Your body makes nitric oxide two different ways. Almost every pump supplement on the shelf only feeds one of them.
That is the entire argument for the Pump Matrix, and it is not marketing. It is a fork in human physiology that has been mapped since the 1990s and sits in every sports nutrition textbook written since. One route runs on an enzyme and needs oxygen. The other runs on a chemical reduction and works better when oxygen runs out. Feed one and you get half the system. Feed both and you get the system.
Here is how each route works, what the research actually shows, the doses that research uses, and the arithmetic problem at the centre of the beetroot industry that nobody selling you a pump product will put in writing.
What is the Pump Matrix?
The Pump Matrix is the pairing of L-Citrulline and beetroot nitrate in one formula to raise nitric oxide through both of the body's production pathways at once. L-Citrulline feeds the enzymatic pathway, converting to L-Arginine and then to nitric oxide via nitric oxide synthase, a process that requires oxygen. Beetroot nitrate feeds the reduction pathway, converting nitrate to nitrite to nitric oxide without any enzyme and without oxygen. The two routes are independent. They do not compete for the same substrate and they do not share a rate limiting step.
In BigDaddy, the Pump Matrix is 8,000mg L-Citrulline and 2,000mg RedNite beetroot concentrate per 20g serving.
The pump is not a vanity metric
Start here, because most people get this wrong.
The tight skin and the visible veins are the symptom. The mechanism underneath is vasodilation, and vasodilation is a performance variable. Wider vessels mean more blood into working tissue. More blood means more oxygen and more substrate arriving, and more metabolic waste leaving. Nitric oxide sits at the centre of blood flow regulation, muscle contractility and mitochondrial respiration.
That matters on set four when your forearms are full of acid and your grip is going. It matters in round three when your shoulders are burning and your hands drop. The pump is the visible edge of a delivery and clearance system, and that system decides how many reps you get before the wheels come off.
Chase the feeling if you want. The reason it works is plumbing.
Pathway one: L-Citrulline and the enzymatic route
L-Citrulline is a non essential amino acid found naturally in watermelon. Swallow it and it travels to the kidneys, converts to L-Arginine, and L-Arginine is the direct substrate for nitric oxide synthase, the enzyme that produces nitric oxide.
Why citrulline and not arginine
If arginine is the substrate, why not just take arginine? Because arginine taken orally gets destroyed. It is heavily metabolised in the gut and liver before it reaches circulation, so a large oral dose produces a disappointing rise in blood arginine. Citrulline bypasses that first pass problem entirely and raises plasma arginine more effectively than arginine itself does.
That is not a marketing preference. That is why the entire industry moved off arginine.
Citrulline malate versus pure L-Citrulline
This is where labels get slippery, so run the maths yourself.
Citrulline malate is L-Citrulline bound to malic acid, usually in a 2:1 ratio. Two parts citrulline, one part malate. So 6,000mg of citrulline malate contains roughly 4,000mg of actual L-Citrulline. The other 2,000mg is malic acid.
Malic acid is not useless. It is a Krebs cycle intermediate and there is an argument for it. But it is not citrulline, and when a label shouts a number, check whether that number is the compound or the active.
A tub advertising 4,000mg citrulline malate is giving you around 2,600mg of citrulline. The research standard is 6,000mg to 8,000mg of citrulline. That product is at a third of the dose while the label looks respectable.
You're not weak. You're underdosed.
What the citrulline research shows
Be honest about the size of the effect, because the honest version is still good.
Pérez-Guisado and Jakeman gave trained men 8g of citrulline malate one hour before training and found a significant increase in bench press repetitions, plus reduced muscle soreness at 24 and 48 hours. Wax and colleagues found similar upper body improvements at the same dose. Trexler's 2019 meta analysis of acute citrulline supplementation concluded there is a small positive effect on high intensity strength and power performance, while flagging real uncertainty about optimal dosing.
A separate meta analysis by Rhim found citrulline reduced rating of perceived exertion, muscle soreness and blood lactate after exercise. That is the mechanism people actually feel. The set does not get lighter. It feels lighter, and you get more out of it.
There is also a muscle protein synthesis angle. Citrulline appears to stimulate mTOR signalling through the PI3K/MAPK/4E-BP1 pathway independently of insulin, and Goron's work suggests it does this by reallocating ATP consumption toward protein synthesis. That is a secondary benefit, not the headline, and anyone selling citrulline as a mass builder is overreaching.
