HR Labs Defib is your All-in-One Stimulant Pre-Workout Stack

Defib, available in New Zealand through Strom Sports, is a stimulant pre-workout built for athletes who want a complete formula in a single scoop. Where many stimulant pre-workouts load up on caffeine and filler with a handful of underdosed performance ingredients to pad the label, Defib was designed to deliver meaningful doses across every system that determines how you perform: Stimulation, Cognitive Endurance, Blood Flow, and Hydration.

Each of these systems interacts with the others. Better blood flow delivers more of the cognitive ingredients to the brain and more of the acid-buffering compounds to working muscles. Better hydration maintains the cellular environment in which all of these processes operate. Better cognitive stamina determines how hard and how long you are willing to push. Defib was designed as a system, not a collection of standalone ingredients.

The Stimulant and Dopamine Complex: Caffeine, Juniper Berry, SalidroPure™, and Sabroxy®

Caffeine Anhydrous (400mg)

Caffeine has always been a foundation inclusion in previous Defib formulas and HR Labs has no interest in changing that.

Its primary mechanism is blocking adenosine receptors. Adenosine is the molecule that builds up in the brain during waking hours and exercise to signal fatigue. By blocking it, caffeine produces the familiar increase in alertness and perceived energy, while also pushing greater release of dopamine and noradrenaline. This amplifies the motivational and focus effects driven by the other cognitive ingredients in the formula. Athletes are very familiar with the advantages and disadvantages of caffeine, but if you want to read further on its role in sporting performance the ISSN position stand is highly recommended: "International society of sports nutrition position stand: caffeine and exercise performance" (2010). [1]

The 400mg caffeine dose in Defib sits at the upper end of what is commonly used in pre-workout formulations and corresponds to approximately 5mg/kg for an 80kg individual, this is within the range most consistently associated with performance benefits in the research literature. For individuals who are sensitive to caffeine or who are stacking with other caffeine sources, HR Labs always suggests Defib at a half-serve. This has been a consideration in the formula design since version one and HR Labs has maintained that for this latest release.

Juniper Berry Extract (500mg)

Juniper berry extract is included in Defib as a complementary ingredient to the caffeine and broader stimulant experience. Juniper berry contains a range of active plant compounds, including alpha-pinene and limonene, which are of interest for their effects on alertness and nervous system activity.[2]

The practical value of juniper berry extract in a pre-workout context is in shaping the "feel-experience" of the stimulant effect. Where caffeine provides the primary drive, juniper berry contributes to a smoother, more rounded stimulant feel by shifting the adrenaline response. For athletes who find high-caffeine formulas to produce a narrow, jittery stimulation, the juniper berry helps round out the experience into something more functional - especially during complex, sport-specific training that requires more planning and fidelity.

SalidroPure™ (30mg)

SalidroPure™ is a pure salidroside produced by precision fermentation, stepping in as a replacement to the RhodioPrime™ 6X that was used in the previous Defib formula. Salidroside is the primary bioactive compound in the Rhodiola plant, and SalidroPure™ delivers it without the variability, taste issues, or sustainability concerns of traditional rhodiola extracts.

Salidroside shifts the dopamine balance in your favour through two mechanisms. First, it increases the activity of tyrosine hydroxylase (TH), the enzyme that controls how fast your brain can convert tyrosine into dopamine. More TH activity means greater dopamine production capacity. Second, it inhibits MAO-A and MAO-B, the enzymes that break down dopamine and noradrenaline after they have been released. This allows the neurotransmitters you produce to remain active longer before being cleared.[3][4]

In a randomised, double-blind, placebo-controlled trial, the salidroside group maintained exercise performance across a 16-day study period while the placebo group declined. The salidroside group also showed reduced muscle damage markers, preserved mood state, and higher predicted oxygen uptake during high-intensity intermittent exercise.

