As an endurance athlete, your training demands are intense—pushing your body day in and day out to increase stamina, improve cardiovascular efficiency, and delay fatigue. Whether you're logging hundreds of miles on the road, crushing long-distance cycling routes, or preparing for your next triathlon, marathon, or CrossFit competition, optimizing your nutrition and supplementation strategy is critical for consistent progress and peak performance. The right supplements can enhance endurance, accelerate recovery, support hydration, and fuel your body more efficiently during prolonged training sessions. In this guide, we’ll break down the best supplements for endurance athletes so you can train harder, recover faster, and gain the competitive edge you need to outperform the rest.
Why Endurance Athletes Need Supplements
Endurance athletes face unique physiological challenges that place a high demand on energy systems, muscle recovery, and nutrient utilization. While a well-balanced diet is foundational, supplementation can provide targeted support to enhance performance and recovery. For example, beta-alanine is a proven supplement that increases intramuscular carnosine levels, helping buffer acid buildup during high-intensity exercise, thus delaying fatigue and improving performance in endurance events lasting 1–4 minutes or more (Trexler et al., 2015). Citrulline malate, a compound that supports nitric oxide production and improves blood flow, has been shown to reduce perceived exertion and improve aerobic energy production by enhancing oxygen delivery to working muscles (González et al., 2017). Additionally, strategic intake of carbohydrates before, during, and after prolonged exercise helps maintain glycogen stores, improve endurance capacity, and support faster recovery (Burke et al., 2011). These supplements, when used appropriately, can help endurance athletes train longer, recover quicker, and optimize overall performance.
6 Supplements For Endurance Athletes To Maximize Performance
1. Kre-Alkalyn
Kre-Alkalyn: One of the Best Supplements for Endurance Athletes
Kre-Alkalyn is a pH-corrected form of creatine, developed to improve stability and absorption compared to traditional creatine monohydrate. Creatine is one of the most researched and effective sports supplements, consistently shown to increase muscle force, power, and athletic performance by enhancing the body’s ability to regenerate ATP—the primary energy currency during high-intensity exercise (Kreider et al., Journal of the International Society of Sports Nutrition, 2017).
How Kre-Alkalyn Enhances Endurance and Performance
Kre-Alkalyn works by increasing phosphocreatine stores in muscle tissue by up to 20%, which in turn supports rapid ATP production during strenuous activity. This translates to improvements in strength, speed, and explosive power. What sets Kre-Alkalyn apart from standard creatine is its impact on VO2 Max—a critical marker of aerobic performance and endurance capacity.
VO2 Max refers to the maximum amount of oxygen your body can utilize during intense exercise. Since oxygen consumption is directly related to aerobic energy expenditure, improvements in VO2 Max reflect an athlete’s ability to sustain high-intensity output over time (Bassett & Howley, Medicine & Science in Sports & Exercise, 2000).
Clinical Research on Kre-Alkalyn and VO2 Max
A clinical study conducted by physicians at Greenberg Medical Center evaluated 24 male Olympic-level athletes over a 4-month period. One group supplemented with 750 mg of Kre-Alkalyn daily, while the second group used 750 mg of creatine monohydrate. While both groups experienced similar gains in lean muscle and strength, the Kre-Alkalyn group showed a significantly greater increase in VO2 Max, indicating improved aerobic capacity and endurance performance.
Why Kre-Alkalyn Benefits Endurance Athletes
Endurance sports like CrossFit, cycling, and distance running place intense demands on both aerobic and anaerobic energy systems. By improving VO2 Max and increasing the rate of ATP regeneration, Kre-Alkalyn helps athletes train harder, recover faster, and delay muscle fatigue. The result: enhanced performance, faster times, and improved stamina during prolonged high-intensity efforts
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2. Beta-Alanine (CarnoSyn)
Beta-Alanine: A Proven Supplement for Endurance and Performance
Beta-alanine is a non-essential beta-amino acid that has become one of the most effective supplements for endurance athletes due to its proven ability to delay muscle fatigue and reduce lactic acid buildup during high-intensity exercise. It plays a critical role in forming carnosine—a dipeptide that acts as a buffer against acid accumulation in muscle tissue, helping maintain optimal pH levels during training.
