C.J. Alfiero,C.L. Dumke FACSM, B.C. Ruby FACSM, M.W. Bundle

University of Montana, Missoula, MT

US wildland firefighters administer over 30,000 physical tests per year to qualify candidates for the occupational demands of fire suppression. The primary assessment is the arduous pack test (APT) a 4.83 km hike that must be completed in 45 min while wearing a 20.45 kg pack. Delivery of individual feedback to guide the physical training of candidates is hampered by two factors; first, passing the pack test is widely considered the minimum performance level necessary needed for this occupation, and second, the binary nature of the assessment presents candidates with a task representing an unknown and self-selected exercise intensity. PURPOSE: To determine the cardiorespiratory response elicited by the APT within a subject population whose aerobic capacity and body masses vary. METHODS: 61 young (age = 22.8 ± 3.2 yrs) adults (36 males, Mb = 79.5 ± 8.8kg; 25 females, Mb = 67.5 ± 13.5kg; study range: 55.4 - 119.6 kg) performed the APT and subsequently underwent a hiking inclined-treadmill test to VO2peakwhile wearing a skin mounted heart rate (HR) monitor and 20.45-kg pack. RESULTS: 50 of the 63 subjects achieved the 45-min cutoff with a finishing time of 41.8 ± 2.1min, the non-passers had a mean time of 47.7 ± 2.7 min. Non-passers were 77% female and 23% male. The VO2peakvalues of the passing and non-passing groups were 49.4 ± 7.2 and 42.6 ± 9.6 mlO2kg-1 min-1, respectively; the study range was 62.1 to 30.8 mlO2kg-1 min-1. HR, whether expressed as a fraction of the subject’s maximum rate (passers = 81.2 ± 17.1 and non-passers = 79.9 ± 12.7% of HRmax), or as the fraction of the HR reserve (passers = 68.0 ± 7.9 and non-passers = 67.7 ± 15.3% of HR reserve) were not different between the groups. Regression of VO2peakon completion time yielded a negative relationship (R2 = 0.45). In contrast, the HR responses and completion time were consistent among the participants (R2< 0.01 for both % of HRmaxand % of HR reserve). CONCLUSION: To successfully complete the APT candidates must achieve a HR reserve of 68% or less while maintaining a walking speed of 1.8 m s-1. These data suggest that monitoring HR during load carriage may be used to identify candidates with adequate and inadequate pre-fire season readiness.

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