**3. Why women have more MSD in upper limbs than men?**

Zwart [11] and his colleagues collected data from a questionnaire answered by a large sample of German workers, men and women. For their analysis, they divided the data by age and the demand at work (heavy or light physical demands, mental demands, or mixtures of physical and mental demands). Data shows that men and women are affected by back problems, but women refer more frequent problems in the neck and upper limbs. Reviews performed by NIOSH [12] and Artazcoz [13] show several studies with the same situation.

A first approach to explaining these differences in women's working conditions and their exposure to risk factors are based in several beliefs, not all of which are sufficiently well-founded: smaller people have more problems, because tools are too big for small hands; the duration of work (in years of service) with a higher-risk exposure; women have less muscle strength than men, the same conditions have greater effects on them; family responsibilities combined with working conditions increase the risk; hormonal factors alone or in interaction with working conditions

produce a greater risk; and women express their problems more psychologically, so women react more to organizational factors that combine with physical factors to produce musculoskeletal problems [14].

However, these explanations are apparently logical and do not support a more in-depth analysis. The most relevant factor is that it can make direct comparisons between the tasks performed by men and those performed by women. Men and women occupy different spaces in the labor market, a way to mark that one could almost speak of separate labor forces. In Sweden, only 10% of women and men work in mixed jobs [15]. This segregation means that men and women are not exposed to the same working conditions.

Within a single economic sector, women occupy different jobs than men; for example, in women's clothing factories in Canada, women work by sewing and ironing clothes, while men are pattern cutters. In the automotive industry, women sew seat linings, while men handle the assembly of vehicles. Even when men and women occupy the same position, the tasks performed are different. In a turkey meat industry, men and women worked in the same production chain; however, men worry about hanging the animal and making large cuts (descading, large cuts, peeling), while women make small cuts (wings, breast, legs) and did the finishing work (cut off excess fat, clots, etc.).

Men and women have different sizes and so, also different reaches. Because of this, they can perform their tasks differently. Karlqvist [16] in his study showed that women work with the computer keyboard in postures more uncomfortable than men because the length of their arms is smaller. However, after many years of female employment in certain productive sectors, furniture, tools, and workplaces have been modified to the dimensions of their workers (anthropometric adaptations), not only obeying gender differences, necessary for implementing productive technologies in other countries (anthropotechnology). In this way, the jobs have been adapted over time to the working population, so that in the positions traditionally occupied by women, the physical configuration is mostly adapted, so these positions could be more injurious to a population with different anthropometric characteristics, including male labor population.

Another reason that may explain the differences between men and women is the work history at long term. Torgén et al. [17] showed that on average, women did not change their physical workload over a 24-year period, while men gradually decreased it. It seems that women stay longer in the same jobs, and it exposes them more time to the same risk factors. Also, when the damage occurs, female workers develop strategies to avoid pain and to be able to work. When men are in these situations, they are more likely to drift toward other positions. The proportion of men doing repetitive work in slaughterhouses decreases with age, while age does not influence the proportion of women in repetitive work. What it probably wants to say is that men withdraw from those jobs.

Other factors that increase the risk of musculoskeletal problems are the lack of rest. Women combine wage labor with housework and complain more often that they are fatigued. Most researches show that women spend more hours on domestic, unpaid work and that this increases with the number of children in the family [18]. The physical and mental demands of domestic/unpaid work are stronger for women than for men (**Figure 1**) and may increase the risk of musculoskeletal problems. This dual presence, both physical and psychosocial, increases the exposure of women to the effects of work and creates an imbalance between the productive and reproductive periods of work and rest that has an impact on the health of women. However, this factor also refers to the greater resilience of women to physical and mental stress caused by work.

Women report more symptoms than men regardless of the region of the body being studied. For example, in a review of computer work and musculoskeletal problems, Punnet and Bergqvist [19] showed that women report more complaints but have fewer

**13**

**Figure 2.**

**Figure 1.**

*Women, Ergonomics and Repetitiveness DOI: http://dx.doi.org/10.5772/intechopen.82065*

clinical diagnoses than men. One explanation may be that the perception of pain differs between men and women. The perception of pressure pain is more developed in the woman. It could be seen as a weakness, but in reality it proves to be a protective factor which produces a preventive action from the woman at the first symptoms (could be a

*Percentage of women workers reporting a specific health problem, by risk factor exposition, EU-27, ESWC 2005.*

An experimental, cross-sectional study was conducted between 2015 and 2016 with a semi- probabilistic sample composed of 300 workers (150 women and 150 men) from three industrial plants in Valencia, Venezuela; Santa Cruz de Aragua, Venezuela; and Tijuana, Mexico, in sectors of electrical fan manufacturing, snack