SalidroPure™ complements the stimulant complex because its mechanism is distinct from caffeine. Caffeine forces greater neurotransmitter release and blocks fatigue signalling. SalidroPure™ supports the supply chain that produces dopamine and noradrenaline and slows the clearance process that removes them. This means SalidroPure™ is functioning to assist your body in getting the most out of the caffeine you consume.

For the full science behind SalidroPure™, the human trial data, and why it replaced RhodioPrime™ 6X, see the dedicated article.

Sabroxy® (150mg)

Sabroxy® is a standardised extract of the bark of Indian trumpet tree, providing a minimum 10% oroxylin A. Oroxylin A acts on dopamine through a mechanism distinct from caffeine and SalidroPure™. It inhibits the dopamine transporter (DAT), which is responsible for pulling dopamine back out of action and into storage. By slowing this reuptake process, oroxylin A allows dopamine to remain active longer, extending the motivational and focus signal.

Where SalidroPure™ promotes dopamine production and slows dopamine breakdown, Sabroxy® slows dopamine clearance. These are two different parts of the same removal system, and having both covered means dopamine released during training has the longest possible window of action. Combined with caffeine forcing greater release in the first place, this three-way approach to dopamine management is the core of Defib's stimulant and drive architecture.

A bonus to Sabroxy® is its action on GABA-A receptors. GABA is the brain's main "slow down" signal, it reduces neural activity. Too much GABA activity can dampen sharpness, reaction time, and the sense of drive. Sabroxy® reduces GABA-A receptor responsiveness, easing this braking effect without blocking GABA entirely. The result is a state of alert, focused cognition without the sedation that comes from suppressing GABA too aggressively. This is particularly valuable because frequent hard training and sleep deprivation, common among athletes, tend to push GABA activity higher, and Sabroxy® helps bring it back toward a more functional level.

For the full breakdown of how Sabroxy® supports focus and cognitive function under training fatigue, see the standalone article.

Cognitive Stamina: Mitochondrial Function and Acetylcholine

Sustained cognitive output during training depends on two things: the energy supply to your brain cells, and the availability of acetylcholine, the neurotransmitter your brain uses for focus, working memory, and coordinating muscle movement. As a session progresses, your brain's energy demand climbs and acetylcholine gets used up faster. If the brain cannot keep pace with both demands at once, you get the familiar cognitive fade that sets in during longer or more complex sessions: slower reactions, reduced coordination, and difficulty maintaining technical focus under fatigue.

ALCar and Citicoline address these two requirements directly.

Acetyl-L-Carnitine (ALCar)(1000mg)

Acetyl-L-Carnitine (ALCar) is a form of L-carnitine that crosses into the brain far more effectively than standard L-carnitine. Its role in the Defib formula is supporting energy production inside brain cells. ALCar shuttles fatty acids into the mitochondria, the energy generators inside every cell, where they are burned to produce ATP. This directly fuels the energy output your brain depends on to stay sharp during demanding training sessions.

This matters because brain cells are among the most energy-hungry cells in the body. During exercise, energy requirements climb sharply as motor planning, reaction processing, and muscle coordination all compete for the same fuel. When your mitochondria cannot keep up, cognitive function drops before your muscles give out. ALCar helps maintain that brain energy supply under load, and also helps reduce oxidative stress in brain tissue through its role in mitochondrial metabolism.

A meta-analysis of randomised controlled trials found that ALCar supplementation significantly improved cognitive function, particularly attention and mental stamina. The benefits are attributed to better mitochondrial output in brain cells and protection against neuronal damage. Doses of 1000 to 2000mg per day are most commonly used in human trials, and 1000mg in Defib sits at the clinically relevant threshold.[5][6]

Citicoline (500mg)

Citicoline (CDP-choline) is a compound that occurs naturally in the brain. When consumed, your body breaks it down into two useful parts: choline and cytidine. The choline feeds directly into acetylcholine production, and this is significant because choline availability is the bottleneck in how much acetylcholine your brain can make. The cytidine converts to uridine, which supports the repair and maintenance of brain cell membranes.

