Hi, good afternoon. My name is Dr. Laura Regan and I'm presenting today's topic on physical hazards and ergonomics. And I'll just give you the briefest background on myself. I trained originally in internal medicine and then went back and did a fellowship in occupational medicine at UC San Francisco. And part of my training was to do the master's of public health, which I did at Cal Berkeley. And I took a semester long course in ergonomics, where we worked with other physicians and engineers, safety professionals on how to do ergonomic assessments, how to analyze that information. So I'm going to share a little bit about what I learned there, as well as what I've learned from my experience as a practicing occupational medicine physician. I currently am an attending for the University of Pennsylvania Health System and work at two of their hospitals. Okay, so disclosures, this is required to include in the presentation. I don't have any specific investment, financial or otherwise, in any of the available products used for ergonomic assessments. And we're not going to be discussing any of this specific commercial products. And the reason for that is that if you end up doing these or reading these reports, using this information, typically the companies that you'll be working with, they already have their own programs that are in use. So if you went to work for a corporation, as part of the medical team, they would already have a system like this in place. At some point, they might update it or change it, and you might be part of that team to do that. But I didn't think it was necessary to include that information from an educational point of view. Also, all of the photos and tables that are included in this presentation are my personal photos and except as noted. So I'll let you know when it's something that was sent from the internet. Okay, so what are our learning objectives for this time that we have together? First of all, for this module, I'm sure some of the other modules also are talking about the main ways that you control hazards in occupational medicine. And we'll discuss those, but we're also going to talk specifically about how do they pertain to the areas of physical hazards and ergonomics. And we're going to discuss physical hazards kind of individually and talk about which types of occupations that are relevant for those hazards. And I think that will sort of be clear as we move through that. And then we're going to spend the majority of our time together talking about the role of body mechanics, positioning, equipment design, and how that can adjust, how it can contribute or decrease ergonomic risk in the workplace. Okay, the term ergonomics was first developed in the 1950s from the Greek word ergon, meaning work, and is inclusive concept of fitting the task to the worker, not the other way around. And prior to World War II, there was a strategy that industrial equipment was designed, and then they would just hire workers that had the physical characteristics that they needed to operate the equipment. For instance, if the machine happened to be very tall, then they would just hire tall individuals to work at that particular piece of equipment. Some time ago, factories were actually built with very short stories so that they wanted to hire children or short employees to work as they could get more productivity out of people if they stack the equipment on top of each other. So after World War II, there were, during World War II, many women joined the workforce and it became really clear that equipment that was designed for people who were six foot two, that was not going to be a practical option for accommodating 50% of the workforce. And so that contributed to the development of the field of ergonomics. It's somewhat expanded so that it also includes the study of efficiency in the work environment. In other words, is it more efficient if an employee moves from one part of a machine to another, or should we move the product from one side to the other and have different employees work on this, sort of like the assembly line technique? Is it better if one person does one task versus several people doing the same thing simultaneously? Also improving workspaces to reduce injury is kind of more of a modern concept of how we use ergonomics. And you probably are familiar with the term ergonomics because you see it in equipment. They talk about ergonomic chairs, ergonomic design, ergonomic tools. Basically a lot of that is just sort of a buzzword, meaning it's adjustable. An ergonomics chair isn't necessarily the perfect chair for every single person, but that you can make changes to it to adjust the height, the depth, and other aspects of it to make it more comfortable for most workers. Okay, so here are the principles that we talk about in occupational medicine in general. And I'm hoping that this is a review and that they've covered some of this in some of your other modules. So when we talk about hazard control, we talk about engineering controls, workstation redesign, and that is getting in at the very beginning. When you're designing a new process, we try to say, how can we make this fit the majority of workers? And if that's not possible, how can we make adjustments so that individuals with handicaps are able to use the equipment that we're designing? And that's very important, but a lot of factories, manufacturing, or retail, other things, they already have the equipment. So if you can't do a redesign, then we want to use one of these other methods of hazard control. Administrative controls, that includes things like job rotations during the work shift. So a person might be on one task where they do this. They work on that task for a period of one to two hours, and then they rotate to a different task. And this enables a business to have continuity so that they have more workers trained in more tasks. It also tends to make it more interesting for the employees, and also it's safer so that they're not doing the same repetitive task throughout their workday. Also using good body mechanics, where a person positions themselves well for doing a particular task, I consider that a sort of administrative control. And then when we talk about personal protective equipment, or PPE, hopefully you've heard about that ad nauseum. I know we all have in the context of COVID. I think even members of the public all became quite knowledgeable about PPE. But in this context, PPE would refer to splints or other supportive devices. And the main difference here is that these personal protective equipment is applied to the worker rather than something that's available in their workplace. So other types of adjustments might be building a platform so that employees of various heights could work on an area. And we generally consider that to be the gold standard, which is workstation or workplace design or redesign. Personal protective equipment, especially as it pertains to ergonomics, is considered the least desirable and least effective means of creating a safe work environment. Okay, we're going to talk about physical hazards in the workplace. And a number of these you will know about from your own life experience. And I think some of these are covered at length in other modules. So I just made this list kind of to be somewhat comprehensive. For instance, radiation exposure. There are certainly uses of radiation in medicine and science, where a worker is potentially exposed. And there's a great deal of federal regulation related to that. So I felt that that was kind of like a topic on its own. And there are so I'm not developing that at great length here. But if