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Biomechanical Engineering – Product Liability and Machinery Cases

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Biomechanical Engineering – Product Liability and Machinery Cases

In the world of insurance claims and civil litigation, when one hears the word Biomechanical Engineering very often the mind leaps immediately to terms like Delta V, C4 vertebrae and preexisting condition and that's where it stays. Basically, with biomechanical engineering, one thinks of Low Speed Accidents and the resulting injuries, claims and law suits that they bring. Yes, the discipline of biomechanical engineering can be very useful in determining what happened and to what extent in these accidents. But, limiting the use of biomechanics to MVA investigations could be a serious mistake.

Biomechanical Engineering is a bioengineering sub discipline which applies prindyciples of mechanical engineering to biological systems.
It's fairly obvious how important this discipline can be useful when investigating product and machinery cases, but the levels and degrees of just how a biomechanical engineer can assist you can be staggering. Let's look at a few examples.
One category of biomechanical studies that is applicable to machinery and equipment accidents and injuries is Anthropometric Design Considerations. Conceptually, anthropometric design is similar to ergonomics. Machines, whether they are industrial machinery or recreational equipment, must fit the user population. The use
r population will vary in size, and the equipment design must account for this range of sizes.
There are three ways in which a design can fit the user:
a. Single Size For All – A single size may accommodate all members of the population. A workstation which has a switch located within the reach limit of the smallest person, for instance, will allow everyone to reach the switch.

b. Adjustment – The design can incorporate an adjustment capability. The most common example of this is the automobile seat.
c. Several Sizes – Several sizes of equipment may be required to accommodate the full population size-range. This is usually necessary for equipment or personal gear that must closely conform to the body such as clothing and space suits

All three situations require the designer to use anthropometric data. A mishap involving this equipment may then require a biomechanical engineer to analyze the design for both appropriateness and effectiveness. One of the things the biomechanical engineer would study would be body size considerations. These studies are so detailed as to include not only the body size, but also the clothing likely to be required when operating these machines, e.g. Protective work clothing or ski gloves.

Joint Motion Design Considerations
The biomechanical engineer can also look at joint motion design considerations. When humans interact with machines (products) there is always motion involved. The movement range of a single joint is often drastically reduced by the movement of an adjacent joint. In other words, joint movement ranges are not always additive. For example, an engineering layout may show that a foot control (maybe an emergency brake) is reachable with a hip flexion of 50 degrees and the knee fully extended (0 degrees flexion). Both of these ranges may be within the individual joint ranges . However, perhaps the hip flexion is reduced by over 30 degrees when the knee is extended. The control would, therefore, not be reachable for a certain portion of the population. The emergency brake could not be engaged and an accident ensued.


A biomechanical engineer is trained to look at such things as joint motion, functional reach limits and envelopes, head range of motion, and human grip strength. All of these aspects could be critical contributory factors in an accident.

The National Institute for Occupational Safety and Health (NIOSH) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. Knowledge of NIOSH and their guidelines can be essential in many product and machinery cases. Having a biomechanical engineer escort you through the mazes of publications and databases that NIOSH maintains can be crucial to a successful resolution of a case or claim. For example, a product designer could demonstrate that they used NIOSH recommendations to make alterations to a product in order to minimize the injury potential to users (such as adding handles to something that requires lifting, or by altering its dimensions to reduce strain on the user); such guidelines can also inform decisions such as when to put warning labels on a product.
Yes, biomechanical engineers are essential when investigating low speed accidents but their value goes far beyond determining injuries in MVAs. Seeking their insight and assistance when examining a product or machinery case can be very beneficial.

Featured Engineer: Grant Bevill, Ph.D., P.E. – Biomechanical/Mechanical Engineer

Photo Source: NASA, Anthropometry and Biomechanicas. Fig. 3.1.2-1, Fig.

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