and Combination Tool
described in the Biomechanical Analysis of Grubbing Technique
Lois Sicking, Mechanical Engineer
Ergonomics is the study of optimizing the human tool system, thereby reducing the potential for injury, improving safety, and increasing productivity. Ergonomic principles can be used to prevent or minimize injuries in firefighters using fire handtools in wildland firefighting. The ergonomic emphasis is on changing the tool, the user technique, and the work environment, rather than on changing people to fit a particular tool. In this way, priority is given to the capabilities, needs, and limitations of people.
A progressive effort has been made to evaluate and redesign handtools used in wildland fire service for fireline construction. In recent years, fire tool testing by the San Dimas Technology and Development Center (SDTDC) in San Dimas, CA, has focused on tool design. The present focus is on firefighter biomechanics.
Biomechanical measurements provide insight into the abilities and limitations of the human body in performing grubbing motions with fire handtools. Identification of the optimum biomechanics associated with the use of handtools can contribute to improved performance with reduced ergonomically induced injuries.
SDTDC was tasked to:
The information from this
study will be used to train firefighters for ergonomic efficiency, improve
their performance, and increase worker safety. In addition, handtool
design modifications were derived from these kinematic measurements.
The standard pulaski, super pulaski, and combination (combi) handtools
were tested with a sample of 22 firefighters.
It is important to fully master each principle before moving to the next principle. Start with training firefighters to skillfully use the combi tool. Progress to the standard pulaski.
of Feet Relative to Fireline
Use three wooden stakes and brightly colored wooden dowels, rulers, or sticks. Mark off 3 inches from the bottom tip of the first stake with a permanent marker. Write "ground" just below the mark. Pound the stake into the ground until the word "ground" can no longer be seen. Measure 12 inches above the “ground” mark and mark this level "combi.” Secure a colored dowel at this point, perpendicular to the stake. Repeat the procedure with the other two stakes and colored dowels, using 20 inches for the Pulaski, and 23 inches for the super pulaski. See figure 3. The firefighter will learn to lift the head of the tool only the distance marked on the stake for that particular tool.
Or, tie flagging, string, or cording to the tool head at the handle and measure to the proper length, with a wad of flagging adding weight to the end. These materials are readily available at fire camp and could alert regular firefighters to the proper tool lift height.
This positioning combined with the difference in hand separation contributes to the drastic difference observed in left shoulder flexion/extension in the super pulaski. The regular firefighter has the front, nondominant hand further down the tool handle as the blade drops. This increases the loading on the lower back because the regular firefighter is stretched out and more stooped over than the skilled firefighter.
Hand SeparationSkilled firefighters have a hand separation of 23 inches for the combi tool, 16 inches for the standard and super pulaskis. The following step will teach the firefighter to grub at the optimum hand separation.
Obtain a 36-inch length of 1-inch elastic band, available from the notions section of a general store for a cost of less than $1. Measure 2 inches from one end and mark; measure 16 more inches, mark, and write "Pul”; measure 7 more inches, mark, and write "Com"; and measure 2 inches more and cut. Loop and tie the ends of the elastic to the wrist straps of each glove at the appropriate mark for the tool in use (figure 4). The hand separation is 23 inches for the combi tool and 16 inches for the standard pulaski and super pulaski.
Cycle Time or Stroke Rate
Record an audiotape of a metronome set at 75 beats per minute or buy a battery-powered metronome with a loud beep and a speed range up to 100 beats per minute at a cost of $12 to $22. The work cycle time for the combi tool is 0.7 second or 86 beats per minute. The work cycle time for a complete stroke is 0.8 second, which equals 75 beats per minute for the standard and super pulaskis. Workers can speed up or slow down in pace with the metronome (figure 5).
Buy a 10-ounce plastic sack of rice. Open the sack at one end. Pour out one-half of the rice and fold over the end of the sack onto itself. The sack should be about 3 by 4 inches, loosely filled. Wrap the sack securely with duct tape, keeping the sack loose in general shape. Attach a short cord to the rice sack. Use duct tape to secure the bag into position approximately 3 inches below the armpit of your shirt on your nondominant side or arm—usually the left arm.
Or, with a short cord around the rice bag secure it in position and attach the other end to your fire shirt. Position the rice bag 3 inches below the armpit and against the upper torso by applying pressure with the upper arm as shown in figure 6. Try to keep the bag against the torso, especially in the up-stroke phase. This results in a narrow right shoulder angle and a short arm reach.
This detailed training program needs to be developed further with the assistance of crew bosses to include hard copy and electronic computer training modules, posters, and videos. This program would teach firefighters—especially Type II crews—the necessary skills to use fire handtools more effectively and safely: using leg and trunk muscles, key biomechanics parameters, and pacing for a sustainable work rate. This program would also teach Type I crews to enhance efficiency.
For further information or to share comments and recommendations for further study, contact SDTDC by phone at 909-599-1267 or by e-mail at email@example.com.
Project Leader, Fire Management
San Dimas Technology & Development Center
444 East Bonita Avenue, San Dimas CA 91773-3198
Phone 909-599-1267; TDD: 909-599-2357; FAX: 909-592-2309
Information contained in this document has been developed for the guidance of employees of the Forest Service, United States Department of Agriculture (USDA), its contractors, and cooperating Federal and State agencies. The USDA assumes no responsibility for the interpretation or use of this information by other than its own employees. The use of trade, firm, or corporation names is for the information and convenience of the reader. Such use does not constitute an official evaluation, conclusion, recommendation, endorsement, or approval of any product or service to the exclusion of others that may be suitable.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD).
To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.