Obesity effect on perceived postural stress during static posture maintenance tasks

Sex differences in perceived discomfort during seated static posture holding

This study investigated how sex modifies postural discomfort perception during a sagittally-symmetric, seated static posture holding (SPH) task. Ten male and 10 female participants performed SPH and conducted subjective discomfort ratings in a total of 108 task conditions. A regression analysis found that the impacts of the body joint reactive moments on perceived discomfort were larger for the female group than the male whereas that of the shoulder joint angle was more pronounced for the male than the female. Also, some of the 108 task conditions were found to be more uncomfortable for the male group, while some others, for the female. The observed sex impacts are thought to be due to the sex differences in physical work capacities (muscular strength and joint flexibility). The results suggest that new posture analysis tools allowing sex-specific analyses are needed as they would improve the accuracy and precision of ergonomics posture analyses. Practitioner summary: This study empirically investigated how sex modifies postural discomfort perception during a seated posture holding (SPH) task. Sex was found to modify the impacts of joint reactive moments and the shoulder joint angle. The study results seem to reflect the sex differences in muscular strength and joint flexibility.

Association between the time of physical laboral activities and leisure over shoulder pain in fruitculture workers: A cross-sectional study

BACKGROUND

Fruitculture workers are exposed to shoulder pain disorders due to long working times in overhead activities.

OBJECTIVE

This study aims to analyze the association between the time of physical work and leisure activities over the perception of shoulder pain intensity in fruit growing workers.

METHODS

This is a descriptive and correlational cross-sectional study. The sample consisted of 180 fruit-growing workers. Multivariable logistic regression was used, with an estimate of the Odds Ratio (OR) and 95% confidence intervals. The dependent variable: Numeric Pain Rating Scale (NPRS) (0-10 points), was categorized as low and high, with cutoff points of NPRS > 3 and NPRS > 4, and was associated with the independent variables (level of physical activity, personal, labour and psychosocial).

RESULTS

Workers which are insufficiently active in leisure time are more likely to report high-intensity shoulder pain, NPRS > 3 (OR: 2.39; p = 0.049) and NPRS > 4 (OR: 2.85; p = 0.036). In addition, working time in overhead activities is a risk factor for high-intensity pain for NPRS > 3 and NPRS > 4 (OR = 1.01; p < 0.001). Underweight and normal-weight workers were less likely to report shoulder pain in NPRS > 3 (OR = 0.35; p = 0.020) and in NPRS > 4 (OR = 0.20; p = 0.001).

CONCLUSION

Fruit-growing workers had a high prevalence of severe shoulder pain. In addition, workers who are insufficiently active at leisure, overweight and obese are more likely to report severe pain. It was observed that overhead tasks increase the chances of reporting high-intensity shoulder pain among workers.

Obesity impacts on task performance and perceived discomfort during seated foot target reaches

This study examined obesity impacts on task performance and perceived discomfort during seated foot target reaches. Three independent variables, participant group, movement distance, and, movement direction, were considered. The task performance measures employed were reaction time, movement time and task performance time. Perceived discomfort was measured using a modified Borg CR-10 scale. Statistical analyses revealed that: obesity was associated with increases in movement time, reaction time and performance time; movement distance significantly affected the three task performance measures and discomfort rating; and, movement direction significantly affected movement time, performance time and discomfort rating. The obesity impacts observed are thought to reflect the decelerating effects of the extra fat mass in the obese body during foot reaches and possibly obesity-related physiological and cognitive changes. Design improvements of foot-operated systems, such as reducing distances to targets, increasing target sizes and avoiding forward foot reaches, may help counteract the observed obesity impacts. Practitioner Summary: This study empirically investigated the obesity impacts on task performance and perceived discomfort during seated foot target reaches. Obesity was found to be associated with increases in movement time, reaction time and performance time. The observed obesity impacts seem attributable to the anthropometric, motor and cognitive characteristics of the obese.Abbreviations: ANOVA: analysis of variance; BMI: body mass index; ROM: range of motion; Borg CR-10: Borg's category ratio 10 scale.

