VMI Sports KXR Stacked: More Pumps, More Brain Power, Less Buzz

VMI Sports KXR Stacked brings pumps, focus, and 200mg caffeine with MAX Catalyst absorption. Is this the smarter pre-workout you've been missing?

VMI Sports KXR Stacked is the brand's answer to a real question: what if you want the "KXR experience" but with more ergogenics and less caffeine and alpha-yohimbine along for the ride? If you've heard Tom Reilly talk about VMI's formula philosophy on the PricePlow Podcast, you know the brand doesn't chase stimulant stacks for the sake of marketing. KXR Stacked reflects that same thinking -- build something well-rounded that actually works, and let the formula speak.

KXR Stacked: VMI Sports' Other PEZ Pre-Workout

Where K-XR leans hard into high-stim energy, KXR Stacked tilts toward pumps, ergogenics, and cognitive support. Net caffeine comes in at 200mg from the same tri-source MAXed Caffeine Blend (caffeine citrate, caffeine anhydrous, and Infinergy dicaffeine malate for extended release), but the real story here is what surrounds it: 6g citrulline malate, 500mg VitaCholine, 300mg DMAE, 300mg theobromine, and MAX Catalyst branded piperine to tie it together. It's a formula that makes a compelling case for the pre-workout user who wants to feel sharp and full without feeling like they're running from something.

The PEZ Sours collaboration flavors make KXR Stacked one of the harder-looking tubs in the VMI lineup, too. If you've seen what VMI has done with PEZ across their carnitine and pump products, you know they take the flavor execution seriously.

VMI Sports KXR Stacked Ingredients

Each 1 Scoop (16.8g) serving provides the following, but we're going to start with MAX Catalyst because it touches so many of the other ingredients:

• MAX Catalyst™ (Piper nigrum Fruit Extract, 95% Piperine) - 3mg

  MAX Catalyst is UseTheMAX's structurally modified, atmospheric plasma-processed form of piperine, the bioactive alkaloid in black pepper. At 3mg per scoop, it's the smallest ingredient by mass in KXR Stacked, but it's designed to touch nearly everything else in the formula.

  How Piperine Enhances Absorption

  Piperine's bioavailability-enhancing properties trace to two primary mechanisms. First, it selectively inhibits CYP3A4, the cytochrome P450 enzyme that metabolizes an estimated 70% of consumed drugs and food ingredients during their first pass through the liver and small intestinal epithelial cells.^[1] Second, piperine impairs UDP-glucuronosyltransferase (UGT) activity in intestinal cells, slowing the glucuronidation process that "tags" compounds for urinary excretion before they reach circulation.^[2] Piperine can also slow gastric emptying and prolong intestinal transit time, giving ingredients more time for uptake.

  Standard piperine has a well-known limitation: it works well on slow-absorbing compounds like curcumin, but most supplement actives are absorbed before conventional piperine reaches the window where it can meaningfully inhibit those pathways. MAX Catalyst is built to fix this:

  What Makes MAX Catalyst Different

  UseTheMAX has structurally altered the piperine molecule and applied atmospheric plasma processing, a technique that modifies particle surface area and molecular arrangement without chemicals or enzymes. This shifts the timing of MAX Catalyst's inhibitory activity so it acts in sync with faster-absorbing ingredients, not just slow ones. The scanning electron microscope images in the MAX Catalyst technical documentation show a visibly different surface morphology compared to standard piperine, consistent with this structural modification.

  The performance data UseTheMAX reports is based on preliminary internal human clinical testing and has not been published in peer-reviewed literature. With that context, the numbers are worth noting for KXR Stacked specifically: their internal data shows:

  

  • citrulline absorption up ~71%,
  • beta-alanine up ~119%,
  • taurine up ~20%, and
  • tyrosine up ~475% compared to controls

  MAXed Caffeine - Even More Data

  The caffeine data is more nuanced: rather than a single absorption figure, MAXed Caffeine testing reportedly showed:

  • 47% more perceived energy,
  • 32% greater motivation,
  • approximately 40% less jitter response,
  • 47% less crash, and
  • a roughly two-hour longer energy window

  compared to standard caffeine.

