Pre-Workout

Pre-workout is a food supplement category rather than a single ingredient. It covers stimulant formulas built around caffeine and stimulant-free formulas built around ingredients studied for blood flow and hydration, such as inositol-stabilised arginine silicate (sold as Nitrosigine), citrulline and glycerol. This page lists every pre-workout stocked at Free Muscle, compared on the named ingredients and amount per serving, servings per pack and independent batch testing. These are food supplements for adults and are sold for consumption.

What is a pre-workout?

The label tells you which of two products you are looking at. A stimulant pre-workout relies mainly on caffeine, often with beta-alanine, and is marketed on that basis. A stimulant-free pre-workout leaves caffeine out and instead combines ingredients that have been studied for their effect on blood vessel dilation and cell hydration. The two are not interchangeable, and a stimulant-free product will not feel like a caffeinated one.

The product we currently stock, NitraGlyc, is stimulant-free and contains two ingredients. Nitrosigine is a patented complex of the amino acid arginine bonded to silicate and stabilised with inositol. Arginine is an amino acid that the body uses, among other things, as a substrate for the enzyme nitric oxide synthase. Glycerol, also called glycerine, is a sugar alcohol present in the body as the backbone of triglycerides. It has been studied since the 1980s in the context of hydration before endurance exercise in the heat.

Neither ingredient has an authorised health claim in the UK or EU. The European Food Safety Authority has assessed and rejected performance and blood flow claims for arginine, and no claim has been authorised for glycerol or for Nitrosigine as such. That means no performance, pump, blood flow or hydration claim can lawfully be made for this product, and this page does not make one. What follows is a description of what published studies measured in their participants.

What the published research reports

• Safety and pharmacokinetics of inositol-stabilised arginine silicate (2015). An open-label study in ten healthy men measured plasma arginine and salivary nitric oxide markers over 14 days of daily intake. The study was small, open-label and unblinded, and the authors called for further work. Kalman DS, et al. A clinical evaluation to determine the safety, pharmacokinetics, and pharmacodynamics of an inositol-stabilized arginine silicate dietary supplement in healthy adult males. Clin Pharmacol. 2015;7:103-109. PMID: 26504409.
• Acute vasodilation with Nitrosigine or citrulline malate (2020). A randomised, double-blind crossover in 24 healthy young adults measured flow-mediated dilation of the brachial artery at rest after a single serving of Nitrosigine, of citrulline malate or of placebo, and reported differences between the active servings and placebo in that resting marker. The study measured a vascular marker at rest, not exercise performance, and lasted a single session. Rogers JM, et al. Acute effects of Nitrosigine and citrulline malate on vasodilation in young adults. J Int Soc Sports Nutr. 2020;17(1):12. PMID: 32093766.
• Meta-analysis of glycerol hyperhydration (2007). Pooling 14 studies of glycerol taken with large volumes of fluid, the authors reported greater fluid retention than with water alone and judged the evidence on endurance performance inconclusive. Goulet ED, et al. A meta-analysis of the effects of glycerol-induced hyperhydration on fluid retention and endurance performance. Int J Sport Nutr Exerc Metab. 2007;17(4):391-410. PMID: 17962713.
• Review of glycerol use around exercise (2010). An evidence review of glycerol before, during and after exercise reported that side effects were uncommon but included nausea, gastrointestinal discomfort and headache, mostly at large doses or with too little fluid. van Rosendal SP, et al. Guidelines for glycerol use in hyperhydration and rehydration associated with exercise. Sports Med. 2010;40(2):113-129. PMID: 20092365.

The glycerol studies used doses in the tens of grams dissolved in large volumes of fluid, which is a very different quantity from the amount in a capsule. These are summaries of what the studies measured, and none of them is a claim about the product on this page.

Brands of pre-workout we stock

• Free Muscle NitraGlyc, stimulant-free pump pre-workout, 60 capsules. Our own brand, containing Nitrosigine and glycerol in capsule form, 60 capsules per pack. No caffeine or other stimulant. The exact amount of each ingredient per serving is on the label. Every Free Muscle batch is assayed by Janoshik Analytical, an independent laboratory, and the certificate for the batch you receive is available by email on request. View NitraGlyc, 60 capsules.

At present this is the only pre-workout we stock. Other brands will be added to this page when held in stock.

How to compare them

Compare pre-workouts on the milligrams of each named ingredient per serving, not on the total scoop or capsule weight, and check that every ingredient has a stated quantity. Then divide the price by servings per pack for a cost per session. Be wary of proprietary blends that give a total without breaking out each ingredient, and of labels that list ingredients with no quantity at all. Finally, check the batch certificate for identity and the stated quantities.

Batch testing and certificates of analysis

A certificate of analysis (COA) reports what an independent laboratory found when it tested a sample from a specific batch: the identity of each named ingredient and the measured amount, together with the laboratory name, method, batch number and date. Every Free Muscle batch is tested by Janoshik Analytical, which we neither own nor control. To request the certificate for your pack, email us with the batch number printed on it.

A generic PDF with no batch number, no date or no named laboratory is not a batch certificate. For third-party brands we show a certificate only where the manufacturer supplies one for the batch we hold. See our lab testing page for how to read one.

Legal status in the UK

Pre-workout products are food supplements in the UK, sold under the Food Supplements Regulations and labelled under the retained Regulation (EC) No 1924/2006 on nutrition and health claims. Because no health claim is authorised for arginine silicate or glycerol, none is made here. These products are not medicines and are not regulated by the MHRA. Neither arginine nor glycerol is on the current WADA Prohibited List. Glycerol was listed as a plasma expander until it was removed on 1 January 2018, so older sources may still describe it as banned. Athletes subject to testing should still favour batch-tested products to reduce contamination risk. Free Muscle sells to adults aged 18 or over. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.

Storage and handling

Keep the container tightly sealed in a cool, dry place away from direct sunlight and heat. Glycerol is hygroscopic, meaning it draws in moisture, so reseal the pack promptly after opening. Keep the batch number until the pack is finished, and keep out of the reach of young children.

Delivery and returns

Free Muscle is a UK company, FreeMuscle LTD, based in Scunthorpe. Every order ships with free tracked UK delivery in plain packaging. Orders placed before 2pm Monday to Friday are processed the same working day. EU delivery takes 3 to 7 working days. Unopened items can be returned within 30 days. Customers must be 18 or over. See shipping and our guarantee for the full terms.

Related reading

• Nitrosigine: How It Works Without Stimulants
• Creatine and Taurine: What the Evidence Actually Supports
• Push Pull Legs: The Complete PPL Routine
• What Is Janoshik Analytical? Third-Party Testing Explained
• How to Read a Certificate of Analysis (COA)

Related collections: Creatine, Performance nutrition, Bioreactive Series, Free Muscle brand.

Pre-workout products on this page are food supplements for adults, not medicines, and have not been evaluated by the MHRA, EMA or FDA. No health claim is authorised for the ingredients and none is made. Food supplements should not replace a varied, balanced diet and a healthy lifestyle. You must be 18 or over to order. Nothing on this page is medical advice.