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GSN Xtreme Fury Pre-Workout
⚡ 310mg of caffeine (anhydrous + guarana) — equivalent to ~3 espressos per serving
💉 3077mg L-citrulline DL malate + 700mg L-arginine AKG — maximum pump
🔥 3065mg beta-alanine + 1000mg taurine — extreme endurance
🧠 300mg N-acetyl-L-tyrosine + 282mg choline bitartrate — intense focus
🇧🇪 Belgian brand — NSF & cGMP certified — 30 servings per 300g jar
What is GSN Xtreme Fury Pre-Workout?
GSN Xtreme Fury is the high-stimulant pre-workout in the GSN Labs range — the counterpart to the stimulant-free Vaso Pump, designed for the training sessions where maximum intensity is the objective. Each 10g serving delivers 310mg of caffeine (300mg anhydrous + 10mg from guarana extract), 3077mg of citrulline DL malate, 3065mg of beta-alanine and a nootropic stack of N-acetyl-L-tyrosine and choline bitartrate. Eight active ingredients, all individually declared, no proprietary blend.
GSN Labs is explicit about this product: 310mg of caffeine is a high dose — approximately three espressos per serving — intended for sessions where full intensity is required, not for daily routine use. The brand recommends avoiding consumption after 4pm due to the caffeine's half-life, and not combining with other significant caffeine sources on the same day.
The caffeine comes from two complementary sources: 300mg of caffeine anhydrous for an immediate, sharp energy onset, and 100mg of guarana extract standardised to 10% caffeine (contributing 10mg additional caffeine) for a slightly slower-releasing, sustained caffeine fraction that extends the energy curve beyond what anhydrous caffeine alone produces.
Beyond the stimulant dimension, Xtreme Fury provides a genuine pump and endurance stack: 3077mg of citrulline DL malate as a NO precursor for vasodilation, 700mg of L-arginine AKG 2:1 to compound the blood flow effect, and 3065mg of beta-alanine for intramuscular acid buffering. The nootropic layer — N-acetyl-L-tyrosine (300mg) and choline bitartrate (282mg) — supports catecholamine production and neurotransmitter signalling for sustained mental sharpness throughout the session.
Available in 300g (30 servings) across two flavours: Tropical Mango and Fruit Punch.
⚠️ High caffeine content: 310mg per serving. Avoid after 4pm.
310mg of caffeine. The sessions where limits are meant to be broken.
| Flavour | Fruit Punch or Tropical Mango |
| Brand | GSN Labs |
| Size | 300 gr |
How GSN Xtreme Fury Pre-Workout supports your objectives
⚡ 310mg caffeine — anhydrous + guarana — immediate and sustained energy
The dual caffeine source of Xtreme Fury is a deliberate formulation choice. Caffeine anhydrous (300mg) is absorbed rapidly, producing a sharp, clear energy onset within 15 to 30 minutes. Guarana extract (100mg, 10% caffeine = 10mg) is metabolised more slowly due to the tannins and other compounds naturally present in the guarana seed that regulate caffeine absorption — extending the energy curve beyond the initial anhydrous spike. At 310mg total, the dose exceeds the 200mg threshold at which EFSA confirms that caffeine contributes to increased endurance performance, and the 75mg threshold for increased alertness and concentration — both EU-authorised health claims.
💉 3077mg L-citrulline DL malate + 700mg L-arginine AKG — the compound NO stack
Citrulline and arginine both act as substrates for nitric oxide (NO) synthesis, but through different pathways. Citrulline is converted to arginine in the kidneys, steadily replenishing the arginine pool. L-arginine AKG provides direct arginine substrate. By combining both at 3077mg and 700mg respectively, Xtreme Fury creates a sustained NO production stimulus that produces the pump and vasodilation effect throughout the session rather than at a single peak.
🔥 3065mg beta-alanine — intramuscular acid buffering at a meaningful dose
Beta-alanine at 3065mg is above the minimum effective dose studied for carnosine synthesis (2 to 3g). Carnosine is the primary intramuscular buffer against hydrogen ion accumulation during high-intensity exercise — the direct cause of the burning sensation that limits repetitions and sprint duration. Higher carnosine content delays this threshold, extending the number of effective repetitions per set and the duration of high-intensity intervals. The characteristic tingling sensation (paresthesia) is normal, harmless and expected at this dose.
💧 1000mg taurine — cellular hydration during high-intensity training
Taurine supports the osmotic regulation of muscle cells and modulates calcium-dependent muscle contraction. At 1000mg per serving, it contributes to maintaining intracellular hydration during the high sweat rates typical of intense training sessions.
