the powerful couple: nutrition for athletes

How beta-alanine and HMB can push you further, stronger

By Iris Saar, M.s. Applied Exercise Science candidate, ACSM CPT, RRCA

What are Ergogenic aids?

Ergogenic aids are any performance-enhancing source which has been scientifically backed by evidence-based research, preferably a placebo controlled, double blind studies. For the educated coach and athlete, selection of an ergogenic aid should be based on the category of evidence; three distinctions have been established by the International Society of Sports Medicine (ISSN): “Strong Evidence to Support Efficacy and Apparently Safe”, “Limited or Mixed Evidence to Support Efficacy” and “Little to No Evidence to Support Efficacy and/or Safety” (Kerksick et al., 2018). This critique will discuss two ergogenic aids which are legal, pertain to the first category of “strong evidence” and are of relevance to athletic performance.

β-hydroxy β-methylbutyrate (HMB)

When the branched-chain amino acid Leucine is metabolized to increase protein synthesis in the tissues, approximately 20% is left to metabolize into HMB (5% of the leucine) and the rest into another key metabolite, α-ketoisocaproate (α-KIC). Both are metabolized in the skeletal muscles (Ananieva et al., 2016). HMB is known to have a profound effect on protein synthesis; it also stabilizes the cell’s membrane during cholesterol synthesis in the mitochondria (Smith-Ryan & Antonio, 2013). As such, HMB has anabolic properties which make the substrate a positive potential aid in lean mass increases and exercise performance.

Mechanism of action- what is happening in the body

HMB operates in five main mechanisms. After leucine has metabolized, HMB targets and activates mTOR1 signaling pathways. mTOR1 is a hub regulating cell metabolism and growth (Laplante & Sabatini, 2009). mTOR1 is a highly anabolic function in the body and reduces catabolic processes. Second, HMB stimulates the synthesis of insulin-like growth factor 1 (IGF-1), which is also purely anabolic to muscle cells. This, however, requires further research and is more apparent in animal cells. Third, HMB stimulates the proliferation of muscle stem cell to a degree greater than IGF-1, which is significant. Specifically, an elevation in MyoD protein which is a marker spread of muscle cells and mostly in fast-twitch muscle cells (Kaczka et al., 2019). Fourth, HMB stabilizes the cell’s membrane, or more precisely the sarcolemma, through its availability for cholesterol synthesis which is required for muscle cells to operate (Smith-Ryan & Antonio, 2013). Fifth, HMB acts as an antagonist for protein degradation. The degradation of protein in the muscle cells has a negative effect on performance as it leads to cellular impairment and fatigue, and HMB can slow this process by binding to another specific protein called ubiquitin (Kaczka et al., 2019).

Positive effects and specific impact on performance

It is through the metabolic mechanism that HMB affect exercise performance. Due to its anti-catabolic properties, HMB can have positive effects on exercise adaptations such as muscle hypertrophy, body composition through increased fat oxidation, decreased muscle damage (especially when HMB is combined with creatine) and applications to endurance, as aerobic fitness may also be improved through those MB work mechanisms. It is important to notice that HMB might contribute more to the less-trained and older populations as it has been shown to be effective in cases of sarcopenia and rehabilitation periods, when exercise less frequent (Rawson et al., 2018). HMB may be applied more specifically to high-intensity resistance exercise as it can benefit strength outcomes related to percentage of fast-twitch muscle fibers and lean body mass.

Potential negative effects on performance

While HMB has not been noted to have negative effect on blood chemistry, its effect on documented performance is still under research. It appears that highly trained athletes might not benefit from HMB at the same rate due to their higher muscle damage requirement to elicit physiological adaptations; Safety wise, studies have shown that a dose of 6 grams a month is safe for healthy adults (Kaczka et al., 2019). Research design is varying and according to Gentles and Phillips (2017), several studies lacked consistency in placebo and control groups which were given HMB interventions as well as some troubling statistical analysis and results might be skewed. As with other supplements, athletes should consult with a physician to verify no contra indications exist and refer to the source mentioned by the ISSN, the Physician’s Desk Reference (PDR) for nutritional supplements to search for side effects (Kerksick et al., 2018).