  At 3mg, MAX Catalyst sits within the dose range where piperine has been shown to modulate these enzyme pathways. Whether you're after the pump from citrulline, the endurance support from beta-alanine, or the sustained energy curve from the caffeine blend, MAX Catalyst is the formula's under-the-hood mechanism for helping get more from each ingredient you're already dosing.

Power & Performance Matrix Blend

• MAXed L-Citrulline Malate 2:1 - 6g

  MAXed L-Citrulline Malate 2:1 comes in at 6g, delivering roughly 4g of free citrulline alongside ~2g of malate. Unlike L-arginine, orally supplemented citrulline bypasses gut arginase and hepatic clearance, traveling to the kidneys where it converts back to L-arginine and drives nitric oxide (NO) production.^[3] That NO output supports vasodilation and blood flow to working muscle, the pump mechanism this formula is built around.

  Malate is a tricarboxylic acid (TCA) cycle intermediate that may support aerobic ATP production and buffer lactate during high-intensity efforts, and citrulline may also assist ammonia clearance through the urea cycle to help delay training-induced fatigue.^[4]

  

  A meta-analysis by Vårvik et al. found that citrulline malate can support repetition performance in resistance training, with most positive results clustered around 8g doses.^[5] Beyond this, MAX Catalyst's internal (unpublished) data reports a roughly 71% increase in citrulline absorption with co-administration, which would theoretically bring this 6g dose's effective delivery closer to that studied range.

• Beta-Alanine - 3.2g

  Beta-alanine is the rate-limiting precursor to carnosine, a dipeptide synthesized in skeletal muscle when beta-alanine bonds with L-histidine (the essential amino acid). Carnosine's key role during high-intensity work is buffering hydrogen ions (H+) that accumulate as intensity climbs, helping sustain muscular output before fatigue sets in.^[6] Multiple meta-analyses support the ergogenic potential of consistent beta-alanine loading, with benefits most pronounced in efforts lasting one to ten minutes.^[7][8]

  The 3.2g dose matches the per-serving amounts used across most clinical trials. The ISSN goes even further, recommending 4 to 6g daily in divided doses for loading, so that carnosine accumulation builds with regular use over weeks rather than a single session.^[6] The familiar skin tingling is paresthesia: a dose-dependent sensory response with no known harm, and a reliable sign the ingredient is active.

  MAX Catalyst's internal (unpublished) data reportedly shows beta-alanine absorption up roughly 119% compared to standard delivery, which could meaningfully accelerate carnosine loading over time.

• L-Taurine - 1.5g

  

  L-Taurine is one of the most concentrated free amino acids in skeletal muscle, where it acts as an osmolyte, helping regulate cell volume and maintain hydration under physical stress.^[9] That cellular fluid balance matters during training, when muscle contractions depend on tight electrolyte and calcium signaling dynamics.^[10]

  On the performance side, a meta-analysis of human trials found taurine supplementation associated with meaningful improvements in endurance exercise performance.^[11] Research also shows taurine may support eNOS activity, the enzyme responsible for endothelial nitric oxide production, which complements the citrulline malate dosed alongside it.^[12] Taurine further contributes through mitochondrial support, where it helps facilitate proper mitochondrial tRNA modification and electron transport chain function.^[13]

  At 1.5g, this sits above the starting end of studied performance doses. A systematic review noted benefits across roughly 1g to 6g, with aerobic outcomes tending to favor the higher end of that range.^[14] MAX Catalyst's internal (unpublished) data reportedly shows a ~20% increase in taurine absorption, which may close some of that gap even more.

• Betaine Anhydrous - 1.25g

  Betaine anhydrous, also known as trimethylglycine, operates through two distinct mechanisms in a performance context. As an organic osmolyte, it draws water into muscle cells to help maintain cell volume and protein stability under the osmotic stress of intense training.^[15] As a methyl donor, it transfers a methyl group to homocysteine, producing methionine, which the liver converts to S-adenosylmethionine (SAM), a key substrate for endogenous creatine synthesis.^[16]

  Clinical research has primarily used 2.5g per day. At that dose, Hoffman et al. reported improved lower-body squat endurance and repetition quality at high power outputs after 15 days of supplementation. Pryor et al. found roughly a 5.5% increase in cycling sprint peak power after 7 days.^[17] KXR Stacked's 1.25g dose sits below that studied threshold, which is worth noting for performance expectations.