🧠 N-acetyl-L-tyrosine (300mg) + choline bitartrate (282mg) — the nootropic stack
N-acetyl-L-tyrosine is the acetylated, more bioavailable form of L-tyrosine — the precursor to dopamine and norepinephrine. These catecholamines drive motivation, alertness and the mental intensity needed to push through difficult sets. Choline bitartrate provides the precursor to acetylcholine — the primary neurotransmitter of neuromuscular signalling. Together, the two nootropics address both the motivational (dopamine/norepinephrine) and the neuromuscular (acetylcholine) dimensions of training focus.
🎯 Goal guide
🏋️ Mass gain: 1 serving pre-workout on high-intensity training days. Maximum energy and pump for volume sessions.
🔥 Weight loss / cutting: 1 serving before morning or early afternoon training sessions. High-dose caffeine thermogenic effect alongside training performance support.
⚖️ Strength and power: 1 serving before heavy compound sessions. Stimulant energy for maximal effort lifts.
Serving suggestion
Mix 1 scoop (10g) in 200 to 300ml of cold water. Shake well for 15 seconds. Consume 20 minutes before training. Do not exceed 1 serving per day. Do not combine with other caffeinated beverages on the same day. Not recommended for children, pregnant or breastfeeding women, individuals sensitive to caffeine or individuals with cardiovascular conditions. Store in a cool, dry place away from sunlight.
⚠️ Avoid after 4pm — with a caffeine half-life of approximately 5 to 6 hours, a serving taken at 4pm may maintain meaningful plasma caffeine levels until 10pm, disrupting sleep onset and quality.
⚠️ Beta-alanine paresthesia: a harmless tingling sensation in the skin (face, neck, hands) approximately 15 to 30 minutes after consumption is normal at this beta-alanine dose. It is a completely safe physiological reaction. The sensation diminishes with regular use.
Best times to enjoy it
🌅 Morning training (6 to 10am)
The ideal window: full caffeine effect during the session, complete clearance by evening. Morning use also benefits from the overnight fasting state, during which caffeine sensitivity is at its highest — meaning 310mg produces a stronger effect than the same dose consumed later in the day when prior caffeine intake has already raised baseline tolerance.
⚡ Early afternoon (11am to 2pm)
The second optimal window for training with Xtreme Fury — allowing complete caffeine clearance by 10pm for a 2pm consumption. The post-lunch cortisol dip coincides with this window, making the caffeine stimulus particularly effective against the natural afternoon energy decline.
🚫 Avoid after 4pm
GSN Labs explicitly recommends against use after 4pm. With 310mg of caffeine and a 5 to 6-hour half-life, a serving at 5pm maintains approximately 155mg of active caffeine at 11pm — a level sufficient to significantly delay sleep onset and reduce sleep quality. Sleep is the primary recovery tool in any training programme; its protection is non-negotiable.
Xtreme Fury vs Vaso Pump — choosing the right pre-workout
| Criterion | Xtreme Fury | Vaso Pump |
|---|---|---|
| Caffeine | 310mg | 0mg |
| Citrulline | 3077mg | 8000mg |
| Beta-alanine | 3065mg | 4000mg |
| Evening use | Not recommended | Full compatibility |
| Primary effect | Energy + focus + pump | Pump + endurance + focus |
| Best for | Maximum intensity sessions | Any session, any time |
Full ingredient list
Beta-alanine (3065mg), caffeine anhydrous (300mg), L-citrulline DL malate 2:1 (3077mg), taurine (1000mg), L-arginine AKG 2:1 (700mg), N-acetyl-L-tyrosine (300mg), choline bitartrate (282.1mg), guarana extract standardised at 10% caffeine (100mg = 10mg caffeine). Flavourings, colourant (natural), sweetener (sucralose).
Eight active ingredients. Every milligram declared. No proprietary blend.
Complete ingredient breakdown per 10g serving
| Ingredient | Per 10g serving | Role |
|---|---|---|
| Beta-alanine | 3065mg | Carnosine precursor; intramuscular acid buffer; endurance |
| Caffeine anhydrous | 300mg | Primary stimulant; immediate energy onset; alertness; performance |
| L-citrulline DL malate 2:1 | 3077mg | NO precursor; vasodilation; pump; blood flow |
| Taurine | 1000mg | Muscle cell osmotic balance; cellular hydration |
| L-arginine AKG 2:1 | 700mg | Direct NO substrate; compounds citrulline pump effect |
| N-acetyl-L-tyrosine | 300mg | Bioavailable tyrosine; catecholamine precursor; motivation and focus |
| Choline bitartrate | 282.1mg | Acetylcholine precursor; neuromuscular signalling |
| Guarana extract (10% caffeine) | 100mg (= 10mg caffeine) | Sustained caffeine release; extends energy curve beyond anhydrous peak |
| Total caffeine | 310mg | Anhydrous 300mg + guarana 10mg |
| Total calories | 16.5 kcal | — |
| Total fibre | 3.8g | — |
Allergens
No major allergens declared. No added sugar, gluten-free, GMO-free. Always refer to the current product label for the most up-to-date allergen information.