that's not something that is developed at great length, then the other reason to the other presentations, there certainly are other resources, some of which we talk about at the end of this talk, where you could receive additional information. Noise exposure. This is a huge area and could easily you could have you can attend up to eight hour conferences where all they do is talk about hearing conservation, noise measuring and monitoring control. So that I'm specifically excluding from this because I think it's adequately addressed in other learning experiences that you have had already or that you will have. So we're going to focus more on these other things. Hyperbaric oxygen or hyperbaric pressure, rapid decompression, high altitude, temperature extremes and vibration. OK, so hyperbaric pressure. There are a number of occupations where they're doing have exposure to hyperbaric pressure. So this would include deep underwater diving, caisson work for tunnels or for bridges. And from a health care point of view, working in a multi-place hyperbaric oxygen medical treatment facility that will give the workers exposure themselves. There are two different types of hyperbaric oxygen treatment facilities available. One is what they call mono place or one place, and that is a sort of a cylinder in which the patient rests and receives their treatment normally in a supine position. And that is typically used for people who have stable conditions medically. But there are facilities that where they have multi-place, in other words, several patients are in the treatment facility simultaneously. And this is mainly used when individuals need to have medical treatment or monitoring, say their blood pressure or other things during the treatment. And so the workers themselves are exposed to this high pressure oxygen during the treatment intended for the patient. So this is important for individuals who may have sinus problems or congestion of the middle ear, because if you're not able to equilibrate, then as you can imagine, just like flying in an airplane or scuba diving on your own, if you've done that, if you're not able to equilibrate, then you're basically not able to function in that setting. So for patients, if they have middle ear problems that interfere with their treatment, they see an ENT doctor and they put tubes in their ears and that automatically equilibrates between the interior of the middle ear and the ambient pressure. I don't believe that's typically done for workers. If you're not able to tolerate that, then that's just not a type of work that you'd be pursuing. Interestingly, normal nitrogen levels at sea level or 78% can be toxic themselves when they're under pressure and typically would cause the individual to have altered mental status as a symptom or early finding of that. Okay, so along with hyperbaric treatment or hyperbaric work, then you would have the individual needs to return to sea level at some point at the end of their shift or at the end of their treatment. So if this occurs too rapidly, then nitrogen bubbles and other gases that are dissolved under pressure actually come out and form tissue bubbles in the tissue. And this can occur in the joints, in blood vessels, and around the spinal cord. And the symptoms associated with this are called decompression sickness. And when this occurs, the treatment often involves immediate return to depth, putting the person back in to the hyperbaric chamber if it's in a treatment facility, optimally within 15 minutes. And then you can bring them back to ambient pressure within taking a much slower rate of ascent. That's the optimal treatment. Now, this rapid decompression is also known as caisson disease, because a number of workers involved in tunnels and bridges have developed this. And probably the most famous case involving this actually pertains to the building design and construction and opening of the Brooklyn Bridge in New York City. So the bridge itself was designed by an engineer named John Roebling, and he and his son were doing some surveying at that site on a dock that was in the river. The dock was hit actually by a barge in the river. It severed several of his toes. And the John Roebling Sr. actually died of tetanus as a result of the injury. Fortunately, not for him, but fortunately for those of us who've been to the Brooklyn Bridge, he had completed the design phase. So then his son actually, who was an engineer, also took over the production supervising the construction. But he developed caisson disease after rapid ascent, and he was paralyzed from the waist down. And then his wife, who was an engineer, took over the final completion of the project, which took approximately 11 years. So most people aren't aware of that, but I think it's a kind of interesting side story, the importance of medical aspects of work on this type of dangerous occupation. So high altitude is kind of the opposite effect. It typically affects only a few occupations, mainly aviation, even things like building design, where the multi-story buildings are not really high enough to be making a difference. I guess you could say tour guides in remote areas that are extremely elevated. Most of those individuals are fully acclimated and don't come down to sea level routinely. So it's less of a problem from an occupational point of view. So it's mainly a problem for hikers and mountaineers. And the usual threshold for developing symptoms occurs at about 8,000 feet, but some individuals will become symptomatic at 5,000 feet, which is similar to cities. Some cities in the U.S. are at that level. So if you live there, you become acclimated to that. But if you're a visitor, then you have to be especially careful. Denver is a little bit more than 5,000 feet. And there are places in New Mexico where cities are at 8,000 feet. So symptoms of this include nausea, vomiting, shortness of breath, and sleep disturbance. And of course, returning to a lower altitude reverses the symptoms almost immediately. But when that's not practical, there are other things that individuals can do, including taking acetazolamide. And in the Andes, they actually use cocoa leaves. They offer these to tourists who are going to Machu Picchu, for instance. And it does, in fact, contain cocaine. I think that does have some therapeutic benefit, or at least it makes you feel better like you don't care. So what about elevated temperature? This is a significant concern with various parts of the United States. Outdoor work in a hot climate, metal foundry, confined space work, firefighting, and others that require full-body PPE. So here's a case where the PPE is designed to protect you from fire or whatever, but it's actually part of the hazard because your body temperature is going to be elevated inside of this protective equipment. So when we think about control measures, we say, what could that individual do? What can we do for this group of workers? Providing cold beverages, frequent breaks in a cool environment can be helpful. Allowing time for acclimation. And that's typical if you work in an outdoor situation where you're going, you go through the season. So if you're a landscaper in Arizona, well, it's hot most of the time. So your body's probably fully acclimated to this. But where I'm at in Pennsylvania, it's really cold in the winter time, but then you have the gradual change of the seasons so that an outdoor worker is going to have time to adapt. And these efficiencies in losing heat, basically that's increased sweating. And sweating is a primary mechanism that your body has to remove heat fairly efficiently. So for individuals who are doing