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Among workers performing hand-intensive tasks, musculoskeletal disorders in the upper extremities are more frequent in women than in men. However, risk assessments are generally not sex-specific, and it is not known whether exposures in regular work differ between females and males. The aim of this study was to compare measured wrist joint velocity and muscle activity between men and women performing identical tasks. Participants (28 female–male pairs) performed one of eighteen hand-intensive on-site tasks. Wrist velocity was measured using inertial units. Forearm muscle activity was measured via surface electromyography and normalized to maximal voluntary electrical activation (MVE). The 10th, 50th, and 90th percentiles and time in muscle recovery (< 0.5 %MVE) were computed. Between-sex differences were tested using the Wilcoxon signed-rank test. Wrist angular velocities did not significantly differ between sexes in any percentile (all p > 0.374). The muscle activity was significantly higher in female workers (p < 0.001–0.004), ranging from 1.3 to 2.8 times higher, and they spent less time in muscle recovery (p < 0.001). In hand-intensive tasks involving women and men, risk assessments should prioritize assessments of women to ensure protection against work-related musculoskeletal disorders for all workers.

Background: Exposure assessment of wrist velocity and muscular activity in hand-intensive work are pillars in risk assessment of hand-intensive work in workplaces. Workers who are engaged in hand-intensive work, such as assembly and food processing, have an increased risk for musculoskeletal disorders (MSDs) and carpal tunnel syndrome (CTS) diagnosis. Foremost, the MSD and CTS prevalences are notably higher in females. We lack knowledge of whether wrist velocity and muscular activity are the same in women and men in identical tasks. This might lead to over- or underrating of risk in males and females, hence missing out on optimal risk-reducing actions to sufficiently protect women and men. Risk assessment which sufficiently protects both sexes from ill-health, supports a sustainable working life for women and men equally.  Therefore, it is essential to investigate if exposure is the same in women and men in identical tasks, in regular work. 

Purpose: We aimed to investigate if wrist velocity and muscular activity are the same in females and males in identical hand-intensive tasks. 

Methods. Participants comprised 28 female-male pairs (56 individuals) who worked in one of 18 different hand-intensive occupational tasks in their regular workplace. Wrist angular velocity was measured with inertial measurement units placed on the dorsal hand and distal forearm, and characterized by the 50th percentile (median). Forearm muscular activity was measured in the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) with surface electromyography. This was normalized to the maximal voluntary electrical activation (MVE). The 50th percentile (median) was computed, and also the time spent in muscular recovery (<0.5 %MVE). To test between-sex differences, the Wilcoxon signed rank test was used. 

Results: Median wrist angular velocities did not significantly differ between sexes (p= 0.374). The muscular activity for FCR and ECR was significantly higher in females than in males, double compared to males (FCR p=0.001, ECR p=0.003). The time spent in muscular recovery was less in females (than in males (FCR p < 0.001, ECR p=0.002), for both FCR (females 0% of the time; males 8.1%) and ECR (0%; 0.2%).

Conclusion: In regular identical hand-intensive work tasks, females' muscle activity was higher, and muscular recovery time lower than that of males. 

Implication: These findings have a direct impact on risk assessments in hand-intensive work. In jobs where female workers are involved, the risk assessment should be based on females. When using observational risk assessment methods, the risk criteria level should ensure a safe level for women to execute the job with a low risk of acquiring work-related musculoskeletal disorders.

