Alterations in Metabolic and Cardiovascular Risk Factors During Critical Training in Wildland Firefighters

Abstract

Objective:To identify physiologic stressors related to cardiovascular disease via changes in metabolic, inflammatory, and oxidative stress biomarkers during 2 weeks of preseason training in wildland firefighters (WLFFs).Methods:Participants were recruited from a local hotshot crew and monitored during preseason training. Fitness was assessed via the Bureau of Land Management fitness challenge. Venipuncture blood was collected on days 1, 4, 8, and 11 and analyzed for changes in a lipid and glucose panel, C-reactive protein, and oxidative stress markers 8-isoprostane (8ISO), 3-nitrotyrosine (3NT), lipid hydroperoxides (LOOH), and protein carbonyls.Results:The high physical demands of training resulted in significant (P < 0.05) reductions in total cholesterol, glucose, and hemoglobin A1c. A main effect for time was observed in 8ISO, 3NT, and LOOH.Conclusions:Alterations in metabolic and oxidative stress markers suggest an acute, high-intensity physical stress during WLFF preseason training.

Wildland Firefighter Critical Training Elicits Positive Adaptations to Markers of Cardiovascular and Metabolic Health

“…Notably, these alterations are despite normal pretraining levels of these markers in an already fit population. These results are similar to those of a previous report from our laboratory 18 but expand the generalizability since each IHC undergoes a unique training stimulus. This study also demonstrated a significant PV expansion over the course of 2 wk.…”

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters

“…However, pre-season critical training typically occurs before WLFFs begin fire assignments, meaning the potential influence of chronic exposure to the stressors of sleep disturbance and wood smoke are not present. 33,34 Support for these acute benefits in cardiovascular risk profiles can be gleaned from fundamentally similar investigations of Alaskan backcountry hunting expeditions. For example, examinations of risk profiles in hunters completing such expeditions up to 12 days revealed similar rapid improvements in total cholesterol (À44 mg dL À1 ), LDL-cholesterol (À25 mg dL À1 ), VLDL-cholesterol (À7 mg dL À1 ), triglycerides (À35 mgdL À1 ), triglyceride:HDLcholesterol ratio (À0.5), intrahepatic lipids (À0.3% water peak), body mass (À1.5 kg), and total fat mass (À1.7 kg).…”

“…For example, studies examining WLFFs during an 80-hour (over ∼ 11 days) “critical training” (conditioning) period prior to the fire season indicate transient improvements in total cholesterol (−11%), 33 LDL-cholesterol (−18%), 33 body fat percentage (−2% to −1%), 33 ’ 34 and lean body mass (+1 kg), 34 resulting in a more favorable cardiovascular risk profile. However, pre-season critical training typically occurs before WLFFs begin fire assignments, meaning the potential influence of chronic exposure to the stressors of sleep disturbance and wood smoke are not present 33,34 . Support for these acute benefits in cardiovascular risk profiles can be gleaned from fundamentally similar investigations of Alaskan backcountry hunting expeditions.…”

“…For example, examinations of risk profiles in hunters completing such expeditions up to 12 days revealed similar rapid improvements in total cholesterol (À44 mg dL À1 ), LDL-cholesterol (À25 mg dL À1 ), VLDL-cholesterol (À7 mg dL À1 ), triglycerides (À35 mgdL À1 ), triglyceride:HDLcholesterol ratio (À0.5), intrahepatic lipids (À0.3% water peak), body mass (À1.5 kg), and total fat mass (À1.7 kg). 35 The preparatory critical training phase for WLFFs 33,34 and the Alaskan backcountry hunting expeditions [33][34][35][36] differ in the availability or consumption of dietary nutrients, wherein WLFFs are typically well fed but Alaskan backcountry hunters experience high levels of energy deficit (À 10 to -9 MJ day À1 ). Variations in energy balance are therefore important in that multi-day bouts of moderate intensity physical activity typically produce favorable outcomes in serum lipid remodeling and body composition changes 37 ; a finding that does not appear to result following the multifactorial stressors associated with seasonal wildfire suppression.…”

“…We recognize that the season-long findings from this investigation may be quite different than the episodic changes in other parts of the firefighting season. For example, studies examining WLFFs during an 80-hour (over ∼ 11 days) “critical training” (conditioning) period prior to the fire season indicate transient improvements in total cholesterol (−11%), 33 LDL-cholesterol (−18%), 33 body fat percentage (−2% to −1%), 33 ’ 34 and lean body mass (+1 kg), 34 resulting in a more favorable cardiovascular risk profile. However, pre-season critical training typically occurs before WLFFs begin fire assignments, meaning the potential influence of chronic exposure to the stressors of sleep disturbance and wood smoke are not present 33,34 .…”