  

  The VitaCholine (500mg) in this formula is a natural complement here: choline is an endogenous precursor to betaine through hepatic oxidation, so the two may support overlapping methylation pathways.

• Theobromine - 300mg

  Theobromine (3,7-dimethylxanthine) is the primary methylxanthine in cocoa, related to caffeine but with a substantially different pharmacokinetic profile. Where caffeine peaks in plasma within 30 to 40 minutes and clears in 2.5 to 5 hours, theobromine peaks 1 to 3 hours post-ingestion with an estimated half-life of 7 to 12 hours.^[18] Its primary mechanisms include antagonism of adenosine receptors (A1 and A2A subtypes) and inhibition of phosphodiesterase, which elevates intracellular cAMP and supports smooth muscle relaxation and cardiac output.^[19]

  At the formula level, theobromine's longer half-life fills the gap caffeine leaves once it clears, supporting sustained energy through training and into recovery. Mitchell et al. found that 700mg theobromine lowered blood pressure relative to placebo, while combining it with caffeine produced mood effects similar to caffeine alone, but without the blood pressure increase. The 300mg dose here sits within the range where theobromine has measurable physiological activity while maintaining tolerability confirmed across human trials.^[18][20]

  Preclinical research by Jang et al. found theobromine may support healthy fat metabolism via activation of β3-adrenergic receptors and AMPK, upregulating thermogenic markers in fat cells.^[21] That mechanism pairs naturally with the formula's caffeine trio, and MAX Catalyst's absorption modulation extends the overlap window for both methylxanthines.

Cognition Enhancing Matrix Blend

• L-Tyrosine - 1g

  

  L-Tyrosine is a conditionally essential amino acid and the direct precursor to the catecholamines dopamine and norepinephrine.^[22]

  Tyrosine's cognitive value comes from a demand-dependent mechanism: it enhances catecholamine synthesis primarily in actively firing neurons, so it's most relevant when your brain is actually working hard. Research shows it may help maintain working memory and attentional performance during demanding tasks, with the most consistent support seen when neurotransmitter pools are temporarily taxed by stress or sustained cognitive effort.^[23]

  At 1g, this sits toward the lower end of studied doses. MAX Catalyst's unpublished internal data claims a roughly 475% increase in tyrosine absorption with co-administration, which, if accurate, would meaningfully change what this gram actually delivers. The VitaCholine and DMAE pairing covers complementary cholinergic pathways, giving the cognitive matrix dual-system reach across both catecholamine and acetylcholine signaling.

• Choline Bitartrate (VitaCholine®) - 500mg

  Choline bitartrate is a form of choline that delivers 41.1% choline by molecular weight, so this 500mg dose provides roughly 205mg of active choline.^[24] Choline is a rate-limiting precursor to acetylcholine (ACh), the neurotransmitter governing muscle contraction, attention, and working memory. Plasma choline rises within an hour of supplementation, and ACh levels in the brain elevate within roughly 40 minutes and remain elevated for at least 90 minutes.^[25]

  Naber et al. demonstrated in a placebo-controlled trial that a single choline bitartrate dose improved visuomotor performance and accuracy in healthy subjects, with effects attributed to enhanced cholinergic signaling through nicotinic ACh receptors.^[25] That's the kind of neuromuscular precision that carries over to tracking bar path and coordinating complex movements under fatigue.

  

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  Choline also functions as a methyl donor, supporting one-carbon metabolism and contributing to phosphatidylcholine synthesis for healthy cell membrane integrity. The VitaCholine branded form is a well-studied, food-grade choline bitartrate source using naturally-derived tartaric acid to ensure that the L-bitartrate form is used only. Co-formulating it with the Vitamin B12 (methylcobalamin) in this product is mechanistically sound, as B12 deficiency is linked to reduced blood choline concentrations.^[24]

• Dimethylethanolamine DL-Bitartrate (DMAE) - 300mg

  Dimethylethanolamine (DMAE) is a choline analog with two methyl groups instead of three. It's been studied for cognitive support, and its mechanism is more indirect than most people expect.

