Ergonomic Risk Factors — Force, Posture, Repetition

• Force — how hard you have to push, pull, lift, or grip. Heavy loads and forceful movements are directly linked to low back disorders.
• Awkward posture — bending, stooping, kneeling, twisting, or reaching overhead instead of working in a neutral position.
• Static posture — holding one position (like a bent-over or overhead hold) without moving, which starves muscles and fatigues them.
• Repetition — doing the same motion over and over so the tissue never gets to recover.
• Vibration — whole-body vibration from riding equipment and hand-arm vibration from power tools; both are recognized low-back and hand risk factors.
• Contact stress — pressing part of your body against a hard edge or tool.
• Duration — how long you're exposed. Even a mild task becomes a hazard when you do it all shift.

One factor by itself might be manageable. The danger is the combination. Lifting a heavy block (force) while bent and twisted (awkward posture), a hundred times a day (repetition, duration) is a different animal than lifting it once, close to your body, at waist height.

NIOSH's own risk-scoring approach adds exertion, posture, repetition, duration, and vibration together — because that's how the body experiences them. When you size up a task, don't ask 'is this one thing bad?' Ask 'how many of these am I doing at once, and for how long?'

You can't always change the material, but you can usually change one or more factors. Cut the force with a cart or a lighter load. Cut the awkward posture by staging material at waist height. Cut repetition and duration with job rotation and rest. Every factor you remove drops the total risk — you don't have to fix all of them to make a real difference.