Citrulline also plays a role in the urea cycle, helping clear ammonia. Ammonia accumulation is a fatigue signal. Clearing it faster is part of why citrulline shows up in the fatigue literature.
Research dose: 6,000mg to 8,000mg of L-Citrulline, taken roughly 60 minutes before training.
Pathway two: beetroot nitrate and the reduction route
Now the half of the system almost everyone ignores.
Dietary nitrate does not need nitric oxide synthase. Swallow nitrate and bacteria on your tongue reduce it to nitrite. Nitrite enters circulation and gets reduced again, this time to nitric oxide. No enzyme. No oxygen requirement.
Why that independence is the whole point
The enzymatic route needs oxygen to run. Set four, round three, last 200 metres, the tissue is hypoxic and acidic. That is precisely when the oxygen dependent route starts to struggle.
The nitrate route does the opposite. Nitrite reduction to nitric oxide is potentiated by low oxygen and low pH. The harder and more acidic the environment, the better that pathway works.
Read that again, because it is the argument. The pathway that struggles when it gets hard and the pathway that improves when it gets hard, running in the same formula. That is not two ingredients doing the same job twice. That is redundancy engineered into the physiology.
What the nitrate research shows
Nitrate is not just a blood flow ingredient. Coggan and Peterson's review documents that dietary nitrate enhances the contractile properties of human skeletal muscle. Haider and Folland found nitrate supplementation improved excitation contraction coupling at low stimulation frequencies, improving explosive force production. The proposed mechanism involves altered calcium handling, specifically increased intracellular calcium and greater myofilament calcium sensitivity.
Nitrate also improves mitochondrial efficiency, and Bailey's work showed enhanced muscle contractile efficiency during knee extensor exercise. Translation: the same work costs less oxygen.
On performance, Mosher found that a nitric oxide enhancing supplement providing 400mg of nitrate over six days significantly increased bench press repetitions to failure. Nyakayiru found beetroot juice supplementation improved high intensity intermittent exercise performance in trained footballers.
It does not always work. Boorsma found beetroot juice did not improve performance in elite 1500m runners, either acutely or over eight days. Nitrate's effect appears larger in less trained athletes and smaller as training status rises.
Research dose: roughly 300mg to 800mg of nitrate, with 400mg (6.4 mmol) as the workhorse dose across the beetroot juice literature.
What happens when you combine them
Here is the honest state of the evidence, because you deserve it and because the internet will not give it to you.
The combination research is thin. Two studies matter.
Burgos and colleagues, 2022. The only long term randomised double blind placebo controlled trial of this exact pairing. Thirty two trained male triathletes, four groups of eight, nine weeks. The combination group took 3g/day of citrulline plus 2.1g/day of nitrate rich beetroot extract providing 300mg/day of nitrate.
The result: a significant group by time interaction for estimated VO2max, favouring the combination group over placebo and over citrulline alone. On the strength tests there was no significant interaction between groups. However, only the combination group improved significantly on the horizontal jump and the one minute abdominal test between the start and end of the study.
Read that carefully. The combination was the only condition that improved on strength measures, but the difference between groups did not reach significance. With eight men per group, that is a suggestive result, not a proven one. The authors say as much and call for larger samples.
Trexler and colleagues, 2019. A randomised double blind crossover study using 8g citrulline malate and beetroot juice providing 400mg of nitrate, examining blood flow, energy metabolism and performance during maximal leg extension.
And the study that cuts against it: Le Roux-Mallouf gave older adults 6g citrulline plus 520mg nitrate and found improvements in some cardiorespiratory variables such as VO2, but no benefit to knee extension performance.
So: the mechanism is textbook and the pathways are genuinely independent. The trial evidence that combining them beats either one alone is early, small and mixed. Anyone telling you the synergy is proven has not read the papers.
The physiology is sound. The proof is incomplete. Both of those things are true at once and you should be suspicious of any brand that only tells you the first one.
The nitrate arithmetic nobody shows you
This is the part the industry does not put on a label, so here it is with the maths visible.
Raw beetroot powder runs at roughly 0.1% nitrate by weight. To get a research dose of 400mg from raw beetroot powder you would need around 400g of it. That is not a supplement. That is a bag of compost.
