Wildland Firefighter Safety: 20 years of chasing urine, blood and muscle on the firelines of the west Brent Ruby, Ph.D., FACSM The University of Montana
Brent Ruby, Ph.D., FACSM Director, Montana Center for Work Physiology and Exercise Metabolism Walter Hailes, M.S. Senior researcher John Cuddy, M.S. Senior researcher
20 years in wildland fire
Wildland Fire Physiology WPEM Work Patterns Dictate Energy Demands and Thermal Strain During Wildland Firefighting. Cuddy JS, Sol JA, Hailes WS, Ruby BC. Wilderness Environ Med. 2015 Mar 12. pii: S1080-6032(14)00429-3. doi: 10.1016/j.wem.2014.12.010. [Epub ahead of print] Seasonal heat acclimatization in wildland firefighters. Lui B, Cuddy JS, Hailes WS, Ruby BC. J Therm Biol. 2014 Oct;45:134-40. doi: 10.1016/j.jtherbio.2014.08.009. Epub 2014 Sep 1. High work output combined with high ambient temperatures caused heat exhaustion in a wildland firefighter despite high fluid intake. Cuddy JS, Ruby BC. Wilderness Environ Med. 22(2):122-5, 2011. Glycogen levels in wildland firefighters during wildfire suppression. Cuddy JS, Slivka DR, Tucker TJ, Hailes WS, Ruby BC. Wilderness Environ Med. 22(1):23-7, 2011. Efficacy of Eat-on-Move Ration for Sustaining Physical Activity, Reaction Time, and Mood. Montain SJ, Baker-Fulco CJ, Niro PJ, Reinert AR, Cuddy JS, Ruby BC. Med Sci Sports Exerc. 40(11):1970-1976, 2008. Effects of an electrolyte additive on hydration and drinking behavior during wildfire suppression. Cuddy J.S., J.A. Ham, S.G. Domitrovich-Harger, D.R. Slivka, and B.C. Ruby, Wilderness and Environ. Med. 19(3):172-178, 2008. Supplemental feedings increase self-selected work output during wildfire suppression. Cuddy JS, Gaskill SE, Sharkey BJ, Harger SG, Ruby BC. Med Sci Sports Exerc. 2007 Jun;39(6):1004-12. Wildland firefighter load carriage: effects on transit time and physiological responses during simulated escape to safety zone. Ruby, B.C.; Leadbetter III, G. W.; Armstrong, D. W.; Gaskill, S. E. 2003. International Journal of Wildland Fire 12(1): 111-116. Water turnover and changes in body water and composition during arduous wildfire suppression. B.C. Ruby, D.A. Schoeller, B.J. Sharkey, C.A. Burks, and S. Tysk. Medicine and Science in Sports and Exercise, 35(10):1760-1765, 2003. Total energy expenditure during arduous wildfire suppression. B.C. Ruby, T.C. Shriver, T.W. Zderic, B.J. Sharkey, C. Burks, and S. Tysk. Medicine and Science in Sports and Exercise, 34(6): 1048-1054, 2002.
Unique ultra-endurance Field settings and techniques Extreme endurance and the metabolic range of sustained activity is uniquely available for every human not just the elite few. Ruby BC, Cuddy JS, Hailes WS, Dumke CL, Slivka DR, Shriver TC, Schoeller DA. Comparative Exerc Physiol. 2015;11(1):1-7. Blood Oxidative Stress Markers During a High Altitude Trek. Miller LE, McGinnis GR, Kliszczewicz B, Slivka D, Hailes W, Cuddy J, Dumke C, Ruby B, Quindry JC. Int J Sport Nutr Exerc Metab. 2012 Sep 19. [Epub ahead of print]. Water turnover and core temperature on Mount Rainier. Hailes WS, Cuddy JS, Slivka DS, Hansen K, Ruby BC. Wilderness Environ Med. 23(3):255-9, 2012. Substrate use and biochemical response to a 3,211-km bicycle tour in trained cyclists. Slivka DR, Dumke CL, Hailes WS, Cuddy JS, Ruby BC. Eur J Appl Physiol. 112(5):1621-1630, 2011. Maximal Sustained Levels of Energy Expenditure in Humans during Exercise. Cooper JA, Nguyen DD, Ruby BC, Schoeller DA. Med Sci Sports Exerc. 43(12):2359-67, 2011. Physiological responses of middle-aged women during marathon running. Cuddy, J.S. and B.C. Ruby. Marathon and Beyond. Volume 14, Issue 6, Nov/Dec 2010. Metabolic profile of the Ironman World Championships: a case study. Cuddy, J.S., D.R. Slivka, W.S. Hailes, C.L. Dumke, and B.C. Ruby. Int J Sports Physiol Perform. 5(4):570-6, 2010. Effects of 21 days of intensified training on markers of overtraining. Slivka DR, Hailes WS, Cuddy JS, Ruby BC. J Strength Cond Res. 24(10):2604-12, 2010. Glycogen synthesis after road cycling in the fed state. Reinert A.R., D.R. Slivka, J.S. Cuddy, and B.C. Ruby. Int J Sports Med. 30:545-9, 2009. Muscle Glycogenolysis and Resynthesis in Response to a Half Ironman Triathlon: A Case Study. T.L. Gillum, C.D. Dumke, Brent C. Ruby. Int. J. Sports Phys. and Perf., 1(4): 408-413, 2006. Hydration status and water turnover of dogsled drivers during an endurance sled dog event in the arctic. Cox CE, Ruby BC, Banse HE, Gaskil, HE. Int J Circumpolar Health. 65(1):45-54, 2006.