Type of athlete to benefit from HMB

Resistance training seems to benefit from HMB supplementation, as it can increase muscle strength (although might be tissue-specific). Power lifting and body building may be a good example of such resistance training. Additionally, HMB was found to increase peak anaerobic power and therefor can be used in team sports such as volleyball and soccer (Fobar, 2014). Most studies focus on HMB in resistance training, however endurance athletes might benefit too as HMB can attenuate the muscle loss caused by and during prolonged activities (Park et al., 2013).

ß-alanine (BA)

BA is an endogenously-produced amino acid and is considered a legal ergogenic aid when supplemented orally from dietary sources. The importance of BA is in fact in its metabolized substrates, especially carnosine. When BA in ingested, it produces carnosine, together with L-histidine. Muscle performance is affected by levels of carnosine due to its buffering qualities (Kerksick et al., 2018).

Mechanism of action- what is happening in the body

When BA binds with histidine through an enzymatic operation, carnosine is formed. It can be found both in skeletal muscles, the brain and in the plasma. BA is the rate-limiting precursor for carnosine, meaning BA is the determinant of the produced carnosine levels. During exercise, muscle contractions are more frequent through active myosin-actin binding sites. Increased ATP hydrolysis leads to acidosis, a state of reduced plasma pH (Adeva-Andany et al., 2014). Carnosine, also known as the “first line of defense” is an efficient shield which acts in the cell through the buffering of accumulated hydrogen ions (H+) (Hobson et al., 2012). The rational for carnosine efficacy is that oxidative stress, or acidosis, leads to fatigue and higher levels of carnosine can increase the time to fatigue through the buffering of H+. Ergogenic dietary intake of BA has been shown to affectively increase carnosine levels; animal sources contain higher levels of BA of approximately 330 grams/day, with vegetarians presenting reduced levels of about 20%, due to the limited availability of BA in plant-based foods (Jones, 2017).

Positive effects and specific impact on performance

BA can enhance performance through the improved oxygen capacity of the muscle cells. Dose-dependent, BA positively affect exercises lasting up to four minutes (Kerksick et al., 2018). Interestingly, BA does not seem to increase force production but to increase exercise capacity through decreased time to relaxation of the muscle fibers (Hannah et al., 2015). Muscle-force ratio is positively affected by BA as shown by alpine skiers, as the sport involves explosive power (fast, reoccurring muscle contractions) and intermittent bouts, lasting less than four minutes long (Gross et al., 2014). A good example of BA is the 800’s distance, where runners showed faster race times following a 28-days BA protocol (Ducker et al., 2013).

Potential negative effects on performance

Although BA has shown to be mostly safe as an ergogenic aid, one noticeable side effect which might negatively affect performance is Paraesthesia, a tingling sensation to the skin. Dosages higher than 800 mg that are sustained may cause paraesthesia, mostly in the upper extremities and is transient (Trexler et al., 2015). While paraethesia itself might not be harmful, it can hurt performance when strategic coordination and precise movement is required, for example fencing. Another adverse effect is the competitive nature of BA with Taurine, a potential anti-oxidant acid. In animals’ tissues, BA limited taurine intake due to a shared transporter. This again can theoretically impair performance due to reduced plasma levels of anti-oxidants acids (namely, taurine). Further research is needed to study adverse effects of chronic, high-dosage BA supplementation.

Type of athlete to benefit from ß-alanine

BA can benefit high intensity efforts lasting 60-240 seconds (Ducker et al., 2013). As such, many athletes can benefit from it; the 800-1,500 run distances and repeated track sprinting, skiers (intermittent, high-intensity exercise) and possibly even prolonged exercises over 4 minutes, however to smaller degree. Interestingly, the commercial market is saturated with BA supplements for marathon runners and further education can be helpful.


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