خ²-Alanine supplementation and military performance ... meat, poultry and fish consumption is...
Embed Size (px)
Transcript of خ²-Alanine supplementation and military performance ... meat, poultry and fish consumption is...
DOI 10.1007/s00726-015-2051-9 Amino Acids (2015) 47:2463–2474
β‑Alanine supplementation and military performance
Jay R. Hoffman1 · Jeffrey R. Stout1 · Roger C. Harris2 · Daniel S. Moran3,4
Received: 24 March 2015 / Accepted: 10 July 2015 / Published online: 24 July 2015 © The Author(s) 2015. This article is published with open access at Springerlink.com
enhancing combat-specific performance. This appears to be most relevant for high-intensity activities lasting 60–300 s. Further, limited evidence has recently been presented sug- gesting that β-alanine supplementation may enhance cogni- tive function and promote resiliency during highly stressful situations.
Keywords Soldiers · Performance · Dietary supplement · Nutrition
During prolonged high-intensity military training or simu- lated combat exercises, significant decreases in physical and cognitive performance measures have been reported (Lieberman et al. 2002; Nindl et al. 2007; Weeks et al. 2010; Welsh et al. 2008). To compensate for the physiologi- cal and psychological fatigue associated with military train- ing and combat, a number of pharmacological interventions have been examined. However, recently several members of the US Army Medical Corps have expressed a need to examine non-pharmacological alternatives to counteract the fatigue associated with military combat (Russo et al. 2008). The use of nutritional supplements among military person- nel is quite common. Fifty-three percent of the American soldiers at various military installations around the world (outside of the combat theater) indicated that they used nutritional supplements on a regular basis (Lieberman et al. 2010). Knapick et al. (2014) estimated the prevalence of dietary supplement use for the US Army, Navy, Air Force and Marine Corps men to be 55, 60, 60 and 61 %, respec- tively; while for women the corresponding values were 65, 71, 76 and 71 %, respectively. Cassler et al. (2013) have indicated that up to 72 % of the US Marines deployed to
Abstract During sustained high-intensity military train- ing or simulated combat exercises, significant decreases in physical performance measures are often seen. The use of dietary supplements is becoming increasingly popu- lar among military personnel, with more than half of the US soldiers deployed or garrisoned reported to using dietary supplements. β-Alanine is a popular supplement used primarily by strength and power athletes to enhance performance, as well as training aimed at improving mus- cle growth, strength and power. However, there is lim- ited research examining the efficacy of β-alanine in sol- diers conducting operationally relevant tasks. The gains brought about by β-alanine use by selected competitive athletes appears to be relevant also for certain physiologi- cal demands common to military personnel during part of their training program. Medical and health personnel within the military are expected to extrapolate and imple- ment relevant knowledge and doctrine from research per- formed on other population groups. The evidence support- ing the use of β-alanine in competitive and recreational athletic populations suggests that similar benefits would also be observed among tactical athletes. However, recent studies in military personnel have provided direct evi- dence supporting the use of β-alanine supplementation for
* Jay R. Hoffman email@example.com
1 Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL 32816, USA
2 Junipa Ltd, Newmarket, UK 3 School of Health Science, Ariel University, Ariel, Israel 4 Givat Washington College of Education, Givat Washington,
2464 J. R. Hoffman et al.
Afghanistan used a nutritional supplement. However, lit- tle is known regarding the efficacy or safety of many of these supplements with regard to various specific military performances.
With regard to tactical performance, nutritional supple- ments can be divided into two separate categories: supple- ments to prepare personnel for the rigors of combat and supplements that are used for acute performance improve- ments. In addition, some supplements consumed during training are also intended to assist in recovery from train- ing. Supplements that have been suggested to enhance physical development of military personnel should improve strength and muscle size during training. Often, these types of supplements are consumed in conjunction with strength and conditioning programs.
