By Jamie Thompson
WASHINGTON — The weight and material of firefighter boots can have significant impacts on the way wearers move and perform, according to preliminary results from a new NIOSH study.
Researchers are evaluating the effect of boot weight and design on firefighters' oxygen consumption, peak flows, joint loading, dynamic balance and gait characteristics
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The three-phase study, which began toward the end of last year and should be completed in the coming months, has seen firefighters in leather and rubber boots tested for oxygen consumption, joint movement and walking patterns.
According to NFPA statistics, firefighters suffered about 80,100 occupational injuries in 2007 — with 50 percent of these due to either overexertion or falls. NFPA officials believe boot weight may contribute to the stress of firefighting.
Data collected from the NIOSH study is likely to be included in future revisions and updates to NFPA 1971 Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting.
Researchers began by comparing leather boots with rubber, which are generally 3 pounds heavier than the former but about half the price.
Preliminary findings from the first phase of the study suggest firefighters must adjust their walking patterns and postures when wearing the heavier boots, walking more slowly and taking wider steps.
In addition, for each stride firefighters in the study took, the percentage of time when both feet were in contact with the floor was longer with the heavier footwear, suggesting the need for more time to balance their body during walking.
The weight of the boots was also found to affect the way participants naturally moved their lower bodies. Resultant joint loadings at hips and knees were significantly increased when wearing rubber boots during normal gait.
These heavier boots limited ankle, knee and hip motions, with NIOSH researchers believing such restrictions may affect firefighters' ability to maintain balance or cross obstacles effectively during fireground operations.
Participants have taken par in exertion tests — including walking on a treadmill while carrying a hose and climbing a revolving staircase — to monitor the physiological effects of boot weight.
Initial findings indicate oxygen consumption, the amount the participant breathed and their heart rate were significantly greater when wearing rubber boots. During the treadmill test, those wearing rubber boots had a reduced SCBA duration by several minutes.
The second phase of the study focused on the physiological and biomechanical effects of stitched- and cement-soled boots on firefighters.
According to preliminary data, there was a "significant" (4 to 5 percent) decrease in oxygen consumption observed for those wearing cement-soled boots compared to stitched-soled during treadmill walking, and an "insignificant" (2 to 3 percent) decrease in oxygen consumption observed during stair climbing.
The final phase of the study will examine how different boots perform during obstacle crossing and ladder climbing to determine effects of weight, material and sole type on risk of trips/falls.
Final results of the study should be released around mid-2010.