Article Title



Lisa T. Jansen1,3, Jorge Granados2, Weston Castillo3, Stephen Vanderbeck3 & Matthew R. Kuennen3

1 University of Arkansas, Fayetteville, Arkansas; 2 Texas A&M University, College Station, Texas; 3 West Texas A&M University, Canyon, Texas

Beetroot juice supplementation (BRJ) is touted to improve performance during scripted exercise [1]. Reported effect amongst others is reduced oxygen consumption while performing a given workload, ultimately suggesting an increase in overall exercise efficiency [1,2,3]. PURPOSE: This study investigated whether BRJ (140ml,8.4mmol NO3-) can reduce the physiological strain associated with performing a 45 minutes simulated military desert march. METHODS: Ten healthy non-acclimated males (Age: 24 ± 1 yrs; Body fat: 13.3 ± 1.7%; VO2max: 51.3 ± 1.5 ml/kg/min-1) supplemented with either BRJ (~ 4.2 mmol NO3- / 70 ml) or PL (0.4mmol/ NO3- /70 ml) utilizing a randomized, double-blind crossover design. After a familiarization trial at ambient temperature (~22° C/30% RH), subjects entered two six-day supplementation periods, each concluded by a 45 min simulated military march (3mph/1% incline, summer uniform [MOPP gear], body armor [6.8kg], and loaded back pack [13.6kg]) in a hot environment (~41° C / 15% RH). Plasma nitrate concentration was assessed at onset and termination of each march. Oxygen consumption (VO2), carbon dioxide production (VCO2), ventilation (VE), respiratory quotient (RQ), oxygen saturation (SPO2), heart rate (HR), rectal (TCore) and skin temperature (TSkin) were measured at 5min intervals. Alongside, standardized scales were employed to measure ratings of perceived exertion (RPE), thermal sensation, and generalized discomfort. Mean body temperature (TBody)[4], and physiological strain index (PSI)[5] were calculated. A 2-factor [Time*Condition] repeated measures ANOVA was used to discern differences between groups. Significance was set at p < 0.05 and Tukey post hocs were used where appropriate. RESULTS: Plasma nitrate content increased during the BRJ condition. Despite RQ there were no significant differences between conditions for all indirect calorimetric and physiological variables. CONCLUSION: 6 day BRJ supplementation showed no improvement of thermodynamic efficiency when performing a loaded battle march in hot climatic conditions. The demographics of this cohort exactly emulated those of US military recruits; gear and workload replicated US Army standard operating procedures, and the climatic conditions of desert deployment. As such, data do not suggest BRJ would benefit soldiers in avoidance of exertional heat illness.

(This research was supported with grants provided by Gatorade Sports Science Institute and the West Texas A&M University Kilgore Research Center)

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