Automated and Continuous Fatigue Monitoring in Construction Workers Using Forearm EMG and IMU Wearable Sensors and Recurrent Neural Network.

About 40% of the US construction workforce experiences high-level fatigue, which leads to poor judgment, increased risk of injuries, a decrease in productivity, and a lower quality of work. Therefore, it is essential to monitor fatigue to reduce its adverse effects and prevent long-term health problems. However, since fatigue demonstrates itself in several complex processes, there is no single standard measurement method for fatigue detection. This study aims to develop a system for continuous workers' fatigue monitoring by predicting the aerobic fatigue threshold (AFT) using forearm muscle activity and motion data. The proposed system consists of five modules: Data acquisition, activity recognition, oxygen uptake prediction, maximum aerobic capacity (MAC) estimation, and continuous AFT monitoring. The proposed system was evaluated on the participants performing fourteen scaffold-building activities. The results show that the AFT features have achieved a higher accuracy of 92.31% in assessing the workers' fatigue level compared to heart rate (51.28%) and percentage heart rate reserve (50.43%) features. Moreover, the overall performance of the proposed system on unseen data using average two-min AFT features was 76.74%. The study validates the feasibility of using forearm muscle activity and motion data to workers' fatigue levels continuously.

Data Quality and Reliability Assessment of Wearable EMG and IMU Sensor for Construction Activity Recognition.

The workforce shortage is one of the significant problems in the construction industry. To overcome the challenges due to workforce shortage, various researchers have proposed wearable sensor-based systems in the area of construction safety and health. Although sensors provide rich and detailed information, not all sensors can be used for construction applications. This study evaluates the data quality and reliability of forearm electromyography (EMG) and inertial measurement unit (IMU) of armband sensors for construction activity classification. To achieve the proposed objective, the forearm EMG and IMU data collected from eight participants while performing construction activities such as screwing, wrenching, lifting, and carrying on two different days were used to analyze the data quality and reliability for activity recognition through seven different experiments. The results of these experiments show that the armband sensor data quality is comparable to the conventional EMG and IMU sensors with excellent relative and absolute reliability between trials for all the five activities. The activity classification results were highly reliable, with minimal change in classification accuracies for both the days. Moreover, the results conclude that the combined EMG and IMU models classify activities with higher accuracies compared to individual sensor models.

Effect of video-game experience and position of flight stick controller on simulated-flight performance.

The purpose of this study was to determine the effects of video-game experience and flight-stick position on flying performance. The study divided participants into 2 groups; center- and side-stick groups, which were further divided into high and low level of video-game experience subgroups. The experiment consisted of 7 sessions of simulated flying, and in the last session, the flight stick controller was switched to the other position. Flight performance was measured in terms of the deviation of heading, altitude, and airspeed from their respective requirements. Participants with high experience in video games performed significantly better (p < .001) than the low-experienced group. Also, participants performed significantly better (p < .001) with the center-stick than the side-stick. When the side-stick controller was switched to the center-stick position, performance scores continued to increase (0.78 %). However, after switching from a center- to a side-stick controller, performance scores decreased (4.8%).

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.

Drivers׳ merging behavior data in highway work zones.

There have been growing research interests in finding a suitable work zone layout to improve work zone safety and traffic efficiency. This paper contains data supporting the research article entitled: Effects of work zone configurations and traffic density on performance variables and subjective workload (Shakouri et al., 2014 [1]). A full factorial experiment was conducted to compare the efficiency of two work zone configurations by using a driving simulator with two levels of work zone configuration, two levels of traffic density and three levels of sign placement as fixed factors. Seven female and 23 male participants completed the experiment. In this paper we present the data relating to demographic information of participants, driving simulator data and subjective workload evaluation of participants for each work zone.

Interaction of physical and mental work.

The objective of the research was to determine the effect of mental load on the physical capacity of an individual. An experiment involving 9 combinations of lifting tasks, 1 lowering task, and 3 treadmill tasks was conducted. Heart rate was measured and maximum acceptable weight of lift was determined using the psychophysical method. A simple multiplication task was used as the mental load. The output variables were determined with and without the mental task. The results indicate that the individual's physical capacity decreased with the mental task while lifting from floor to knuckle and shoulder to reach lifting heights.

Health risks from exposure to metal-working fluids in machining and grinding operations.

Metal-working fluids (MWFs) are used in machining and grinding operations to cool the tool and work, reduce the friction between the tool and work, improve the surface integrity of the work piece, and increase tool life and productivity. Health problems have been reported among workers exposed to MWFs, including incidences of respiratory, digestive and skin cancers, and increased rates of cough and phlegm. This paper reviews and discusses issues concerning health risks from exposure to MWFs in machining and grinding operations, the various factors that influence the degree of exposure, and control methods to reduce exposure to metal-working fluids.

Effects of work zone configurations and traffic density on performance variables and subjective workload.