So concentrated extracts exist. RedNite is a fresh beetroot concentrate standardised to 1.5% to 2.75% natural nitrate, free from nitrites and synthetic nitrates. It carries roughly 25 times the nitrate of beetroot itself, and it is standardised, meaning every serving is identical rather than swinging with the harvest, the seed variety and the weather. That standardisation problem is real and it is why concentrates like RedNite exist at all.
Now the number.
At 2.75%, hitting a 400mg research nitrate dose requires 14.5g of RedNite. At 1.5% it requires 26.7g.
A BigDaddy 20g serving is 20g total. Every ingredient. Citrulline, beta alanine, caffeine, tyrosine, choline, theanine, the lot.
There is no full spectrum pre workout on earth that contains a research dose of beetroot nitrate. Not one. Including ours. The arithmetic forbids it. You cannot fit 14.5g of a single ingredient into a 20g serving that also has to hold 8g of citrulline and 3.5g of beta alanine.
That is exactly why beetroot shots exist as a separate category. A 70ml shot delivers 400mg of nitrate because it does not have to share the container with anything else.
Anyone selling you a pre workout on the promise that its beetroot matches the beetroot research is either not doing the maths or hoping you won't.
What is actually in the BigDaddy Pump Matrix
Full transparency, per 20g serving. 18 servings per tub at 20g.
8,000mg L-Citrulline. Pure L-Citrulline, not citrulline malate. That is 8,000mg of active, not 8,000mg of a compound that is one third malic acid. It sits at the top of the 6g to 8g research range, and it is the highest citrulline dose of any mainstream UK pre workout. This is the engine of the Pump Matrix and it is fully dosed with nothing hidden.
2,000mg RedNite. Standardised to 1.5% to 2.75% natural nitrate, roughly 25 times the nitrate of raw beetroot, with the betalains and polyphenols intact. RedNite's own clinically studied serving range is 500mg to 3g, with reported findings on increased mean peak EMG amplitude and lowered motor unit firing rates, both markers of neuromuscular efficiency. Our 2,000mg sits inside that studied range.
What 2,000mg of RedNite does not do is deliver 400mg of nitrate. It delivers roughly 30mg to 55mg. We are not going to pretend otherwise, because you can do that sum in ninety seconds and we would rather you heard it from us.
What it does is open the second pathway. The one that works when the oxygen runs out.
How to actually use this
Three things worth knowing that most articles skip.
Timing is different for each ingredient. Citrulline research typically doses around 60 minutes before training. Beetroot research doses far earlier, commonly 2 to 2.5 hours before exercise, because plasma nitrite takes hours to peak. Taking a pre workout 20 minutes before you lift is close to optimal for the caffeine and the citrulline. It is not optimal for the nitrate.
Nitrate rewards consistency, not timing. Skeletal muscle stores nitrate. Wylie's work showed the muscle nitrate reservoir responds to dietary intake, and Piknova's research positions skeletal muscle as central to whole body nitric oxide homeostasis. Chronic daily intake builds those stores. That is why the nine week Burgos protocol used a modest daily dose rather than one large hit. Take it every day, including rest days, and the nitrate side works better than it does taken sporadically.
If you want a research nitrate dose, stack a beet shot. Nothing stops you. Take your pre workout 30 minutes out and a 70ml beetroot shot two hours out. That is the honest answer, it costs us a sale, and it is what we would tell a training partner.
The bottom line
Two pathways. One enzymatic and oxygen dependent, one reductive and enhanced by exactly the hypoxic acidic conditions that shut the first one down. That is the Pump Matrix, and the physiology behind it is not in dispute.
What is in dispute is how much the combination adds over either ingredient alone. The trials are small, early and mixed. We are not going to inflate them.
What is not in dispute is the citrulline. 8,000mg of pure L-Citrulline (20g serving) is a fully dosed, top of range, research standard delivery of the single best studied pump ingredient in sports nutrition, in a UK market where the norm is 4,000mg of citrulline malate pretending to be 4,000mg of citrulline.
Everything else on this page you can go and check. That is the point.
Get to work.
Frequently asked questions
What is the Pump Matrix? The Pump Matrix is the combination of L-Citrulline and beetroot nitrate in a single formula, targeting both of the body's nitric oxide production pathways at once. L-Citrulline feeds the enzymatic pathway via L-Arginine and nitric oxide synthase. Beetroot nitrate feeds the reduction pathway, converting nitrate to nitrite to nitric oxide without an enzyme. In BigDaddy this is 8,000mg L-Citrulline and 2,000mg RedNite per 20g serving.