Plus size and obese workers: anthropometry estimates to promote inclusive design

A significant proportion of the adult population globally is overweight, obese or classed as 'plus size'. This has led to variability in size and shape across the working population and exclusion in the workplace. A new dataset of the anthropometry of plus size people has been created. Length dimensions were similar to other data, but breadth, circumference, and depth measurements were substantially larger. The hip breadth and abdominal depth were important for predicting largeness in this population. These data help explain the high exclusion rates from design and the number of fit, reach, posture and clearance issues reported by participants with a high BMI: generally, the higher the BMI the greater prevalence of problems. It is hoped that a better understanding of the anthropometric characteristics of the plus size worker will inform the design of safe, productive work environments to promote inclusion for a wider range of people. Practitioner Summary: A new anthropometry dataset of plus size people has been created. The higher the BMI the greater the problems with design in the workplace for fit, reach, posture and clearance. To ensure inclusion and reduce stigma it is important to understand more about the size and shape of this population.

Obesity effects on muscular activity during lifting and lowering tasks

Obesity is an emerging health problem and its incidence has been increasing throughout the workforce. In industrial workstations, vertical handling tasks (VHT), including lifting and lowering, are very common and can cause a significant muscular overload for the involved workers. During these tasks, muscular activity may be considerably affected by workers' body conditions. This study aims to analyze and compare the muscular activity in subjects with different obesity levels, using surface electromyography (EMG), during predefined VHT. Six different VHT (combining 5, 10 and 15-kg loads with two task styles) were performed. EMG data normalization was based on the percentage of maximum contraction during each task (MCT%). The results show that obesity influences the MCT%, which in turn increases the muscular effort during VHT. The current investigation demonstrates that obesity is a relevant musculoskeletal risk factor regarding VHT. The engineering analysis and design implications of this work can thus be perceived.

Acute muscle stretching and the ability to maintain posture in females with adolescent idiopathic scoliosis

BACKGROUND

Physiotherapy scoliosis specific exercises include exercises to attain and maintain proper posture, as well as flexibility movements such as stretching.

OBJECTIVE

To examine the effect of prior muscle stretching on the performance of posture exercise in females with adolescent idiopathic scoliosis (AIS).

METHODS

Eighteen females with AIS were randomly assigned to perform a posture maintenance task for three minutes preceded by either stretching protocol (group A) or no-stretching (group B). A second session was carried out after three days, where the same procedure was repeated in a reverse order between groups. During each session, three outcomes were tested: the ability to complete the task, the ability to maintain postural body alignment, and the perceived effort.

RESULTS

All participants completed the task in both sessions. Subjects' ability to preserve the required lower trunk alignment decreased following stretching compared to no-stretching. Lower-trunk angle changed toward flexion by 10∘ and 4.3∘ respectively, p= 0.032. There was no difference in perceived effort.

CONCLUSIONS

Prior muscle stretching has a negative effect on the ability to preserve body positional alignment during posture exercise. The present findings should be considered by practitioners when designing protocols for scoliosis-specific exercises. Stretching immediately prior to posture maintenance exercises should be avoided.

Central adiposity and mechanical, perceptual and physiological loading during long duration, repetitive lifting

BACKGROUND

There is an absence of information regarding the impact of central adiposity on loading during long duration, repetitive lifting, and very limited information of the impact of elevated body mass on mechanical loading of the lumbar spine. This information is important in evaluation of the validity of injury prevention standards and interventional approaches in this segment of the population.

METHODS

This study evaluated the mechanical, physiological, and perceptual loading during repetitive lifting in participants with central adiposity compared to participants with normal body mass index. Videography, accelerometry, heart rate and perceived exertion measures were used to examine alternations in kinematic, kinetic, and exertional parameters during a 1-hour lifting task (3 × 20-min sets; 4 lifts/min; self-selected mass).

FINDINGS

Low back torque [+69.1 (11.5) Nm], compressive force [+1036.6 (153.6) N] and heart rate [+7.0 (3.5)%] were substantially elevated in participants with central adiposity, however perceived exertion and self-selected mass did not differ between groups. With central adiposity a compensatory mechanism was observed, involving a reduction in trunk vertical displacement [-5.8 (1.9) cm], hip flexion [-6.4 (3.1) deg] and lower-trunk flexion [-10.0 (2.7) deg], which attenuated expected increases to work [9.8 (2.3)%], power [9.5 (4.0)%] and physiological effort.

