Part 3: Force and Repetition

Excessive force over time may be a cause of injury. This is the reason for the prevalent shoulder injuries in pitchers, due to the torque created in the shoulder. In work situations, an example of a forceful action is carrying and hoisting heavy loads, such as in furniture movers, or lifting boxes of copy paper.

Repetition of a task causes the muscles to be worked constantly, and without adequate rest, they can be overworked especially if each cycle is short. An example of a short cycle is typing: the cycle of typing one letter is fairly short, less than a second at times. It is the repetition without rest that causes fatigue and injury. The common speed of typing is 40-60 words per minute, resulting in hundreds of keystrokes a minute.

This ergo-tip is a part of an ergo-tip series about musculoskeletal injuries. Please visit the table of contents at for other available posts. There will be one post released every Tuesday.