An accurate rating of hand activity and force is essential in risk assessment and for the effective prevention of work-related musculoskeletal disorders. However, it is unclear whether the subjective ratings of workers and observers correlate to corresponding objective technical measures of exposure. Fifty-nine workers were video recorded while performing a hand-intensive work task at their workplace. Self-ratings of hand activity level (HAL) and force (Borg CR10) using the Hand Activity Threshold Limit Value® were assessed. Four ergonomist observers, in two pairs, also rated the hand activity and force level for each worker from video recordings. Wrist angular velocity was measured using inertial movement units. Muscle activity in the forearm muscles flexor carpi radialis (FCR) and extensor carpi radialis (ECR) was measured with electromyography root mean square values (RMS) and normalized to maximal voluntary electrical activation (MVE). Kendall’s tau-b correlations were statistically significant between self-rated hand activity and wrist angular velocity at the 10th, 50th, and 90th percentiles (0.26, 0.31, and 0.23) and for the ratings of observers (0.32, 0.41, and 0.34). Significant correlations for force measures were found only for observer-ratings in five of eight measures (FCR 50th percentile 0.29, time > 10%MVE 0.43, time > 30%MVE 0.44, time < 5% −0.47) and ECR (time > 30%MVE 0.26). The higher magnitude of correlation for observer-ratings suggests that they may be preferred to the self-ratings of workers. When possible, objective technical measures of wrist angular velocity and muscle activity should be preferred to subjective ratings when assessing risks of work-related musculoskeletal disorders.

Background: Accuracy of risk assessment tools in hand-repetitive work is important. This can support precision in the risk management process and for a sustainable working life for women and men equally. Musculoskeletal disorders, MSDs, from the hand, wrist, and forearm, are common in the working population. Women report a higher prevalence of MSDs in these regions. 

Objective: The objective of this study was to compare if women and men who performed the identical hand-intensive work task were rated equally using the Hand Activity Threshold Limit Value® (HA-TLV) when self-rated and observer-rated. 

Method: Fifty-six workers from eight companies participated, with various intensities in hand-repetitive work tasks. In total, 18 unique identical hand-intensive work tasks were executed in 28 pairs of a woman and a man. Hand activity and force levels were assessed. Each worker executed the work task for 15 minutes, which was also video recorded. Data was collected on workers who self-rated directly after the execution of the work task. Also, experienced observers performed ratings from videos of the same work tasks. For comparing means between women and men, paired samples t-tests were used.

Results: The main results showed that there was no difference in self-ratings of hand activity level and force by women and men who executed the same work task. Further, there was no difference between observer ratings of hand activity level. However, the observer force ratings of women and men differed significantly (p=0.01).

Conclusion: Hand activity and force levels are rated equally in women and men when self-rated, also by observers for hand activity. However, it is an observandum that observer force rating is rated higher for women and lower for men. This indicates the need of comparing force ratings with technical measures.

We compared hand activity and force ratings in women and men doing identical hand-intensive work tasks. Musculoskeletal disorders are more common in women and hand-intensive work leads to an increased risk of these disorders. Knowledge of the gender influence in the rating of work exposure is lacking. The aim of this study was to investigate whether women and men performing identical hand-intensive work tasks were equally rated using hand activity and normalized peak force levels with the Hand Activity Threshold Limit Value®. Fifty-six workers participated, comprising 28 women-men pairs. Four observers-two woman-man pairs-were also involved. Self-ratings and observers' ratings of hand activity and force level were collected. The results of these ratings showed no significant gender differences in self-rated hand activity and force, as well as observer-rated hand activity. However, there was a significant gender difference in the observer-rated force, where the women were rated higher (mean (SD): women 3.9 (2.7), men 3.1 (1.8) (p = 0.01)). This difference remained significant in the adjusted model (p = 0.04) with grip strength and forearm-finger anthropometrics. The results provide new insights that observers' estimates of force can be higher in women compared with men in the same work tasks. Force should be further investigated and preferably compared to objective measurements.

Background: With medical information widely available, patients often have preconceived ideas regarding diagnostic procedures and management strategies.

Objectives: To investigate whether expectations, such as beliefs about the source of symptoms and knowledge about diagnostic tests, influence pain perception during a clinical diagnostic test.

Design: Cross-sectional study.

Methods: Pain was induced by intramuscular hypertonic saline infusion in the thenar muscles. In line with sample size calculations, fifteen participants were included. All participants received identical background information regarding basic median nerve biomechanics and basic concepts of differential diagnosis via mechanical loading of painful structures. Based on different explanations about the origin of their induced pain, half of the participants believed (correctly) they had ‘muscle pain’ and half believed (incorrectly) they had ‘nerve pain’. Pain intensity and size of the painful area were evaluated in five different positions of the median nerve neurodynamic test (ULNT1 MEDIAN). Data were analysed with two-way analyses of variance.

