A pilot study of minimum operational flow for loose-fitting powered air-purifying respirators used in healthcare cleaning services.

The objective of this pilot study was to determine the minimum operational flow for loose-fitting powered air-purifying respirators (PAPR) used in healthcare cleaning services. An innovative respiratory flow recording device was worn by nine healthcare workers to obtain the minute volume (MV, L/min), mean inhalation flow (MIF, L/min), and peak inhalation flow (PIF, L/min) while performing "isolation unit work" (cleaning and disinfecting) of a patient room within 30 min. The MV and PIF were compared with the theoretical values obtained from an empirical formula. The correlations of MV, MIF, and PIF with subjects' age, weight, height, body surface area (ADu), and body mass index (BMI) were analyzed. The average MV, MIF, and PIF were 33, 74, and 107 L/min, with maximal airflow rates of 41, 97, and 145 L/min, respectively, which are all below the current 170 L/min minimum operational flow for NIOSH certified loose-fitting PAPRs.

A biomechanical shoulder strain index based on stabilizing demand of shoulder joint.

Work-related shoulder joint disorders contribute considerably to absenteeism in the workplace. To identify the tasks that are stressful to the shoulder joint, a strain index was formulated based on the concept of concavity compression-a shoulder stabilizing mechanism. The magnitude and direction of the shoulder joint reaction forces were used in formulating the strain index. A two phase experiment was conducted. In Phase 1, participants performed 30 different manual handling tasks. The tasks were categorized into low, medium and high strain tasks based on their strain index values. In Phase 2, out of the 30 tasks, repetitive exertions of three tasks (low, medium and high strain index values) were simulated using three external loads (0.91, 1.81 and 2.72 kg). The muscle activity data recorded from eight shoulder muscles showed that tasks with higher strain index values induced significantly greater activation and muscle fatigue than tasks with lower strain index values.Practitioner Summary: The strain index developed in this study is a conclusive estimation of the concavity compression required for shoulder joint stabilization. It can be used to identify the activities that may contribute to the risks of shoulder disorders. Abbreviation BLS Bureau of the Labor Statistics.

Cervical occupational hazards in ophthalmic plastic surgery.

PURPOSE OF REVIEW: To increase awareness of cervical musculoskeletal disorders (cMSD) in ophthalmic plastic surgeons (OPS) and review strategies for management and prevention. RECENT FINDINGS: There are objective data that show OPS spend the majority of their time operating in awkward, prolonged, static, asymmetric postures. These postures increase cervical load and cMSD. Loupes and headlamps further increase this cervical loading by 40%. Risk for cMSD is not limited to the operating room. Muscular demands in the anterior deltoid and cervical trapezius are increased in slit lamp biomicroscopy and indirect ophthalmoscopy. Furthermore, the majority of the office visit is spent keyboarding into the electronic medical record which is associated with cMSD. Habitual postural faults result from these cumulative exposures. These must be addressed to prevent further insult and debilitating injury. Successful management requires education in neutral posture, therapeutic exercise, environmental adjustments in the workplace and home, and supported neutral sleep posture. SUMMARY: The risks of cMSD in OPS are well established, and nearly 10% of cervical injury will end a career. Neck pain must not be ignored, and experienced professional help is critical. A long-term approach that incorporates exercise, manual therapy, and education is essential for management and prevention.

The assessment of material-handling strategies in dealing with sudden loading: the effect of uneven ground surface on trunk biomechanical responses.

As a major risk factor of low back injury, sudden loading often occurs when performing manual material-handling tasks on uneven ground surfaces. Therefore, the purpose of the current study was to investigate the effects of a laterally slanted ground on trunk biomechanical responses during sudden loading events. Thirteen male subjects were subjected to suddenly released loads of 3.4 and 6.8 kg, while standing on a laterally slanted ground of 0°, 15° and 30°. The results showed that 8.3% and 5.6% larger peak L5/S1 joint compression forces were generated in the 30° condition compared with the 0° and 15° conditions, respectively. The increase of L5/S1 joint moment in the 30° condition was 8.5% and 5.0% greater than the 0° and 15° conditions, respectively. Findings of this study suggest that standing on a laterally slanted ground could increase mechanical loading on the spine when experiencing sudden loading. Practitioner Summary: Sudden loading is closely related to occupational low back injuries. The results of this study showed that the increase of slanted ground angle and magnitude of load significantly increase the mechanical loading on the spine during sudden loading. Therefore, both of these two components should be controlled in task design.