The study correlates three variables, considering the biomechanical performance in terms of force and movement range: job hazards (biomechanics, repetition and postures; psychosocial, quantitative psychological requirements), workers'

Biomechanical risk for repetitiveness was assessed by the OCRA index method [20]. Postural risk was assessed using the OWAS method [21]. Psychosocial risk was assessed using the ISTAS/COPSOQ method [22], specifically through the section on quantitative psychological requirements. The health assessment focused on the

pre-pathological stage) that induces her to change the way of working.

packaging, and assembly of hydraulic connections (**Figures 2** and **3**).

health assessment, and average labor productivity.

*Gender differences in daily paid/unpaid work. Global Gender GAP Report 2017.*

### *Women, Ergonomics and Repetitiveness DOI: http://dx.doi.org/10.5772/intechopen.82065*

#### **Figure 1.**

*Safety and Health for Workers - Research and Practical Perspective*

produce musculoskeletal problems [14].

exposed to the same working conditions.

work (cut off excess fat, clots, etc.).

say is that men withdraw from those jobs.

produce a greater risk; and women express their problems more psychologically, so women react more to organizational factors that combine with physical factors to

However, these explanations are apparently logical and do not support a more in-depth analysis. The most relevant factor is that it can make direct comparisons between the tasks performed by men and those performed by women. Men and women occupy different spaces in the labor market, a way to mark that one could almost speak of separate labor forces. In Sweden, only 10% of women and men work in mixed jobs [15]. This segregation means that men and women are not

Within a single economic sector, women occupy different jobs than men; for example, in women's clothing factories in Canada, women work by sewing and ironing clothes, while men are pattern cutters. In the automotive industry, women sew seat linings, while men handle the assembly of vehicles. Even when men and women occupy the same position, the tasks performed are different. In a turkey meat industry, men and women worked in the same production chain; however, men worry about hanging the animal and making large cuts (descading, large cuts, peeling), while women make small cuts (wings, breast, legs) and did the finishing

Men and women have different sizes and so, also different reaches. Because of this, they can perform their tasks differently. Karlqvist [16] in his study showed that women work with the computer keyboard in postures more uncomfortable than men because the length of their arms is smaller. However, after many years of female employment in certain productive sectors, furniture, tools, and workplaces have been modified to the dimensions of their workers (anthropometric adaptations), not only obeying gender differences, necessary for implementing productive technologies in other countries (anthropotechnology). In this way, the jobs have been adapted over time to the working population, so that in the positions traditionally occupied by women, the physical configuration is mostly adapted, so these positions could be more injurious to a population

with different anthropometric characteristics, including male labor population. Another reason that may explain the differences between men and women is the work history at long term. Torgén et al. [17] showed that on average, women did not change their physical workload over a 24-year period, while men gradually decreased it. It seems that women stay longer in the same jobs, and it exposes them more time to the same risk factors. Also, when the damage occurs, female workers develop strategies to avoid pain and to be able to work. When men are in these situations, they are more likely to drift toward other positions. The proportion of men doing repetitive work in slaughterhouses decreases with age, while age does not influence the proportion of women in repetitive work. What it probably wants to

Other factors that increase the risk of musculoskeletal problems are the lack of rest. Women combine wage labor with housework and complain more often that they are fatigued. Most researches show that women spend more hours on domestic, unpaid work and that this increases with the number of children in the family [18]. The physical and mental demands of domestic/unpaid work are stronger for women than for men (**Figure 1**) and may increase the risk of musculoskeletal problems. This dual presence, both physical and psychosocial, increases the exposure of women to the effects of work and creates an imbalance between the productive and reproductive periods of work and rest that has an impact on the health of women. However, this factor also refers to the greater resilience of women to physical and mental stress caused by work. Women report more symptoms than men regardless of the region of the body being studied. For example, in a review of computer work and musculoskeletal problems, Punnet and Bergqvist [19] showed that women report more complaints but have fewer

**12**

*Percentage of women workers reporting a specific health problem, by risk factor exposition, EU-27, ESWC 2005.*

clinical diagnoses than men. One explanation may be that the perception of pain differs between men and women. The perception of pressure pain is more developed in the woman. It could be seen as a weakness, but in reality it proves to be a protective factor which produces a preventive action from the woman at the first symptoms (could be a pre-pathological stage) that induces her to change the way of working.