Uniquely, beta-alanine is a key component of carnosine and anserine, as well as vitamin B5 (pantothenic acid). Once ingested, beta-alanine is transported through the bloodstream into skeletal muscle, where it binds with the amino acid L-histidine to synthesize carnosine (Trexler et al., Journal of the International Society of Sports Nutrition, 2015).
Why Beta-Alanine Supports Endurance Athletes
Carnosine serves as the body’s first line of defense against rising hydrogen ion concentrations that occur during anaerobic exercise. As hydrogen ions accumulate, muscle pH decreases, resulting in the burning sensation and premature fatigue experienced during intense effort. Supplementing with beta-alanine significantly increases muscle carnosine levels—up to 58% in 4 weeks and up to 80% in 10 weeks—which delays fatigue and enhances overall performance (Hill et al., Amino Acids, 2007).
For endurance athletes, this means higher training volume, longer time to exhaustion, and improved performance in sports that rely on sustained high-intensity effort like CrossFit, cycling, running, and HIIT. By buffering acid more efficiently, beta-alanine helps athletes push through fatigue and maintain peak output longer.
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3. Citrulline Malate
Citrulline Malate: The Ultimate Endurance Booster for Athletes
Citrulline Malate is a powerful supplement that combines the non-essential amino acid L-Citrulline with malate, a compound derived from malic acid that plays a vital role in aerobic energy production through the Krebs cycle. This combination has been extensively studied and shown to significantly improve aerobic performance, muscular endurance, nitric oxide production, and recovery, making it one of the best supplements for endurance athletes.
Unlike other performance supplements that only target strength or size, Citrulline Malate is uniquely positioned to support sustained energy output, delay the onset of muscle fatigue, and enhance oxygen utilization, all without the need for stimulants or heavy loading phases.
Why Citrulline Malate Is One of the Best Supplements for Endurance Athletes
One of Citrulline Malate’s most impressive benefits is its role in increasing aerobic ATP production, which fuels sustained efforts during long-duration training. A landmark study published in the British Journal of Sports Medicine found that a 6-gram daily dose of Citrulline Malate led to a 34% increase in oxidative ATP production during exercise and a 20% faster phosphocreatine recovery rate following intense physical activity (Bendahan et al., BJSM, 2002). This helps reduce muscle fatigue and allows for longer, more intense training sessions—critical for athletes who run, cycle, swim, or perform high-rep functional fitness workouts.
Citrulline Malate has also been shown to reduce the perception of fatigue and soreness. Research published in the Journal of Strength and Conditioning Research demonstrated that resistance-trained individuals who supplemented with CM experienced a 40% increase in the number of reps performed and reduced post-exercise muscle soreness by 40% (Perez-Guisado & Jakeman, 2010)—a benefit that translates directly to better training consistency and recovery in endurance athletes.
Enhanced Nitric Oxide Production for Performance Gains
In addition to its effects on ATP and energy systems, Citrulline Malate is also known to dramatically boost nitric oxide (NO) production, which acts as a vasodilator. Vasodilation expands blood vessels, allowing for greater blood flow, oxygen delivery, and nutrient transport to working muscles without raising blood pressure. The result is improved muscular endurance, faster recovery, and reduced fatigue during extended efforts.
By increasing nitric oxide, Citrulline Malate can help you:
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Increase time to exhaustion during cardiovascular activity
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Maintain higher training intensities for longer durations
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Improve oxygen efficiency during sustained efforts
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Delay the onset of muscle fatigue
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Recover faster between training sessions
These performance benefits make Citrulline Malate one of the most effective, research-backed supplements for endurance athletes looking to optimize both aerobic and anaerobic capacity.
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4. L-Glutamine
L-Glutamine: Essential for Recovery, Immunity, and Muscle Preservation
Your training doesn’t end when your workout is over—it ends when you recover. For endurance athletes, recovery is not just important; it’s critical for maintaining performance, preventing overtraining, and continuing to make progress. One of the most overlooked but essential recovery supplements is L-Glutamine—the most abundant conditionally essential amino acid in the human body.