Product characteristics:
- 310mg caffeine per serving (high dose — see warnings)
- 0.01g sugar
- 16.5 kcal per serving
- 3.8g dietary fibre per serving
- Gluten-free
- GMO-free
- NSF certified
- cGMP certified production
Nutritional values per serving (10g)
| Nutritional values | Per 10g serving |
|---|---|
| Energy | 16.5 kcal |
| Fat | 0g |
| Carbohydrates | trace |
| of which sugars | 0.01g |
| Dietary fibre | 3.8g |
| Protein | 0g |
| Salt | 0g |
| Total caffeine | 310mg |
Active ingredient profile per serving — fully declared
| Active ingredient | Per serving |
|---|---|
| Beta-alanine | 3065mg |
| L-citrulline DL malate 2:1 | 3077mg |
| Taurine | 1000mg |
| L-arginine AKG 2:1 | 700mg |
| Caffeine anhydrous | 300mg |
| N-acetyl-L-tyrosine | 300mg |
| Choline bitartrate | 282.1mg |
| Guarana extract (10% caffeine) | 100mg (= 10mg caffeine) |
| Total caffeine | 310mg |
Jar duration guide
| Format | Net weight | Servings (at 10g/day) |
|---|---|---|
| Standard | 300g | 30 servings |
Q1 — Why 310mg of caffeine — is that not dangerously high?
310mg is a high but safe dose for most healthy adults. EFSA sets the tolerable single dose of caffeine at 200mg for the general population, but notes that 400mg per day is safe for healthy adults who are caffeine-tolerant. For regular caffeine consumers — who represent the primary audience for a high-stimulant pre-workout — 310mg in a single dose is a strong but manageable stimulus. GSN Labs is transparent about this: the product is designed for sessions where maximum intensity is needed, not for daily habitual use. First-time users or caffeine-sensitive individuals should start with a half scoop (5g = 155mg caffeine) to assess their individual tolerance.
Q2 — What is the difference between Xtreme Fury and Vaso Pump?
They are complementary products that serve different training needs. Vaso Pump (0mg caffeine, 8000mg citrulline) is designed for the pump effect without any stimulant load — suitable for any training session at any time of day, and stackable with any caffeinated drink. Xtreme Fury (310mg caffeine, 3077mg citrulline) is designed for maximum intensity sessions where the energy and focus demand is as high as the physical demand — not recommended for evening sessions or daily use. Athletes who want both effects can combine them, but this is only appropriate for caffeine-tolerant individuals training in the morning or early afternoon, as the combined caffeine load (310mg from Xtreme Fury alone) already approaches the upper daily intake limit.
Q3 — Why does Xtreme Fury use N-acetyl-L-tyrosine instead of plain L-tyrosine?
N-acetyl-L-tyrosine (NALT) is an acetylated form of L-tyrosine with greater water solubility and reported improved bioavailability compared to free-form L-tyrosine — making it more effective at lower doses in a powder matrix. Both forms serve as precursors to dopamine and norepinephrine; NALT's formulation advantages make it the preferred choice for a concentrated 10g powder serving where space for individual ingredients is limited.
Q4 — Can I use Xtreme Fury every day?
GSN Labs explicitly designs Xtreme Fury for the sessions where maximum intensity is needed — not for daily use. Daily high-dose caffeine supplementation (310mg per day) rapidly builds tolerance, progressively diminishing the perceived energy effect and requiring higher doses for the same stimulus. More importantly, consistent high caffeine intake disrupts sleep architecture even when consumed in the morning, and reduces the recovery quality that training adaptations depend on. Using Xtreme Fury 2 to 3 times per week on the heaviest or most demanding sessions — with stimulant-free Vaso Pump or no pre-workout on lighter days — preserves both caffeine sensitivity and recovery quality.
Q5 — How long does one 300g jar last?
At 10g per serving and one serving per training day, the 300g jar provides exactly 30 servings. For athletes who use Xtreme Fury 3 times per week (the recommended maximum frequency), one jar provides 10 weeks of supply. For athletes who use it on every training day (5 to 6 times per week), one jar provides 5 to 6 weeks.