firefighting and other work where it's episodic, active surveillance for signs of heat stroke or exhaustion can be really helpful monitoring blood pressure, heart rate, and mental status. So the opposite, which this does not occur I guess in Arizona, but here in Pennsylvania and many places further north, there are individuals who work out of doors in a cold climate. And there are individuals who work in a sort of artificial cold and climate. And that would be in like meat processing, processing and storage of frozen foods. One of the clients that I've worked with actually is food processing. And every place except for the main office is below 32 degrees. Otherwise, if it isn't, then the frozen food will not be frozen. It's very inefficient to to manage the product in that case. So you don't have super adaptive mechanisms. Shivering is not a very efficient way of increasing temperature. Vasoconstriction, although that can certainly keep your core temperature improved, that causes increased hazards with your extremities. So the best protection is keeping a dry layer against your skin, wearing multiple insulated layers. And for outdoor work, especially creating a windshield because the wind increases your heat loss. And also heating technology, which many people use like in things that they wear that maybe have a battery powered heater attached to them, you know, can be in socks or gloves. Those can be very helpful for maintaining temperature. Now, in terms of vibration exposure, there are the main one we worry about from an occupational point of view is segmental vibration. And that means it's vibrating a part of your body. Typically, that would be the upper extremities. So this would include workers who are using chainsaws, riveting guns, pneumatic drills, jackhammers, this type of equipment that literally shakes your body when you're using it. And the risk, it turns out, of vibration is compounded when the individual is exposed to low ambient temperatures. So you can imagine like if you had a water main break in the wintertime, the workers who are out there exposed, they're going to be using a jackhammer, it's going to be 20 degrees outside, and they're also going to be exposed to ice or getting their clothing wet and then cold. So those are particular hazards when we see them all together in combination. Typically, the vibrations that cause the most hazard for the human body are low pitched vibrations, which occur between five and 300 hertz. Those are associated with hand-arm vibration syndrome, which some people refer to as vibration white finger. This is an asymmetric blanching of the digits associated with spasm in the digital arteries, similar to Raynaud's syndrome. Raynaud's syndrome typically is more of an annoyance. The person comes back in, the problem goes away. Whereas this hand-arm vibration syndrome, sometimes the damage to the blood vessels is permanent and it's not improved with rewarming. So we're particularly concerned about that. Now, when we think about these frequencies, it's just good to kind of keep in mind what other types of exposures, what frequencies do those occur in. And when we think about noise exposure, sort of the lowest threshold for that, that we measure when we do hearing tests is 500 hertz. And that goes up as high as 8,000 hertz. So you can see the frequency here is much lower than that, which would be affecting the human ear. So how can we mitigate the effects of vibration? So here we have our three main methods of hazard control. We can have anti-vibration gloves, which can be matched to the frequency of the vibrating equipment. And that would be considered a personal protective equipment. Equipment redesign, which would be looking at how can we muffle the vibration by attaching a certain absorbing interface between the machinery and the worker. That would be an engineering control. And task rotation, of course, that's an administrative control. So if we take the individual who's doing this, having vibration exposure, the goal is that we're rotating them through other tasks where they're not having that type of exposure. Now when we talk about full body vibration, well, this is kind of a different thing altogether because it's not really clear whether this is harmful or not. For instance, commercial truck drivers and heavy equipment operators, they're sitting in the cab of their vehicle or their equipment and they are absolutely exposed to whole body vibration at a low level for long periods of time. But it's not really clear that that is specifically harmful. In fact, NASA developed equipment that causes whole body vibration as a means of preventing loss of bone density for astronauts during space travel. And it's also been looked at, I think, less successfully in treating osteoporosis where you stand on something that vibrates as a means of improving bone density. But these devices, they have been shown to improve gait and balance in individuals with cerebral palsy, probably because you're making little micro corrections in your balance to stay on the vibrating equipment. So it is also used clinically, as I'm sure many of you know, to downregulate pain with cutaneous stimulation or TENS. There are several different devices that are available. We're not going to talk about those here. But the main thing is to say all vibration is not bad, but specifically bad is upper extremity low frequency vibration, whereas whole body vibration, not clear that that's harmful. Okay, so that's just kind of an overview. It's not meant to be exhaustive. But when you're doing an assessment of an individual who may be having exposures to physical hazards, it's always good to be keeping in mind what physical problems that individual might have and how those might interface with those physical hazards. For instance, medications that inhibit sweating, such as anticholinergics, can increase the risk of exposure to hot environments. And I know when I worked with a company that had a plant in Arizona, this was a significant hazard because they would have to go up onto the roof of the facility where the temperature would be like over 130 degrees. So we want to make sure that our individuals are safe in that type of environment. No one would do that for prolonged periods of time. And there would always be in constant communication with others in case there was a problem. But very, very important to be aware of the individual's medical history if they're going to have some unusually difficult or stressful physically exposure. Other things like allergic myonitis and other kind of chronic eustachian tube dysfunction can impact a worker's tolerance for hyper or hypobaric oxygen environments. We want to be especially mindful of that when we're in the pre-placement process. There can be an extensive amount of training involved in working in these facilities. So we want to make sure that the employee is able to physically tolerate the conditions before we do that. And individuals who have Raynaud syndrome or just general peripheral artery disease, they are definitely at increased risk of frostbite with prolonged cold exposure. So these are key things to be looking at mostly on the pre-placement setting. But sometimes it's difficult to provide an accommodation if that's an essential part of their job. We want to make sure that it's safe for them to be doing this type of work. Okay. So what about employee adaptions to the physical environment? So sometimes employees can through administrative controls or PPE, they can become more adapted to their physical environment. And I thought this situation that came up with me somewhat recently kind of illustrated