Mechanics of human factors
When we are designing products and systems, the things that are at the forefront of our minds are usually the requirements, available resources and funds, and how we can devise a plan to balance all of those things to find a solution. A very important factor to consider within our designs is how the people that use and assemble our products will interact with them. I had the chance to learn more about considering users and their experience last semester in a course called Human Factors, IE 340.
One of the topics that was of particular interest to me was biomechanics. One area of focus was physical labor involving lifting. To begin, we calculated forces on the muscles in a person’s arm while they lifted an object, which we did through force balance. This was an interesting application of the statics we learn in TAM 210, but instead of balancing the forces acting on a beam, we balanced the forces acting on the human arm as if it was a non-moving, non-deforming system.
This class was all about considering the human experience in a technical system to prevent injury and improve overall experience. Applying this idea to biomechanics and lifting in the workplace, we had to ensure the lift won’t be too physically taxing and possibly cause lower back injuries, which account for nearly 20% of all injuries in the workplace. There are a few equations that help us calculate limitations for a set of parameters on a particular lift. One equation that we studied in detail was the NIOSH equation. It starts with a base 51-pound load that is multiplied by a series of weights that factor in difficulties in a lift. (Think distances of the weights from the ground, the degree of twisting necessary, ease of grip of object.) At the end, this equations spits out a weight that should not be exceeded given the parameters of the task. This helps us to understand a reasonable task assigned to a worker.
In my Human Factors class, we were asked to create an open-ended project, and I had an interest in studying devices involved in care taking. For context, my parents and I have been caretakers for my grandmother, and we had to help her move and lift her in extended times when she was not able to do so herself. Over time, we learned a few techniques to help ourselves, one of which was using a gait belt to assist in moving her. I could feel the physical difference in helping my grandma to her feet when I had the gait belt wrapped around her waist, but I was excited by the opportunity to study the science behind it.
So, my group and I created an experiment to test the performance of the gait belt against unassisted lifts. One metric that can be used to measure physiological workload is heart rate. We had all of our participants wear my group member’s fit bit, waited for their heart rate to settle to rest, and then we monitored the increase in their heat rate as they performed the three lifts on our group member who kindly acted as the patient. In one lift, we asked participants to lift our patient using the gait belt around his waist, another lift featured the patient putting his arm around the participant to aid in the lift, and the final lift consisted of the participant picking up the patient by wrapping their arms around him. All lifts involved pivoting the patient from one chair to the next.
From the raw heart rate, we calculated heart strain. We tested 10 college students between the ages of 20 and 24, and found that in 7 out of 10 cases, the weight belt produced the lowest or second lowest heart strain of all three types of lifts. In addition to distributing the force from the weight of the patient, the gait belt also helps balance the patient as they steadied themselves to stand.
For me, it was exciting to explore the physiological effects of a simple device that I routinely interact with and knew was helpful. I also believe that designing with the user in mind is crucial to making good devices. If you agree with me, then Human Factors (IE 340) would be a great class to take as a technical elective!