In the final part of this series, part 3, we’ll finish discussing 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.

Many of these stimulants and supplements claim to enhance performance during training to deliver more mental focus, energy, endurance, strength, and fat loss. However, the question is, what do they actually do and how do they work? Are there risks and/or benefits? Let’s check it out.


L-carnitine is one of the most common nutrients found in a wide variety of weight loss products and supplements. It’s an amino acid composite that is made from lysine and methionine. Carnitine is synthesized in the liver and kidney, and approximately 98 percent of the carnitine of the human body is present in skeletal and heart muscle.

Carnitine functions as an important transporter of fatty acids into the mitochondria of the cell (Kraemer 2008). It’s important to realize that in the overnight, or fasted state, and during exercise of low to moderate intensity, fatty acids are the main source of fuel used by the body, including skeletal muscle. In theory, increased cell concentration of carnitine increases the transport of fats and thus enhances the use of more fat as fuel. L-carnitine is actually highly prevalent in large quantities in meat and has gained more popularity over the last several decades. The principle claim of carnitine is that it enhances fat metabolism, decreases fat mass, and increases muscle mass. Considering this, carnitine is often used to lose weight or reduce body fat.

Here’s the deal—carnitine’s role in weight loss is based on the assumption that regular oral ingestion of carnitine increases muscle carnitine concentration. A second assumption is that if muscle carnitine levels increase, fat oxidation also improves, resulting in a steady loss of body fat. However, two early studies that were more tightly controlled (Barnett 1994, Vukovick 1994) reported that oral carnitine ingestion (up to 6 grams/day for fourteen days) doesn’t change the muscle carnitine concentration. More recent evidence also reports that the overwhelming conclusions of l-carnitine shows that it does not affect muscle carnitine content (Smith 2008), fat metabolism, aerobic or anaerobic exercise performance, and/ or weight loss in overweight or trained people (Villani 2000, Brass 2000).

In terms of power output, results are a bit mixed. Overall, science suggests that l-carnitine supplementation in all its forms does not increase acute power output when ingested once before exercise (3 grams/day for eight weeks in middle aged men and women) (Smith 2008). In addition markers of physical performance (i.e. strength, power, get up and go) were not affected when ingesting 3 days/week for three weeks (Ho 2010).

However, one study noted slight increases in sprint power and increased work capacity, possibly derived from decreased lactate build-up following 4.5 grams once before exercise (Jacobs 2009). A similar report showed that over a supplementation period of 28 days, there was increased power during sprints from ingesting 1.5 grams whereas 3–4.5 grams reduced power output for cycle spring performance (Jacobs 2010).

Regarding performance outcomes, Wall and colleagues (2011) gave a placebo or a supplement of carnitine tartrate and carbs (2 grams carnitine with 80 grams of carbs twice a day) to trained endurance athletes training for a triathlon three to five times a week. Throughout the study, participants did two, thirty-minute repeated bouts of exercise (the first at fifty percent V02 max and the second at eighty percent), followed by an all-out thirty-minute performance trial. After 24 weeks of supplementation, the carnitine group increased performance from baseline by eleven percent in the exercise trials while the control group showed no change. Participants who took carnitine also reported (rating of perceived exertion) the eighty percent V02 max to be easier compared to baseline while the placebo had no difference in rating of perceived exertion.

Now, let’s clarify something. It takes a long supplementation period to increase muscle carnitine levels and thus gain any benefits. From this study, after three months, there weren’t any changes in performance or rate of perceived exertion from baseline, but after six months, those improvements were noticeable.

Also, one interesting aspect is that carnitine doesn’t “load” in muscle unless complemented by high insulin concentrations (i.e. carbs). This means it’s possible that carnitine may be increased and may have some effects on fat metabolism after several months in combination with a large amount of carbs. However, it is too early to make any solid conclusions.