This paper investigates the effect of changing work zone configurations and traffic density on performance variables and subjective workload. Data regarding travel time, average speed, maximum percent braking force and location of lane changes were collected by using a full size driving simulator. The NASA-TLX was used to measure self-reported workload ratings during the driving task. Conventional lane merge (CLM) and joint lane merge (JLM) were modeled in a driving simulator, and thirty participants (seven female and 23 male), navigated through the two configurations with two levels of traffic density. The mean maximum braking forces was 34% lower in the JLM configuration, and drivers going through the JLM configuration remained in the closed lane longer. However, no significant differences in speed were found between the two merge configurations. The analysis of self-reported workload ratings show that participants reported 15.3% lower total workload when driving through the JLM. In conclusion, the implemented changes in the JLM make it a more favorable merge configuration in both high and low traffic densities in terms of optimizing traffic flow by increasing the time and distance cars use both lanes, and in terms of improving safety due to lower braking forces and lower reported workload.

Modified track shoes and their effect on the EMG activity of calf muscles.

Although track and field spike shoes are crafted for runners, these shoes are not designed for regular walking. With such shoes, runners may eventually encounter serious chronic injuries such as plantar fasciitis, shin splints, achilles tendinitis, chondromalacia, and iliotibial band syndrome. To address this problem, a modified spike shoe was tested and compared to a regular spike shoe. The modification consists of adding a removable heel to the shoe sole in order to reduce the flexion of the foot and properly level the foot for walking. Nine healthy participants performed walking drills at 2 and 3 mph, using the original and the modified shoes. Electromyography (EMG) measurements were used to evaluate muscle activities. Participants also rated their discomfort on a 0-10 scale. Results show that the use of modified shoes resulted in a reduction of 22% and 24.25% EMG activity for the tibialis and gastrocnemius muscles, respectively. Comfort ratings increased by an average of 2.7, 2.6, 3.9, and 4.2 points at the knees, calves, ankles, and feet, respectively.

A study of the kinematics of ingress and egress of upright and recumbent seats.

Research has been done on the maximum reach and ingress/egress of upright seats. However, research on recumbent seats and comparisons between recumbent and upright seats is limited. By using an eight-camera Vicon motion capture system and C-motion Visual 3D modeling software, this research compared the ingress/egress joint kinematics and maximal planar reach of an upright seat with a recumbent seat. Mean range of motion and mean peak angle for each ingress/egress task were determined and the values for the upright seat were compared to the values for the recumbent seat. For each reach task, three extreme points were extracted and compared between the upright and recumbent seat. Seat orientation was found to have a statistically significant effect on the range of motion of several joints during the ingress/egress tasks, as well as one of the extreme points during the reaching tasks.

Handwheel valve operation: assessment of four opening methods in terms of muscle loading, perceived comfort, and efficiency.

Injuries due to manual valve handwheel operations are a major concern in the chemical process industry. Manual valves are used to start, stop, and control flow in process lines. The torque required to operate handwheels after the initial "breaking" can vary due to the size, design, and condition of the valve. This study tested four methods of turning the handwheel on a medium-sized gate valve at two different torque requirements (25 Nm and 50 Nm). The methods were compared to each other, in terms of efficiency, subjective ratings of perceived exertion, and electromyography activity of the upper extremity and trunk muscles. The results indicate that different methods and torque requirements are compensated for by the use of different muscles. Also, this use of different muscles, along with the increased mechanical advantage of the wrench, can affect the operator's actual and perceived comfort and efficiency while operating a valve handwheel.

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.

Comparison of current U.S. and Canadian cigarette pack warnings.

Cigarette smoking is the single most preventable cause of death in the United States. From 1985 to date, one of four mandatory cigarette warnings proposed by the Comprehensive Smoking Education Act of 1984 has been displayed on cigarette packages. In addition to cigarette warnings, states like California, Massachusetts, Arizona, Oregon and Maine have implemented "Tobacco Control Programs" (TCP) to reduce the overall number of smokers. However, the decline in the rate of smoking is not occurring fast enough to meet the national health objective by 2010. The present U.S. cigarette warnings are verbal in form and provide information, which is inadequate but appropriate to make it legally adequate. On the other hand, warnings in other countries such as Canada and Brazil are more descriptive and specific and are accompanied by vivid and sometimes gruesome pictures. In the present study, six pictorial Canadian labels and four U.S. verbal labels were analyzed for potential effectiveness among eighty subjects using a survey questionnaire. The survey findings are compared with recent Canadian smoking data. It is concluded that placing pictorial labels on cigarette packages in the U.S. will allow the product to carry warnings that potentially provide better results than current verbal messages and less TCP funds will need to be used.

The effect of work-rest schedules and type of task on the discomfort and performance of VDT users.

