Cornell University Ergonomics Web
A team conducted a Back Injury Assessment of custodial staff at Cornell University. Interviews, direct observation and videotaping, were used as part of a systematic audit of postural risks, poor tool design, and unsafe work practices.
The following is an excerpt from a paper by Deirdre Campbell and Dena Tepper detailing
specific recommendations for the purchasing of equipment and redesign of
The custodial work consists of many activities that require lifting, bending and a variety of other tasks which may place a worker at risk for back injury. The tasks range from mopping large areas to carrying garbage up and down stairs. The concern raised is that these Cornell employees are at high risk of injury, especially to the lower back. Although back injuries can be identified easily, the effects of risky behaviors on the spinal system over time can be lifelong. And although one may realize he or she has incurred a back injury it is not always easily determined the exact nature of the injury (Sanders, 226). Since so many people in the United States are plagued with work related lower back pain, it should be of high interest to not only workers, but employers as well.
It is estimated that 20 to 30% of all workers' compensation claims are back injury related costing over $1 billion. These injuries also lead to approximately 12 million lost work days (Sanders, 225). In all, these injuries cost the nation between $20 and $25 billion annually. Here at Cornell, 49% of workers' compensation claims dollars are spent on back injuries. This amounted to a $4 million cost for the university over the last ten years.
In a three and three quarter year period between July 1990 and March
of 1994 there were 64 reported back and tailbone related injuries by custodians
working for Campus Life. Injuries were incurred through slips and trips
and while engaging in activities requiring, among others, lifting, carrying,
In the course of reviewing the videotapes of the custodial tasks, many tasks that had not been discussed in the custodial interviews, were observed to need improvement. The following is a discussion of the recommendations for these tasks as well as the ones originally targeted.
Bathroom cleaning was videotaped. This included cleaning of the toilet stalls, tubs and showers.
The showers are cleaned using a hose that is attached to an industrial sink, in the custodial closet. The hose is snaked across the floor and around a corner in order for it to reach the shower stalls. A very long hose is awkward to handle, especially when it is pressurized and weighed down with water. Bending down to pull the hose into position or to pull and lift it to coil it up puts the custodian into a risk posture. It also presents a risk of tripping and falling to other custodians who are cleaning other areas of the bathrooms. This risk is further intensified due to the wet and slippery floors.
A recoil hose can reduce some of this risk and ease the task of hosing down the stalls. The recoil hose takes up any extra slack so there are not coils of hose laying around to be tripped over. When the hose needs to be taken out, it only needs to be gripped by a handle on the case and pulled to the necessary length. When the hose is to be put away, there is not a lot of bending and pulling necessary. Some recoil hoses are spring loaded like the cord on a vacuum cleaner and cheaper model require winding of a handle. Transporting the hose from place to place is also easier when the hose is coiled in a compact case with a handle.
The showers are scrubbed with a straight handled scrubber similar to a rough sponge mop. The handle on the scrubber is of a fixed length and the head is fixed at 900 to the handle. The shower stalls are fairly narrow and just getting in them is awkward for a large person. A handle that is too long or short in a confined stall, where the custodians must scrub from the floor to above their heads puts the back into many different risk postures, including reaching, twisting and bending. These postures alone due not necessarily pose a risk of injury to the back, but when combined with the application of force to the scrubber and or two or more of the postures combined together, the risk is greatly increased.
At the very least, the handles should be made adjustable so that the
length of the handle can be varied for different scrubbing positions. After
that an angled handle or a pivoting head would eliminate most of the reaching,
bending and twisting necessary to clean a confined space (Figure 1).
The scrubbing can be eliminated altogether by replacing it with a power hose similar to those used to wash cars (Figure 2). A power hose can be created by attaching a pressurizing gun on to the hose and can be purchased with an detachable soap reservoir. The pressure created by the gun can be equivalent to that created by the custodian scrubbing. The soap reservoir allows for the task to be done entirely with the hose. The shower stall is soaped and scrubbed in one step. The reservoir can then be removed and the gun used to rinse the soap.
The wet and slippery floors provide and unstable base upon which the custodians must perform their tasks. The reduction in traction on the floor, due to the amount of water that is used while cleaning, elevates the risk of bank injury associated with each of the targeted tasks.
Specialized footwear should be provided when tasks are performed on wet
or slippery floors. These can include strap on traction soles, rubberized
boots that slip entirely over the shoe, or full coverage boots that provide
both traction and water resistance below the knees. Note: This recommendation
applies to the buffing and waxing of the floors of the residence halls.
Concern was expressed by the custodians that the floors become very slippery
when newly waxed.
Any modifications made to existing collection equipment, owned by
the county, must first be approved before implemented.
Recyclable material must be brought down to the basement and collected into large recycling bins. The material is brought down from each hall, by elevator, in a smaller bin (Figure 3). The custodian must then reach into the smaller bin, pull out the bags of recycled goods and then deposit them into the larger bins. The smaller bins are actually not that small compared to the size of most of the custodians. The top edge of the bin is above the waist line of the custodian that was observed in the videos (and most custodians for that matter) . Getting the recyclables out of the bottom of the bin required either lifting of one leg or standing on tip toes in order to reach them. This extreme leaning, bending and lifting combination is an example of a possible back injury risk.