the physical difficulties and impairment. An individual I was asked to see by one of the nurses because he sort of flunked the vision testing that was done on a pre-placement basis. The individual was going to be a general surgeon. The nurse checked his vision in the left eye was 20-20 with correction. But in the right eye, he had no light perception. So she was wondering how this might affect his workability. So in a case like that, the patient was put in a room for me to see. And interestingly that on inspection, his eye appeared perfectly normal, but he had no pupillary response. So that was why I was asked to do an assessment in his case. So his history was that he'd had a retinal artery thrombosis at age 17. This is actually a true story. He had extensive workup at the time to, you know, like, was he throwing an embolus? Did he have some other kind of arterial difficulties? There was nothing like that that was found. He had otherwise a completely normal exam. He had no basket or symptoms. He had no events either before that or after that. So at age 17, he was devastated because he said, well, how could I? He'd had a lifelong dream at age 17 to become a surgeon. So he said, well, I'm going to still try to do that. So he went to medical school. He matched in surgery. He completed his residency and no one in school or no other prior employer had ever checked his vision until the applicant came to see me on that day. So monocular individuals like the surgeon that I saw, they are at increased risk of physical hazards that they can't see. And when you think about commercial drivers or even regular drivers, they have difficulty seeing their peripheral vision is going to be less than half of a person with binocular vision. So driving that still to this day, at least as of the time of this presentation, that monocular drivers are required to get special clearance from the Department of Transportation to work as a commercial driver. So employees, though, for their own car, you can have adaptions like putting extra mirrors on the side of your vehicle. This improves your peripheral vision. That would be considered like an engineering change that would improve your peripheral vision. But for this individual, I asked him, what does he do? He says he does more frequent scanning. In other words, moving his eye with perfect vision throughout the field. And according to him, he said, well, I only move one hand at a time and I always watch the hand that's moving. So I thought after all his training and his explanation and his otherwise excellent health, he was cleared for hire. So now we're going to talk a little bit about body positioning hazards. And this is an important part of ergonomics. Prolonged standing is one of the issues that you see. There are many manufacturing and retail operations require a person to stand in the same place for very long periods of time. Static positioning of the upper extremities is also very common. For instance, if you are working on a product coming to you on a conveyor belt, that's usually going to be at approximately waist height. So you're often standing with your elbows flexed for prolonged periods of time. Other kinds of awkward positioning, evolving the head, neck, and wrist can be important. And also issue about rate of control or repetition. Now repetition, I included this, but it is actually somewhat controversial, the role that repetition has in ergonomics. For some people, they're very concerned about it, but I think when we think about certain occupations where like an orchestra conductor or other musicians, they do a lot of repetitious movement, but they are adapted to doing that and it's not clear that that's a hazard for them when they're conditioned for that role. When we think about others in the animal kingdom, like hummingbirds flap their wings approximately 200 times per second. So I just think like how did their muscles have a chance to adapt to that? Of course, I don't know the answer to that. But I know that in humans, we're not capable of doing that type of rapid motion. So when we talk about muscle fatigue, that's the term that I personally like to use when we're talking about ergonomics, rather than the term cumulative trauma, which you'll hear a lot of. But I think cumulative trauma is basically muscle fatigue plus aging. So there are normal changes that occur in your body over time that make you more prone to muscle fatigue. But I don't think it's really scientifically valid to say that the trauma of using your hands accumulates over the course of your career. I think that's more a hypothetical construct than something that we've been able to prove over the last 50 years of research in this area. We know that muscles receive their oxygen and glucose during the relaxation phase of contraction and relaxation. So deconditioning, exposure to below freezing temperature, and as we talked about earlier, segmental vibration, can interfere with the muscles ability to obtain oxygen and glucose during the relaxation phase. And lack of oxygen and glucose interferes with aerobic metabolism and creates lactic acid instead of carbon dioxide as a byproduct. And that's what gives you achy muscles when you're doing something you're not accustomed to. But ironically, lactic acid actually promotes recovery by lowering pH and results in vasodilatation. So it actually will drive more oxygen in after the fact. Minor muscle injury actually helps build muscles back stronger. And you can imagine this is what we call muscle training or physical endurance training, where you do something over time and you actually are able to tolerate more of that activity. So lifting weights makes you stronger because you have minor muscle injury that results in the muscle over time coming back stronger. So our goal with ergonomics is how can we make our minor muscle injury work for us before it becomes a major muscle injury resulting in a work-related injury. So whenever you're adjusting to a new task, whether it's sports or work, playing a musical instrument, if we do that in a gradual fashion, that gives our muscles the time to adapt. But normal aging can decrease the conditioning response and the rate of adjustment should be slower so that we're taking more time for our bodies to physically adjust to this. The other thing that we see is just as conditioning helps us get stronger, deconditioning occurs if you stop doing a task for a period of time. And this occurs with workers who say go on vacation or anyone really who are after a long absence. Maybe they had an appendectomy and they don't return back to work for at least two weeks. Well your muscles actually, if you don't use them, they think you don't need that part of the muscle anymore and they will become weaker. So we want to be especially careful for ourselves and for workers who are away from the work environment. It takes more time for them to reacquire that due to loss of performance. Okay, so now we're going to talk about how can we apply some of these principles to specific regions of the body. So when we think about the human neck, the optimal positioning for the human neck is between neutral, in other words that's straight up and down to a maximum of 15 degrees of flexion and 30 degrees of right or left rotation. In order to prevent what's now called tech neck, that's super important because a human head weighs about 10 to 12 pounds. But if you're keeping your neck flexed forward at 45 to 60 degrees, the amount of force required to hold the head in that position is actually 50 to 60 pounds. So the amount of work or muscle energy required is much greater than the object