The changes of lumbar muscle flexion-relaxation response due to laterally slanted ground surfaces.

Lifting tasks performed on uneven ground surfaces are common in outdoor industries. Previous studies have demonstrated that lifting tasks performed on laterally slanted ground surfaces influence lumbar muscle activation and trunk kinematics. In this study, the effect of laterally slanted ground surfaces on the lumbar muscle flexion-relaxation responses was investigated. Fourteen participants performed sagittal plane, trunk flexion-extension tasks on three laterally slanted ground surfaces (0° (flat ground), 15° and 30°), while lumbar muscle activities and trunk kinematics were recorded. Results showed that flexion-relaxation occurred up to 6.2° earlier among ipsilateral lumbar muscles with an increase in laterally slanted ground angle; however, the contralateral side was not affected as much. Our findings suggest that uneven ground alters the lumbar tissue load-sharing mechanism and creates unbalanced lumbar muscle activity, which may increase the risk of low back pain with repeated exposure to lifting on variable surfaces. PRACTITIONER SUMMARY: Uneven ground surfaces are ubiquitous in agriculture, construction, fishing and other outdoor industries. A better understanding of the effects of laterally slanted ground surfaces on the interaction between passive and active lumbar tissues during lifting tasks could provide valuable knowledge in the design of preventive strategies for low back injuries.

Exploring Perceptions and Needs of Mobile Health Interventions for Nutrition, Anemia, and Preeclampsia among Pregnant Women in Underprivileged Indian Communities: A Cross-Sectional Survey.

According to the National Family Health Survey of 2021, about 57% of women aged 15-49 in India currently suffer from anemia, marking a significant increase from the 53% recorded in 2016. Similarly, a study conducted in southern India reported a 32.60% prevalence of preeclampsia. Several community-based initiatives have been launched in India to address these public health challenges. However, these interventions have yet to achieve the desired results. Could the challenges faced by traditional healthcare interventions be overcome through a technological leap? This study assesses pregnant mothers' perceptions regarding mobile health interventions for managing anemia and preeclampsia. Additionally, the study captures their health awareness and knowledge. We conducted a survey with 131 pregnant mothers in three underserved villages in Jharkhand, India. Statistical analysis was conducted using the SEMinR package in R (Version 2023.06.0), utilizing the non-parametric partial least squares-structural equation modeling. We found that every household had at least one smartphone, with the respondents being the primary users. The main uses of smartphones were for calling, messaging, and social media. A total of 61% of respondents showed interest in a nutrition and pregnancy app, while 23.66% were uncertain. Regarding nutritional knowledge during pregnancy, 68.7% reported having some knowledge, but only 11.45% claimed comprehensive knowledge. There was a considerable knowledge gap regarding the critical nutrients needed during pregnancy and the foods recommended for a healthy pregnancy diet. Awareness of pregnancy-related conditions such as anemia and preeclampsia was low, with most respondents unsure of these conditions' primary causes, impacts, and symptoms. This study serves as a critical step towards leveraging technology to enhance public health outcomes in low-resource settings. With the accessibility of mobile devices and an apparent willingness to utilize mHealth apps, compounded by the pressing need for improved maternal health, the impetus for action is indisputable. It is incumbent upon us to seize this opportunity, ensuring that the potential of technology is fully realized and not squandered, thus circumventing the risk of a burgeoning digital divide.

Variability of Time- and Frequency-Domain Surface Electromyographic Measures in Non-Fatigued Shoulder Muscles.