INTERPRETATION

While mechanical loading increases secondary to elevated body mass are expected, these results provide new insight into origins of such increases for individuals with a central adiposity somatotype. The differences in mechanical, physiological and perceived loading support provision of individual-specific injury prevention strategies, as well as revision of existing mechanical- and physiological-based ergonomic standards.

Use of various obesity measurement and classification methods in occupational safety and health research: a systematic review of the literature

BACKGROUND

This study systematically examined obesity research in occupational safety and health regarding the use of various obesity measurement and classification methods.

METHODS

A systematic search of the PubMed database on English language publications from 2000 to 2015 using related keywords and search of citations resulted in selection of 126 studies. They were categorized into two groups based on their main research question: 1) general physical or mental work-related functioning; and 2) task or body part specific functioning.

RESULTS

Regardless of the study group, body mass index (BMI) was the most frequently used measure. Over 63% of the studies relied solely on BMI to define obesity. In only 22% of the studies, body fat was directly measured by methods such as dual energy x-ray absorptiometry. Abdominal obesity was defined using waist circumference in recent years, and waist-hip ratio in earlier years. Inconsistent cut-offs have also been used across studies investigating similar topics.

CONCLUSIONS

Few authors acknowledged the limitations of using indirect obesity measures. This is in part due to the limited understanding of some occupational safety and health researchers regarding the complex issues surrounding obesity classification and also the mixed recommendations over the past 2-3 decades and across populations. Efforts need to be made to promote appropriate obesity measurement and reporting in this field.

Assessment of Postural Load during Melon Cultivation in Mediterranean Greenhouses

Health and safety at work directly influence the development of sustainable agriculture. In the agricultural sector, many farm workers suffer musculoskeletal disorders caused by forced posture. The objective of this research is to assess working postures during melon cultivation in Almería-type greenhouses. The Ovako Working Posture Assessment System (OWAS) has been used with pictures of the tasks. The variables studied by multiple correspondence analysis were as follows: Subtask, Posture code, Back, Arms, Legs, Load, Risk, and Risk combination. The OWAS analysis showed that 47.57% of the postures were assessed as risk category 2, 14.32% as risk category 3, 0.47% as risk category 4, and the rest as risk category 1. Corrective measures should be implemented immediately, as soon as possible, or in the near future, depending on the risks detected.

Musculoskeletal disorders: OWAS review

The prevention of musculoskeletal disorders (MSD) is very important in the world. Governments and companies are the most interested. The objective of the present work is to review the literature on the applications of the OWAS method in the diverse sectors or fields of knowledge and countries from its publication to March 2017. The use of OWAS method has been classified by categories of knowledge, by country and by year. The search was made by selecting only the main collection of the Web of Science. This was selected by the option "Advanced search" using the term OWAS (ts=OWAS) for the time period of 1900 to 2017. A total of 166 results were found, consisting of conference papers and articles in scientific journals. In conclusion, the OWAS has been applied mainly in two sectors: "Manufacturing industries" and "Healthcare and Social assistance activities". This method needs to be complemented with other indirect or direct methods. Also, whenever the OWAS has been used, whether individually or together with other methods, musculoskeletal disorders risks have been detected, this perhaps being an indicator to review the evaluation parameters because overestimating the risk.

Central and peripheral fatigue development in the shoulder muscle with obesity during an isometric endurance task

BACKGROUND

Fatigue increases the likelihood of developing work-related musculoskeletal disorders and injury. Due to the physiological and neuromuscular changes that accompany obesity, it may alter the fatigue development mechanism and exacerbate injury risk. The upper extremities have the highest incidence rates for work-related musculoskeletal disorders. Therefore, the goals of this study were to investigate the effect of obesity on central vs. peripheral fatigue as well as on the physical signs of fatigue on the middle deltoid muscle.

METHODS

A measure of central activation ratio was used to quantify central fatigue by considering the increment in the torque output by superimposed twitch relative to its corresponding maximum voluntary contraction. For this purpose, electrical stimulation was delivered at the middle deltoid muscles of 22 non-obese (18 < body mass index (BMI) < 25 kg/m2) and 17 obese (30 < BMI < 40 kg/m2) individuals aged 18-32 years old. Participants completed superimposed maximum voluntary isometric contractions of shoulder abduction before and after a sustained isometric fatiguing task at either 30 or 60% of the muscle capacity. Differences in endurance time, torque fluctuation, torque loss, and muscle activity measured by an electromyography sensor were also investigated.