Line Construction Demands of the job Historic and present fitness demands Management of heat stress Shift fuel and safety
1996-1998 2 H 18 O
15 Year Comparison 4,182 kcals/day (2719-6260 kcals/day) (1.8-3.6 xbmr) 4,556 kcals/day (2946-6083 kcals/day) (1.7-3.5 xbmr)
Average hourly energy expenditure and oxygen consumption (5.6 kcals/min x 5 kcals/l) = 1.12 L/min; (1.12 L/min x 1000 ml/l) / 69.7 = 16.1 ml/kg/min USFS Pack Test 22.5 ml/kg/min (5.1 kcals/min x 5 kcals/l) = 1.02 L/min (1.02 L/min x 1000 ml/l) / 78.3 = 13.0 ml/kg/min
Early Collection Sharkey (US), Budd (AU)
VO2 = 16.5 42.7 ml/kg/min 5 kcals/l of O2 consumed Therefore.kcals/min 5 kcals/l = O2 consumed (L/min) Shoveling = 8 kcals/min 5 kcals/l = 1.6 L/min O2 consumed (VO2) Additional conversion considering body weight (kg) 1.6 L/min x 1000 ml/l = 1600 ml/min x BW (kg), assume 75 kg for the example 1600 ml/min / 75 kg = 21.3 ml/kg/min
Sharkey USFS General work rate = 7.5 kcals/min Aerobic capacity considered the primary limiting factor for sustaining hard work throughout the workshift Most fireline tasks result in an overall relative VO2 approximating 22.5 ml/kg/min
1975 Designed to estimate peak VO2 approximating 45 ml/kg/min 1994 Designed to require candidates to sustain an average VO2 approximating 22.5 ml/kg/min over 45 minutes.
Canada WFX Fitness Assessment (2012) Pre-Participation Screening Carry Pump on Back Hand Carry Pump Hose Pack Lift and Carry on Back Charged Hose Advanced Budd et al., 1997 The average work rate of all fireline tasks approximates 1.5 L/min VO2 7.5 kcals/min 2.8 L/min VO2 13.9 kcals/min 178 bpm
MTDC Ingress, Shift, Egress GPS evaluation, 2016 Resource Type n = Combined 131 Type I 89 Type II 36 Training intensity associated with work hardening appears to match fireline requirements (for Type I resources) Type 2 and Engine training intensity >> fireline Engine 3 Average Estimated Oxygen Consumption (mean ± SD) Combined Type 1 Type 2 Engine Combined 25.2 15.7 26.8 15.7 22.4 15.3 17.6 12.7 Access 31.0 19.2 32.6 19.3 24.9 17.0 15.5 10.8 Shift 21.5 15.3 21.4 14.8 21.6 16.0 20.3 15.5 Egress 20.2 14.2 19.3 12.9 21.9 16.4 15.3 12.2 Training 34.4 20.8 34.6 20.8 34.3 11.7 27.3 17.6
Current USFS Pack Test The self-selected speed of the task is proportionate to the VO2 (intensity). Forecasting a WLFF s VO2 peak is of little interest. Forecasting sustainable VO2 (the manageable metabolic intensity you can work at for longer periods of time) Ingress, Line, Egress load carriage of MAJOR interest! What if 1. Complete pack test (self-selected pace <45 min) 2. Input descriptives (height, weight, sex, age) 2. Input pack test data (finish time, HR end ) Breathing new light into the present pack test! Diagnostic Calculation Readiness Progress Present capability = 21 ml/kg Type II goal = PASS (21 ml/kg) Type I goal = 30 ml/kg Training Recommendations
Effects of primary and secondary sources of heat load on select physiological metrics PROBABILITY OF HRI Proposed Approach Composite of skin temp (chest) and heart rate responses = Heat Signature Score Secondary Heat Load Radiant Heat Microclimate due to clothing/equipme nt Metabolic Activity Composite of core temp & heart rate responses = Physiological Strain Index (PSI) Skin Temperature (chest) Core Temperature (rectal) O2 demand Heart Rate Primary Heat Load When core temp rises to critical levels and a skin-core gradient is not maintained. HRI is the result (with varied degrees of severity).
