The research behind every ingredient.

Peer-reviewed studies on the ingredients in BLUD®, SWET™ and TIERZ®, and what each one found. Tap any study to see it up close or read the full paper.

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Citrulline

BLUD®8g citrulline malate

An amino acid your body turns into arginine and then nitric oxide, which helps widen blood vessels for better bloodflow.

Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study Faster time trials and less muscle fatigue22 trained men took 2.4g of L-citrulline a day for a week. They finished a 4 km cycling time trial 1.5% faster than on placebo, put out 2% more power, and reported less muscle fatigue and better concentration afterward.Randomized controlled trial. Suzuki et al., Journal of the International Society of Sports Nutrition, 2016 View study Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis Participants did more reps to failureAcross 8 double-blind studies with 137 people, taking 6 to 8g of citrulline malate 40 to 60 minutes before lifting added about 3 reps to failure (6.4% more) versus placebo. The effect was small, and separate upper and lower body results were not significant.Meta-analysis of 8 studies. Vårvik et al., International Journal of Sport Nutrition and Exercise Metabolism, 2021 View study Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis Increase in strength and powerPooling 12 placebo-controlled studies with 198 healthy people, citrulline (3g or more, at least 30 minutes before) gave a small but significant improvement in high-intensity strength and power. No single study was conclusive on its own.Meta-analysis of 12 studies. Trexler et al., Sports Medicine, 2019 View study Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis Lower effort and less muscle sorenessAcross 13 randomized trials with 206 healthy people (most often 8g citrulline malate before exercise), citrulline lowered perceived effort during exercise and muscle soreness 24 hours later.Meta-analysis of 13 trials. Rhim et al., Journal of Sport and Health Science, 2020 View study

Beetroot

BLUD®8g organic beetroot

Beets are naturally rich in nitrate, which your body converts into nitric oxide.

Factors that Moderate the Effect of Nitrate Ingestion on Exercise Performance in Adults: A Systematic Review with Meta-Analyses and Meta-Regressions Improved exercise performanceAcross 123 randomized trials with 1,705 adults, nitrate gave a small but consistent boost to exercise performance. Beetroot worked better than nitrate salts, and the benefit was clearest in hard efforts lasting 2 to 10 minutes.Meta-analysis of 123 trials. Silva et al., Advances in Nutrition, 2022 View study Ergogenic Effect of Nitrate Supplementation: A Systematic Review and Meta-analysis Better exercise performance in active menPooling 80 placebo-controlled crossover studies in young healthy adults, dietary nitrate improved exercise performance by a small amount. The benefit showed up in recreationally active men but not in well-trained endurance athletes or the few women-only studies.Meta-analysis of 80 studies. Senefeld et al., Medicine & Science in Sports & Exercise, 2020 View study Effect of dietary nitrate ingestion on muscular performance: a systematic review and meta-analysis of randomized controlled trials Increase in muscular enduranceAcross 34 studies, dietary nitrate gave a small but significant boost to muscular endurance and a trivial, though significant, effect on strength. Results held across dose, training level and muscle group.Meta-analysis of 34 studies. Alvares et al., Critical Reviews in Food Science and Nutrition, 2022 View study Effect of dietary nitrate on human muscle power: a systematic review and individual participant data meta-analysis Increase in muscle powerPooling individual data from 19 double-blind crossover studies with 268 people, dietary nitrate increased maximal muscle power by about 5% on average. A single dose before exercise worked better than several days of dosing, and results were similar across age and sex.Meta-analysis of 19 studies. Coggan et al., Journal of the International Society of Sports Nutrition, 2021 View study The Effect of Nitrate Supplementation on Exercise Tolerance and Performance: A Systematic Review and Meta-Analysis Exercised longer before exhaustionAcross 29 studies in healthy people, nitrate had a small but significant effect on how long participants could exercise before exhaustion. It did not improve the time needed to finish a set distance.Meta-analysis of 29 studies. Van De Walle & Vukovich, Journal of Strength and Conditioning Research, 2018 View study

Beta-alanine

BLUD®4g beta-alanine

Raises carnosine in your muscles, which buffers the acid that builds up during hard sets. A mild tingle is normal and harmless.

