due to lateralization and flexion of the neck and back between 20⁰ and up to 60⁰ respectively, as well as extensions in upper limbs for workers. There are also sudden and repetitive movements that cause repetitive posture changes.

Figure 1 Source: Castañeda, Ruge & Zambrano (2019).

As shown in Fig.1, no job is at a low-risk level in the biomechanical evaluation carried out through the REBA Method, there are no jobs either above a score of 11, that is, with a very high-risk level.

For the plastic sector company, 33.34% of the jobs present high-risk of skeletal muscle injuries with ranges between 8 and 10 points, these jobs are those referred to as sealer, blower injectors and offset printing; 52.38% a medium risk level also with a preponderance towards high values of the interval between 6 and 7, and 14.28% of jobs with a low level, see Fig. 2. These results are mainly due to unstable postures, neck and back flexion up to 20⁰ and 60⁰ respectively, repetitive use of hands and wrists, with flexion and lateralization of the same, and flexion of the arms at 60⁰. There are also rapid and abrupt changes in posture.

Figure 2 Source: Manrique & Otero (2019).

In the company of the plastic sector, there are no jobs with scoring levels greater than 11 or very high risk for skeletal muscle injuries, as shown in Fig. 2.

However, in the company of the wood and furniture manufacturing sector, the findings regarding the biomechanical valuation were the following: 43% of the jobs are at a high level of risk; while the remaining 57% have a medium level of risk, with a higher proportion of them with values of 7 points, which represents a considerable level of risk, Fig. 3. These results occur due to flexions of the neck and back in ranges of up to 20⁰ and 60⁰ respectively, rotation and lateralization of the back, repetitive movements in hands with the rotation of wrists, and extension of arms and forearms are also presented.

Figure 3 Source: Aponte, Otarola & Pérez (2019)

In the timber sector company, there are also no jobs with values higher than 11 points REBA risk level, nor jobs with low risk values for skeletal muscle injuries.

Right away in Table 3, there is a comparative table between the three companies, concerning biomechanical evaluation through the REBA method.

As shown in the Table 3, the timber sector company has the highest percentage of jobs with high-risk levels, given its high content of manual jobs and the repetitive movements that make the activities of this sector, a great potential of risk of musculoskeletal injuries in workers. The company in the plastic sector also has a significant number of jobs with a high level of REBA risk, also due to repetitive movements and flexions of the neck and back due to the poor design of the jobs that force the adoption of inappropriate postures of the workers of the organization, and finally, the company of the metalworking sector, which has the lowest rate, however above 50 percent of jobs have an average REBA risk levels. By the shown jobs must be intervened with both engineering and administrative solutions to reduce biomechanical risk levels.

Table 3

Source: Author, adapted from Castañeda, Ruge & Zambrano (2019); Manrique & Otero (2019) and Aponte, Otalora & Perez (2019)

Table 4 shows the different biomechanical risk factors present in the small and medium-size enterprises (SMEs) evaluated, which establishes the characterization of these factors in them.

Table 4

Source: Author, based on Castañeda, Ruge & Zambrano (2019); Manrique & Otero (2019) and Aponte, Otalora & Perez (2019).

As can be seen in the Table 4, the common biomechanical risk factors in the three companies assessed are flexion and lateralization of the neck and back, repetitive movements and flexion/extension of the upper limbs and sudden changes in posture.

A comparison was established between the data obtained from the Nordic questionnaire and those obtained by the REBA method, finding that, in the case of the metalworking company, workers perceive greater discomfort in the back/lumbar area, neck and shoulders, however, the results of REBA method generates critical conditions for the neck, the back/lumbar area which corresponds to the workers perception , but also yields the hands/wrists as a critical area instead of the shoulders, as shown in Table 5.

Table 5

Source: Author based on Castañeda, Ruge & Zambrano (2019); Manrique & Otero (2019) and Aponte, Otalora & Perez (2019).

Concerning the company of the plastic sector, it can be observed that there is a concordance in two of the body areas where workers report feeling discomfort and the data generated by the REBA method, these are wrists and hands and lumbar back region, however, there is a discrepancy in the third critical zone since workers perceive the neck and the REBA methodology refers to the elbow as the third factor with greater biomechanical commitment. See Table 5.

A concordance evaluation between the Nordic Questionnaire was carried out, with the participation of 76 workers and the results determined by the REBA Method applied to the jobs, in order to establish whether there is agreement between both methods, establishing as a null hypothesis H₀= methods do not show concordance and as a hypothesis of the researcher H₁ = the methods have concordance, for which the null hypothesis is rejected in case of a p-value <0.05.

For this, the Statistical Package for the Social Sciences (SPSS), version 25 was used, applying the Cohen´s Kappa statistic. Table 6 shows the results obtained for the shoulder.

Table 6

Source: Author from the SPSS program, version 2 licensed for Universidad El Bosque.

In this sense, it can be seen in Table 6 that there are 41 cases in which both methods agree with the “Yes”, that is, in 41 cases the workers expressed through the Nordic Questionnaire to have presented shoulder discomfort, as well as in 41 workers evaluated with the REBA Method found a risk of skeletal muscle injury of joint involvement, there are also 29 cases of concordance in which both methods agree that they have not presented shoulder ailments (Nordic Questionnaire) and do not present a risk for shoulder skeletal muscle injury (REBA method).

On the other hand, there are 6 cases of disagreement between the two methods, in which, 6 cases showed shoulder ailments, while with the evaluation of the REBA Method no risk was observed for the joint.

Concerning the value of the Cohen Kappa statistic, a value of 0.839 was obtained, which represents a very good agreement between both methods, with a significance level of 0.00, which is less than 0.05.

In the same way, the concordance evaluation was carried out, through the Statistical Package for the Social Sciences (SPSS), using the Cohen Kappa statistic, between the Nordic Questionnaire and the REBA Method, for each of the body zone evaluated: elbow, neck, back, and hand. The values obtained are shown below in Tables from 7 to 10.

Table 7

Source: Author from the SPSS program, version 25, licensed for Universidad El Bosque.

Tabla 8

Source: Author, from the SPSS program, version 25, licensed for Universidad El Bosque.

Table 9

Source: Author, from the SPSS program, version 25, licensed for Universidad El Bosque.

Table 10

Source: Author, from the SPSS program, version 25, licensed for Universidad El Bosque.

The above tables show concordance between both methods with 77.7% for the elbow, 84.2% for the neck, 93.4% for the back and 69.7% for the hand.

However, the results of Cohen's Kappa statistic and the p-value for the shoulder, elbow, neck, back and hand are shown in Table 11.

Table 11

Source: Author, from the SPSS program, version 25, licensed for Universidad El Bosque.

The Cohen Kappa statistic values show agreement between both methods evaluated, for the elbow and the hand, there is a moderate concordance whose Kappa value is 0.545 and 0.402 respectively, the hand being the one with the lowest value of the statistic; for the neck, they show a good concordance with the statistic value of 0.665 and for the back a very good concordance, with a Kappa value of 0.846.

All variables have a p value of 0.000 less than 0.05 which shows a statistically significant result.