These supplements may also have an important role dur- ing sustained combat scenarios where high intensity and prolonged activity can often impair the physical capability of the operator (Committee on Dietary Supplement Use by Military Personnel, (2008). One of the more popular sup- plements being used by competitive athletes to improve athletic performance today is β-alanine (Blancquaert et al. 2015; Maughan et al. 2011). The efficacy of β-alanine to enhance athletic performance has been delineated in sev- eral recent reviews (Artioli et al. 2010; Derave et al. 2010; Hobson et al. 2012; Sale et al. 2010). However, a recent review on the efficacy of β-alanine in military performance suggested that the strength of evidence was not sufficient to support the use of β-alanine by military personnel (Ko et al. 2014). This review, however, was published prior to any studies investigating β-alanine supplementation of mil- itary personnel being conducted and, in addition, largely ignored the biochemical evidence underpinning its known physiological effects. Since Ko et al. (2014), two papers have been published examining the efficacy of β-alanine supplementation on military-specific tasks. As such, an updated review appears to be warranted. This review will examine the potential benefit of β-alanine supplementation among tactical personnel to help prepare them for the rig- ors of combat. It will also critically discuss investigations on β-alanine ingestion and performance in both competitive and tactical athletes, and provide physiological evidence for the use of β-alanine in the military population.
Β-Alanine is a non-proteogenic amino acid, and is one of the two constituents of carnosine (histidine being the sec- ond constituent). The combination of β-alanine raises the pKa of the imidazole ring of the histidine residue to 6.83, placing it in the center of the exercise intracellular pH transit range and enabling it to act as a highly effective pH
buffer. The combination with β-alanine further renders the histidine moiety inert to proteogenic reaction with other amino acids, enabling high concentrations to be accumu- lated in muscle cells, further enhancing its quantitative role as a pH buffer. β-Alanine is considered to be the rate-limit- ing step in carnosine synthesis in at least muscle, due to its low rate of synthesis in vivo (Bauer and Sculz 1994; Har- ris et al. 2006). Thus, the aim of β-alanine supplementation is to increase the carnosine content in skeletal muscle and through this also the intracellular buffering capacity, ena- bling a greater tolerance of sustained anaerobic activity.
Carnosine is found in the skeletal muscle of all verte- brates (Harris et al. 1990), but is especially high in mam- mals that rely on anaerobic metabolism to fuel their activ- ity. The relationship between carnosine content and muscle buffering capacity is strongly positive across all species (Harris et al. 1990; Abe 2000; Parkhouse et al. 1985), with a significantly greater concentration of carnosine found in type II compared to type I muscle fibers (Harris et al. 1998; Hill et al. 2007; Kendrick et al. 2009). Based upon its cross-species distribution, carnosine’s primary physiologi- cal role in muscle appears to be as a pH buffer (Abe 2000; Harris et al. 2006), moderating the decline in intracellular pH with lactate accumulation during intense exercise, or exercise performed under hypoxia. In humans, accumulat- ing evidence suggests that high concentrations of carnosine within muscle delays the onset of peripheral fatigue with intense exercise lasting 1–5 min (Hobson et al. 2012). In only one study has high-intensity training alone been sug- gested to majorly increase muscle carnosine concentra- tions (Suzuki et al. 2004). Such an effect would require an increase in hepatic β-alanine synthesis and/or an increased rate of transport into muscle fibers. Suzuki et al. (2004) reported a doubling in the muscle carnosine content fol- lowing 8 weeks of sprint training involving a total training time of 14 min (i.e., single 30-s sprints performed twice per week for the first 2 weeks and two 30-s sprints performed twice per week for the next 6 weeks with 20-min recov- ery between sprints). However, most other studies examin- ing high-intensity training for durations ranging from 4 to 16 weeks, and where the total training time was in excess of that of Suzuki et al. (2004), have been unable to con- firm these results (Kendrick et al. 2008, 2009; Mannion et al. 1994). An additional effect of training on the mus- cle carnosine content has recently been reported by Bex et al. (2014). In addition, this suggested that the effect of β-alanine supplementation may be increased with training, although a similar effect was not observed by Kendrick et al. (2009) when measured in different muscle fiber types.
Diet has a significant effect in humans on muscle car- nosine concentrations. Muscle carnosine concentrations in omnivo