Nonetheless, if you think about it, for weight loss/fat loss reasons, it seems counterproductive to devour large amounts of carbs in efforts to increase insulin to make sure that carnitine levels only modestly increase and thus merely result in small increases in fat oxidation in the long run. It may be that athletes who have large energy expenditures anyway and consume carnitine with their meals or energy drinks could increase muscle carnitine levels. Despite these speculations, the practical implications are not currently known. For now, there isn’t enough supportive evidence to recommend carnitine for weight loss or to increase fat oxidation.


There’s no doubt that everyone knows about ephedrine (also known as Ma Huang). It is one of the four active components of the herb ephedra and is known within the class of thermogenics, which are designed to stimulate metabolism, increasing energy expenditure and promoting weight loss. Ephedrine is thoroughly studied and a fairly reliable compound. Early reports indicate that the principle mechanism of ephedrine has a direct impact of β-adrenergic receptors of fat tissue, leading to increased thermogenesis (Bukowiecki 1982). An interesting fact, it appears that ephedrine, in and of itself, enhances metabolic rate via resting energy expenditure (REE) independent of exercise. This is contrary to caffeine, which actually requires exercise to induce its fat burning effects to meaningful levels. Further, most people are aware that ephedrine is highly synergistic with caffeine and, for this reason, it’s commonly found in an ECA stack (ephedrine, caffeine, and aspirin).

As most people know, the FDA now bans ephedra. The reason behind this has been based on previous reports of unfavorable effects. In the media, a link between intake of ephedra and numerous severe medical complications has been implied (i.e. high blood pressure, increased heart rate, arrhythmias, sudden death, and heat stroke) (Fleming 2000, Bent 2003).

A wealth of published studies have investigated the safety and efficacy of ephedra/caffeine and ECA type supplements. Many have confirmed that the use of synthetic or herbal sources of ephedrine and caffeine stimulate about two pounds of extra weight loss per month while dieting (with or without exercise) and that ephedra/caffeine supplementation is generally well tolerated in healthy individuals (Greenway 1999, 2000, 2001, 2004; Boozer 2001, 2002; Coffey 2004). A study by Boozer and colleagues (2001) reported that eight weeks of ephedrine (72 mg/day) and caffeine (240 mg/day) supplementation resulted in a nine-pound loss in body mass and a 2.1 percent loss in body fat with minimal side effects. An investigation by Hackman (2006) reported that a nine-month clinical trial employing a multi-nutrient supplement containing 40 mg/day of ephedra alkaloids and 100mg/day of caffeine resulted in weight loss and decreased body fat and improved metabolic markers such as insulin sensitivity without any obvious side effects. Further, another study by Boozer and associates (2002) reported that six months of herbal ephedra/caffeine supplementation resulted in weight loss without any clinically significant side effects in healthy overweight adults.

In terms of performance, nine healthy, resistance trained men ingested 300 mg of caffeine with 60 mg of ephedra sixty and 150 minutes before one rep max bench press and lat pull-down tests. Subjects reported that despite increased attitude and alertness during training, there weren’t any significant differences in strength when compared to 300 mg of a glucose placebo. In another study by Jacobs (2003), subjects were given a higher dose of ephedrine (0.8mg/kg ninety minutes before leg press/bench press supersets to failure) and reported three more reps on the leg press associated with ephedrine versus the placebo (sixteen over thirteen). When combined with caffeine, this was increased to six reps (nineteen over sixteen) with less improvement (one and two extra reps with the bench press). The authors stated that fatigue during supersets may have played a role, but these results were only significant during the first superset test when using a two-minute rest interval.

Sodium bicarbonate

Sodium bicarbonate (also referred to as baking soda) isn’t usually the “go to” supplement to increase performance, and it typically isn’t on the top of the list for those wanting to improve exercise capacity. However, this substance was first reported in literature in the 1930s (Denning 1931) and has been used since the 1970s. The principle mechanism of action of sodium bicarbonate is reducing the effects of acidosis. Simply, acidosis refers to an increase in acidity (usually from very high intensity exercise). By ingesting sodium bicarbonate, acidosis can ideally be decreased and is thought to prolong muscle oxygen capacity. Peart (2012) summarizes that during high intensity exercise, acid (H+) and carbon dioxide (C02) accumulate in the muscle and blood. A method for removing the acidity and C02 is to ingest bicarbonate as the acid. C02 is then removed from the lungs.

