Caffeine

Caffeine is a plant alkaloid substance that primarily works by creating actions in the central nervous system. It’s a very well-researched ergogenic aid that reduces symptoms of both physical and mental fatigue and has both stimulatory and psychological effects.

At normal doses, caffeine’s benefit is most likely due to its action as a nonspecific adenosine antagonist in the nervous system by blocking effects of adenosine and increasing transmission of excitatory neurotransmitters such as dopamine. Effects of caffeine ingestion include increased arousal, perceived energy (mental and physical), reduced sense of effort or fatigue during mental or physical tasks, improved cognition, and increased motor drive from the central nervous system to the muscles. Fat lipolysis, metabolic rate, and 24-hour energy expenditure may also be increased after caffeine ingestion. The half-life of caffeine in the body is approximately 5 to 7 hours. Moderate caffeine intake (~3 mg/kg/d) is generally recognized as safe and doses of up to ~6 mg/kg have been shown to improve physical performance. Some individuals, however, may sense jitteriness or perceive other such negative effects near 3 mg/kg.

Find the caffeine content in popular caffeinated beverages in the table below:

Beverage and Typical Caffeine Content (mg)

8 oz drip coffee: 65–180 mg depending on brew method, beans, and grind

1 oz espresso coffee: 30–50 mg

8 oz energy drink: ~80 mg

8 oz decaffeinated coffee: 2.5 mg

How Does Caffeine Benefit Endurance Performance?

Caffeine’s benefit to endurance performance largely relates to caffeine’s ability to:

• decrease perception of effort during exercise

• increase motivation and perceived energy

• increased motor drive

Caffeine also benefits more powerful, explosive movements, likely by increasing peak force production and the rate of force production in the larger lower body muscles. It’s recommended to ingest caffeine (in coffee or another form) approximately 45 minutes prior to exercise in order to attain maximum benefit from the supplement.

Should you be taking beetroot juice?

Beetroot juice (BRJ) is often ingested by athletes for its purported benefits on improving exercise capacity and exercise performance through conversion into nitric oxide (NO). NO is active in physiological mechanisms such as vasodilation, immune function, neurotransmission, mitochondrial respiration and skeletal muscle contraction. Dietary nitrate supplementation has been associated with reduced blood pressure, improved muscular contractile function, improved exercise economy, exercise tolerance and cognitive function (Jones et al. 2021). The reduction pathway of nitrate-nitrite-NO is particularly active under conditions when oxygen is limiting, suggesting it may benefit high intensity exercise and possibly performance in high altitude environments.

When dietary nitrate is ingested, the bacteria present in the mouth begins the process of reducing nitrate to nitrite which then increases circulating levels of nitrite which can ultimately be reduced to NO in the circulation and other tissues. Athletes who maintain a diet rich in leafy green vegetables and beets would ingest some amount of dietary nitrate through these food sources. However, many athletes also choose to supplement with BRJ as it can deliver a higher, measurable concentration of nitrate in an easy-to-ingest supplement that can be timed appropriately prior to training or competition. An individual’s ability to benefit from dietary nitrate is dependent on the health of the oral microbiota; and, use of antibacterial mouthwash can also inhibit the reduction of nitrate to nitrite. The composition of the oral microbiome appears to differ between women and men suggesting women may benefit less from nitrate supplementation (Wickham et al. 2019). Interestingly, compared to a high carbohydrate diet, a low-carbohydrate high fat diet also alters the composition of the oral microbiome (Murtaza et al. 2019), suggesting dietary strategies of athletes can also influence the efficacy of nitrate supplementation.

While it has been suggested that dietary nitrate supplementation may have an ergogenic effect, the mechanisms that may improve markers related to endurance exercise appear to be more prevalent in recreational athletes versus in highly trained (Senefeld et al. 2020) but it is possible that highly trained athletes may observe a benefit of supplementation on high intensity performance (Jones et al. 2018). It is not clear why elite athletes may not benefit from supplementation compared to their less trained counterparts, but possible reasons may include elite athletes already having high baseline concentrations of nitrate and nitrite and diets that are habitually high in dietary nitrate. Likewise, women do not appear to benefit from supplementation compared to males, possibly due to higher baseline nitrite levels and the oral microbiome; however, studies in women are extremely limited in the literature (Wickham and Spriet 2019). However, the ergogenic effects of dietary nitrate appear to be highly individual and complex. Recommended dose of BRJ supplementation is suggested to be >300 mg (5 mmol) or higher up to 25 mmol (Senefeld et al. 2020) for trained athletes, ingested at least 90 minutes up to 3.5 h (Jones et al. 2021, Senefeld et al. 2020) prior to exercise. Both acute and multi-day supplementation protocols may be effective (Senefeld et al. 2020).