International society of sports nutrition position stand: Beta-Alanine More work before fatigue sets inThe International Society of Sports Nutrition concluded that 4 to 6g a day for at least 2 to 4 weeks improves exercise performance, most of all in all-out efforts lasting 1 to 4 minutes, and reduces neuromuscular fatigue.Expert position stand. Trexler et al., Journal of the International Society of Sports Nutrition, 2015 View study β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis Improved exercise capacityPooling 40 placebo-controlled studies with 1,461 healthy people, beta-alanine gave a small but significant overall benefit. It helped most in hard efforts lasting about 30 seconds to 10 minutes, especially tests of how long you can keep going.Meta-analysis of 40 studies. Saunders et al., British Journal of Sports Medicine, 2017 View study β-alanine improves punch force and frequency in amateur boxers during a simulated contest Harder, faster punches in boxers16 amateur boxers took 1.5g of beta-alanine 4 times a day or placebo for 4 weeks. In an all-out 10 second burst after a simulated 3 round bout, punch force rose by 20kg versus 1kg on placebo, and punch count also improved.Placebo-controlled trial. Donovan et al., International Journal of Sport Nutrition and Exercise Metabolism, 2012 View study

Caffeine

BLUD®220mg natural caffeine from guarana

Natural caffeine from guarana for energy and focus when you train.

International society of sports nutrition position stand: caffeine and exercise performance Better performance and sharper focusThe International Society of Sports Nutrition found that 3 to 6mg per kg of body weight, usually taken about an hour before exercise, consistently improves performance, from strength and muscular endurance to sprinting and aerobic endurance. It also improves attention and alertness.Expert position stand. Guest et al., Journal of the International Society of Sports Nutrition, 2021 View study The Effect of Acute Caffeine Ingestion on Endurance Performance: A Systematic Review and Meta-Analysis More power and faster endurance timesAcross 46 placebo-controlled studies, caffeine improved endurance time trials, raising average power by about 3% and cutting completion time by about 2%. The effect was small but clear at moderate doses of 3 to 6mg per kg, though some studies saw no benefit.Meta-analysis of 46 studies. Southward et al., Sports Medicine, 2018 View study Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis Increase in strength and jump powerPooling 10 strength studies and 10 power studies, caffeine produced small but significant improvements in 1 rep max strength and vertical jump power. The strength gain was significant for the upper body but not the lower body.Meta-analysis of 20 studies. Grgic et al., Journal of the International Society of Sports Nutrition, 2018 View study Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine Works even for daily coffee drinkersAcross 60 studies, caffeine gave a small, significant boost over placebo for endurance, power and strength, and habitual caffeine intake did not change that. Doses up to 6mg per kg worked; doses above 6mg per kg did not reach significance.Meta-analysis of 60 studies. Carvalho et al., Sports Medicine, 2022 View study Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis Sharper attention, accuracy and speedReviewing 13 crossover studies in sport (5 pooled in a meta-analysis), caffeine significantly improved attention, accuracy and speed. The wider evidence suggests low to moderate doses before or during exercise can also lift self-reported energy and mood.Systematic review of 13 studies. Lorenzo Calvo et al., Nutrients, 2021 View study Effects of acute caffeine consumption following sleep loss on cognitive, physical, occupational and driving performance: A systematic review and meta-analysis Sharper focus when short on sleepPooling 45 publications on sleep-deprived or sleep-restricted people, caffeine improved attention, reaction time, executive function and driving control. Studies also generally showed benefits for memory and for physical performance.Meta-analysis of 45 publications. Irwin et al., Neuroscience & Biobehavioral Reviews, 2020 View study

L-theanine

BLUD®250mg L-theanine

A calming amino acid found in tea, and the classic partner to caffeine.

Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial Lower stress, better sleep and focus30 healthy adults took 200mg of L-theanine a day for 4 weeks. Their stress and anxiety scores dropped, their sleep quality improved, and they scored better on verbal fluency and executive function tests.Randomized controlled trial. Hidese et al., Nutrients, 2019 View study The effects of L-theanine, caffeine and their combination on cognition and mood Caffeine plus theanine improved focusIn a double-blind crossover trial, 250mg L-theanine plus 150mg caffeine improved accuracy, reaction speed and working memory, and made people feel more alert and less tired. Theanine on its own didn't produce these gains, so the pairing is what counts.Randomized double-blind crossover trial. Haskell et al., Biological Psychology, 2008 View study The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review Less stress and anxietyReviewing 9 randomized controlled trials, the authors concluded that 200 to 400mg of L-theanine daily may help reduce feelings of stress and anxiety in people under stressful conditions. They noted longer and larger studies are still needed.Systematic review of 9 trials. Williams et al., Plant Foods for Human Nutrition, 2020 View study

Tart cherry

BLUD®Tart cherry

Tart cherries are packed with polyphenols, plant compounds studied for recovery after hard training.

Tart cherry and pomegranate supplementations enhance recovery from exercise-induced muscle damage: a systematic review Faster recovery after hard trainingA review of 25 studies found tart cherry helped people recover strength and function faster after muscle-damaging exercise, with less soreness and inflammation, especially when taken for several days before and after.Systematic review of 25 studies. Rojano-Ortega et al., Biology of Sport, 2021 View study Tart Cherry Supplementation and Recovery From Strenuous Exercise: A Systematic Review and Meta-Analysis Faster strength recovery, less sorenessPooling 14 studies, tart cherry had a small benefit for muscle soreness and a moderate benefit for recovering strength and power after hard exercise, with a large effect on jump height recovery. Creatine kinase, a muscle damage marker, did not change.Meta-analysis of 14 studies. Hill et al., International Journal of Sport Nutrition and Exercise Metabolism, 2021 View study Montmorency cherry juice reduces muscle damage caused by intensive strength exercise Faster strength recovery after heavy lifting10 trained men took Montmorency cherry juice concentrate or a fruit concentrate for 7 days before and 2 days after 10 sets of 10 heavy single-leg extensions. With cherry, strength recovered faster (about 91% vs 85% of baseline at 24 hours).Controlled crossover trial. Bowtell et al., Medicine & Science in Sports & Exercise, 2011 View study Influence of tart cherry juice on indices of recovery following marathon running Faster strength recovery after a marathon20 recreational marathon runners drank tart cherry juice or placebo for 5 days before and 48 hours after the race. The cherry group regained strength faster and had lower inflammation markers and about 10% higher antioxidant status; other muscle damage markers did not differ.Randomized placebo-controlled trial. Howatson et al., Scandinavian Journal of Medicine & Science in Sports, 2010 View study

Electrolytes

SWET™320mg sodium, 525mg potassium, 50mg magnesium

Sodium, potassium and magnesium are the minerals you lose in sweat. Replacing them helps your body hold on to the water you drink.

Efficacy of Ingesting an Oral Rehydration Solution after Exercise on Fluid Balance and Endurance Performance More of the water you drink stays inAfter 75 minutes of cycling in the heat, 9 trained men rehydrated with water, a sports drink or a high-electrolyte drink. The electrolyte drink kept 30% of the fluid in the body, versus 10% for the sports drink and none for water. 7 of the 9 also rode a later time trial faster than with water.Randomized controlled trial. Fan et al., Nutrients, 2020 View study

Creatine

TIERZ®5g Creapure® creatine

The most researched sports supplement there is. It refuels the quick energy your muscles use for heavy lifts and sprints.

