When it comes to all things training, there is no lifer or competitor I know (myself included) or have trained with who has not engaged in some pre-workout stimulant or supplement routine. Let’s face it: it’s simply ubiquitous when it comes to lifting. A large number of sport supplements are marketed and even targeted to athletes, claiming to enhance muscular strength, power, hypertrophy, and even body composition. But more specifically, the major advantages of pre-workout stimulants and supplements include increased energy and focus, enhanced upper body or lower body strength, weight loss, and fat burning capabilities. It’s noteworthy to mention that there are drawbacks to some stimulants, which include ventricular tachycardia (rapid heartbeat), increased blood pressure, adrenal overload, nausea, and perhaps even vomiting. Anyone who has ever flipped through any of the top fitness magazines has seen a multitude of claims, tag lines, and hyperbole ranging from:

  • 3000% better than Creatine
  • Ripped in 30
  • Amazing Pumps
  • NO-Explode
  • Add two inches to your guns in SIX weeks
  • Ignite Yourself
  • Jacked-3D

This article (Part 1) will focus on some of the most common stimulants and supplements that everyone has been exposed to in some form or fashion. Many of these are supported by the prevailing scientific literature and thus improve exercise and sports performance, and most appear to be safe when ingested for short periods of time by healthy people.

Several of these products claim to enhance performance by delivering more mental focus, energy, endurance, strength, and improving blood flow. However, the question is, “what do they actually do, and how do they work? Are there risks and/or benefits?” Let’s examine this more thoroughly.

What are Stimulants?

The fact of the matter is that most of these stimulants and supplements are centered around caffeine—ranging from the low end of 100mg to 400mg on the high end (in a serving). By pure definition, a stimulant works deliberately to increase the functioning of the central nervous system. The basic physiology of the nervous system works in a hierarchical fashion. It means that stimulants “arouse” the central nervous system directly or indirectly by exciting the lower segments, specifically the sympathetic system. As you might have guessed, this is why stimulants are often termed “sympathomimetics.” Stimulants are widely used by individuals to promote alertness, reduce fatigue, and to prolong physical work (i.e. training). The effect of the stimulant is largely due to the individual’s mental state, dosage, and potency. All stimulants increase blood pressure, heart rate, and body temperature. The body temperature is elevated by the increase in muscle and core temperature and vasoconstriction. This results in an elevated heart rate response and blood pressure via the catecholamine response (i.e. adrenaline). So, considering that many of these stimulants and supplements are based on caffeine, we’ll start with this first.


Make no mistake, caffeine is a powerful (1,3,7-trimethylxanthine) and the most widely consumed drug in the world (which is commonly consumed in coffee, tea, soda, and energy drinks). Its ability to increase muscular work has been evident since the early 1900s. It has also been used since the Stone Age (Escohotado 1999), and its ability to enhance muscular work was first recognized over 100 years ago (Rivers 1907).

Upon ingestion, caffeine is rapidly absorbed and increases in plasma concentrations, generally observed between 30 to 60 minutes following ingestion (Goldstein 2010). Early work reported that the variability in absorption time is dependent on the physicochemical formulation properties of the product dose (Bonati 1982). Caffeine exhibits a strong cardiovascular effect that stimulates an increase in epinephrine (adrenaline) output to a greater extent when ingested via its anhydrous formulation when compared to an equal amount of brewed or instant caffeinated coffee (McLellan 2004).

Goldstein et al (2010) summarized many of the effects of caffeine on exercise performance as follows:

  1. Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg/kg/BM) and overall does not result in further enhancement in performance when consumed in higher dosages (≥ 9 mg/kg/BM).
  2. Caffeine exerts a greater ergogenic effect when consumed in an anhydrous state as compared to coffee.
  3. Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration.
  4. Caffeine is ergogenic for sustained maximal endurance exercise and has been shown to be highly effective for time-trial performance.
  5. The literature is equivocal when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted.
  6. The overall scientific literature does not support caffeine-induced diuresis during exercise, or any harmful change in fluid balance that would negatively impact performance.
  7. It has been shown that caffeine can enhance vigilance during bouts of extended exhaustive exercise, as well as periods of sustained sleep deprivation.

