Effects of Mop Handle Height on Forearm Muscle Activity, Wrist and Upper Arm Posture and Movement During Floor Mopping

OCCUPATIONAL APPLICATIONS

The present study showed that differences in the height of a mop handle affected upper arm postures and movements during floor mopping using a figure-eight method. Higher mop heights increased arm elevation and reduced times at rest. Mop height did not have any significant impact on upper wrist posture, movement or forearm muscle activity. Although the use of a mop at shoulder height increased forearm muscle activity and wrist extension for the lower hand, it did not increase the time spent with substantially-deviated wrist postures. For floor mopping, these results suggest that cleaners should be encouraged to adjust their mop height between shoulder and chin levels in order to utilize the benefits of the telescopic type of mop handle. These results also can be used as a basis for preventive ergonomic training programs and for those involved in developing tools for cleaners.

TECHNICAL ABSTRACT

Background: Floor mopping work involves several risk factors for upper extremity disorders. At present, telescopic mop handles are commonly used by cleaners and hold promise for reducing ergonomic risks. However, uncertainty exists about the effects of mop height on postures and movements. Purpose: This study was conducted to evaluate the effects of mop handle height on upper arm and wrist postures and movements as well as the activities of forearm muscles. Methods: Thirteen subjects performed a standardized floor mopping task while using four different mop handle heights (at shoulder, chin, nose, and eye levels) in random order. An inertial motion capture system was used to measure upper arm elevation, wrist angles and angular velocities (percentiles of angular and angular velocity distributions, as well as percentage of time in predefined zones). Surface electromyographic activity was measured from the flexor carpi ulnaris and extensor carpi radialis muscles. Results: Mop handles adjusted at the shoulder and chin levels led to significantly more neutral upper arm posture, lower angular velocity and more time at rest for the upper-position arm. For the lower-position arm, elevation angles were significantly reduced and more time was spent in a neutral arm posture when the mop was adjusted to chin level as compared to eye level. However, for the lower wrist, use of the mop adjusted at shoulder level significantly increased wrist extension and extensor muscle activity. Even so, the time spent in extreme wrist posture or rest did not differ significantly across the range of mop handle heights. Mop height did not affect upper wrist’s posture, movement or muscle activity. Conclusions: Mop handle heights between shoulder and chin levels can be recommended as a means of reducing poor working postures for the arms and increasing the proportion of time spent on rest.

KEYWORDS:

• Ergonomics
• floor cleaning
• kinematics
• muscle activity
• shoulder
• wrist