actually being held up. So the military, what we call the military posture, where you have your shoulders back, your chin tucked in and your head looking forward, that is actually the most restful position as far as your neck and upper back muscles go. So this is just an illustration of that. You see a number of individuals who look at their phone, they're staring at it at about waist height, and maybe they're searching for the latest medical information, or maybe they're doing other things. But on the left side, you can see this is about a 45 degree angle relative to the angle of the body. And the phone in this case is being held with the wrist in good position. But this is where you would begin to see this pressure of holding this in position would be that 50 to 60 pounds. So to alleviate that, this is actually a better position for the neck. But in the category of your fixed one problem, you cause another problem for this individual. If you were doing this all day long, then you'd be especially concerned about the acuity of the angle at the elbow. Because although this position is restful for the elbow, this position rests the neck but puts stress on the elbow, especially the ulnar nerve, which makes a acute turn at the angle when held in this position. So it's a trade off when you look at these two situations. So in shoulder positioning, this has been studied extensively in ergonomics as well. Biomechanical exposures and physical exams were performed in this group. Here is a reference for the study that I'm referring to. And they looked at positioning between different groups of workers over a period of time. They eliminated people from the baseline who were already symptomatic because they wanted to select a neutral population at baseline. And what they found was that a greater than 18 degrees of shoulder abduction or holding the arms away from the side of the body during forceful hand exertion increased the rate of both shoulder and neck pain by 55%. Now I think it seems sort of intuitive why that would be affecting the shoulder. But why does that affect the neck? And it may be as you're using accessory muscles, such as the trapezius muscle that is extending into the base of the neck. For instance, here is an office worker. The arms are being held in abduction. In other words, this is adduction or right next to the body. This is the safest position for the shoulder and for the neck. But sometimes the height, a common reason why you would need to do this is if the table or desk that the worker is sitting at is too high for them to reach their work product, then they abduct the shoulders in order to correctly position the hands as in this case. So one of the things that could be done in this type of setting is actually raising the height of the work stool or chair, depending on the type of work being done, and that would allow you to put the arms in the correct position. So when we look at wrist and hand positioning, in a longitudinal study that adjusted for age, gender, and force and repetition, the risk of tendinitis was more than doubled with wrist flexion of more than seven degrees with both pinch and power grip. Slight wrist extension, however, and a heavy power grip. So that's like this, a heavy power grip is kind of making a fist, but holding something in your hand. That's a heavy power grip, like the way you would hold a hammer. So wrist extension, slight wrist extension is actually helpful. And that's something, flexion would be this way, and you can try this yourself. You don't have to do it during the presentation. But if you hold an object in your hand like this, you will actually feel that, that you're stronger when you have slight wrist extension. And then you just take what you're holding in your hand and flex your wrist, and you'll see that your grip strength is diminished. So if you have to hold your hand in an awkward position, you have to apply more force in order to make that happen. So this is just an example of a worker using a drill. This is a good ergonomic position where you are able to hold the wrist in neutral or slightly extended at the wrist. And you can see that the worker is able to do this safely. You could actually use some of your upper body strength in applying force to the tip of the drill in this position. So this is the optimal position for using the wrist. But sometimes you're not able to do that, because maybe you have to drill something where you can't stand directly in front of it. So if the worker has to stand to the side with the wrist in a flexed position, you can see that that is going to be super uncomfortable, and the strength applied here is going to be significantly less. So some of the things you can do as an adaption are to use the other hand for support. Now, this is not always an option, but this would be an example of an administrative control that the worker is able to do that. So when we look at pinch grasp, this is an example of how you're not able to hold the object in your hands. You're pinching your fingers together with this type of motion. Now, realistically, you might hold your hand more on top of this, but this is just meant for illustration to show you the type of device, a valve on a pipe. Lots of older industrial settings have this type of valve, especially on a pipe that is almost always kept in the open position, ones that are frequently changed. Sometimes these are updated, but this would be an example, and we're twisting this. You're applying a pincher force like this, and then you're also twisting it, requiring this radial and ulnar deviation of your hand during this process. So this is an example of a type of lever where you would use a power grasp, where you can put your whole hand around the lever. So again, this is on a pipe where it's typically going to be held in the open position, but in the event of some type of repair being done or an emergency where you need to turn the valve off, you're just going to be able to grip this and then turn it towards you without actually rotating the wrist or using the fingers in an awkward way. So other types of industrial settings where they use these, you can see there are other types of valves that can be used beside these, but these two are the most common one, and this is the most updated of the ones that we have. Okay, now what about overhead shoulder work? Just as we talked about that increasing abduction here up to 18 degrees, you can see this is more, in this case, more like 45 degrees, where the worker is trying to raise up a box overhead, and this is a typical mechanism where you're putting large boxes on a shelf, such as in a storage area or warehouse, and this involves simultaneous shoulder flexion or moving the arms forward with abduction, moving them away from the body, and this particular motion increases the risk of shoulder rotator cuff impingement that can be a significant hazard. So what are some ways of addressing this? One might be using smaller boxes to put product in, so you can keep your hands, your arms adducted closer to the body, administrative controls too, like putting the boxes near the floor or providing a ladder if the individual needs to be reaching overhead, then you would be able to do that in a safer way. One of my employers that I work with where they had a large number of workers with shoulder injuries, they actually were able to get their supplier to change how they packaged the product prior to it coming to their plant, and that was kind of an engineering and administrative control, both of those together. So in summary, job design that maintains body in optimal position, decreases muscle fatigue, and