Fuel:One 6th Gear Review

Fuel:One 6th Gear

6th Gear is a pre-workout by Fuel:One, yet another MuscleTech brand, that is contains both pump-enhancing ingredients as well as a simple, yet potentially effective stimulant blend of Caffeine and Higenamine…


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6th Gear is a pre-workout by Fuel:One, yet another MuscleTech brand, that is contains both pump-enhancing ingredients as well as a simple, yet potentially effective stimulant blend of Caffeine and Higenamine…[Skip to the Bottom Line]


Beta-Alanine is the rate limiting amino acid in the synthesis of the dipeptide, Carnosine, which acts as a lactic acid buffer in muscle tissue.  Reducing the build-up of lactic acid can directly enhance muscular endurance, and this has been demonstrated throughout multiple studies in both athletes and non-athletes alike.

A 2002 study from the “Japanese Journal of Physiology” which measured the Carnosine levels of sprinters found that individuals with higher muscular Carnosine levels exhibited higher power outputin the latter half of a 30m sprint (due to less lactic acid build-up).

Multiple studies have confirmed that Beta Alanine supplementation increases muscular Carnosine in a dose dependent manner. In particular, a 2012 study published in “Amino Acids” found that subjects who consumed 1.6 or 3.2 grams of Beta Alanine daily experienced significant increases in muscle Carnosine in as little as two weeks, with the higher dose achieving a higher concentration of Carnosine.

6th Gear contains 1.6mg of Beta-Alanine, the lowest dose that can still be considered “clinical” but that’s assuming daily supplementation. Ideally we’d like to see a little more, but Fuel:One isn’t under-dosing Beta-Alanine.


Arginine Nitrate and Citrulline Nitrate are simply simply the amino acids Arginine and Citrulline bonded with Nitric Acid (Nitrate). There is no evidence that either of these compounds are superior to their individual components, nor is there any reason to suspect that would be the case.

Arginine Nitrate and Citrulline Nitrate provide Nitrates, but don’t provide enough Arginine or Citrulline to be particularly effective. So, in the context of 6th Gear, these ingredients function the same as Beetroot Extract.

Beetroot Extract is the most common Nitrate source we see in pre-workout supplements, as Beets (in whatever form) have been the most extensively studied Nitrate source with regards to exercise performance.  We discuss Nitrates further in this article, but basically the effective range is 300-600mg. 6th Gear contains 320mg which is within that range and therefore moderately effective.


In the past few years, Agmatine has gone from a rare ingredient to a pre-workout staple, though it remains seriously under-researched relative to other popular pre-workout ingredients. Agmatine has been demonstrated to up-regulate Endothelial Nitric Oxide (eNOS), sometimes referred to as the “good” NOS, while inhibiting the other NOS enzymes (the “bad” NOS) in vitro, but human studies are non-existent.

Still, anecdotal reports of Agmatine improving the “pump” are as pervasive as the ingredient itself at this point, so there is something to it.

The effective range (again, based on anecdotal reports) is 500-1500mg. Based on that range, Fuel:One has severely under-dosed the Agmatine in 6th Gear. It is listed last in a 301mg proprietary blend which it shares with Caffeine (150mg) and Lotus (unknown amount), so it can be no more than 100mg. Not an effective dose.


Caffeine triggers the release of Catcholamines (Noradrenaline, Dopamine, Adrenaline, etc.), generally inducing a state of alertness and increased focus.

Caffeine also directly enhances calcium-ion release in muscle tissue, which directly increases muscle contraction force. Rather than discuss dozens of studies, we’ll leave it at this: Caffeine is an effective performance enhancer (and mental stimulator), but a tolerance is generally built-up with continuous use.

Fuel:One lists the amount of Caffeine in 6th Gear at 150mg per serving, not a particularly high dose, but one that may be effective in individuals with a low stimulant tolerance.


Nelumbo Nucifera (Fuel:One refers to it as Lotus), is a flowering plant which has been shown to have anti-obesity effects in mice. The fat-loss benefits are mostly attributed to the Higenamine, although there are other compounds which may potentiate these effects. Higenamine is a Beta(2) Adrenergic Agonist (same mechanism as Ephedra), meaning it stimulates the Beta(2) Adrenergic Receptors which initiate fat-burning.

Higenamine has also been shown to stimulate Acetylcholine release in mice, but there has been no further investigation in human subjects.

Fuel:One discloses that this particular Lotus extract contains 1% Higenamine, but the total amount of Lotus is unknown. We’d estimate 6th Gear contains about 10mg of Higenamine per serving.


6th Gear contains technically effective doses of Beta-Alanine and Nitrates, but Agmatine is no doubt under-dosed, so the pump aspect is not particularly special. The combination of Caffeine and Higenamine may provide some enhances focus and energy, but those who consume Caffeine regularly may need two servings of 6th Gear to feel it. At about $1 per serving, 6th Gear isn’t necessarily a bargain, but isn’t too over-priced either.  There are better options out there though, that’s for sure.


[expand title=”REFERENCES” tag=”h5″]

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