International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine More strength and power from trainingThe International Society of Sports Nutrition reviewed decades of research. Creatine raises the creatine stored in muscle, improves high-intensity performance and leads to greater training gains. It may also help recovery, and doses up to 30g a day for 5 years were safe in healthy people.Expert position stand. Kreider et al., Journal of the International Society of Sports Nutrition, 2017 View study Creatine Supplementation and Lower Limb Strength Performance: A Systematic Review and Meta-Analyses Stronger squats and leg pressAcross 60 randomized placebo-controlled trials with about 1,300 people, creatine improved lower body strength in efforts under 3 minutes, including squat and leg press. The effect was small but consistent across age, sex, training status, dose and duration.Meta-analysis of 60 trials. Lanhers et al., Sports Medicine, 2015 View study Creatine Supplementation and Upper Limb Strength Performance: A Systematic Review and Meta-Analysis Stronger bench and chest pressPooling 53 randomized placebo-controlled trials (563 people on creatine, 575 on placebo), creatine improved upper body strength in efforts under 3 minutes, including bench press and chest press. The benefit held regardless of age, sex, training, dose or duration.Meta-analysis of 53 trials. Lanhers et al., Sports Medicine, 2017 View study Meta-Analysis Examining the Importance of Creatine Ingestion Strategies on Lean Tissue Mass and Strength in Older Adults More muscle and strength in older liftersIn older adults doing resistance training, creatine added more lean mass and strength than placebo regardless of dosing strategy. Taking it only on training days also worked, and studies with a loading phase (20g or more daily for 5 to 7 days) drove the strength gains.Meta-analysis. Forbes et al., Nutrients, 2021 View study Creatine supplementation for optimization of physical function in the patient at risk of functional disability: A systematic review and meta-analysis Stronger and leaner in older adultsAcross 33 randomized trials with 1,076 older adults and adults at risk of losing physical function, creatine improved sit-to-stand performance, upper body and grip strength, and added about 1.1kg of lean mass versus placebo. The authors rated evidence quality as low.Meta-analysis of 33 trials. Davies et al., JPEN Journal of Parenteral and Enteral Nutrition, 2024 View study Creatine ingestion augments dietary carbohydrate mediated muscle glycogen supercompensation during the initial 24 h of recovery following prolonged exhaustive exercise in humans More muscle fuel stored after exerciseAfter 14 healthy men cycled to exhaustion, those taking 20g of creatine daily with a high carb diet stored noticeably more muscle glycogen than placebo within the first day of recovery, and the advantage lasted through day 6.Placebo-controlled trial. Roberts et al., Amino Acids, 2016 View study Putting to rest the myth of creatine supplementation leading to muscle cramps and dehydration No link to cramps or dehydrationThis review found that published studies have refuted claims that creatine causes muscle cramps or dehydration. Newer reports suggest it may even help with temperature regulation in the heat, with little evidence of added risk.Expert review. Dalbo et al., British Journal of Sports Medicine, 2008 View study

Collagen

TIERZ®10.8g multi-collagen

The main protein in your tendons, ligaments, cartilage and skin.

The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review Less joint pain, better joint functionA review of 15 randomized trials found that collagen peptides, taken alongside exercise, were most helpful for improving joint function and reducing joint pain, with some gains in body composition, strength and muscle recovery.Systematic review of 15 trials. Khatri et al., Amino Acids, 2021 View study

Hyaluronic acid

TIERZ®55mg hyaluronic acid

Holds water in your skin and joints, keeping them hydrated and cushioned.

Oral hyaluronan relieves wrinkles: a double-blinded, placebo-controlled study over a 12-week period Fewer wrinkles, more supple skin60 adults took 120mg of hyaluronic acid or a placebo every day for 12 weeks. The hyaluronic acid groups had fewer wrinkles than placebo, and their skin's glow and suppleness improved.Randomized controlled trial. Oe et al., Clinical, Cosmetic and Investigational Dermatology, 2017 View study

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These studies tested each ingredient on its own, at the dose and timing listed in each paper. They did not test Steel Monkey products.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.