OCCUPATIONAL APPLICATIONSLocalized Muscle Fatigue (LMF) can be monitored or predicted based on the relative change in the values of surface electromyography (sEMG) measures with respect to the "fresh" or no-fatigue condition. Quantification of LMF based on relative change, though, relies on the assumption that the sEMG measures recorded in a no-fatigue condition can serve as an appropriate reference. Results of this study indicate that sEMG measures in a no-fatigue condition are affected by various work-related factors and provide further guidance on the variability of commonly used time- and frequency-domain sEMG measures to assist the ergonomist in improving the accuracy of LMF assessment.

Background: Surface electromyography (sEMG) is widely used to monitor or predict localized muscle fatigue (LMF). sEMG signals are often analyzed in time and frequency domains ­ Root Mean Square (RMS), Mean Absolute Values (MAV), and Zero Crossings (ZC) are common time-domain measures; Mean Power Frequency (MnPF), Median Power Frequency (MdPF) and Power Frequency Bands (PFB) are the common frequency-domain measures. LMF prediction is based on the relative change in the values of these measures with respect to "fresh" or no-fatigue conditions. To our knowledge, the assumption that the sEMG measures do not change/vary under no-fatigue conditions due to factors other than LMF has not been thoroughly tested.Purpose: The goal of this study was to quantify the variability of sEMG measures in non-fatigued shoulder muscles and the implication of this variability for assessing LMF.Methods: Twelve participants performed 120 occupationally-relevant static tasks under various conditions of joint angles, anatomical planes, force levels, and force directions. sEMG data were recorded from seven shoulder muscles ­ supraspinatus, infraspinatus, middle deltoid, anterior deltoid, posterior deltoid, biceps, and triceps.Results: For these shoulder muscles, the variability of RMS, MAV, ZC, MnPF, MdPF, and PFB ranged from 7.9 to 11.1%, 7.1 to 10.1%, 10.2 to 11.0%, 8.6 to 11.4%, 8.7 to 12.2%, and 5.3 to 7.9%, respectively.Conclusions: Both time- and frequency-domain sEMG measures vary due to various work-related factors under no-fatigue conditions. Therefore, it is critical to consider the variability ranges of sEMG measures while monitoring or predicting LMF due to sustained exposure to work-related factors.

A survey study of occupational pain and injury in ophthalmic plastic surgeons.

PURPOSE: To determine factors associated with pain/injury related to practicing ophthalmic plastic and reconstructive surgery. METHODS: A 29-question electronic survey was sent to the American Society of Ophthalmic Plastic and Reconstructive Surgery's listserv. The Chi-Squared Automatic Interaction Detector technique was used to generate a decision tree using SPSS software. The levels of dendograms were limited to 8. Significance was pre-established at α = 0.05. RESULTS: One hundred thirty surveys were completed, and 72.5% reported pain associated with operating, 80.9% reported use of loupe magnification, 68.7% reported use of a headlight, 42.5% reported modification of their operating room practice, and 9.2% reported stopping operating due to pain or spine injury. Most respondents regularly exercise, with 55.7% characterizing the amount of exercise as less than necessary; 60.8% and 57.3% agreed that loupe use and headlamp use, respectively, can lead to spine problems.Chi-Squared Automatic Interaction Detector analysis found that 62.7% (n = 47) with neck pain had modified their operating room practice, compared with 13.5% (n = 7) without pain (χ = 30.42; df = 1; p < 0.001); All surgeons that had to stop operating (n = 9) had tried modifying their operating room practice; over half (57.6%, n = 38) of practicing surgeons had changed their operating room practice (χ = 6.09; df = 1; p = 0.014). The majority who exercised 5 hours or less had modified their operating room practice (70.2%, n = 33), compared with 26.3% (n = 5) who exercised more. CONCLUSIONS: Many oculoplastic surgeons experience discomfort due to operating, and an alarming minority have stopped operating due to pain or neck injury. Participants identified loupe and headlamp use as a special concern.

The effect of task rotation on activation and fatigue response of rotator cuff muscles during overhead work.