Background Current Practice(s) MCO 6200 Heat Injury Prevention Program (2002) WBGT weather/flag conditions (work/rest regulations) WBGT weather/flag conditions (hydration recommendations)
More heat injuries in younger active duty and recruit trainees More heat injuries in service members in combat specific occupations Watch your trainees and younger, less-experienced crews. Ensure front line crews and (initial attack/hot shots) adhere to reasonable work:rest ratios!
Body Weight 71.9 70.9 kg TBW 42.9 42.0 L Five days (at upwards of 5,000 kcals/day) the water budget was 35 liters (7 l/day x 5 days). After 5 days they came up 1 liter shy of balance (1.3% drop in BW)
3 days (at upwards of 5,000 kcals/day) the water budget averaged 28.5 liters (9.5 l/day x 3 days). After 3 days they came up 0.3 kg less in BW (0.4% drop in BW)
N = 17 7.0 L/24 hours N = 14 6.7 L/24 hours N = 10 6.6 L/24 hours N = 15 9.5 L/24 hours 220 work days 2,640 hours N=56 Average = 7.5 L/24 hours 24 Hour value
Badwater WS 100 Kona Hours 12 12 Liters 1 liter/hr 26% total body water 27 18 Liters 0.7 liters /hr 42% total body water 45 35 Liters 0.8 liters/hr 88% total body water (50 110%)
What is/are the mechanism(s) that lead to HRI? Does this suggest that the AM safety briefing needs revision?
CASE STUDY - Overheating Emergency! 1400 41.00 1200 drinking volume (ml/hr) core temp ( C) 40.4 C Drinking Volume = 6.8 L* Total # of drinks = 216 40.00 1000 Mean drink size = 31 ml Drinking Volume (ml/hr) 800 600 Mean TBD = 6.1 minutes * volume prior to overheating 39.00 38.00 Core Temperature ( C) 37.00 400 200 36.00 0 35.00 0 17 34 51 68 85 102 119 136 153 170 187 204 221 238 255 272 289 306 323 340 357 374 391 408 425 442 459 476 493 510 527 544 561 578 595 612 Workshift Time (min) 629 646 663 680 697 714 731 2 hours 46.78 C 2.32 L 748 765 782 799 816
Run Time (mins) 35 30 25 20 Of those who ran slower than 24 minutes (N=20), 16 were "At Risk" or "DNF." Only 4 were "Not at Risk." Of those who ran between 21 and 24 minutes, 10 were "Not at Risk" and 9 were "At Risk." 15 10 5 All those who ran faster than 21 minutes were "Not at Risk" (N=17). Not at Risk At Risk DNF 0 0 2 4 6 8 10 12 Max PSI
2000-2006 >> EATING EPISODES!
SHIFT FUEL STRATEGIES/MINDSET AN item every 60-75 minutes Goal 25 to 40 grams CHO
Normal to Hard Ops 1 for 1 (1 food item for 1 hour) Staging to Moderate Ops 1 for 1.5 (1 food item for 1.5 hours)
Normal to Hard Ops 1 for 1 (1 food item for 1 hour) Staging to Moderate Ops 1 for 1.5 (1 food item for 1.5 hours) Hard Ops 1 for 1 (1 L for 1 hour) Staging to Normal Ops 1/2 for 1 (1/2 L for 1 hour)
Normal to Hard Ops 1 for 1 (1 food item for 1 hour) Staging to Moderate Ops 1 for 1.5 (1 food item for 1.5 hours) Hard Ops 1 for 1 (1 L for 1 hour) Staging to Normal Ops 1/2 for 1 (1/2 L for 1 hour) Recovery RESTORE MUSCLE FUEL RESTORE NORMAL HYDRATION REST FOR NEXT OP
Normal to Hard Ops 1 for 1 (1 food item for 1 hour) Staging to Moderate Ops 1 for 1.5 (1 food item for 1.5 hours) Recovery RESTORE MUSCLE FUEL RESTORE NORMAL HYDRATION REST FOR NEXT OP Hard Ops 1 for 1 (1 L for 1 hour) Staging to Normal Ops 1/2 for 1 (1/2 L for 1 hour) Heat Stress and Heat Injury RISK 1. Observe adequate work:rest 2. Hydration will not compensate for fitness
Conclusions you can take to the line Fire crews will always have to contend with environmental stress (heat), the energy demands will always be there. Changes in hydration status over multiple days of training limited (ad libitum adequate some experience required). You CANNOT hydrate yourself to safety if your heat production is off the charts. Management of work:rest is critical (especially for less-experienced crews). Feeding strategies matter! Revision of the catering contract? Pre-Season aerobic fitness is critical - effects readiness/safety Next level strategies to improve seasonal readiness
Questions: brent.ruby@umontana.edu WPEM