RESULTS

A greater reduction of voluntary activation of motor units (p = 0.001) with fatigue was observed for individuals who are obese. Contrary to the effect of obesity on central fatigue, a trend toward reduced peripheral fatigue (p = 0.06) was observed for the obese group compared to the non-obese group. On average, a 14% higher rate of torque loss per second was observed among individuals with obesity in comparison to non-obese participants.

CONCLUSIONS

The observed greater contribution of central fatigue during the sustained endurance tasks suggests that among young healthy obese individuals, the faster fatigue development with obesity, commonly reported in the literature, is most likely due to the central elements rather than the peripheral factors. This finding has implications for fatigue prevention programs during sustained exertions and can help to develop training, work, and rest schedules considering obesity.

Muscular Power during a Lifting Task Increases after Three Months of Resistance Training in Overweight and Obese Individuals

Background: This study evaluates the effect on power produced during a modified lifting task in the overweight and obese after three months of either resistance or aerobic training. Methods: Seventeen male subjects divided randomly into two groups performed deadlift and deadlift high pull, both with increasing weights up to maximal power, prior to and after the training programs (three sessions per week). Results: Their mean power increased significantly during the deadlift at 20 kg (14.3%, p = 0.026), 30 kg (17.7%, p = 0.008), 40 kg (16.5%, p = 0.011), 50 kg (14.5%, p = 0.020), and 60 kg (14.3%, p = 0.021) and during the deadlift high pull at 30 kg (9.9%, p = 0.037), 40 kg (10.1%, p = 0.035), and 50 kg (8.2%, p = 0.044) after the resistance training. However, the group that participated in the aerobic training failed to show any significant changes in power performance during either the deadlift or deadlift high pull. Conclusion: Three months of resistance training enhances power outputs during a lifting task with weights from 30 to 50 kg (~40–60% of 1-repetition maximum) in the overweight and obese. Because this test was sensitive in revealing pre-post training changes in lifting performance, it should be implemented in the functional diagnostics for overweight and obese individuals and also complement existing testing methods.

Differences between obese and non-obese drivers in preferred vehicle interior components setting and driving posture

This study compared obese and non-obese drivers in the preferred seat and steering wheel setting and preferred driving posture. Twenty-one extremely obese and 23 non-obese drivers participated. Each participant determined the most preferred setting of the interior components using an adjustable vehicle mock-up; the preferred components setting and corresponding preferred driving posture were recorded. The participant groups exhibited significant differences in the preferred interior components setting. The obese group created larger steering wheel-seat space than the non-obese, with greater rearward seat displacement, more upright steering wheel angle and smaller steering wheel column displacement. It also exhibited more upright seatback angle deemed necessary for facilitating steering wheel reach with the increased steering wheel-seat distance. The between-group differences in the preferred driving posture were less pronounced: no significant group mean angle differences were found except for the elbow joint angles. Also, the mean hip joint centre positions did not significantly differ. Practitioner Summary: To contribute to larger driver packaging, this study compared obese and non-obese drivers in the preferred vehicle interior components setting and driving posture. The obese group created significantly larger space between the steering wheel and seat than the non-obese, through interior components adjustments. The between-group postural differences were less pronounced.

Overweight, obesity and work functioning: the role of working-time arrangements

BACKGROUND

Obesity is associated with productivity loss, but little is known about how obese workers function at work and also the role of working-time arrangements on this association is lacking. Therefore, the aim of this study was to examine the association of overweight and obesity with work functioning (WF), and to determine whether the associations differ between workers with different working-time arrangements.

METHODS

A cross-sectional study was conducted within the sampling frame of the 'Shift Your Work' study that examined the effect of irregular working-times in relation to health and functioning at work. We included N = 622 Dutch employees, of which N = 384 (62%) were shift-workers, N = 171 (27%) on-call workers and N = 67 (11%) day-workers. Overweight and obesity were defined as BMI 25-30 and ≥30, respectively. WF was assessed using the Work-Role Functioning Questionnaire.

