Effect of ketone monoester supplementation on elite operators' mountaineering training

Abstract

Introduction: Special Operations Forces (SOF) often conduct operations in physiologically stressful environments such as severe heat, cold, or hypoxia, which can induce decreases in a variety of cognitive abilities. Given the promising empirical demonstration of the efficacy of exogenous ketone monoester (KME) supplementation in attenuating cognitive performance decrease during hypoxia at rest in a laboratory setting, we conducted a real-world, field experiment examining KME's efficacy during high-altitude mountaineering, an austere environment in which US SOF have conducted increasing numbers of operations over the past two decades.

Methods: Specifically, 34 students and cadre at the US Army 10th Special Forces Group Special Operations Advanced Mountaineering School (SOAMS) participated in a randomized, double-blind, placebo (PLA)-controlled crossover trial (KME vs. PLA) over 2 days of tactical mountain operations training. The participants ascended from 7,500 ft in altitude (basecamp) to 12,460 ft on 1 day and 13,627 ft the other day (in randomized order), while performing various training activities inducing high physical and cognitive loads over 8-12 h, and consumed six doses of KME or PLA 2-3 h apart throughout each training day.

Results and discussion: While KME increased blood ketone levels and decreased glucose levels, there were no clear indications that the elevated ketone level enhanced physical or cognitive performance. KME also produced a greater incidence of heartburn, nausea, and vomiting. In these elite operators, high-altitude mountaineering had a limited impact on cognitive performance, and KME supplementation did not demonstrate any benefit.

Keywords: cognitive performance; high altitude; hypobaric hypoxia; military; resilience; β-hydroxybutyrate.

FIGURE 1

Schematic illustration of the data collection schedule.

FIGURE 2

(a–l) Sleep and readiness metrics derived from the Oura Ring plotted by the baseline testing day, alpine training day 1, and alpine training day 2. The effort bars denote the standard error: (A) Oura readiness score; (B) Oura sleep score; (C) lowest heart rate during sleep from the night before in beats per minute (BPM); (D) average heart rate during sleep from the night before in BPM; (E) RMSSD during sleep from the night before; (F) average respiratory rate during sleep from the night before in respiration per minute (RPM); (G) 3-day average of the lowest heart rate during sleep from the night before in BPM; (H) 3-day average of the average heart rate during sleep from the night before in BPM; (I) 3-day average of RMSSD during sleep from the night before; (J) 3-day average of the average respiratory rate during sleep from the night before in RPM; (K) sleep duration from the night before in minutes; (L) 3-day average of sleep duration from the night before in minutes; (M) partial correlation matrices between the sleep metrics that were derived from the Oura Ring and cognitive performance at the baseline testing (left panel), as well as at the high altitude (11,000 or 14,000 ft: simpleRT and ImpulseControl in SWAY) and post-training at the basecamp level (7,500 ft: ANAM variables) on alpine days 1 (middle panel) and 2 (right panel). cdd, code substitution—delayed; cds, code substitution learning; gng, go/no-go; m2s, matching to sample; mth, mathematical processing; pro, procedural reaction time; spd, spatial processing; sr2, simple reaction time second time; srt, simple reaction time first time; st6, memory search. All ANAM variables are the median reaction time for correct trials from the given test.

FIGURE 3

Proportion of the IFT time by the heart rate intensity zone. IFT, incline fitness test. Heart rate zones are defined by the American College of Sports Medicine defined zones and are calculated based on the percentage of age-predicted heart rate max. Very light <57% HR_max; light, 57%–63%; moderate, 64%–76%; vigorous, 77%–95%; maximal, >95%.

FIGURE 4

Summary of heart rate zones across each route by treatment (KME vs. PLA). (A) Total time in hours to complete the ascent portion of the routes. (B) Percentage of the total completion time spent in the light-intensity activity heart rate zone (57%–63% HR_max). (C) Percentage of the total completion time spent in the moderate-intensity activity heart rate zone (64%–76%). (D) Percentage of the total completion time spent in the vigorous-intensity activity heart rate zone (95%). Heart rate zones are defined by the American College of Sports Medicine defined zones and are calculated based on the percentage of age-predicted maximum heart rate.

FIGURE 5

(A) Model-estimated means of blood glucose levels in mg/dL plotted by treatment and time point, where placebo = PLA, ketone monoester = KME, mountaineering day 1 = D1, and mountaineering day 2 = D2. (B) Model-estimated means of blood ketone levels in mmol/L plotted by treatment and time point. (C) Model-estimated means of blood glucose levels in mg/dL plotted by treatment and mountaineering route. (D) Model-estimated means of blood ketone levels in mmol/L plotted by treatment and mountaineering route. The error bars denote 95% CI.

FIGURE 6

Model-estimated means of Borg RPE (A) and Samn–Perelli Fatigue Scale (B) ratings plotted by the treatment condition and the route, where PLA = placebo and KME = ketone monoester. The error bars denote 95% CI.

FIGURE 7

Model-estimated means of ANAM code substitution—delayed (CDD: (A), code substitution—learning (CDS: (B), go/no-go (GNG: (C), matching to sample (M2S: (D), mathematical processing (MTH: (E), procedural reaction time (PRO: (F), spatial processing (SPD: (G), simple reaction time (SRT: (H), simple reaction time—repeat (SR2: (I), and memory search (ST6: (J) plotted by treatment and time point. All in milliseconds. PLA, placebo; KME, ketone monoester. Mountaineering day 1, D1; mountaineering day 2 = D2.

FIGURE 8

Model-estimated SWAY simple reaction time (A) and model-estimated impulse control (B) plotted by the treatment condition and time point. PLA, placebo; KME, ketone monoester. Mountaineering day 1, D1; mountaineering day 2, D2. The error bars denote 95% CI.

FIGURE 9

Blood ketone level (mmol/L) plotted by the incident of vomiting (no or yes) and the treatment condition (PLA or KME).