Overhead work is known as one of the ergonomic risk factors that can lead to shoulder overload and injury. Anatomical alignment of rotator cuff muscles makes them the most vulnerable to injuries during overhead work. In this study, the effect of task rotation, as one of the administrative controls to reduce the risk of injury during overhead work, on the fatigue response of rotator cuff muscles was investigated. Twelve participants performed three submaximal exertions (5, 20, and 35% of maximum voluntary contraction (MVC)) using four task rotation sequences (increasing, decreasing, upward parabolic, and downward parabolic). Median frequency of surface electromyography (EMG), shoulder strength, and ratings of perceived exertion (RPE) were used to study the fatigue response of rotator cuff muscles. Although the average normalized muscle activity was similar in all sequences, the task rotation sequence had a significant effect on the median frequency. The effect of task rotation sequence on the strength and RPE was similar to that of the median frequency but was statistically not significant. The upward parabolic task rotation sequence resulted in the lowest fatigue among all the task sequences. Performing intense exertions apart from each other, warm-up exertions, and the presence of active recovery after the intense exertions could be the factors that produced the lowest fatigue during this sequence.

Sex Differences in Rotator Cuff Muscles' Response to Various Work-Related Factors.

OCCUPATIONAL APPLICATIONSDespite the frequency and cost of rotator cuff injuries among male and female workers, very little is known about the strength, endurance, and perceived exertion and electromyographic response of rotator cuff muscles to different exertion levels. In this study, sex differences were studied using muscle-specific maximal and submaximal exertions of the supraspinatus, infraspinatus, and teres minor muscles. Females showed lower strength and endurance, but higher muscle activity and perceived exertion compared to males. The baseline data presented in this paper can assist ergonomic practitioners in determining the worker capacity to ensure that physically-demanding shoulder exertions can be performed without incurring injurious stress. Such data is also essential to establish population norms for the better design of workplace tasks.

TECHNICAL ABSTRACTBackground: Baseline strength, endurance, perceived exertion, and muscle activity data are essential to characterize sex-specific responses of the rotator cuff muscles to the workplace tasks to minimize risk of injury due to overexertion. Purpose: This study was conducted to measure sex differences in strength, endurance time, activity, fatigue, and perceived exertion for the rotator cuff muscles. Method: Muscle-specific maximum voluntary contractions (MVCs) were used to measure the maximum torque for the supraspinatus, infraspinatus, and teres minor muscles among 10 male and 10 female participants. Four submaximal exertions (15, 30, 45, and 60% MVC) were used to measure differences in endurance time, muscle activation, fatigue, and perceived exertion between sexes. Surface electromyography was used to measure muscle activity and fatigue. Results: Strength was the highest for the infraspinatus followed by teres minor and supraspinatus regardless of sex. Strengths for females were 70, 50, and 48% that of males for the infraspinatus, supraspinatus, and teres minor muscles, respectively. Muscle activity was significantly higher for females than males during the sub-maximal exertions. Among males, muscles with higher activity developed fatigue faster. Females exhibited lower endurance during all sub-maximal exertions. Perceived exertion ratings showed an increasing trend with %MVC, and females exceeded an acceptable limit at lower %MVC levels compared to males. Conclusions: Sex differences observed in this study suggest that a safe level of %MVC level for females is approximately 15% lower compared to males.

Understanding the effect of speed of exertion on isokinetic strength using a multiaxial dynamometer.

In this study a multiaxial isokinetic dynamometer was used to measure strength during various upper-body isokinetic exertions. Ten male participants performed 7 different upper-body isokinetic exertions. In addition, to evaluate the effect of speed on strength, each participant performed sitting pull exertions at the speed of 0.026, 0.130, and 0.260 m/s. Average isokinetic strength increased from 236.6 +/- 39.1 to 291.8 +/- 65.8 N with the initial increase in speed from 0.026 to 0.130 m/s. The average isokinetic strength decreased to 276.7 +/- 87.2 N with a further increase in speed to 0.260 m/s. The curve between isokinetic strength and speed followed a bell-shaped curve (fitted with the Gaussian function, R(2) = .9). The results of this study could be useful in deciding on the work pace of various manual material handling tasks requiring maximal and/or near maximal exertions.