During intense and prolonged endurance training, glutamine levels become depleted faster than your body can restore them. This depletion can lead to a catabolic state, where the body breaks down lean muscle mass for energy. Low glutamine levels can also compromise immune function, increasing the risk of illness and infection—especially after high training volumes or endurance races.
Why L-Glutamine Is One of the Best Supplements for Endurance Athletes
Glutamine plays a crucial role in preserving lean muscle mass, supporting immune health, and accelerating post-exercise recovery. A study conducted by Oxford University’s Department of Biochemistry examined 200 elite endurance athletes, including long-distance runners and rowers. Participants consumed either 5g of glutamine or a placebo immediately post-exercise and again two hours later. After seven days, 81% of the glutamine group remained infection-free, compared to only 49% in the placebo group, highlighting glutamine’s immune-protective effect (Castell et al., European Journal of Applied Physiology, 1996).
Immune suppression is common following intense endurance training, often referred to as the “open window” period where susceptibility to illness is increased. Supplementing with L-glutamine helps bridge that gap, keeping you healthy so you can stay consistent with your training.
Faster Muscle Recovery and Reduced Soreness
Glutamine also plays a key role in post-workout muscle repair and recovery. In a double-blind, placebo-controlled crossover study conducted by Dalhousie University’s School of Health and Human Performance, researchers investigated glutamine’s effects on muscle strength and soreness after eccentric exercise. Participants who supplemented with L-glutamine experienced faster recovery of peak torque (a marker of muscle strength) and significantly reduced muscle soreness compared to the placebo group (Street et al., Amino Acids, 2011).
For endurance athletes, this means:
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Less post-workout soreness
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Shorter recovery time between sessions
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Higher training volume and intensity
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Reduced risk of muscle breakdown
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Improved long-term performance consistency
L-Glutamine isn’t just a recovery supplement—it’s a performance enabler.
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5. Clean Carbs
Clean Carbs: The Best Whole Food Carbohydrate Supplement for Endurance Athletes
For endurance athletes, carbohydrate intake is one of the most critical components of performance, energy, and recovery. Swolverine’s Clean Carbs stands out as a top-tier carbohydrate supplement because it’s made with 100% real, whole-food ingredients, not processed corn starch or maltodextrin like many other carbohydrate powders. With a clean, slow-digesting, and nutrient-dense profile, Clean Carbs fuels prolonged activity while supporting glycogen replenishment and recovery.
What Makes Clean Carbs Different?
Unlike standard carbohydrate supplements, which often rely on cheap, fast-acting sugars like glucose polymers, maltodextrin, or corn syrup solids, Clean Carbs is formulated with a unique blend of whole-food complex carbohydrate sources, including:
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Carb10® – A low-glycemic, fast-digesting pea starch designed for clean energy without insulin spikes
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Yam Powder – A nutrient-dense root packed with B vitamins and complex carbs for sustained energy
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D-Ribose – A five-carbon sugar that helps regenerate ATP and supports cellular energy recovery
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Coconut Sugar – A natural sweetener with a lower glycemic index and added minerals like potassium and magnesium
These ingredients work synergistically to provide both fast and sustained energy, making Clean Carbs a highly effective tool for long-distance runners, cyclists, CrossFit athletes, and anyone performing endurance-based training.
The Role of Carbohydrates in Endurance Performance
Carbohydrate supplements help replenish muscle glycogen stores that are rapidly depleted during high-intensity and long-duration training. For endurance athletes who train or compete for 60 minutes or longer, maintaining glycogen levels is critical for power, speed, and stamina. Research shows that ingesting carbohydrates before, during, and after exercise improves performance outcomes and shortens recovery time (Jeukendrup et al., Journal of Sports Sciences, 2004).
In a study conducted at the University of California, Davis, 16 male and female athletes cycled at 75% VO₂ max for 80 minutes followed by a 10km time trial. Athletes who consumed 0.6g of carbs per hour in the form of gels, chews, or drinks completed the trial significantly faster than those who consumed water alone—demonstrating the direct role carbohydrates play in exercise performance and glycogen preservation.