Results/findings: Changes in pain in the ULNT1 MEDIAN positions were different between the ‘muscle pain’ and ‘nerve pain’ group (p < 0.001). In line with their expectations, the ‘muscle pain’ group demonstrated no changes in pain throughout the test (p > 0.38). In contrast, pain intensity (p ≤ 0.003) and size of the painful area (p ≤ 0.03) increased and decreased in the ‘nerve pain’ group consistent with their expectations and the level of mechanical nerve loading.

Conclusion: Pain perception during a clinical diagnostic test may be substantially influenced by pain anticipation. Moreover, pain was more aligned with beliefs and expectations than with the actual pathobiological process.

Operators of mobile machines within forestry work long hours in seated postures while being exposed to whole-body vibration (WBV) that is associated with pain in the lower back and neck. Still, little is known about the contribution from postural loads. In this study postural loads and shock-type WBV exposure on drivers operating a forwarder during terrain-like conditions was measured and quantified using inertial measurement units (IMUs). Five male drivers drove a forwarder repeatedly over standardized steel obstacles using a predefined speed and posture followed by driving over natural obstacles along a terrain course using a self-selected speed and posture. IMUs were affixed along the spine, on the back of the head of the driver and on the seat to detect orientation, velocity, and acceleration. The result shows that the methodology for measuring WBV and postural load with IMUs is feasible. Postural loads, expressed as range of motions (ROMs), when driving over a single standardized obstacle at a speed of 3.3 km/h were up to 21 degrees in the neck segments. Increasing vehicle speed and size of obstacles increased postural loads. The terrain course resulted in higher ROMs in all body segments compared to a standardized obstacle, a difference in sideway seat acceleration but no differences regarding angular velocities of the head. Mechanical shocks at the seat were prevalent but the action limit value was exceeded only for one driver. Postural loads remained small during all conditions indicating that the spine can remain stable during exposure to shock-type WBV of this nature.

Background: Lower back and neck pain is common among persons who drive vehicles in their profession. The vehicle occupants are exposed to whole-body vibration (WBV) that may include mechanical shocks which are believed to increase the likelihood of injury further. Mechanical shocks are especially generated when driving on rough terrain and may challenge drivers' postural equilibrium. Little is known about the contribution of postural load to injury risk and thus objective measurements are necessary.

Purpose: The purpose of the study was to assess the feasibility of registering and analyzing seated postural load and shock-type WBV synchronously using inertial measurement units (IMUs) among drivers of forest machines during terrain-like conditions.

Methods: Five male participants (18-34 years old) drove a forest machine 6 times over three different standardized steal obstacles along a gravel course using a predefined speed and posture. Participants then drove the same vehicle 3 times over natural obstacles along a terrain course using a self-selected speed and posture. Three IMUs were affixed along the spine (at S2, Th2 and C4) and one to the head of participants as well as one to the seat. Data from the IMUs regarding accelerations and orientation in sagittal, frontal and horizontal plane were then analyzed.

Results: Postural load, expressed as the range of motions (ROMs) in the upper neck, lower neck, trunk and pelvis were less than 22° in all directions during maneuvers on the standardized course. The size of obstacle and the vehicle speed had significant effects on the ROMs. No significant differences between courses were evident regarding seat accelerations and angular velocities at the drivers head. The WBV analysis of the terrain course indicated that mechanical shocks were prevalent but exceeded the exposure action value for only one driver and not the exposure limit value according to health and safety requirements within the European Union (EU directive 2002/44/EC).

Conclusion(s): IMUs may objectively be used to register and present seated postural load and shock-type WBV exposure synchronously when driving on terrain. There seems to be a low risk of injuries from mechanical shocks since the magnitude of postural load (ROMs) during tested conditions was not considered to increase injury risk even though vehicle speed and the size of obstacles had a significant effect.

Implications: Postural load when driving a forest machine during terrain-like conditions appears low in this study but more long-term field measurements on more drivers are needed before definite conclusions can be made. IMUs are regarded as promising tools for registering and representing seated postural load and shock-type WBV exposure. Future development could provide drivers with feedback regarding potentially injurious postures and/or high shock-type WBV exposure.