Consideration of the literature survey indicates that video display terminal (VDT) operators tend to have a high incidence of musculoskeletal problems, visual fatigue, and job stress. Although a number of ergonomic improvements in workstation design and work environment can help to reduce these problems, a proper work-rest schedule deserves consideration since it is easily applicable and inexpensive. The objective of this study was to compare the work-rest schedules for VDT operators considering data entry and mental arithmetic tasks. An experiment was conducted with 10 male college students as participants. The methodology included a discomfort questionnaire and performance measures. The independent variables were the work-rest schedule (60-minute work/10-minute rest, 30-minute work/5-minute rest, and 15-minute work/micro breaks) and the type of task (data entry and a mental arithmetic task). The results were analysed using multiple analysis of variance followed by separate analyses. The 15/micro schedule resulted in significantly lower discomfort in the neck, lower back, and chest than the other schedules for data entry task. The 30/5 schedule followed by 15/micro schedule resulted in the lowest eyestrain and blurred vision. Discomfort in the elbow and arm was the lowest with the 15/micro schedule for the mental arithmetic task. The 15/micro schedule resulted in the highest speed, accuracy, and performance for both of the tasks, compared with the 60/10 and 30/5 schedules. The data entry task resulted in significantly increased speed, accuracy, and performance, and lower shoulder and chest discomfort than the mental arithmetic task.

Effects of VDT monitor placement and single versus bifocal glasses on somatic discomfort and postural profiles in data entry tasks.

A study was conducted to determine the effects of VDT monitor positions and the use of single vision versus bifocal glasses on somatic elements in the data entry task. Eight male subjects performed data entry using a word processor in eight half-hour sessions with the four different monitor placements, i.e. "eye-level", "shoulder-level-front", "shoulder-level-side", and "sunken-level", wearing the two types of glasses. A subjective discomfort rating questionnaire covering 12 somatic elements was completed by the subject after each session. The head inclination and angle of gaze to the monitor were measured with a goniometer. The results revealed that the somatic elements which were affected significantly by the placement of the VDT monitor and the type of glasses were discomfort in the neck and back regions and eyestrain, respectively. The neck-back discomfort scores were highest at the "eye-level", lowest at the "sunken-level", and intermediate at the "shoulder-level-side" position. The "shoulder-level-front" position was not significantly different in the discomfort from other three positions. The eyestrain was significantly greater with the bifocal than with the single vision glasses. The lower the monitor was placed, the more forward was the head and gaze inclined. The head was inclined less forward, or even more backward, and the gaze was inclined more forward, with the bifocal than with the single vision glasses. As a conclusion, the VDT operators were advised to avoid the "eye-level" and "shoulder-level-side" positions and to prefer the "sunken-level" and "shoulder-level-front" positions as the first and second best choices, respectively. The preference becomes more critical for the wearers of bifocal glasses that suffer from postural constraints in viewing.

Effects of complex aural stimuli on mental performance.

The objective of this study is to investigate the effect of complex aural stimuli on mental performance. A series of experiments were designed to obtain data for two different analyses. The first analysis is a "Stimulus" versus "No-stimulus" comparison for each of the four dependent variables, i.e. quantitative ability, reasoning ability, spatial ability and memory of an individual, by comparing the control treatment with the rest of the treatments. The second set of analysis is a multi-variant analysis of variance for component level main effects and interactions. The two component factors are tempo of the complex aural stimuli and sound volume level, each administered at three discrete levels for all four dependent variables. Ten experiments were conducted on eleven subjects. It was found that complex aural stimuli influence the quantitative and spatial aspect of the mind, while the reasoning ability was unaffected by the stimuli. Although memory showed a trend to be worse with the presence of complex aural stimuli, the effect was statistically insignificant. Variation in tempo and sound volume level of an aural stimulus did not significantly affect the mental performance of an individual. The results of these experiments can be effectively used in designing work environments.

Biomechanics and electromyography of a common idiopathic low back disorder.

STUDY DESIGN: In vivo feline preparation groups loaded into lumbar flexion at different magnitudes and an unloaded control group. OBJECTIVE: To demonstrate that a static, constant load flexion of the lumbar spine results in a complex neuromuscular disorder. SUMMARY OF BACKGROUND DATA: Epidemiology suggests that static lumbar flexion is a cause of low back disorders. There is little direct experimental evidence describing the physiologic and biomechanical processes that elicit the disorder. Recent evidence shows that static flexion of the spine under constant displacement results in muscular spasms and a prolonged recovery period. The response of the spine to flexion under constant load of various magnitudes (as opposed to constant displacement) is not known. It was hypothesized that static lumbar flexion under constant load may elicit creep in spinal ligaments, discs, etc., causing microdamage and development of a neuromuscular disorder. METHODS: The lumbar spine of the feline was subjected to 20 minutes of constant load static flexion at physiologic load intensities from light to heavy while creep of lumbar viscoelastic tissues and EMG from the multifidus muscles of L3-L4 to L5-L6 were recorded. Recordings were continued over a 7-hour rest period after the static flexion was terminated. RESULTS: Spasms and decreasing reflexive EMG were evident during the loading period, and a transient surge of EMG activity occurred at the beginning of the rest period. A second surge of EMG activity was seen 3-4 hours later. The four components of the neuromuscular disorder were present regardless of the load magnitude. A model was developed to quantify the disorder. CONCLUSION: A four-component neuromuscular disorder was elicited by a 20-minute constant load static flexion even when very light loads were applied. The disorder was elicited by creep of the viscoelastic tissues, which resulted in spasms and muscular hyperexcitability lasting for >24 hours. Although the disorder was transient, the physiologic and biomechanical principles associated with its development could also explain cumulative trauma disorders.