lowers the rate of musculoskeletal symptoms. So it's not just job design, but also administrative controls, as we talked about rotation between different work activities can also be helpful. So now we're going to talk about applying ergonomic analysis to different types of settings. So who would be doing these analyses? Usually it's a trained professional. Usually it's a safety professional or industrial hygienist, but it could be a nurse practitioner or a PA could certainly learn how to do this and incorporate that in your skill set in occupational medicine. So how is this done? You actually observe workers at some time back in the day, you'd have a little stopwatch and clipboard in order to do these assessments. Now often we take video clips of the individuals doing different tasks, and then we just multiply how many times they're doing a particular activity, and then we multiply how many hours a day they're doing that. We can measure force with special equipment, we can use angle, a goniometer or something to measure angles, and then you can use formulas that help to assess that. Usually the math part of this is done by the ergonomics program. So the skills are mainly observation and recording and making sure the information is accurate. So there are several commercially available computer programs that synthesize this data and will tell you how many repetitions you're doing of what type. So that's, I'm not going to emphasize that part, but it's used to be making recommendation for job changes and for causation assessments. So when would employers do an ergonomic analysis? So typically the first time you do that is when you have a new equipment or a new process that's brought into the workplace that has a worker machine interface, which is most of the equipment that individuals would be working with. Or another time might be if there are major changes made in the manufacturing process. In other words, if the product itself is being redesigned, requires the equipment to be reconfigured, if that's a significant change, it's customary to do an ergonomic analysis because the people designing the equipment and the product are not necessarily considering the effect that it's having on the worker who works with that equipment. The other time an employer might do this is when they have a cluster of similar injuries occur in a group of employees that work together. Commonly you would say if you have shoulder or rotator cuff problems, wrist tendinitis or lateral epicondylitis, in my experience, these specific diagnoses are actually the most common reasons that these types of analyses are done. And often these things will be correlated. You'll have a group of employees who have symptoms right around the time when they make adjustments to the equipment. And part of this is that, again, we talked about that concept of muscle fatigue and muscle conditioning that your body gets used to however you were doing it before. So even if there's a better way to do it coming your way now, thanks to an industrial engineer, it takes time for the individual to learn that new process. And during that time, they may be at increased risk for injury. So I'm going to show you an actual example of the results from one of these assessments. The slides are actually ones that I put together from the assessments that we did. So in this case, there were a group of employees in the same department. They all developed similar problems involving a shoulder. I think most of them were of the dominant arm, but five of these employees required surgery for repair of their rotator cuff. And one of those five individuals, even though he had surgery, was not able to return successfully to the pre-injury job. So this is considered a bad outcome as far as a situation. No employer wants to see this, certainly no group of employees wants to be similarly situated. So all of these individuals, I don't want you to think we're just rushing them off for surgery. We certainly, from a clinical point of view, all of the affected employees were matched conservatively with oral medication, with application of eyes, physical therapy, and were all switched temporarily to a non-shoulder-intensive type of work. It's just that among these individuals, there were five of them that did not successfully respond to that conservative care. Okay, so here is the job analysis that occurred prior to the intervention. And you can see they, I highlighted in red, this may be difficult to see on your slide. So if that's the case, my apologies, I tried to make it, the font as big as possible. But you can see significant risk here of shoulder abduction and shoulder flexion with repetition. This particular task that they were doing really was not causing much problem for the elbow or forearm, but they had awkward risk and hand grip, wrist flexion. That's this motion, which we talked about how that significantly decreases strength. Also, they were doing radial and ulnar deviation with repetition using the pinch grip. So you can see a number of those things that we discussed as being difficult or particularly stressful were affected in this area. So in this case, the data for this was collected by an industrial hygienist. And then there were a group of the ergonomics committee, which was the medical team, safety, and this was a union plan. So we had a union representative and the department manager were all involved in looking for interventions. So what were the interventions that we looked at? We were able to have a platform built, was actually adjustable, so that employees of different heights were able to get the equipment closer to between shoulder and waist height, so that no one had to reach over shoulder or overhead in order to do this work. And the knobs on the equipment that were used for changeover, those were those ones where you use the pincher grass, those were removed and replaced with levers that allowed for a power grip. And the automatic boxing machine was added at the end of this particular operation so that the workers were not doing as much manual work while working on this station. So this was the post-intervention analysis. And I just highlighted some of the interventions that were made. And just to let you know, this type of actual situation would probably take about six months between when you do the original assessment, when you create some ideas, when you figure out which ideas you can implement, when you figure out if you have a budget for implementing those, then obtaining the expertise to make the interventions, and then doing retraining on individuals. So it's a fairly prolonged process, but this was the outcome that now you can see these areas of concern, shoulder, abduction, flexion. Those were improved hand grip and awkward wrist, improved much less in the way of radial and ulnar deviation. And we were able to make some pinched wrists, but without the awkward wrist done simultaneously. So after this intervention was put in place, then the department was monitored to see if there were ongoing issues. and actually we were very successful that we had no new cases of shoulder problems within 12 months of when this implementation occurred. Okay, so now what's another way that you can use ergonomic information? And one would be to assess causation, in other words, trying to determine if these risk factors were associated with employee symptoms or not. And this is typically done kind of as a research, academic type of setting, not necessarily something that one individual employer would undertake. So this was a longitudinal study of 174 industrial workers, and they were studied repeatedly by symptom assessment