  Rather than converting directly to choline, DMAE appears to raise circulating choline by blocking its breakdown. In mice, DMAE administration inhibited both choline kinase and choline dehydrogenase in the kidney, the two primary enzymes responsible for choline clearance, producing a fourfold increase in free kidney choline and elevated blood choline levels.^[26] That freed choline can then enter the brain and support acetylcholine synthesis. On the phospholipid side, DMAE incorporates into membranes as phosphatidyldimethylethanolamine (PDME), which can be further methylated to phosphatidylcholine (PC) via the PEMT pathway, with IV infusion studies in rats showing selective hepatic enrichment with polyunsaturated PC species.^[27]

  At 300mg, DMAE pairs logically with VitaCholine ahead of it in the Cognition Enhancing Matrix. Where VitaCholine delivers choline directly, DMAE may help preserve and extend what's already circulating.

• Huperzine A 1% - 3mg

  

  VMI Sports expands their PEZ Candy collaboration with L-Carnitine 3000 and L-Carnitine 1500 Heat. Pure metabolic support vs thermogenic fat burning, both in PEZ Grape and Cherry. Because carnitine doesn't need to taste clinical.

  Huperzine A is a reversible, highly selective acetylcholinesterase (AChE) inhibitor derived from the Chinese club moss Huperzia serrata. Its primary action is straightforward: by inhibiting AChE, the enzyme responsible for breaking down acetylcholine (ACh) at the synapse, it extends the duration and intensity of cholinergic signaling in the brain.^[28] What makes huperzine A distinctive is its selectivity. Compared to tacrine and even donepezil, it shows dramatically higher specificity for AChE over butyrylcholinesterase, meaning its activity stays targeted to the central nervous system rather than spilling into peripheral pathways.^[28]

  The downstream result is elevated cortical and hippocampal ACh -- regions tied directly to working memory, focus, and attentional control. Research in freely-moving rats showed huperzine A dose-dependently increased ACh in the medial prefrontal cortex and hippocampus, and the effect held up after 30 days of daily administration without tolerance developing.^[29] That same study also noted a corresponding rise in dopamine in both brain regions -- a neurotransmitter relevant to motivation and reward signaling during training.

  For a pre-workout, this maps cleanly onto the mind-muscle connection. The 30mcg active dose from this 1% extract sits within range, and it pairs logically with the VitaCholine and DMAE already in this formula -- both of which support cholinergic substrate availability on the supply side while huperzine A preserves ACh on the breakdown side.

Energy Matrix Blend

• MAXed Caffeine Blend - 292mg (yielding 200mg net caffeine)

  Caffeine Citrate, Caffeine Anhydrous, Dicaffeine Malate (Infinergy®)

  

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  The MAXed Caffeine Blend provides 200mg net caffeine across a staggered absorption curve rather than a single spike.

  The mechanism is well-established: caffeine competes with adenosine at A1 and A2A receptors in the CNS, blocking the inhibitory brake adenosine places on neurotransmitter release. This raises concentrations of dopamine, norepinephrine, and acetylcholine, supporting alertness, focus, reduced perceived exertion, and muscular output.^[30] A review by McLellan et al. found roughly two-thirds of strength and high-intensity exercise studies reported ergogenic effects from caffeine, alongside consistent reductions in perceived effort.^[31]

  The three-source structure is deliberate. Caffeine citrate absorbs fastest as an ionized salt; anhydrous provides the primary working dose; Infinergy® dicaffeine malate's malate-bound form smooths the tail end and helps reduce post-energy crash. Together they extend the useful energy window without requiring a higher total dose.

  At 200mg, this is a moderate, manageable level for most users. Theobromine elsewhere in the formula adds complementary xanthine stimulation without compounding jitter risk. UseTheMAX's internal (unpublished) testing with MAX Catalyst co-administration reportedly showed 47% more perceived energy, roughly 40% less jitter response, and approximately two hours of additional energy duration compared to standard caffeine alone.