RESULTS

The prevalences of overweight and obesity were 48% and 10% in all workers, 49% and 11% in shift-workers, 45% and 10% in on-call workers, and 49% and 6% in day workers, respectively. In all workers, obesity was associated with lower WF scores for physical demands (adjusted estimate, aB = -5.5). In shift-workers, obesity was associated with lower WF scores for output and physical demands (aB = -8.8 and -6.8, respectively). In day and on-call workers, overweight and obesity were not associated with WF.

CONCLUSIONS

Overweight and obesity are highly prevalent in the working population. Obesity might reduce the executive function performance beyond physical limitations, and limit the ability to accomplish tasks successfully, especially in shift workers.

Influences of Obesity on Job Demands and Worker Capacity

Evidence suggests that the growing prevalence of obesity in the workforce has resulted in an increase in the incidence and cost of musculoskeletal injuries. Obesity can modify job demands and affect worker capacity in terms of anthropometry and occupational biomechanics, which may place workers at greater risk of injury. This paper presents a review of studies quantifying the work-relevant impacts of obesity, specifically related to work task demands, capacities, and their potential imbalance. The increased body fat that accompanies obesity leads to larger anthropometric dimensions and inertial parameters, particularly in the trunk and thigh areas. Consequently, individuals who are obese adjust their work postures and motions as an accommodation. These changes may affect the biomechanical demands on the joints and increase the burden on the musculoskeletal system. Independent of job demands, obesity-related differences also occur with respect to strength, fatigue, and task performance. Directions for future research are provided, focusing on the need for workplace redesign to account for changing workforce demographics.

Body shape analyses of large persons in South Korea

Despite the prevalence of obesity and overweight, anthropometric characteristics of large individuals have not been extensively studied. This study investigated body shapes of large persons (Broca index ≥ 20, BMI ≥ 25 or WHR>1.0) using stature-normalised body dimensions data from the latest South Korean anthropometric survey. For each sex, a factor analysis was performed on the anthropometric data set to identify the key factors that explain the shape variability; and then, a cluster analysis was conducted on the factor scores data to determine a set of representative body types. The body types were labelled in terms of their distinct shape characteristics and their relative frequencies were computed for each of the four age groups considered: the 10s, 20s-30s, 40s-50s and 60s. The study findings may facilitate creating artefacts that anthropometrically accommodate large individuals, developing digital human models of large persons and designing future ergonomics studies on largeness.

PRACTITIONER SUMMARY

This study investigated body shapes of large persons using anthropometric data from South Korea. For each sex, multivariate statistical analyses were conducted to identify the key factors of the body shape variability and determine the representative body types. The study findings may facilitate designing artefacts that anthropometrically accommodate large persons.

Job stress and work schedules in relation to nurse obesity

OBJECTIVES

This study aimed to examine the relationship between job stress/work schedules (JS/WS) and obesity among nurses.

BACKGROUND

Job stress and shift work are known risk factors for obesity, yet comprehensive measures of JS/WS in relation to nurse obesity have been little investigated.

METHODS

Secondary data analysis used survey data from 2,103 female nurses. Obesity was measured using body mass index estimates. Binomial logistic regression models incorporated independent components of JS/WS and adjusted for demographics, nursing position, mental/emotional distress, health behaviors, and family-related covariates.

RESULTS

Approximately 55% of the sample was overweight/obese (OW/OB). When compared with underweight/normal weight nurses, OW/OB nurses reported that their jobs had less physical exertion (odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.72-0.95, P = .01) and more limited movement (OR = 1.14, 95% CI = 1.02-1.28, P = .03). Long work hours (OR = 1.23, 95% CI = 1.08-1.40, P < .01) were significantly associated with being OW/OB as compared with underweight/normal.

CONCLUSIONS

Findings suggest interventions to limit adverse work schedules. Access to healthy food and optimal meal breaks should be investigated.

Obesity, ergonomics and public health

Obesity within today's workforce is increasingly recognized as a challenge for both public health professionals and ergonomists. The two disciplines share a scientific, evidence-based approach to practice and now have the opportunity to address a common health issue, namely obesity. This paper shows, through an overview of the current literature, how and where obesity is impacting on the workplace and how the health of the workforce is being affected. Ergonomics and public health priorities have been mapped and challenges suitable for the application of existing knowledge and further research have been identified. Areas of common endeavour, for example how sedentary work may be exacerbating obesity, have been identified as candidate topics for joint activity by ergonomists and public health professionals.