Though NO has a very short half life in the body, it remains possible that NO can be oxidized back into nitrate and nitrite. If a high level of nitrate supplementation is regularly ingested, there may be associated health risk factors including the formation of carcinogenic nitrosamides and nitrosamines (Zamani et al. 2020). The risks of BRJ are not well studied in the literature but warrant investigation to ensure the safety as an ergogenic aid. Interestingly, Gallardo and Coggan (2019) investigated the nitrate and nitrite content of 45 commercially available BRJ supplements and found that only five of the supplements contained at least 5 mmol nitrate per serving with a moderate-large variability between samples of the same product and large variability between products. Not only are the supplements unregulated, most products do not indicate nitrate content on the label and very rarely are the supplements independently tested to ensure content accuracy.

Should you be taking BCAAs?

BCAAs (branched chain amino acids), leucine, isoleucine, and valine, are three of the nine essential amino acids (EAAs), meaning our body cannot synthesize them, so we must consume them in our diet. BCAAs are present in complete protein sources such as animal proteins (eggs, dairy, poultry, meat, fish) as well as in soy. Many sports nutrition foods and protein powders have added BCAAs and whey and soy protein powders provide all the EAAs including BCAAs.  

BCAAs are unique in that they are the only amino acids that the muscle can directly take up and utilize for energy. As glycogen depletes leucine oxidation increases; however, the amount of BCAA oxidation is still generally small during prolonged endurance exercise (>90 min), compared to carbohydrate and fat. BCAAs are also important for triggering the anabolic process of muscle protein synthesis (MPS), although leucine appears to be the primary driver for this. Finally, BCAAs have been suggested to counteract aspects of “central fatigue”. 

Like all amino acids, BCAAs flux in and out of the body’s amino acid pool and are used by the body as needed based on the relative demand. Provided an athlete is ingesting adequate protein in their diet and eating high-quality proteins that provide all EAAs, there should be a sufficient amount of BCAAs available in the AA pool for the body to use when needed. In theory, supplementing with BCAA during endurance efforts could support BCAA oxidation, possibly delaying fatigue and improving performance or exercise capacity. However, there is a lack of evidence to suggest that BCAA supplementation actually improves performance. If an athlete is not able to regularly meet protein needs through the regular diet, it is possible that supplementing with BCAAs or with protein and carbohydrate during exercise could be beneficial, especially if the athlete is not meeting during-exercise carbohydrate needs. 

Regarding MPS and recovery, leucine is the primary driver of the anabolic response. Likewise, if an athlete is ingesting sufficient protein in the regular diet with adequate leucine, BCAA supplementation is likely not necessary. Research examining the effect of BCAA supplementation compared to a placebo does indicate elevated markers with respect to MPS response, but when compared to a complete protein like whey, BCAAs do not appear to perform better.

Factors related to central fatigue during prolonged exercise are complex and it has been suggested that exercise-induced increases in serotonin may contribute to sensations of fatigue. In theory, it might be expected that BCAA ingestion can blunt the increase in serotonin, thereby decreasing fatigue factors. However, research has been inconclusive in this area and fatigue remains a complex phenomenon. 

If you regularly fall short on your protein intake, it would be worth trying supplementation with a complete protein supplement that is high in EAAs and BCAAs like whey. There may be days when you do very long training sessions (or ultra-distance races) and it’s not possible to ingest all your daily protein in regular meals. In this case, you may consider trying a BCAA supplement during exercise and then ingest a high-quality recovery drink and meal ASAP post-exercise. Again, the response to BCAA supplementation is generally equivocal in the literature but you may find that it works for you. 

A BCAA supplement may contain ~1.7-3.5 g leucine per serving. For reference, 20-25 grams of whey protein would also provide the recommended amount of leucine.
Taking current evidence into consideration, it makes sense to 

• Hit your daily protein target by choosing complete protein sources and complementary plant protein sources as often as possible. Both quantity and quality matter! 

• Eat a mixed meal (carbohydrates with some protein) prior to training 

• Take in the recommended amount of carbohydrate per hour (as best you can)

• Try adding BCAA or protein+carb if you cannot meet your during-exercise carb needs (e.g. during ultra-endurance activity) 

• Consider additional strategies to help performance, for example there is strong evidence that caffeine combined with carbohydrate may improve performance and counteract central and peripheral fatigue factors. However, if you feel like BCAAs provide a benefit to you as well, the psychological edge may be worth it. 

PMID: 22150425, 33106933, 18577773, 24791922, 30854370