The School of Technology at Kent State University (KSU) in Kent, Ohio, was retained by The White Rubber Corp. (Ravenna, Ohio) to conduct testing to compare worker performance using insulated gloves versus bare-hand labor. Beyond meeting the industry standards, the manufacturer was interested in understanding how insulated gloves might affect worker safety beyond providing protection from live line contact. KSU conducted the study based on glove test methodology developed by NASA using comprehensive glove effectiveness testing protocols. These procedures measure performance related to working conditions and the cumulative effect of fatigue, impact on productivity and increased likelihood of injury.

Why the NASA Standard?

Gloves used on space missions protect the hands of astronauts but exact a toll in terms of decreased performance. Electric utility linemen face challenges similar to those encountered by astronauts. Both linemen and astronauts must wear fairly restrictive multilayer protective gloves. They both operate under severe environmental conditions, and glove failure could result in dire consequences. Due to the extreme working conditions, both linemen and astronauts experience fatigue. Linemen, however, have the exacerbating factor of wearing their gloves for extended periods of time.

This study adapted the NASA test methodology and applied it to electric utility lineman gloves. Four different categories of tests were conducted: strength, dexterity, integrated hand performance and fatigue. Testing was conducted over several days with male subjects between 20 and 29 years of age. Each of the subjects were tested bare hand and using Type 1, Class 2, 16-inch, size 10, straight-cuff insulated gloves.

In a review of published literature on the subject, researchers can predict the incidence rate of cumulative trauma disorders. Studies have established that tendon stress increases linearly with increasing grasp force. The researchers also found that increased grip force and wrist angles individually and interactively increase the likelihood of cumulative trauma.

The KSU test set out to verify these concerns in the four NASA test categories.

Grip Strength

It is a part of every lineman's day to perform tasks that require having a good grip. For the strength test, two different tests were conducted for each hand in the different glove tests. Grip strength was measured by having the subject squeeze a hydraulic grip dynamometer, and key pinch strength was measured by having the subject pinch a hydraulic pinch gauge. The test results showed that the use of gloves reduced grip strength by 12% to 18%. The use of gloves had little effect on key pinch strength.

Dexterity

Technicians are also routinely required to try to remove the bolts from a switch cabinet while in an aerial lift or on a pole, or are required to attempt to secure a harness with snap/D rings all while wearing gloves. The dexterity test was a nut and bolt assembly test. Three bowls were placed in front of each subject. One bowl contained stainless steel hex nuts; a second bowl contained stainless steel hex bolts. Two nuts had been previously turned on to each bolt and jammed together so they formed a stop from the end of the bolt. Each subject was asked to complete as many nut and bolt assemblies as possible by picking up a nut from one bowl, a bolt from the other bowl, and assembling them until the nut made contact with the stop. The finished assembly then had to be placed in the third bowl. Subjects first completed one practice trial in their bare hands and gloves. Results were recorded for the number of completed assemblies as well as the number of times an assembly was accidentally “dropped.”

The lab tests showed that gloves had a large effect on dexterity. The 12 subjects were able to complete only 38% to 41% as many assemblies wearing gloves as they could with their bare hands. Dexterity drops ranged from 2 to 2.5 times with gloves versus bare hands.

Integrated Test

Each of the subjects conducted two integrated hand tests. The first test required the subject to close a wire grip without the use of a tool. The wire grip was placed in front of the subject, and at the “go” signal the subject picked it up and closed it as quickly as possible. The time required to close it was recorded with a stopwatch. The first task required a 14% to 20% increase in time to complete when wearing gloves.

For the second test, we had each subject turn a nut on a cable terminal using an adjustable wrench. The cable terminal was supported in a vice, which required the subject to continuously remove and replace the wrench on the nut in order to complete the task. The wrench was placed on the table in front of the subject, and at the “go” signal the subject picked it up and began turning the nut as quickly as possible. The time required to turn the nut to the far end of the cable terminal was recorded with a stopwatch. For each of the integrated tests, each subject completed a practice trial in their bare hands and gloves. The second task required a 52% to 67% increase in time to complete when wearing gloves.

Fatigue Test

The glove fatigue test was the last test conducted each day. In the lab, subjects squeezed a hydraulic grip dynamometer with 50% of their maximum bare-hand strength for as long as possible and again times were recorded with a stopwatch. Diminished strength varied only slightly between left-hand and right-hand tests. Left-hand fatigue times ranged from 75% to 98% and right-hand fatigue times were 75% to 92% of the bare-hand standard.

Other Studies

In light of other industry research and the insulated glove testing performed at KSU, care should be taken to select gloves that minimize the required force a worker must exert for a given task. As a result, utilities should review their work practices and determine when and what insulated gloves should be used to prevent injury and optimize productivity.

Darwin L. Boyd is an assistant professor in the School of Technology at Kent State University. He has worked as a research associate and also has been a NASA-ASEE Summer Faculty Fellow at NASA Lewis (now Glenn) Research Center in Cleveland, Ohio. Boyd received his PhD in physics from Kent State University in 1991. dboyd@kent.edu