An experimental, cross-sectional study was conducted between 2015 and 2016 with a semi- probabilistic sample composed of 300 workers (150 women and 150 men) from three industrial plants in Valencia, Venezuela; Santa Cruz de Aragua, Venezuela; and Tijuana, Mexico, in sectors of electrical fan manufacturing, snack packaging, and assembly of hydraulic connections (**Figures 2** and **3**).

The study correlates three variables, considering the biomechanical performance in terms of force and movement range: job hazards (biomechanics, repetition and postures; psychosocial, quantitative psychological requirements), workers' health assessment, and average labor productivity.

Biomechanical risk for repetitiveness was assessed by the OCRA index method [20]. Postural risk was assessed using the OWAS method [21]. Psychosocial risk was assessed using the ISTAS/COPSOQ method [22], specifically through the section on quantitative psychological requirements. The health assessment focused on the

**Figure 3.** *Snack packaging (Venezuela) and hydraulic connections (Mexico) assessed processes.*

functional status of the upper limbs, especially the wrists and forearms (search for initial states of De Quervain pathology, carpal tunnel syndrome, trigger fingers, bursitis, etc.) it performed using dynamometry and goniometry, and also applying Kuorinka questionnaires [23] to identify painful symptoms. We also tested the functional status of the legs, required by the posture of sitting and prolonged standing. Health outcomes were assessed according to the number and severity of injuries. The level of mental load impairment was assessed using the Maslach Burnout Inventory [24]. Productivity was extracted directly from the payroll system (production bonds).

Hand dynamometry (**Figure 4**) assessed the biomechanical performance to measure the interaction between the hand and objects, making a follow-up by day and week. Also, the workflow was video recorded to assist the repetition counter and to apply the measure of movement arches, using a computer-based photo-goniometer.

Variables were correlated, and it got several odds. First, conditions of biomechanical risk were correlated with the occurrence of musculoskeletal disorders. Second, mental load at work, correlated with the emotional exhaustion of the subjects. A third correlation analysis was carried out on the combined effect of biomechanical and psychosocial risks with the occurrence of musculoskeletal disorders, by gender. The synergetic effect of physic and mental work load was assessed through the performance analysis to state cause-effect relations.

Finally, a longitudinal analysis of the productivity (including absences due to rest and rotation of personnel) of each gender was performed, from the perspective of marginal returns and the Cobb-Douglas [25] model curve.

Women were found to have had a lower biomechanical involvement in the upper limbs in the presence of a similar exposure to the male, having, on average, a higher rate of productivity, especially with low force demands, performing repetitive tasks involving a prehensile effort of less than 15 N or manual loads of less than 50 Gr per repetition.

**15**

**Figure 5.**

*Women, Ergonomics and Repetitiveness DOI: http://dx.doi.org/10.5772/intechopen.82065*

higher exposure risk was found.

(mental astreinte).

It was found that the working conditions (biomechanical and psychosocial) were the same for each gender group in each work facility, but there is a difference that should be considered in the results, since the frequency of technical actions (repetitive movements) was slightly higher in the female group than in the male group, for which the OCRA indexes were also higher in the group of women, and a

With more repetitiveness, the mental load is also higher, so there is also a greater

In terms of musculoskeletal affections, greater presence of biomechanical and psychosocial risk would be expected. However, although the pain perception was slightly higher in the female group, the health evaluation found a greater number of

Among the causes of the observed phenomena, it can be attributed to the fact that men used, on average, more strength than strictly necessary for the accomplishment of the task (which was evidenced with the dynamometer), mobilizing a

Another observed phenomenon is that the male group always started the day (weekly and daily) with peaks of productivity (higher than the average productivity of the female group), but this was decreasing throughout the day and week; however, the productivity of the female group remained more constant and finally was, on

The group of women also showed a greater resilience to conditions of high repetitiveness that impose high-quantitative psychological demands and still maintain productivity rates over time, which did not happen in the group of men, evidencing also lower rates of turnover and absenteeism due to musculoskeletal disorders. Women showed a more constant productive rate over time, since the repetition factor hardly changed during the weekly lapses, while the male group showed a marginal productivity distribution similar to the Cobb-Douglas (**Figure 5**) function.

lesions in the male group, some with functional limitations.