Peripheral median nerve block impairs precision pinch movement.

OBJECTIVE: The objective of this study was to investigate the effects of a simulated peripheral median nerve lesion on precision pinch movement by the thumb and index finger. METHODS: A median neuropathy was created by blocking the median nerve at the wrist using an anesthetic. The subjects (n=5) were asked to perform pulp-to-pulp precision pinch movements before and after the nerve block. Digit motion data was obtained with a marker-based motion analysis system. RESULTS: The radial offset of the thumb tip, as defined by the minimum distance of the thumb tip to the flexion-extension plane of the index finger, showed an increase of 11.2mm after the nerve block. For the thumb, the nerve block caused a decrease in the range of motion at the metacarpophalangeal (MCP) joint, and a compensatory increase in the range of motion at the interphalangeal (IP) joint. The range of motion ratio (MCP:IP) changed from 1:4.8 (pre-block) to 1:1.0 (post-block). The maximum flexion angle at the MCP joint increased from 18.8 degrees (pre-block) to 33.7 degrees (post-block), and maximum flexion angle at the IP joint decreased from 42.6 degrees (pre-block) to 18.8 degrees (post-block). For the index finger, the nerve block caused a decrease in the range of motion at the MCP joint, and compensatory increases in the ranges of motion at the proximal and distal interphalangeal (PIP and DIP) joints. The range of motion ratio (MCP:PIP:DIP) changed from 1:1.1:0.7 (pre-block) to 1:2.4:1.8 (post-block). The maximum flexion angle at the MCP joint decreased from 56.8 degrees (pre-block) to 34.6 degrees (post-block), and the maximum flexion angle at the PIP joint increased from 51.2 degrees (pre-block) to 76.0 degrees (post-block), but the change at the DIP joint was insignificant. CONCLUSIONS: The median nerve block caused remarkable degradation of the pinch performance as quantified by an inaccurate pulp-to-pulp contact of the thumb to the index finger and an alteration of joint motion of the digits. SIGNIFICANCE: Many fine manual tasks require accurate pulp-to-pulp positioning of the thumb to the index finger. Within the hand, the median nerve is critical to the fine sensorimotor function due to the motor supply and the sensory endings to the thumb and index finger. People with median neuropathies (for example, carpal tunnel syndrome) experience clumsiness while performing simple manual tasks. The current approach to the examination of precision pinch movement may be utilized to quantify the apparent hand clumsiness observed in individuals with peripheral neuropathy such as carpal tunnel syndrome.

Comparison of Fourier and wavelet analysis for fatigue assessment during repetitive dynamic exertion.

The comparative ability of the Fourier transform (FFT) and discrete wavelet transform (DWT) algorithms in assessing muscle fatigue during sub-maximal repetitive dynamic exertion was investigated in this study. Surface electromyography data recorded from the upper trapezius muscle during forty minutes of repetitive upper extremity exertion performed by 10 male participants were used in the analysis. Multi-model regression analysis was performed to study the trend in the power values of the different frequency bands estimated using the FFT and DWT algorithms. Less variability and higher statistical significance was observed for the power value trend computed using the DWT algorithm compared to the FFT algorithm. The regression models provided a better fit for the power values estimated under more fatigued condition compared to the less fatigued condition. The lower frequency bands of 23-46 Hz and 46-93 Hz exhibited the expected and consistent power trend independent of the algorithm (DWT or FFT) used. For the exertions tested in this study, a cubic or curvilinear model explained the fatigue development process with a higher precision than the linear models.

Impact of shoulder position and fatigue on the flexion-relaxation response in cervical spine.