This membrane support matters during exercise. Brain cell membranes get used up faster during sustained physical and mental effort as signalling activity ramps up. Without adequate resupply, the structural integrity of these membranes can be compromised. Citicoline ensures the building blocks for membrane maintenance are available when demand is highest.

The uridine generated from citicoline also contributes to dopamine receptor sensitivity, supporting the stimulant stack discussed above. This adds a secondary benefit to what is primarily an acetylcholine and membrane support compound in the Defib formula.[7][8]

For the full breakdown of how uridine modulates dopamine receptor density and sensitivity, including the D1/D2 receptor remodelling research, see the Uridine Monophosphate article.

Blood Flow: Oxygen and Nutrient Delivery Under Load

Blood flow is the physical constraint on performance and recovery. Blood delivers the oxygen and nutrients your muscles need to produce energy, and carries away the waste products that build up during intense work and force you to slow down or stop.

Citrulline Malate 2:1 (8000mg)

Citrulline converts to arginine in the body, which is then used to produce nitric oxide (NO). Nitric oxide relaxes blood vessel walls, increasing blood flow to working muscles. Citrulline is more effective than supplementing arginine directly because your body absorbs it better and converts it more steadily. The 8g dose in Defib provides approximately 5.3g of free-form citrulline, placing it at the upper end of clinically studied dosing for both acute performance and multi-day use. This handles the primary blood flow pathway during aerobic and moderate-intensity work.

The malate (malic acid) component in citrulline malate is not inert filler. The practical benefit of the malate form is improved gut tolerance and absorption of the citrulline itself. HR Labs uses citrulline malate 2:1 because the majority of positive human performance trials have been conducted using this form, and matching the form used in research is a sensible default when the evidence on isolated components is still developing.

For a detailed explanation of how citrulline works alongside nitrate and PeakATP® blood flow pathways across aerobic and anaerobic conditions, see the full HR Labs Proven article.

PeptiPump™ (500mg)

PeptiPump™ is an AI-discovered peptide complex derived from lentils. It works through a different mechanism to citrulline. Rather than helping produce nitric oxide, PeptiPump™ inhibits angiotensin-converting enzyme (ACE), an enzyme that narrows blood vessels. By blocking this constriction signal, PeptiPump™ helps keep blood vessels open under stress. This complements the citrulline pathway and helps sustain blood flow when demand is high.

For more in detail on how PeptiPump™ enhances blood flow through natural ACE inhibition, see the standalone article.

Cellular Hydration: Osmolyte Support for Sport Performance

Hydration in a performance context is about more than drinking water and replacing electrolytes. Inside every muscle cell, water content must be maintained within a tight range for the cell to function properly. Too little water and the cell shrinks, protein breakdown accelerates, and force production drops. Too much and the cell swells beyond its operating range. While everyone is familiar with electrolytes, there are other molecules responsible for fine-tuning water balance inside cells. These are called osmolytes, and Defib includes two of the most studied: taurine and betaine.

Taurine (1500mg)

Taurine is the most abundant free amino acid in skeletal muscle and serves as a primary osmolyte. It accumulates inside cells to draw water in without disrupting the electrolyte balance that the cell depends on. When cells face dehydration stress, taurine transporter activity increases to pull in more taurine and consequently more water, restoring normal cell volume.

A meta-analysis of ten human studies using doses from 1 to 6g daily found that taurine supplementation significantly improved endurance performance, with benefits from both single doses and continued use.[9][10]

Defib provides 1500mg of taurine per serve, within the 1 to 2g range most commonly associated with exercise performance benefits. For athletes using Proven (2000mg taurine) as their primary pre-workout, switching to or stacking with Defib maintains meaningful taurine intake. When stacked with WATTR™ (1500mg) or HydroEAA (1500mg), total daily taurine intake moves into the higher dose ranges of 3 to 4.5g where additional benefits for muscle damage reduction have been observed.

