No Effect of a Ketone Monoester on Markers of Stress and Performance in a Live-Burn Search and Rescue in Firefighters

Abstract

Waldman, HS, Bryant, AR, Shepherd, BD, Egan, B, and McAllister, MJ. No effect of a ketone monoester on markers of stress and performance in a live-burn search and rescue in firefighters. J Strength Cond Res 36(3): 763-771, 2022-Firefighters experience a range of stressors that impair performance and elevate the risk for developing cardiometabolic diseases. b-Hydroxybutyrate (bHB) has been shown to mitigate markers of oxidative stress and inflammation and serve as an alternative fuel with implications to physical performance. On 2 occasions in a double-blind, counterbalanced, and crossover design, 14 professional firefighters performed a live-burn, search and rescue (S&R) 30 minutes after ingestion of a ketone monoester (KME; 0.5 g•kg 21 ) or a placebo (PLA). Dependent variables collected before and after the S&R included salivary markers of stress and inflammation (cortisol, a-amylase, interleukin-1 beta, uric acid), perceptual markers (profile of mood state [POMS]), gastrointestinal distress (GI), rating of perceived exertion [RPE]), time to completion, and capillary blood measurement of bHB and glucose. KME resulted in capillary bHB concentrations of approximately 2.1-3.2 mM throughout the protocol. Capillary glucose concentrations were lower for the KME compared with PLA (;7%) (interaction effect, p , 0.001). Salivary markers of stress, GI, and time to complete the S&R (;10 minutes) did not differ between trials, although KME ingestion resulted in significantly higher RPE after the live-burn S&R (KME,6 6 1; PLA, 4 6 1). However, POMS data showed the KME also lowered subjective states of nervousness (KME, 0.0 6 0.0; PLA, 0.6 6 0.8) and anxiety (KME, 0.0 6 0.0; PLA, 0.6 6 0.7) before the S&R (all p , 0.05; large effect sizes). Compared with PLA, ingestion of a KME by firefighters did not mitigate the rise in various markers of salivary stress or impact physical performance during a live-burn S&R. However, differences in RPE and POMS variables were observed, suggesting a possible cognitive role for bHB.

Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future

“…Additionally, because the various types of EKS vary in their effectiveness to elevate [R-βHB] (Table 1 ), we contend that the accurate measurement of [R-βHB] is an important consideration in human studies, especially during mild ketosis, that is, in the ~ 0.3 to 1.0 mM range. Many studies on acute ingestion of EKS have used handheld point-of-care (POC) devices to measure whole blood [R-βHB] [ 34 , 37 , 42 , 45 , 46 , 50 , 51 , 53 , 55 – 59 , 61 , 62 , 64 , 67 – 72 , 78 , 81 , 83 – 87 , 107 ]. These POC devices were originally developed to monitor and manage ketoacidosis in clinical populations [ 113 – 115 ].…”

“…Greater incidences of GI symptoms with the ingestion of ketone esters compared with control conditions has been observed with ~ 37 g of R,S-BD AcAc KDE ingested in the 60 min prior to a 31.2-km cycling TT [ 35 ], ~ 59 g of R-BD R-βHB KME ingested 20 min prior to and during an intermittent running protocol lasting ~ 80 min [ 49 ], ~ 32 g (females) and ~ 46 g (males) of R-BD R-βHB KME ingested 30 min prior to a 35-min pre-load at ventilatory threshold (VT) followed by a 3-kJ.kg −1 cycling TT [ 38 ], ~ 50 g of R-BD R-βHB KME ingested during a warm-up in the hour prior to a 30-min cycling TT [ 72 ], and ~ 58 g of R-BD R-βHB KME ingested 25 min prior to and during an intermittent running protocol lasting ~ 100 min [ 86 ]. However, there are also several studies where greater incidences of the GI symptoms are not observed [ 42 , 54 , 59 , 62 , 70 , 78 , 81 ]. In a comprehensive series of studies, ingestion of R-BD R-βHB KME was observed not to increase GI peak symptom load or frequency during exercise [ 59 ].…”

“…This lack of effect on RPE is consistent with most studies of acute ingestion of EKS observing no differences in RPE compared with control conditions. When there has been higher RPE observed in such studies [ 38 , 42 , 81 ], outcomes of the performance tests were not negatively impacted. One notable observation was across a cohort of n = 19 males and females; higher RPE compared with the control condition was associated ( r = 0.64; p < 0.01) with reduced 3-kJ.kg −1 cycling TT performance after ingestion of R-BD R-βHB KME [ 38 ].…”

“…The broad category encompassed by EKS currently includes ketogenic precursors such as BD and medium chain fatty acids (MCFA) and triglycerides (MCT), isolated KBs in the form of R-βHB and R,S-βHB ketone salts (KS), and ketone esters (described in more detail in Table 1 ). Ketone esters have been prominent in the exercise science literature [ 35 , 38 , 42 , 44 , 47 – 49 , 54 , 58 – 60 , 66 – 68 , 70 – 72 , 78 , 81 , 86 , 87 , 99 ], and include the R-3-hydroxybutyl R-3-hydroxybutyrate (R-BD R-βHB) ketone monoester (KME) [ 34 , 44 , 100 ], originally developed to improve the physical and cognitive performance in warfighters [ 101 ], and the R,S-1,3-butanediol acetoacetate (R,S-BD AcAc) ketone diester (KDE) [ 35 , 102 , 103 ]. Other ketone esters that have been reported in the peer-reviewed literature to date include a compound of βHB and the short chain fatty acid butyrate (βHB-BA) [ 104 ], and a diester of hexanoic acid (a ketogenic MCFA) and R-1,3 butanediol (BH-BD) [ 39 , 105 , 106 ].…”

“…In the time since 2016 when the first peer-reviewed article detailing the effects of acute ingestion of EKS in humans on exercise metabolism and endurance performance was published [ 44 ], there has been a dramatic increase in the number of articles investigating the effects in humans of acute ingestion of EKS of various types on exercise metabolism, physical and cognitive performance, and recovery from exercise [ 21 , 35 – 38 , 42 , 44 – 49 , 51 , 52 , 54 , 56 – 62 , 64 , 66 – 73 , 78 , 81 , 82 , 84 – 86 ], and in other studies investigating short-term (~ 10 d to 6 weeks) daily consumption [ 74 , 83 , 87 , 99 , 107 – 110 ]. Therefore, this review provides an update on investigations into the effects of EKS on exercise performance and recovery outcomes relevant to athletic performance, as well as discussion of methodological considerations and future directions in this field.…”