and examination with electrodiagnostics, EMG, and nerve conduction study. And the participants were examined every five years, so even after 17 years, they were able to track down 166 of the original cohort, and it wasn't, that's actually pretty good for this length of a study. So in this case, they were specifically trying to address risk factors for carpal tunnel syndrome to determine if there were modifiable risks that could be made with these other things that we talked about, the ergonomic controls, engineering controls, or administrative controls. So when we look at this, you can see they measured all of the things that we'd be potentially looking at, repetitions, force, keyboard use, vibrations, the maximum amount of force required, they looked at cigarette smoking, they looked at male and female, a dichotomous variable in this particular study, the age at which they entered this study, and so the odds ratio compared the high risk group and the low risk group. Now, an odds ratio is just basically the risk in one group divided by the risk in the other group, and that's why you see these decimal points in here. So if the answer, if it's above one, then you'd say that would be a higher risk. And if it's below one, it might be a lower risk compared. So it turned out, for instance, looking at this, more repetition had a lower risk than few repetitions. So we don't even know if that's important. How do we know it's important? The answer is we look at the p-value, which is a statistical measure of the likelihood of this occurring by chance. So when we look at repetitions, for instance, the p-value is 0.84. So we'd say, no, no, that particular result could have occurred as a result of chance. So what we're really interested in, not just the odds ratio, but where was there a significant difference, and that occurs when the p-value is, at least in most studies, we say if it's less than 0.05. So we can see on this particular table, the only risk factor out of all of these things where there was a significant p-value occurred when we compared the risk of carpal tunnel syndrome in women employees versus the risk of carpal tunnel syndrome in male employees. And it turns out, this shouldn't really surprise anyone, the risk in women was six and a half times the risk in men, and that was very significant. Even the risk in employees by age, you think, oh, older people are more likely to get this. That was actually not the case. Older people were more likely to get it, but it didn't matter how old they were when they started the study. So when we look at body mass index and carpal tunnel syndrome, the reference range in this case is individuals who had a low normal BMI, and then these were done by quintiles. You can see these are not our traditional ways of measuring BMI, but these were just in the study population. It turns out that anyone who had a BMI in the upper range of normal to above that, all of them had a significant increased risk of getting carpal tunnel syndrome. So the conclusion of this particular 17-year study was that elevated BMI and female sex were the only significant risk factors. All these other variables that they looked at, vibrating tools, hand force, repetition, keyboarding, and heavy lifting were not significantly associated with carpal tunnel. So this is a controversial conclusion. It's not meant to be an exhaustive discussion of this area. Certainly there are studies that show different things in different populations, but it does give you an example of how you can use ergonomics to answer very important clinical questions and also helps us to say, what should we be focusing on in terms of our interventions for individuals who have this? And one of the other things that we look at in a study like this is to say, is there a bias? I don't think there was a bias in terms of the conclusion for this particular study, but because it was a longitudinal study where they're looking at individuals for 17 years, well, there is what we call the healthy worker effect, meaning that people could have dropped out of the study because they developed carpal tunnel syndrome and then the, or whatever, and became lost to follow up. So we always want to consider what are some other factors that could have influenced that, and then how can we maybe look at future studies, maybe that are not linked to your place of employment where we're looking at those factors. So no one study, we wouldn't expect any health policy to be based on that. I'm just kind of using it as an example for this important area. So is there a role for personal protective equipment? And this has been looked at, and it turns out that lumbar supports are no more effective than no intervention or in training in preventing low back pain. And it's also unclear, here's the reference, for lumbar supports are really, it's not even clear if they help if you have back pain. So our enthusiasm about this particular type of personal protective equipment has gone dramatically down since these studies came out. And there were actually three really well done studies looking at lumbar supports. One was done at a large box home improvement facility. One was done at the U.S. military, another at the U.S. Postal Service, all of whom struggle with back injuries among their employee population. That is the basis for this information. So it turns out that teaching people how to prevent back injuries, we just incorporate some of that into our general training, but it turns out doing specific exercises in an asymptomatic population is probably not helpful. And so this could be a starting point if you want to look at other information. This is an exhaustively studied area. So I think it can be really helpful. So one thing it did, we saved a lot of money by no longer recommending back supports as a preventive measure. Now similar results were found with knee braces. So they found this was studied primarily in athletes who are more prone to knee injuries. And they found that if you wore prophylactic braces, it actually did not prevent you from having injuries. So they are not recommended in the workplace setting. However, if an individual worker maybe has a preexisting knee problem, there may be a role, a clinical role for knee braces, but it's not on the ergonomic side or the prevention side. Same way with, you know, like for skiing, an individual, if you have a torn ACL that you're choosing not to repair, well, it might be appropriate to be wearing a knee stabilizer for a vigorous sports activity. Okay, so how about wrist and arm supports? Some studies suggest that wrist splints actually increase pressure inside the carpal tunnel. So if a worker is wearing one of these splints and is trying to forcibly make their hand move a certain way, that's actually counterproductive. So in a meta-analysis of interventions to position the hand and wrist, supports and splints were not effective, again, as preventive measures. So I think that basically is how we want to think about these. They can be good tools for clinical care of specific patients, but not in a general way in the workplace. Okay, what about working from home? So there was a study looking at the risks of working at home during the pandemic. So I thought, just try to be all cutting edge and bring in the latest information. This was a one-year prospective cohort study studying over 2,500 Japanese workers who work from home, and their work environment was assessed by questionnaire. They didn't have the manpower to go and look at everybody's workstation, but they found that work impairment, decreased productivity, and physical comfort, lack thereof, was