How does the understanding of biomechanics, specifically the forces acting on the human body during lifting, inform the design of safe material handling procedures in industrial settings?
Understanding biomechanics, particularly the forces acting on the human body during lifting, is crucial in designing safe material handling procedures in industrial settings. Biomechanics is the study of the mechanics of living bodies, specifically how the musculoskeletal system interacts with forces. In the context of lifting, this means analyzing how forces such as gravity, muscle contraction, and inertia act on the body and how these forces can contribute to injuries if not managed properly. By applying biomechanical principles, we can create material handling practices that reduce stress on the body and minimize the risk of musculoskeletal disorders (MSDs).
When lifting, several forces come into play. First and foremost is the force of gravity acting on the load being lifted. This force is equal to the weight of the object and exerts a downward pull that must be counteracted by the muscles and skeletal structures of the lifter. Secondly, there is the force produced by muscles to lift and stabilize the object. These forces can become substantial and strain the muscles, tendons, ligaments, and joints if the lift is not done correctly. Thirdly, the force of inertia also comes into play when starting or stopping a lift, or changing its direction, adding to the stress on the musculoskeletal system. Finally, the posture of the body during the lift greatly affects the forces on the spine and supporting muscles. For example, a rounded back during lifting increases the compressive forces on the vertebral discs, raising the risk of back injuries. When these forces are not managed well, they lead to increased stress, strain and ultimately injuries.
Several biomechanical concepts directly inform the design of safer material handling procedures:
1. Load Placement and Proximity: Biomechanics emphasizes the importance of keeping the load close to the body to minimize the moment arm (the perpendicular distance between the line of force and the axis of rotation at a joint, such as the spine or shoulder). The larger the moment arm, the greater the force the muscles must exert to lift or hold the object. For example, keeping a box close to the body reduces the strain on the back and shoulders during a lifting task, compared to lifting the same box with the arms outstretched away from the body. So, material handling procedures need to require that workers always position the load in close proximity to their center of mass.
2. Lifting Posture: Maintaining a neutral spine posture—keeping the back straight and the head aligned with the body—is critical to minimize compressive forces on the vertebral discs. Bending at the knees instead of at the waist ensures that the leg muscles rather than the back muscles bear the majority of the lifting load. Industrial settings should provide training that emphasizes proper lifting techniques like squatting instead of stooping, using proper grip, and avoiding twisting while lifting.
3. Lifting Frequency and Duration: Reducing the frequency and duration of lifting tasks is crucial because repetitive lifting causes cumulative strain and fatigue. Biomechanics informs the design of workflow to minimize the need for continuous lifting tasks, or the use of automated systems or mechanical aids to assist workers with repetitive tasks. Task rotation, where employees switch between different types of work that involve varying movements and muscle groups, helps to reduce strain by giving specific muscles adequate rest time.
4. Weight and Size of the Load: The heavier the load, the greater the forces on the body. Biomechanics informs us to limit the weight of the object lifted to within the capacity of the worker and to break down heavy loads into smaller, more manageable units, or to use mechanical assists, like forklifts, hoists, and material handling carts, for very heavy objects. Large or oddly shaped objects can also cause strain, so ergonomic designs should focus on making loads easier to handle with proper grip handles and minimized bulk.
5. Body Mechanics: Understanding how the muscles and joints interact during lifting informs the design of training programs that help workers use their body most efficiently. Training should emphasize techniques like using a wide stance to stabilize the body, keeping the back straight, and using the leg muscles to lift. The training should also involve exercises that help workers understand where their bodies are in space and how the different parts of their bodies function with the movement.
Examples of material handling procedures informed by biomechanics include:
Implementing lift assist devices: These devices, such as hoists, cranes, and vacuum lifters, take a large portion of the load off the worker, reducing the need for manual effort and minimizing strain. These devices should be easy to use, accessible, and properly maintained.
Redesigning work areas: Workstation heights are adjusted to minimize reaching or bending. Using adjustable height tables and conveyors can ensure items are always in a comfortable lifting zone. This also includes reorganizing material placement so that frequent use items are easily accessible and within a short reach.
Using material handling carts and dollies: These help workers to transport items rather than carrying them, reducing stress on the back, shoulders, and arms. The carts need to be designed with proper dimensions, wheels, and handles to ensure they are ergonomically friendly and functional.
Implementing task rotation: Workers are rotated between different tasks that utilize different muscle groups, reducing the risk of overuse injuries.
By applying biomechanical principles, industries can reduce the risk of worker injuries and illnesses, minimize worker fatigue, and increase productivity and efficiency. This is achieved by not just preventing injuries, but also through creating an environment that respects and protects the capabilities and limitations of the human body. Ultimately, a solid understanding of biomechanics allows for the development of evidence-based practices that create a healthier and safer industrial environment.