There are many possible solutions to this problem. The first suggestion
is to put a spring loaded platform at the bottom of the bin (Figure 4).
As the load in the bin is lessened the platform will rise up to a level
that is reachable to the custodian. Springs, like those on automobile and
motorcycle shocks, can be set for different stiffnesses. This will accommodate
different densities of material.
Another alternative is to create a flap that can be folded down, on one
side of the bin (Figure 5). This would reduce the effective height and eliminate
the need to reach over a high ledge. One more alternative is to add a stand
to the back of the bin, similar to a kick stand on a bicycle (Figure 6).
The bin can then be leaned over and rested on the stand. The custodian then
has a lowered bin with an angled reach.
Figure 5 Figure 6
Lifting garbage bags out of both the garbage bins and recycling bins causes a vacuum to be created underneath the plastic bag and consequently a suction force that adds greatly to the force required to lift the bag. This increases the moment created on the spine due to bending and lift a large load.
A hole or series of holes, drilled either on the bottom of the bin, or if wet garbage is present, around the perimeter of the bin at a sufficient height from the base, would eliminate the suction created and ease the load created on the spine.
The large recycling bins that are in the basement are placed side by side, up against a wall. The large bins are in a corner of the basement and fit next to each other with no room in between. The lid on each bin must be opened and the appropriate recyclables transferred from the small bins. The lid of each bin is very large and requires a far reach in order to open it and lean it up against the back wall, as well as to close it.
A stiff strap added to the middle of the forward edge of the lid would
allow the custodian to open the lid fully with less of an effective reach
(Figure 7). The reach to close the lid is also reduced. This strap can be
attached (e.g. riveted) easily to the existing equipment. A two bar linkage
could alternatively be added to the side of the lid requiring a much smaller
reach than even that of the strap (Figure 8).
Figure 7 Figure 8
Garbage must sometimes be brought outside to an industrial sized dumpster. The top of the dumpster is almost taller than some of the custodians. The leads are proportionately large. Lifting the lid to one section poses the same problems as in the above task and the same recommendations can apply. Depositing the garbage into the dumpster is often done by throwing it over the edge. This load applied to the spine while twisting at the waist is one of the more dangerous postures for the spine.
One simple alternative would be to add a platform that the custodian
can step up onto in order to deposit the garbage into the dumpster (Figure
9). The step can be made of lightweight material and would therefore be
easy to carry to the dumpster site. A small step attached to hooks can be
placed on the side of the dumpster and left there until the dumpster is
retrieved (Figure 9). The step can be folded up flat against the side of
the dumpster so it does not create and obstruction.
The mop pails used by the custodians have a bisected water bucket, one side for clean, soapy water, the other for dirty mop water, and a removable roller system to squeeze the water out of the mop. In order to activate the rollers, the custodian must bend over and push or pull on a short lever arm with considerable force. At the same time the bucket must be prevented from rolling by either holding it with another hand, or placing a foot in front of the wheels.
The lever arm of the rollers would need to be made longer in order to reduce the necessary force needed to expel the water from the mop. This is not possible as a longer arm would stick out further and would present itself to be a greater obstruction. This would increase the possibility of tipping the pail or causing injury to a person. Adding a pivoting handle provides a longer lever arm when needed but one that can be folded down and out of the way. The handle should be able to lock into place when the arm is being used but also have a release that allows it to be easily folded down when not needed. A pedal could also be added to activate the rollers which would eliminate the need for any bending or load added to the spine. This would necessitate a redesign of the pail by the manufacturer. Either or both of these modifications should include a wheel lock that activates when the rollers are used to eliminate the awkward need to hold the pail in place and prevent it from traveling or tipping.
The bisected bucket that slips into the mop pail is a single unit. In order to lift it out a single, thin handle is provided. It must filled and emptied at an industrial sink. The risk of injury to the spine from bending over to lift the bucket, full of water, out of the pail, is further increased by the lack of adequate grip provided by the handle. This increases risk by decreasing postural stability.
At the very least the bucket should contain two handles that fold down to either side. A better approach would be to increase the diameter of the handle. This should be done with a material that provides traction, and can be compressed somewhat, in order to increases the possible grip strength.
Although this study was performed on the custodians at four residence halls on campus, the findings and recommendations made apply to custodial work across the entire campus and anywhere else where similar equipment is used, or similar tasks are performed. The findings of this audit revealed that the tasks that custodians feel are the most difficult, are not necessarily the ones that put them at risk to back injuries.
This ergonomic audit focused solely on back injury prevention. There are many other ergonomic issues that are involved in designing tasks such as those performed by the custodians in the residence halls on Cornell's campus. These issues need to be addressed in conjunction with those that apply to back injuries in order to provide a completely ergonomically sound workplace and process.
Redesigning tasks and/or tools is not fully effective without changing employee behaviors. Employee training is critical in ensuring that employees do not engage in tasks, in a way that puts themselves at risk to injury. Traditional training methods, including seminars and videos, have met with limited success. These training methods must also be redesigned in order to complement and reinforce the redesign of the tasks that are performed. New methods should be considered.
Follow-ups should be performed after any recommendations are implemented in order to monitor improvements and ensure that things are satisfactory.