Typically, the standard doses (200–500 mg/kg) appear to benefit performance prior to short power exercises and upon exercise-induced acidosis. Benefits can be achieved with a single dose sixty to ninety minutes before exercise. However, bicarbonate supplementation should be used carefully as its use has been associated with gastrointestinal side effects (Cameron 2010) if a large dose is taken at once or if it’s consumed too quickly. Previous reports indicate that bicarbonate loading taken sixty to ninety minutes prior to exercise (or 5 grams taken twice per day for five days) has been shown to be an effective way to buffer acidity during high intensity exercise lasting one to three minutes in duration (Kraemer 1995, McLaughton 1999). This is likely to improve exercise performance in events like the 400- or 800-meter run or the 100- or 200-meter swim. Lingh (2008) concluded that sodium bicarbonate supplementation improved 200-meter freestyle performance time in elite male competitors, most likely by increasing buffering capacity.

There are a wide variety of supportive findings with sodium bicarbonate. Some have reported no benefit. Sodium bicarbonate supplementation of 300 mg/kg (in 500mL Powerade) 65 minutes prior to sprint testing in elite rugby players failed to improve performance despite increasing bicarbonate (Cameron 2010). Other studies have reported that 300 mg/kg sodium bicarbonate also failed to benefit five repeated sprints of 24 seconds (Prince 2010) but benefited high intensity thirty-second sprint performance in healthy men (Siegler 2010).

In a similar study by Siegler (2010), competitive, non-elite swimmers were given 300 mg/kg sodium bicarbonate prior to swim testing and reported a two percent increase in performance (by swim times on eight, 25-meter front crawls with five seconds of rest in between each crawl) associated with bicarbonate versus the placebo. Another study assessed elite athletes in 56,10-meter sprints in a simulated water polo game and reported no benefit associated with supplementation ninety minutes prior (Tan 2010).

With resistance training (which is what most of us really care about), there are limited findings. One study had subjects perform leg presses (four sets of twelve with a set to failure) and preloaded with 300 mg/kg sodium bicarbonate 105 minutes before activity. Results indicated that increases in lactate and pH occurred, but bicarbonate ingestion didn’t improve performance (Portington 1998) A similarly study also failed to find a significant benefit associated with supplementation (Webster 1993). Therefore, these two studies failed to find a benefit associated with sodium bicarbonate ingestion and resistance training as a pre-workout tool.

Based on the science, although mixed results are present, sodium bicarbonate can be an effective pre-workout supplement, but it should be taken up to an hour before exercise. If taken closer to training time, there is an increased risk of gastrointestinal distress. It also seems unlikely that ingesting sodium bicarbonate would be beneficial to single bout exercise because its benefits come from acid-based recovery between bouts or repeated high intensity efforts. The dosage range of 200–300 mg/kg is probably best for usage prior to exercise, with lower doses likely to reduce stomach discomfort.

Bottom line

Many of these stimulants and supplements discussed in parts one through three of this article series are/may be banned in significant doses for competitions by organizations including the USOC and the NCAA. For those individuals competing within these organizations or even others, it is encouraged that the individual cross-reference all the ingredients with a banned substance list in the chosen sport. For example, caffeine is banned in certain doses. Therefore, it is recommended that the substance be cleared with the specific organization. Further, often times athletes take or consume products fairly regularly and over time may become immune or desensitized to them, particularly caffeine and even everyone’s favorite “ammonia salts or caps”. I get it though—many times you need some “stimulants” for a long and heavy strength training session to offset the mental fatigue that often accompanies the stress response. Also, it’s always a good idea to cycle on and off of these products. Usually, this will help counteract many of the potential side effects of these pre-workout stimulants and supplements.


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