A significant increase in maximal bench press strength has been observed in resistance-trained women after caffeine ingestion (Goldstein 2010). Astorino (2011) reported increases in training volume after acute caffeine consumption in the first two sets of performing the leg press to exhaustion, and knee extension/flexion (Astorino 2010), while Duncan (2011) reported an increase in bench press to exhaustion at 60% of 1RM. However, Hendrix (2011) found no changes in 1RM in the bench press and leg extension exercises in untrained males after consumption of 400 mg of caffeine.

 Ammonia Inhalants

This stimulant is undoubtedly the most popular amongst powerlifters, strongman, and strength and power athletes, in addition to other sports such as boxing, football, mixed martial arts, and hockey. The use is well known by athletes by temporarily increasing athletic performance during training or competition (McCrory 2006). This practice among various athletes is used as a way to ‘‘psych up,’’ and most frequently is used for their purported benefit of enhancing muscular strength for short periods of time.

Most commonly referred to as “smelling” or “sniffing” salts, the main and active ingredient for this stimulant is Ammonia Carbonate.  It is most notable for its use, prevention, and treatment of dizziness and fainting, Ammonium carbonate is described as a respiratory stimulant that elicits its powerful physiological effect when inhaled or sniffed. McCrory (2006) reported that when inhaled, it causes a rapid and extreme irritation of the lungs, nose, and mucus membranes of the nasal cavity. This results in a simultaneous and rapid inhalation reflex that produces involuntary inhalation. This reflex then stimulates the muscles that regulate breathing, which increases breathing and stimulates a higher degree of consciousness.

One would think that the prevalence of AI use amongst athletes would create the need for more scientific literature; however, scientific literature examining the use of AI amongst athletes is virtually nonexistent, and there is currently no research investigating the prevalence of AI use amongst athletes. Nonetheless, the scope of use of AIs is primarily due to anecdotal reports and observation via popularity and extent of use. The primary time of use among athletes is immediately before or during competition. During training, AI use is often before or during high-intensity resistance training, usually seen before 1RM attempts such as the squat, bench press, and deadlift.

Although the use of all stimulants do and can pose some risk and side effects, particularly when used frequently or over long periods of time, AIs are generally considered safe for their specific use in treating fainting,or dizziness. Yet, to date there is no evidence on their safety or performance advantage when used by athletes during training or competition. It’s worth mentioning that a very early study by Herrick (1983) reported a case of anaphylaxis in a female powerlifter as a result of AI use. In this specific case, the athlete experienced an acute case of anaphylaxis during a competition after the inhalation of an AI.  As the lifter was preparing for an attempt at a national powerlifting record, the lifter inhaled the contents of an AI and immediately began suffering worsening signs and symptoms of anaphylaxis. One noteworthy aspect to mention is that the regular use of AIs, combined with their psychological effects, may influence athletes to attempt a lift at an intensity at which they may not be able to complete, thus increasing the risk of injury. However, no such evidence exists, and more importantly, competitors and lifters should always know what they are capable of doing and their limitations. Although more research is needed with this particular stimulant, the use of AIs certainly does give athletes an advantage.



Yohimbine is the active chemical found in yohimbe bark. Yohimbe bark contains approximately six percent yohimbine, but it’s also available in its synthetic form—yohimbine hydrochloride (HCl). Yohimbine has been investigated mainly for its effect on fat loss and sexual desire. Despite the numerous physiological interactions and effects of yohimbine, we’ll concentrate on more of the performance aspects. The primary and most researched mechanism of yohimbine is antagonism (inactivation) of the Alpha-2 (A2) Adrenergic receptors. This means that by blocking A2-adrenergic receptors, yohimbine prevents a negative feedback mechanism that blocks norepinephrine (adrenaline) release, yielding higher norepinephrine levels.

It’s best known for its effects on fat loss, in that it acts upon the adrenergic receptors of fat cells (which regulate thermogenesis). Yohimbine itself can potentially induce fat loss through the release of adrenaline, and adrenaline itself is an activator of beta-adrenergic receptors (Reiner 2010). However, this increase of adrenaline likely fades within a two-week period and thus loses its effectiveness (Galitzsky 1990). Interestingly though, in the U.S. yohimbine is completely legal for use in dietary supplements. Yet, nearly every major manufacturer has stopped using it in its formulas due to liability risks and related insurance concerns.