*Cobb-Douglas curves: total product, marginal product, and average product.*

average, slightly higher than male group.

greater number of muscle groups than those used by the female group.

psychosocial risk in the group of women. The evaluated work stations denoted conditions of high monotony associated with drowsiness, psychic laxity, decreased performance, reduced adaptability, low reactivity, and high variability of heart rate. Hypovigilance conditions were also observed, accompanied by reduced performance in terms of perception and detection of signals, fundamentally in light monitoring tasks. Thus, for both groups, a similar influence of external factors (mental contraite) was found but with a marked difference in the way it affected genders

**Figure 4.** *PC-based hand dynamometer used (probe detail).*

#### *Women, Ergonomics and Repetitiveness DOI: http://dx.doi.org/10.5772/intechopen.82065*

*Safety and Health for Workers - Research and Practical Perspective*

functional status of the upper limbs, especially the wrists and forearms (search for initial states of De Quervain pathology, carpal tunnel syndrome, trigger fingers, bursitis, etc.) it performed using dynamometry and goniometry, and also applying Kuorinka questionnaires [23] to identify painful symptoms. We also tested the functional status of the legs, required by the posture of sitting and prolonged standing. Health outcomes were assessed according to the number and severity of injuries. The level of mental load impairment was assessed using the Maslach Burnout Inventory [24]. Productivity

Hand dynamometry (**Figure 4**) assessed the biomechanical performance to measure the interaction between the hand and objects, making a follow-up by day and week. Also, the workflow was video recorded to assist the repetition counter and to apply the measure of movement arches, using a computer-based photo-goniometer. Variables were correlated, and it got several odds. First, conditions of biomechanical risk were correlated with the occurrence of musculoskeletal disorders. Second, mental load at work, correlated with the emotional exhaustion of the subjects. A third correlation analysis was carried out on the combined effect of biomechanical and psychosocial risks with the occurrence of musculoskeletal disorders, by gender. The synergetic effect of physic and mental work load was assessed

Finally, a longitudinal analysis of the productivity (including absences due to rest and rotation of personnel) of each gender was performed, from the perspective

Women were found to have had a lower biomechanical involvement in the upper limbs in the presence of a similar exposure to the male, having, on average, a higher rate of productivity, especially with low force demands, performing repetitive tasks involving a prehensile effort of less than 15 N or manual loads of less than 50 Gr per repetition.

was extracted directly from the payroll system (production bonds).

*Snack packaging (Venezuela) and hydraulic connections (Mexico) assessed processes.*

through the performance analysis to state cause-effect relations.

of marginal returns and the Cobb-Douglas [25] model curve.

**14**

**Figure 4.**

*PC-based hand dynamometer used (probe detail).*

**Figure 3.**

It was found that the working conditions (biomechanical and psychosocial) were the same for each gender group in each work facility, but there is a difference that should be considered in the results, since the frequency of technical actions (repetitive movements) was slightly higher in the female group than in the male group, for which the OCRA indexes were also higher in the group of women, and a higher exposure risk was found.

With more repetitiveness, the mental load is also higher, so there is also a greater psychosocial risk in the group of women. The evaluated work stations denoted conditions of high monotony associated with drowsiness, psychic laxity, decreased performance, reduced adaptability, low reactivity, and high variability of heart rate. Hypovigilance conditions were also observed, accompanied by reduced performance in terms of perception and detection of signals, fundamentally in light monitoring tasks. Thus, for both groups, a similar influence of external factors (mental contraite) was found but with a marked difference in the way it affected genders (mental astreinte).

In terms of musculoskeletal affections, greater presence of biomechanical and psychosocial risk would be expected. However, although the pain perception was slightly higher in the female group, the health evaluation found a greater number of lesions in the male group, some with functional limitations.

Among the causes of the observed phenomena, it can be attributed to the fact that men used, on average, more strength than strictly necessary for the accomplishment of the task (which was evidenced with the dynamometer), mobilizing a greater number of muscle groups than those used by the female group.

Another observed phenomenon is that the male group always started the day (weekly and daily) with peaks of productivity (higher than the average productivity of the female group), but this was decreasing throughout the day and week; however, the productivity of the female group remained more constant and finally was, on average, slightly higher than male group.

The group of women also showed a greater resilience to conditions of high repetitiveness that impose high-quantitative psychological demands and still maintain productivity rates over time, which did not happen in the group of men, evidencing also lower rates of turnover and absenteeism due to musculoskeletal disorders.

Women showed a more constant productive rate over time, since the repetition factor hardly changed during the weekly lapses, while the male group showed a marginal productivity distribution similar to the Cobb-Douglas (**Figure 5**) function.

#### **Figure 5.**

*Cobb-Douglas curves: total product, marginal product, and average product.*

A more longitudinal analysis of the marginal productivity per worker in the last year shows even more definitive results, with the female sample having an annualized productivity 18.3% higher than the male sample, considering the effect of absence, rest, and labor rotation.
