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Pulaski and Combination Tool
Skilled Grubbing Technique
Training Program

As described in the Biomechanical Analysis of Grubbing Technique
In the Use of Fire Handtools

Lois Sicking, Mechanical Engineer

INTRODUCTION
Ergonomics—sometimes called human factors—is the study of biomechanics, human behavior, abilities, limitations, and other characteristics applied to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe, comfortable, and effective human use.

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:

  • Conduct a biomechanical evaluation of firefighters using fire handtools.
  • Determine the critical biomechanical parameters associated with grubbing.
  • Describe and conduct a comparative analysis of the biomechanics of regular and skilled grubbing techniques.
  • Report findings.
Figure 1. Biomechanical field testing.
Figure 1. Biomechanical field testing.

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.
Applicable biomechanical parameters were determined to be left and right shoulder joint angle profiles, wrist range of motion, joint angular velocity profiles, peak angular velocities, body posture at maximum tool lift height and at tool impact, motion cycle time, tool lift height, tool head path, and tool acceleration/force on impact. These parameters can be further simplified to five basic principles used in skilled grubbing technique: tool lift height, work cycle time, hand separation, right shoulder angle, and position of feet. Each of these principles involves the primary use of leg and trunk muscles. Detailed information regarding this effort is published in the "Biomechanical Analysis of Grubbing Technique in the Use of Fire Handtools,” 0051 1201—SDTDC. The training program described below is synopsized from the report.

PROPOSED TRAINING PROGRAM
Skill development is achieved through instruction and practice. A practical training program ensures greater success of implementation. The following training has been developed to implement the five principle factors of skilled grubbing with the primary use of leg and trunk muscles: position of feet relative to fireline, tool lift height, hand separation, work cycle time or stroke rate, and right shoulder angle.Train firefighters to these principles, one step at a time.

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.

Position of Feet Relative to Fireline
Skilled firefighters position their feet and have a body posture as shown in figure 2.
Figure 2a. Position of feet relative to fireline.

 

 

 

Figure 2b. Position of feet relative to fireline.

Figure 2. Position of feet relative to fireline.  

Tool Lift Height
Skilled firefighters use a tool lift height that does not exceed 12 inches for the combi tool, 20 inches for the standard pulaski, and 23 inches for the super pulaski. The following steps will teach the firefighter to grub at the optimum tool lift height.

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.

Figure 3. Tool lift height indicator with a stake and colored dowels.
Figure 3. Tool lift height indicator with a stake and colored dowels.

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.

Figure 4. Hand separation maintained within set parameters by elastic cord.
Figure 4. Hand separation maintained within set parameters by elastic cord.

Work Cycle Time or Stroke Rate
Skilled firefighters have a work cycle time for the combi tool of 0.7 second or a stroke rate of 86 strikes per minute. Skilled firefighters have a work cycle time of 0.8 second or a stroke rate of 75 strikes per minute for the standard and super pulaskis. The next step will teach the firefighter to grub at the optimum work 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).

Figure 5. Pace tool strikes with a metronome.
Figure 5. Pace tool strikes with a metronome.

Right Shoulder Angle
Skilled firefighters start a grub cycle with a right shoulder angle of 6 degrees when leading with the right hand and a comparable left shoulder angle when leading with the left hand. Either of the following steps will teach the firefighter to grub at the optimum right shoulder angle.

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.

Figure 6. Bag in position to maintain a narrow right shoulder angle and a short arm reach.
Figure 6. Bag in position to maintain a narrow right shoulder angle and a short arm reach.

RECOMMENDATIONS
Top priority should be given to the broad field implementation of the combi tool, to increasing field acceptance, and to expanding its use in crew tool mixes—especially for Type II crews. The combi tool should be the first training tool used by regular firefighters in developing skilled technique and should also be used to train experienced firefighters to become more efficient. In addition, the combi tool should be designated as the preferred grubbing tool based on low energy cost, high productivity, and safety when compared with the standard and super pulaskis. The super pulaski, as currently designed, should not be used by regular firefighters.

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 mailroom_wo_sdtdc@fs.fed.us.


TD logo
For Additional Information Contact:
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
E-mail: mailroom_wo_sdtdc@fs.fed.us

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