BACKGROUND: Neck pain is common among general population with a high prevalence among the people who are routinely exposed to prolonged use of static head-neck postures. Prolonged static loading can cause localized muscle fatigue which may impact the stability of the cervical spine. In this study, flexion-relaxation phenomenon was used to study the post fatigue changes in the stability of cervical spine by evaluating the synergistic load sharing between muscles and viscoelastic elements. METHODS: Thirteen male participants were recruited for data collection. The variables that influence cervical flexion-relaxation were studied pre- and post-fatigue using neutral and shrugged shoulder postures. The Sorensen protocol was used to induce neck extensor fatigue. Surface electromyography and optical motion capture systems were used to record neck muscle activation and head posture, respectively. Findings The flexion-relaxation phenomenon was observed only in the neutral shoulder position pre- and post-fatigue. The flexion relaxation ratio decreased significantly post-fatigue in neutral shoulder position but remained unchanged in shrugged shoulder position. The onset and offset angles and the corresponding durations of the silence period were significantly affected by the fatigue causing a post-fatigue expansion of silence period. Interpretation The muscular fatigue of neck extensors and shoulder position was found to modulate the cervical flexion-relaxation phenomenon. Early shifting of load sharing under fatigued condition indicates increased demands on the passive tissues to stabilize the cervical spine. Shrugging of shoulder seems to alter muscular demands of neck extensors and make cervical flexion-relaxation phenomenon disappear due to continuous activation of the neck extensors.

Cervical flexion-relaxation response to neck muscle fatigue in males and females.

In this study the effect of muscle fatigue on the cervical spine flexion-relaxation response was studied. Twenty healthy participants (10 males and 10 females) were recruited for data collection. The Sorenson protocol was utilized to induce neck muscle fatigue. Surface electromyography and optical motion capture systems were used to measure neck muscle activation and head-neck posture, respectively. A post-fatigue reduction in the Flexion-Relaxation Ratio (FRR) and higher FRR for females compared to males were observed. A post-fatigue decrease was also observed in the onset and offset angles resulting in an expansion of the myoelectric silence period. Gender had no effect on the onset and offset angles of the silence period. Post-fatigue shift in the onset and offset angles and the expansion of the silence period indicate an increased contribution by the passive viscoelastic tissues in stabilizing the cervical spine under fatigued condition.

Biomechanical loading of the shoulder complex and lumbosacral joints during dynamic cart pushing task.

The primary objective of this study was to quantify the effect of dynamic cart pushing exertions on the biomechanical loading of shoulder and low back. Ten participants performed cart pushing tasks on flat (0°), 5°, and 10° ramped walkways at 20 kg, 30 kg, and 40 kg weight conditions. An optoelectronic motion capturing system configured with two force plates was used for the kinematic and ground reaction force data collection. The experimental data was modeled using AnyBody modeling system to compute three-dimensional peak reaction forces at the shoulder complex (sternoclavicular, acromioclavicular, and glenohumeral) and low back (lumbosacral) joints. The main effect of walkway gradient and cart weight, and gradient by weight interaction on the biomechanical loading of shoulder complex and low back joints was statistically significant (all p < 0.001). At the lumbosacral joint, negligible loading in the mediolateral direction was observed compared to the anterioposterior and compression directions. Among the shoulder complex joints, the peak reaction forces at the acromioclavicular and glenohumeral joints were comparable and much higher than the sternoclavicular joint. Increased shear loading of the lumbosacral joint, distraction loading of glenohumeral joint and inferosuperior loading of the acromioclavicular joint may contribute to the risk of work-related low back and shoulder musculoskeletal disorder with prolonged and repetitive use of carts.

Discrete wavelet transform analysis of surface electromyography for the fatigue assessment of neck and shoulder muscles.

Assessment of neuromuscular fatigue is essential for early detection and prevention of risks associated with work-related musculoskeletal disorders. In recent years, discrete wavelet transform (DWT) of surface electromyography (SEMG) has been used to evaluate muscle fatigue, especially during dynamic contractions when the SEMG signal is non-stationary. However, its application to the assessment of work-related neck and shoulder muscle fatigue is not well established. Therefore, the purpose of this study was to establish DWT analysis as a suitable method to conduct quantitative assessment of neck and shoulder muscle fatigue under dynamic repetitive conditions. Ten human participants performed 40min of fatiguing repetitive arm and neck exertions while SEMG data from the upper trapezius and sternocleidomastoid muscles were recorded. The ten of the most commonly used wavelet functions were used to conduct the DWT analysis. Spectral changes estimated using power of wavelet coefficients in the 12-23Hz frequency band showed the highest sensitivity to fatigue induced by the dynamic repetitive exertions. Although most of the wavelet functions tested in this study reasonably demonstrated the expected power trend with fatigue development and recovery, the overall performance of the "Rbio3.1" wavelet in terms of power estimation and statistical significance was better than the remaining nine wavelets.

