Royal Sport Castle Review

Castle is a pre-workout by Royal Sport, a Cellucor brand, which is somewhat similar to C4 Mass, though with more of an emphasis on the stimulant aspect…

Royal Sport Castle



Although Maltodextrin is often criticized as a “filler” agent in supplements, in the context of Castle it actually serves a purpose.  Maltodextrin is a quickly-absorbed carbohydrate, capable of supplement the body with “real” energy, as opposed to the perceived energy brought about by Caffeine.

Creatine Monohydrate

Creatine is one of the most reliable performance enhancing ingredients available.   Creatine Monohydrate is the most common form of Creatine, mostly because it is the least expensive and no other form has ever been proven more effective, gram for gram.

Unfortunately, Royal Sport does not disclose the exact dose of Creatine present in Castle, leaving a bit of guesswork to be done.


Beta-Alanine is a precursor to the peptide Carnosine which acts as a lactic acid buffer in muscle tissue. This means higher muscle Carnosine levels can increase muscular endurance.

Beta-Alanine is considered the rate-limiting amino acid in the synthesis of Carnosine and supplementation has been shown to significantly increase muscular Carnosine levels, leading to performance enhancement.

Royal Sport doesn’t list the amount of Beta-Alanine in Castle.


Unfortunately, Royal Sport appears reluctant to leave Arginine in the past, despite a distinct lack of evidence indicating it isn’t particularly effective for enhancing performance.


Citrulline is an amino acid which serves as a precursor to Arginine, and therefore is directly involved in the production of Nitric Oxide.  Unlike supplemental Arginine, however, Citrulline is quite reliable at increasing plasma Arginine and ultimately enhancing performance.

Citrulline has been shown to increase muscular contraction efficiency, meaning less ATP is required for a given workload.  This mechanism explains why subjects who consumed Citrulline were able to perform more reps later on in the workout compared to subjects who consumed a placebo.

Additionally, Citrulline has been shown to reduce muscle soreness effectively making it both a performance enhancing ingredient as well a recovery agent.

Agmatine Sulfate

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 shown 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.

Caffeine Anhydrous

Caffeine is the most widely consumed psychoactive substance in the world, and for good reason: it works! Caffeine can enhance focus, increase perceived energy, cause greater muscle contractions, and encourage fat-oxidation, though individual tolerance tends to vary pretty considerably from person to person.


Tyrosine is a non-essential amino acid (the body can produce it from Phenylalanine) which serves aprecursor to Dopamine (by first being converted into L-Dopa) and Noradrenaline.

Because of this relationship, Tyrosine is alleged to increase levels of these neurotransmitters, which would theoretically lead to performance enhancement. However, research has demonstrated thatTyrosine cannot outright raise Dopamine or Noradrenaline levels upon ingestion, though it can help maintain optimal levels when depletion might otherwise occur.

Upon ingestion, Tyrosine forms substrate pool, which can then be drawn from when an acute stressor (exercise, cold exposure, etc.) causes a temporary depletion of Dopamine/Noradrenaline. For this reason, Tyrosine can be useful for maintaining cognitive function during stressful activity.

In the context of Castle Tyrosine simply serves as a way to maintain cognitive function during training.  We wouldn’t say it’s a particularly critical ingredient, but may contribute to the general cognitive effects of the formula.


Amla, also called Gooseberry, has a history of use as a cognitive enhancement agent, though human studies are lacking at this point.  In the context of Castle, it may contribute to the overall effect but we wouldn’t consider it a “key” ingredient.


Yohimbien is an alpha(2) receptor antagonist, meaning it inhibits the receptor responsible for blocking lipolysis (breakdown of fat). By blocking the action of this receptor Yohimbine allows for more lipolysis than would otherwise be possible from exercise.

Yohimbine may also enhance the effects of other stimulants such as Caffeine, though the degree of efficacy there really depends on individual stimulant tolerance.  It’s not clear how much Yohimbine is present in Castle.


Rauwolscine, also known as Alpha-yohimbine, is a close chemical relative of Yohimbine. In the context of OxyMax XT it has essentially the same function.

Rauwolscine is an Alpha Receptor Antagonist, meaning it blocks the receptors responsible for blocking lipolysis. By blocking these receptors, Rauwolscine is able to potentiate the effects of other stimulant fat-burners and allow more fat-burning than would normally occur from exercise alone.

The Bottom Line

Castle is different from most pre-workouts these days in that it utilizes Maltodextrin as a quick carb-source, providing “real energy” as opposed to only perceived energy (from stims).  That said, it also contains pump-inducing ingredients as well as a stim profile that is similar to other Cellucor products, though perhaps more potent than say, C4.

Still don’t know which pre-workout is right for you? Check out our Top 10 Pre-Workout Supplements list for some recommendations.

[expand title=”REFERENCES” tag=”h5″]

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  2. Stellingwerff, Trent, et al. “Effect of two β-alanine dosing protocols on muscle carnosine synthesis and washout.” Amino Acids 42.6 (2012): 2461-2472.
  3. Wilson, Jacob M., et al. “Beta-alanine supplementation improves aerobic and anaerobic indices of performance.” Strength & Conditioning Journal 32.1 (2010): 71-78
  4. Sale, Craig, Bryan Saunders, and Roger C. Harris. “Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance.” Amino acids 39.2 (2010): 321-33
  5. Suzuki, Yasuhiro, Osamu Ito, Naoki Mukai, Hideyuki Takahashi, and Kaoru Takamatsu. “High Level of Skeletal Muscle Carnosine Contributes to the Latter Half of Exercise Performance during 30-s Maximal Cycle Ergometer Sprinting.” The Japanese Journal of Physiology 52.2 (2002): 199-20
  6. Balsom, P. D., et al. “Skeletal muscle metabolism during short duration high‐intensity exercise: influence of creatine supplementation.” Acta Physiologica Scandinavica 154.3 (1995): 303-310.
  7. Giannesini, Benoît, et al. “Citrulline malate supplementation increases muscle efficiency in rat skeletal muscle.” European journal of pharmacology 667.1 (2011): 100-104.
  8. Bendahan, D., et al. “Citrulline/malate promotes aerobic energy production in human exercising muscle.” British journal of sports medicine 36.4 (2002): 282-289.
  9. Pérez-Guisado, Joaquín, and Philip M. Jakeman. “Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.” The Journal of Strength & Conditioning Research 24.5 (2010): 1215-1222.
  10. Sureda, Antoni, et al. “Effects of L-citrulline oral supplementation on polymorphonuclear neutrophils oxidative burst and nitric oxide production after exercise.” Free radical research 43.9 (2009): 828-835.
  11. Collier, S. R., Ellise Collins, and Jill A. Kanaley. “Oral arginine attenuates the growth hormone response to resistance exercise.” Journal of Applied Physiology 101.3 (2006): 848-852.
  12. Kanaley, Jill A. “Growth hormone, arginine and exercise.” Current Opinion in Clinical Nutrition & Metabolic Care 11.1 (2008): 50-54.
  13. Yeghiayan, Sylva K., et al. “Tyrosine improves behavioral and neurochemical deficits caused by cold exposure.” Physiology & behavior 72.3 (2001): 311-316
  14. Banderet, Louis E., and Harris R. Lieberman. “Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans.” Brain research bulletin 22.4 (1989): 759-762.
  15. Shurtleff, David, et al. “Tyrosine reverses a cold-induced working memory deficit in humans.” Pharmacology Biochemistry and Behavior 47.4 (1994): 935-941.

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