For the complete science on taurine as an osmolyte, including how it regulates cell volume through TauT and volume-regulated anion channels (VRAC), and why muscle tissue gets priority access to taurine stores, see the standalone taurine article.

Betaine Anhydrous (2500mg)

Betaine (trimethylglycine) is another naturally occurring osmolyte that works on the same principle as taurine: it accumulates inside cells to help regulate water content without interfering with normal cell function. Where taurine is the dominant osmolyte in muscle and heart tissue, betaine is found in higher concentrations in the kidneys, liver, and brain, and plays a significant role in maintaining cell volume across a range of tissues under dehydration stress.

Beyond its osmolyte function, betaine serves as a methyl donor. It helps convert homocysteine back to methionine in a key metabolic cycle. This is relevant for athletes because elevated homocysteine is linked to poor blood vessel function and increased oxidative stress, both of which compromise recovery. By supporting this conversion, betaine indirectly supports healthy blood vessel function and helps manage exercise-induced oxidative load.[11]

The research on betaine and exercise performance has examined doses in the range of 1250 to 2500mg per day. A meta-analysis of betaine supplementation and exercise performance found that betaine improved muscular endurance when assessed as total repetitions completed, with more consistent effects observed at the 2500mg dose used in most of the included trials.

How Taurine and Betaine Work Together

Having two osmolytes in the formula is not redundant. Taurine and betaine are stored in different tissues and regulated by different transporter systems. Taurine dominates in skeletal muscle and heart tissue, while betaine covers the liver, kidneys, and brain. During exercise, when multiple systems are under dehydration stress at the same time, having both osmolytes available means the body does not have to drain one tissue's stores to protect another.

For the broader context of how osmolytes fit into a complete hydration strategy alongside electrolytes, prebiotic fibre, and B vitamins, see the WATTR™ article.

Beta-Alanine: Acid Buffering for Sustained Intensity

Beta-Alanine (3200mg): Beta-alanine is the building block your body needs to produce carnosine, a compound stored in muscle that acts as an acid buffer. During high-intensity exercise, acid builds up inside your muscles as ATP is broken down. This acid buildup directly impairs muscle contraction. Carnosine absorbs that acid, slowing the rate at which your muscles become too acidic to function and extending how long you can sustain high-intensity output before you are forced to stop.

Like creatine, the benefits of beta-alanine are dependent on building up muscle carnosine stores over time. A loading period of two to four weeks of consistent daily intake is needed before meaningful performance changes are observed, with carnosine stores continuing to increase over several months of supplementation. Athletes training frequently with the 3200mg beta alanine provided in Defib will accumulate meaningful carnosine increases with consistent use. It can also be stacked alongside Basic, the daily saturation formula Basic, also including 3200mg beta-alanine in order to achieve a maximal 6.4g dose at the upper end of ISSN-recommended daily range.

The tingling sensation (paraesthesia) some people experience after consuming beta-alanine is a well-documented, this side effect has no physical harm attributed to it, being caused by beta-alanine activating sensory neurons in the skin. It typically subsides within 30 to 60 minutes.

Again here, the International Society of Sports Nutrition position stand on beta-alanine is highly recommended if you want to do deeper reading on the ingredient. [13]

AstraGin®: Improving Ingredient Uptake

AstraGin® (30mg): AstraGin® is a blend of astragalus and ginseng plant compounds that improves nutrient absorption. It works by supporting the health of gut wall cells and increasing the activity of nutrient transporters, the mechanisms that move ingredients from your gut into your bloodstream. Research shows it can increase absorption of citrulline by up to 45%, with similar improvements across various botanicals and amino acids. In a formula with this many active ingredients, improving how much of each one actually gets absorbed is a meaningful contribution to overall effectiveness.