Loading and recovery behavior of the human lumbar spine under static flexion.

OBJECTIVE: In this study, the effect of prolonged forward flexion on the recovery process of the reflexive muscle activity of the lumbar musculature to its original state is studied using human participants. METHODS: The behavior of the lower back erector spinae muscle during 20 minutes of forward bending and three hours of recovery was evaluated experimentally using electromyography (EMG) and mathematical modeling. PARTICIPANTS: Ten healthy males participated in this study. The EMG of erector-spinae muscle from two different lumbar levels was recorded and expressed as normalized integrated EMG (NIEMG). RESULTS: In general, the average NIEMG values of the erector spinae muscles demonstrated an exponential decrease during the 20-minute loading period. The biexoponential structure, derived from the animal model, did not completely explain the muscle behavior during recovery period. Inclusion of the "intrinsic loading factor" to the biexoponential structure improved the fit of the recovery model to 100%. CONCLUSIONS: Most of the recovery (almost 50%) of the reflexive activity of erector spinae muscle was observed in the initial 30 minutes; yet by the end of three hours, complete recovery was not observed.

Neck disorders among construction workers: understanding the physical loads on the cervical spine during static lifting tasks.

In this study a common yet very strenuous construction work activity, was evaluated biomechanically by studying electromyography (EMG) of the major neck muscles. The muscles studied were the sternocleidomastoid and the upper trapezius. Fifteen healthy participants (10 males and 5 females) with no history of musculoskeletal abnormalities participated in this study. The participants lifted 25%, 50%, and 75% of their maximum shoulder height static strength at neutral, maximally flexed, and maximally extended neck postures. The weight lifted as well as the neck posture significantly affected the activities of the neck muscles. Increase in the weight increased the activation of the neck muscles. The sternocleidomastoid muscle was most active at the extended neck posture, while the upper trapezius muscle was most active at the flexed neck posture. The results of this study indicate that the neck muscles play an active role during lifting and holding tasks at shoulder height. Thus, such tasks could be probable risk factors associated with neck disorders prevalent among construction workers.

Finger joint motion generated by individual extrinsic muscles: a cadaveric study.

BACKGROUND: Our understanding of finger functionality associated with the specific muscle is mostly based on the functional anatomy, and the exact motion effect associated with an individual muscle is still unknown. The purpose of this study was to examine phalangeal joints motion of the index finger generated by each extrinsic muscle. METHODS: Ten (6 female and 4 male) fresh-frozen cadaveric hands (age 55.2 +/- 5.6 years) were minimally dissected to establish baseball sutures at the musculotendinous junctions of the index finger extrinsic muscles. Each tendon was loaded to 10% of its force potential and the motion generated at the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints was simultaneously recorded using a marker-based motion capture system. RESULTS: The flexor digitorum profundus (FDP) generated average flexion of 19.7, 41.8, and 29.4 degrees at the MCP, PIP, and DIP joints, respectively. The flexor digitorum superficialis (FDS) generated average flexion of 24.8 and 47.9 degrees at the MCP and PIP joints, respectively, and no motion at the DIP joints. The extensor digitorum communis (EDC) and extensor indicis proprius (EIP) generated average extension of 18.3, 15.2, 4.0 degrees and 15.4, 13.2, 3.7 degrees at the MCP, PIP and DIP joints, respectively. The FDP generated simultaneous motion at the PIP and DIP joints. However, the motion generated by the FDP and FDS, at the MCP joint lagged the motion generated at the PIP joint. The EDC and EIP generated simultaneous motion at the MCP and PIP joints. CONCLUSION: The results of this study provide novel insights into the kinematic role of individual extrinsic muscles.