Skyscrapers are built using concrete, but concrete is not a great material to build a tall structure. Tensile strength is the resistance of a material to breaking when there is movement or tension (i.e. from wind, earthquakes, and vibrations). Concrete's tensile strength is very low which limited the height of buildings. In the 19th century, a solution was found to reinforce concrete with steel. A super material was formed, combining high compressive strength from the concrete & high tensile strength from the steel. The era of the skyscraper was born.
Engineers decide which material types & quantities are required to build something. They have turned it into a standardised industry, with material rating systems to ensure the design matches the requirements. Too much force on the wrong material causes failure, which is obviously not great when you’re talking about skyscrapers, bridges, airplanes, etc. And it’s become relatively easy to measure strength - often through using strain gauges to measure how a material fatigues under certain conditions.
Standards have struggled to answer the question of what humans should be able to endure. The International Labour Organization published an information sheet in 1962 that stated limits for lifted weights - these limits were based on statistics of injury & illness. The NIOSH lifting equation was published in 1981 (revised in 1991) and defines what is the maximum weight & repetition rate that should be undertaken. Both these standards (and many others) face the same criticism, they create limits for all humans as if humans are all equal. Never mind if one person is a weight lifter & the other has a fused spine, they are equal in the eyes of the standards. Personally, due to this limitation, it’s surprising that the NIOSH equation is still seen as ‘the truth’ in many industries and, additionally, it’s very complex to use and many estimations end up being used by the assessor (input errors = output errors).
Other standards realised that not all humans are equal and have different recommendations for groups. A couple examples:
When I think back to materials engineering, engineers don’t introduce a material in millions of different applications, wait for failures, and then decide if it’s suitable or not - rather they measure the material itself to make the decision. Likewise, at Soter Analytics we realised we should actually measure how the human is reacting to a particular force requirement, thus we began the development of our intensity model.
How does our intensity model work? Every time a person makes a movement (e.g. lifting an object) we collect high-frequency Inertial Measurement Unit (IMU) data through our SoterSpine wearable device. This data is fed into our neural network which is trained to understand if the person finds the particular movement difficult or not. How does it actually do that? We measure things like the speed of movement, how jerky the movement was, the angle of the back when they finish the movement and are holding the object (some people lean forward more because the object is heavy, others lean back to compensate for the weight), and 29 other features that use data-science but complex to explain. More difficult movements increase the risk of injury as the body nears its limit of capability.
As an ergonomic or health & safety specialist, have you been frustrated with the generic standards?
Have you struggled to take the measurements to fit into complicated formulas?
How could you (and your workers) use the intensity model to manage and reduce the risk of the unique individuals working at your workplace?