How to Use Defib for your Training

Mix one scoop with 300 to 400ml of water and consume 30 minutes before training. Due to the 400mg caffeine content, assess your tolerance with a half scoop if you are new to high-stimulant pre-workouts or if you are stacking with other caffeine sources. Avoid taking Defib within 6 hours of sleep.

For athletes already using HR Labs Proven (stimulant-free pre-workout), the two products are complementary. Proven provides additional blood flow support through PeakATP® and OxyStorm® that Defib does not include, along with a higher tyrosine dose and Uridine Monophosphate for further dopamine support. Stacking a half serve of Defib with a full serve of Proven is a potent combination for athletes who want both a mild stimulant drive and the broadest possible performance base.

For the full breakdown of how Proven's blood flow, cognitive, and hydration systems work, see the Proven article.

Shop DEFIB™ Pre-Workout here

MADE FOR PROGRESS

References

1. Goldstein ER, Ziegenfuss T, Kalman D, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2010;7(1):5.
2. Raina R, Verma PK, Peshin R, Kour H. Potential of Juniperus communis L as a nutraceutical in human and veterinary medicine. Heliyon. 2019;5(8):e02376.
3. Zhong Z, Han J, Zhang J, Xiao Q, Hu J, Chen L. Pharmacological activities, mechanisms of action, and safety of salidroside in the central nervous system. Drug Des Devel Ther. 2018;12:1479-1489.
4. Sas-Nowosielska H, Magiera A, Sas-Nowosielski K, et al. Effects of short-term biosynthetic salidroside supplementation on exercise performance, mood state, and markers of inflammation and muscle damage in healthy active young adults. J Int Soc Sports Nutr. 2024;21(1):2396890.
5. Malaguarnera M, Cammalleri L, Gargante MP, et al. L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians: a randomized and controlled clinical trial. Am J Clin Nutr. 2007;86(6):1738-1744.
6. Parnetti L, Gaiti A, Mecocci P, et al. Pharmacokinetics of IV and oral acetyl-L-carnitine in a multiple dose regimen in patients with senile dementia of Alzheimer type. Eur J Clin Pharmacol. 1992;42(1):89-93.
7. Secades JJ, Lorenzo JL. Citicoline: pharmacological and clinical review, 2006 update. Methods Find Exp Clin Pharmacol. 2006;28 Suppl B:1-56.
8. Wurtman RJ, Regan M, Ulus I, Yu L. Effect of oral CDP-choline on plasma choline and uridine levels in humans. Biochem Pharmacol. 2000;60(7):989-992.
9. Warskulat U, Heller-Stilb B, Oermann E, et al. Phenotype of the taurine transporter knockout mouse. Methods Enzymol. 2007;428:439-458.
10. Waldron M, Patterson SD, Tallent J, Jeffries O. The effects of an oral taurine dose and supplementation period on endurance exercise performance in humans: a meta-analysis. Sports Med. 2018;48(5):1247-1253.
11. Cholewa JM, Wyszczelska-Rokiel M, Glowacki R, et al. Effects of betaine on body composition, performance, and homocysteine thiolactone. J Int Soc Sports Nutr. 2013;10(1):39.
12. Trepanowski JF, Farney TM, McCarthy CG, et al. The effects of chronic betaine supplementation on exercise performance, skeletal muscle oxygen saturation and associated biochemical parameters in resistance trained men. J Strength Cond Res. 2011;25(12):3461-3471.
13. Trexler ET, Smith-Ryan AE, Stout JR, et al. International society of sports nutrition position stand: Beta-Alanine. J Int Soc Sports Nutr. 2015;12:30.

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This content is for educational purposes only and does not intend to cure or diagnose disease, nor make any health claims. There is no intent to slander in any way, but rather produce an informed and accurate third party perspective on the product. Always consult your accredited medical professional before introducing a new supplement. This content is not to be copied or repurposed in any form without express permission from the author.

First published for HRLABS.co.uk 23rd January 2026