How much L-Citrulline should I take for a pump? Research uses 6,000mg to 8,000mg of L-Citrulline, taken around 60 minutes before training. If your product lists citrulline malate rather than pure L-Citrulline, divide by roughly 1.5 to get the actual citrulline content, since citrulline malate is typically a 2:1 ratio of citrulline to malic acid.
Is L-Citrulline better than L-Arginine? Yes, for raising nitric oxide. Oral L-Arginine is heavily broken down in the gut and liver before it reaches circulation, so large doses produce small increases in blood arginine. L-Citrulline bypasses that first pass metabolism and raises plasma arginine more effectively than arginine itself.
What does beetroot nitrate do that citrulline does not? It produces nitric oxide without needing oxygen or an enzyme, and the conversion is actually improved by low oxygen and low pH. Those are exactly the conditions inside a working muscle late in a hard set, when the oxygen dependent citrulline pathway is under most strain. Nitrate has also been shown to improve muscle contractile properties and mitochondrial efficiency.
How much beetroot nitrate is a research dose? Roughly 300mg to 800mg of nitrate, with 400mg (6.4 mmol) as the most common effective dose in the beetroot juice literature. Reaching that from a beetroot concentrate standardised to 2.75% nitrate would require about 14.5g of powder, which is more than an entire 20g pre workout serving. This is why no complete pre workout contains a research dose of nitrate and why beetroot shots exist separately.
Does RedNite contain a lot of nitrate? RedNite is standardised to 1.5% to 2.75% natural nitrate, roughly 25 times the nitrate of raw beetroot. That is a concentration figure, not a dose figure. A 2,000mg serving of RedNite delivers approximately 30mg to 55mg of nitrate. RedNite's own studied serving range is 500mg to 3g.
Do L-Citrulline and beetroot work better together? The mechanism strongly suggests they should, since they use genuinely independent pathways. The direct trial evidence is limited. Burgos found that nine weeks of 3g citrulline plus 300mg nitrate significantly improved estimated VO2max compared to placebo and citrulline alone, and the combination group was the only one to improve on strength measures, though the difference between groups was not statistically significant. Sample sizes were small at eight per group. Another trial in older adults found cardiorespiratory improvements but no performance benefit.
When should I take citrulline and beetroot? Citrulline research doses around 60 minutes before training. Beetroot research typically doses 2 to 2.5 hours before exercise, since plasma nitrite takes hours to peak. Nitrate also builds up in skeletal muscle stores over time, so consistent daily intake matters more for the nitrate side than precise timing on any given day.
- Lundberg JO, Weitzberg E, Gladwin MT. The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics. Nat Rev Drug Discov. 2008;7:156-167. DOI · PubMed
- Burgos J, Viribay A, Fernández-Lázaro D, Calleja-González J, González-Santos J, Mielgo-Ayuso J. Combined effects of citrulline plus nitrate-rich beetroot extract co-supplementation on maximal and endurance-strength and aerobic power in trained male triathletes: a randomized double-blind, placebo-controlled trial. Nutrients.2022;14(1):40. DOI · PubMed · Free full text
- Trexler ET, Keith DS, Schwartz TA, Ryan ED, Stoner L, Persky AM, Smith-Ryan AE. Effects of citrulline malate and beetroot juice supplementation on blood flow, energy metabolism, and performance during maximum effort leg extension exercise. J Strength Cond Res. 2019;33(9):2321-2329. DOI · PubMed
- Trexler ET, Persky AM, Ryan ED, Schwartz TA, Stoner L, Smith-Ryan AE. Acute effects of citrulline supplementation on high-intensity strength and power performance: a systematic review and meta-analysis. Sports Med. 2019;49:707-718. DOI · PubMed