associated with lack of private work area, inadequate lighting and foot space, and inadequate temperature and humidity control. So you can imagine, often, at least in urban areas in Japan, individuals live in fairly small apartments. They may not have a dedicated room that could serve as an office. So they're sharing their bedroom with their kids trying to do homework, because the kids were not in school either. You can see that that would be definitely affecting productivity of workers. So what about administrative controls that we can do? So we know that prolonged sitting leads to decline in cognitive performance. This is very important for many workers, not just in the U.S., but internationally, who do prolonged sitting. So there have been interventions done to try to identify ways of breaking up the sitting, prolonged sitting, such as sit-to-stand workstations, computer on wheels, these are often used in clinical settings, but also in some office settings, and exercycle desks have also been looked at. And so of the cognitive domains which have been assessed, working memory, attention, and psychomotor function all show significant sustained improvement for up to 30 minutes after doing any of these interventions. So in conclusion for administrative controls, we recommend frequent position changes can be useful to sustain benefit, and when you do them, you should be thinking about changing position every 30 minutes. Okay, so how would you go about doing that in a practical work setting? So here is a kind of typical, you know, workstation in a clinical environment, where the employee is in this case sitting on a, like an exam stool, not using a back support, and this type of positioning is adequate for short-term use, where the employee might be sitting here for a few minutes, looking at somebody's results, and then they're walking down the hallway to do something somewhere else. This would certainly not be considered optimal for prolonged sitting. But the worker has, the neck is in good position, the keyboard is in good height. Now, as we talked about earlier, what about the elbow positioning? This is actually a little, a little acute, or in other words, too much of a bend in the angle. Preferably, you would have the chair higher or the desk lower in order to keep this angle closer to 90 degrees. So let's just say this was your work area for all day long, then you would ask your boss to get you an ergonomic chair, and you can consider how would you convert a typical workstation on the cheap into a stand-up workstation. So you can find things in your work area. These were empty boxes that were stacked on top of each other that moved the computer keyboard up higher. If you used a mouse, you would, you would also want to have a platform large enough for the mouse. And you can see actually in the standing position that the angle of the elbow is good. And this is okay, this slight extension at the wrist, that would be fine. The main problem with this jerry-rigged workstation is that the monitor is too low. The worker's trying not to forward flex the neck, but this would be not super comfortable to be looking down at this angle for any length of time. So if you were really going to take this workstation and try to make it adjustable, you would want to put the monitor on a lift device so that it too could go up and down to make the employee more comfortable. Okay, so what are some resources I would add to include this information? How to, where can you learn more about ergonomics? So NIOSH, which is the National Institute of Occupational Safety and Health, hopefully you know that already after completing the other six modules, NIOSH, a branch of the CDC, they have a specific website, which is devoted to ergonomics. And I think this is a good place to start for a beginning kind of introduction to ergonomics. It's not updated that often. So if you're looking for more advanced materials, I think you would find this would get you started but not get you far. So in terms of OSHA enforcement for ergonomics, there was a big push a while back to create an ergonomics standard, like there's a standard for lead or asbestos, but that never completely They got off the ground due to lack of support from the industry, lack of bipartisan political support. So that never was put into place. So OSHA considers ergonomic controls to be under the general duty clause. In other words, the employer has a general duty to provide a safe work environment. And so OSHA absolutely looks at ergonomic hazards and can make recommendation. But as you know, OSHA is the enforcement arm of the Department of Labor. And that NIOSH is typically the one making research on important areas in our field. So if you want to get more training, which of course, I would encourage you to do this. You thought this is a fascinating topic. You can't wait to learn more yourself. So this is an organization that I am not a member of. But so in other words, I'm not giving a shout out to the home team here. But the American Industrial Hygiene Association, this is a very well regarded professional organization that has lots of resources available for the general public and specifically for occupational health professionals to learn more about ergonomics. They offer courses in how to use different programs. And if you as a PA or NP or occupational medicine physician are working in a corporate setting, then often your employer would pay for you to attend this type of training as a continuing education and career enhancement. So that's why I wanted to include that. And in preparing for this talk, I came across what I thought was a really useful article on clinical use of braces and splints. Again, we're not using them for prevention. And they have a number of great photo slides that I did not include for copyright reasons. But I would encourage you to look at the original article, which I think discusses these things in great detail. And the reference is provided here on the slide. Now NIOSH has a free downloadable lifting calculator. And this is also, again, a basic tool just to give you some additional familiarity with this topic. I definitely recommend this. And you can calculate composite index for different types of tasks. So workers can use this same tool because it can increase their awareness about the hazards associated with their specific tasks. And it makes workers more informed about hazards to their musculoskeletal health and can serve as job design guidelines. The photo is courtesy of NIOSH. And then this is just a reference on how you can download this yourself. So in summary, you want to consider specific physical hazards and employee medical problems as a routine part of pre-employment and pre-placement and work injury assessment. We want to implement, not just we, but together with our industrial hygiene and safety professionals, a hierarchy of hazard control, again, in the order of preference, engineering, administrative controls, and personal protective equipment. We can utilize ergonomic job analysis to address causation and apply corrective actions to prevent or decrease risk of ergonomic hazards. And also, this is a very learnable skill, just like anything else, so don't be intimidated. And don't forget, my final piece of advice comes from the one-eyed surgeon, which is only move one hand at a time and keep your eye on the hand that's moving. So thank you so much for your time.

physical hazards

ergonomics

occupational medicine

hazard control

workstation redesign

administrative controls

PPE

muscle fatigue

injury prevention

body positioning

musculoskeletal disorders

sit-to-stand workstations