Vitamins & Minerals

• Vitamin B3 (as niacin) - 35mg

  

  Niacin, supplied here as nicotinic acid, converts to NAD+ and NADP+, the coenzymes central to redox-driven energy production and non-redox signaling processes including DNA repair and gene expression.^[32] NAD+ also activates sirtuins and helps maintain mitochondrial fitness, tying niacin status to cellular energy efficiency during training.^[33] At 35mg, this exceeds the adult male RDA (16mg NE) by more than double. Nicotinic acid also activates GPR109A receptors, prompting vasodilation that may complement the nitric oxide pathway driven by citrulline malate. The dose sits well below thresholds associated with flushing, so that vascular activity comes without the skin response.

• Vitamin B12 (as methylcobalamin) - 35mcg

  Methylcobalamin is the bioidentical coenzyme form of B12, meaning it enters cellular pathways without the conversion step required by cyanocobalamin.^[34] It supports one-carbon metabolism and normal mitochondrial energy production, two processes tied directly to cellular ATP output.^[35][36] Research also shows B12 modulates cholinergic signaling,^[37] a direct synergy with VitaCholine and DMAE in the Cognition Enhancing Matrix. At 35mcg, the dose sits well above the 2.4mcg daily reference value, consistent with ranges studied for supporting normal neurological function.

• Sodium - 150mg (from 384mg Pink Himalayan Salt)

  Sodium is the primary extracellular electrolyte, and its role in a pre-workout formula reaches beyond basic mineral content. Drinking plain water without sodium drops plasma concentration, suppressing vasopressin and triggering a diuretic response that accelerates fluid loss.^[38] Sodium co-ingested with fluids preserves vasopressin activity, helping more of what you drink stay in circulation rather than pass as urine. The 150mg here comes from 384mg Pink Himalayan Salt, providing foundational electrolyte support alongside the formula's broader performance blend.

Flavors Available

Here's an up-to-date list of all flavors of VMI Sports KXR Stacked:

How to Use

• When to take it: One scoop 20 to 30 minutes before training.
• With or without food: Either works, though some users prefer a light meal beforehand to moderate the beta-alanine flush (which could be enhanced by the niacin dose)
• Other notes: If you're sensitive to beta-alanine and/or niacin, start with half a scoop to assess tolerance. The 200mg caffeine dose is manageable for most users, but avoid taking it within 6 hours of sleep.

Stacks Well With

• VMI Sports Protolyte: Post-workout pairing makes sense here. Protolyte's 24g whey isolate and TRAACS chelated mineral complex recover what training depletes, picking up where KXR Stacked leaves off.

Who It's For

• Lower-stim pre-workout users: If K-XR's 400mg caffeine and alpha-yohimbine is more than you want, KXR Stacked gives you a genuinely well-built alternative without compromising on pump and performance ingredients.
• Cognitive performance seekers: The VitaCholine/DMAE/Huperzine A cognitive stack is hard to find these days. If you care about mental sharpness during training and enjoy the feel of this trio, this formula delivers.
• PEZ Sours fans: The collab flavors are limited to KXR Stacked in the pre-workout powder category, so this is your entry point for that collaboration.

Conclusion: The Smarter, Stackable K-XR

Tom Reilly, president of VMI Sports, walks through a decade of building a bootstrapped supplement brand -- from Lone Star Distribution house brand to grocery chains, the PEZ collab, and two mystery canned beverages on the horizon, on Episode #205 of the PricePlow Podcast.

VMI has built KXR Stacked for users who want something thoughtful rather than just intense. The 6g citrulline malate and 300mg theobromine do real work on pump and sustained energy, and the cognitive stack (VitaCholine, DMAE, Huperzine A) is above and beyond what most pre-workouts bother to include. MAX Catalyst rounds it out by supporting absorption of everything else in the tub.

The formula fits cleanly in the VMI ecosystem. Use it before training, stack Protolyte post-workout, and you've covered the two sessions that matter most. Tom Reilly has said publicly that VMI builds for the full picture, and KXR Stacked is a good example of that in practice.

Check current pricing and availability on PricePlow, listen to our podcast with Tom Reilly, and sign up for VMI Sports news alerts so you don't miss new PEZ collab drops or additional flavor releases.