- Pérez-Guisado J, Jakeman PM. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. J Strength Cond Res. 2010;24:1215-1222. DOI · PubMed
- Wax B, Kavazis AN, Luckett W. Effects of supplemental citrulline-malate ingestion on blood lactate, cardiovascular dynamics, and resistance exercise performance in trained males. J Diet Suppl. 2016;13:269-282. DOI · PubMed
- Rhim HC, Kim SJ, Park J, Jang KM. Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: a systematic review and meta-analysis. J Sport Health Sci. 2020;9:553-561. DOI· PubMed · Free full text
- Figueroa A, Wong A, Jaime SJ, Gonzales JU. Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance. Curr Opin Clin Nutr Metab Care. 2017;20:92-98. DOI · PubMed
- Goron A, Lamarche F, Blanchet S, Delangle P, Schlattner U, Fontaine E, Moinard C. Citrulline stimulates muscle protein synthesis by reallocating ATP consumption to muscle protein synthesis. J Cachexia Sarcopenia Muscle.2019;10:919-928. DOI · PubMed · Free full text
- Le Plénier S, Goron A, Sotiropoulos A, et al. Citrulline directly modulates muscle protein synthesis via the PI3K/MAPK/4E-BP1 pathway in a malnourished state. Am J Physiol Endocrinol Metab. 2017;312:E27-E36. DOI · PubMed
- Bendahan D, Mattei JP, Ghattas B, Confort-Gouny S, Le Guern ME, Cozzone PJ. Citrulline/malate promotes aerobic energy production in human exercising muscle. Br J Sports Med. 2002;36:282-289. DOI · PubMed · Free full text
- Coggan AR, Peterson LR. Dietary nitrate enhances the contractile properties of human skeletal muscle. Exerc Sport Sci Rev. 2018;46:254-261. DOI · PubMed · Free full text
- Coggan AR, Baranauskas MN, Hinrichs RJ, Liu Z, Carter SJ. Effect of dietary nitrate on human muscle power: a systematic review and individual participant data meta-analysis. J Int Soc Sports Nutr. 2021;18:66. DOI · PubMed · Free full text
- Haider G, Folland JP. Nitrate supplementation enhances the contractile properties of human skeletal muscle. Med Sci Sports Exerc. 2014;46:2234-2243. DOI · PubMed
- Bailey SJ, Fulford J, Vanhatalo A, et al. Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans. J Appl Physiol. 2010;109:135-148. DOI · PubMed
- Mosher SL, Sparks SA, Williams EL, Bentley DJ, McNaughton LR. Ingestion of a nitric oxide enhancing supplement improves resistance exercise performance. J Strength Cond Res. 2016;30:3520-3524. DOI · PubMed
- Nyakayiru J, Jonvik KL, Trommelen J, et al. Beetroot juice supplementation improves high-intensity intermittent type exercise performance in trained soccer players. Nutrients. 2017;9:314. DOI · PubMed · Free full text
- Boorsma RK, Whitfield J, Spriet LL. Beetroot juice supplementation does not improve performance of elite 1500-m runners. Med Sci Sports Exerc. 2014;46:2326-2334. DOI · PubMed
- Le Roux-Mallouf T, Pelen F, Vallejo A, Halimaoui I, Doutreleau S, Verges S. Effect of chronic nitrate and citrulline supplementation on vascular function and exercise performance in older individuals. Aging. 2019;11:3315. DOI · PubMed · Free full text
- Wylie LJ, Park JW, Vanhatalo A, et al. Human skeletal muscle nitrate store: influence of dietary nitrate supplementation and exercise. J Physiol. 2019;597:5565-5576. DOI · PubMed · Free full text
- Piknova B, Schechter AN, Park JW, Vanhatalo A, Jones AM. Skeletal muscle nitrate as a regulator of systemic nitric oxide homeostasis. Exerc Sport Sci Rev. 2021. DOI · PubMed · Free full text
- Jones AM, Thompson C, Wylie LJ, Vanhatalo A. Dietary nitrate and physical performance. Annu Rev Nutr.2018;38:303-328. DOI · PubMed
- Larsen FJ, Schiffer TA, Borniquel S, Sahlin K, Ekblom B, Lundberg JO, Weitzberg E. Dietary inorganic nitrate improves mitochondrial efficiency in humans. Cell Metab. 2011;13:149-159. DOI
- Gonzalez AM, Trexler ET. Effects of citrulline supplementation on exercise performance in humans: a review of the current literature. J Strength Cond Res. 2020;34:1480-1495. DOI · PubMed
- ENovate Biolife. RedNite® fresh beetroot concentrate: standardised to 1.5% to 2.75% natural nitrate. Product specification