One study (Ostojic 2006) examined the effects of yohimbine supplementation on body composition and exercise performance in professional soccer players. The athletes (20 top-level male soccer players) were allocated to two randomly assigned trials. Subjects in the yohimbine group orally ingested tablets that contained yohimbine at a dose of 20 milligrams per day in two equal doses for 21 days. Subjects in the placebo group ingested an equal number of identical-looking pills that contained cellulose. There were no statistically significant changes in body mass and muscle mass within or between trials after the supplementation protocol. Percentage of body fat significantly decreased in the yohimbine group after the supplementation protocol, and fat mass was significantly lower in the yohimbine versus placebo trial at the post-supplementation assessment (7.1 ± 2.2 vs. 9.2 ± 1.9%). However, there were no changes in exercise performance indicators with bench and leg press, vertical jump, dribble and power test results, shuttle run within or between trials, and no participants reported any side effects from yohimbine. These results indicate that supplementation with yohimbine combined with resistance training does not significantly alter the body mass, muscle mass, or performance indicators in professional soccer players. However, yohimbine supplementation appears to be a modest fat loss strategy in elite athletes.


Dietary supplements containing L-arginine continue to be a popular ergogenic aid proposed to enhance strength, power, and muscle recovery when linked with both aerobic and resistance training (via providing a “pump”). L-arginine is a semi-essential amino acid, which becomes an essential amino acid in special conditions such as catabolic stress, child growth, and intestinal and kidney dysfunction (Morris 2006). Despite the numerous physiological interactions and effects of L-Arginine, we’ll concentrate on more of the performance aspects.

L-arginine’s conversion into L-ornithine and urea by arginase is essential in order to eliminate toxic nitrogen compounds. Furthermore, L-arginine is important for the production of Nitric Oxide (NO), a potent vasodilator that acts by resulting in the relaxation of smooth muscle and vasodilation.

Arginine is commonly used as a pre-workout supplement, claiming to increase muscular blood flow and protein synthesis by converting into Nitric Oxide (NO) and L-Citrulline. Here’s the deal, although muscle blood flow and protein synthesis are increased with nitric oxide, arginine very unreliably increases nitric oxide. There is a term called the “’arginine paradox,’ which refers to specific situations in which L-arginine supplementation appears to stimulate no activity, even when endogenous levels are found in a physiological range. However, the majority of the research regarding L-arginine supplementation has been done with aerobic exercise in order to evaluate its alleged effects on performance.

With regard to resistance, Santos et al (2002) observed increased resistance capacity to muscular fatigue from an isokinetic dynamometer (15 repetitions of concentric knee flexion/extension at 180 degrees/s) after 15 days of oral supplementation with arginine aspartate (3g/day). Fricke et al (2008) reported no significant difference in maximal isometric grip force using a hand dynamometer as well as jump height (cm), peak jump power, and peak jump force performed on a force plate after six months of L-arginine HCl supplementation (18 g) in post-menopausal women. Peak jump force relative to bodyweight was the only variable that showed a significant increase in the L-arginine group (although it was of relatively no importance compared to other performance variables).

Furthermore, in regards to those studies that assess blood flow or pressure during exercise, there are either no significant differences (Fahs 2009) or only a reduction in blood pressure (Bailey 2010). In acute studies, where taking a single dose of L-arginine prior to exercise, 3g of arginine have failed to benefit resistance training (Wax 2012).

Overall, a lack of evidence shows the need to develop acute and chronic studies to assess the underlying mechanism(s) that may be stimulated by L-arginine supplementation linked with exercise (especially with heavy strength training) and changes in blood volume and blood flow. (NO production and strength performance variables). In addition, enhanced nitric oxide production during exercise does appear to occur with L-arginine supplementation, although it is not 100% consistent. Most importantly, it should not be assumed that the positive outcomes on exercise performance (acute or chronic, aerobic or anaerobic) were due to greater NO production via L-arginine supplementation, considering none of the reports explored any underlying mechanisms.

Stayed tune for Part 2!


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