Avoiding the Wall: Why You Need to Fuel Consistently
Your body can only store a limited amount of glycogen—about 300–500g in the muscles and 75–100g in the liver. During an ultra-endurance event, you may need up to 800g of carbohydrates to maintain performance. If you fail to refuel, you risk "bonking," a condition marked by sudden energy crashes, cramping, brain fog, and physical shutdown. Clean Carbs helps prevent this by providing balanced, long-lasting energy without causing GI distress or sugar crashes.
Clean Carbs: Fuel That Supports Performance and Recovery
Whether you're training for a marathon, preparing for a triathlon, or grinding through a WOD, Clean Carbs provides the carbohydrate support you need to:
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Delay fatigue and extend time to exhaustion
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Refuel glycogen stores more efficiently
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Support cellular energy (ATP) production
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Improve performance and recovery without blood sugar spikes
Plus, it’s delicious and versatile—mix it into smoothies, shakes, or just with water for a smooth, naturally sweet energy boost.
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6. Intra Workout Supplements
Intra-Workout Supplements: Fueling Performance in Real Time
Intra-workout supplements are formulated to support training while it's happening—helping you stay energized, hydrated, focused, and strong through prolonged, high-intensity sessions. Whether you're a long-distance runner, CrossFit athlete, cyclist, or ultra-endurance competitor, what you consume during your workout can have a significant impact on your performance, stamina, and recovery.
Intra-workout formulas commonly include a strategic blend of essential amino acids (EAAs), electrolytes, carbohydrates, and performance-enhancing superfoods to help combat fatigue, prevent muscle breakdown, and extend endurance during prolonged exercise.
What’s Inside Swolverine’s INTRA-Workout Supplement?
Unlike most generic intra-workouts, Swolverine’s INTRA delivers a multi-functional blend of high-quality ingredients for fuel, focus, hydration, and recovery in one formula:
Electrolytes for Hydration
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Himalayan Pink Salt
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Calcium Citrate
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Magnesium Chloride
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Potassium Chloride
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Coconut Water Powder
Essential Amino Acids for Recovery
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Leucine, Isoleucine, Valine (BCAAs)
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Lysine, Methionine, Threonine, Phenylalanine, Histidine, Tryptophan
Superfoods & Endurance Support
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Spirulina
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Tart Cherry Extract
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Pomegranate Powder
Focus & Energy Support
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Panax Ginseng
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Vitamin B6
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Vitamin B12
Why Electrolytes Matter for Endurance Athletes
Electrolytes are vital for fluid balance, nerve transmission, and muscle contraction. Even a 1-2% reduction in body weight from fluid loss can cause a significant dip in performance and increase perceived exertion. During intense or long-duration training, you may lose 2–6% or more of your body’s water weight through sweat, especially in hot or humid environments (Casa et al., Journal of Athletic Training, 2000).
Failing to replace these electrolytes can lead to:
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Dehydration
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Cramping
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Mental fog
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Muscle weakness
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“Bonking” or hitting the wall
Sodium, potassium, magnesium, and calcium are key electrolytes needed to retain water and maintain performance. Coconut water is a natural source of potassium and works synergistically with added minerals to support hydration without spiking blood sugar.
🔍 The International Society of Sports Nutrition (ISSN) recommends endurance athletes consume 450–750 mL of fluids per hour, containing adequate electrolytes for optimal hydration (Kerksick et al., JISSN, 2018).
Why Essential Amino Acids (EAAs) Are Critical for Endurance
EAAs are the nine amino acids your body cannot synthesize on its own and must obtain through diet or supplementation. These include:
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Leucine
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Isoleucine
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Valine
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Lysine
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Methionine
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Threonine
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Phenylalanine
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Histidine
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Tryptophan
During endurance training, muscle tissue is broken down to meet energy demands, increasing the risk of muscle catabolism. EAAs help prevent this by stimulating muscle protein synthesis, reducing fatigue, and speeding up recovery.
A systematic review of 39 randomized controlled trials involving 4,274 participants found that EAA supplementation significantly improved muscle strength, reduced fatigue, and enhanced physical function across various populations (Deutz et al., Clinical Nutrition, 2014).
Moreover, prolonged exercise increases brain levels of tryptophan, a precursor to serotonin, which induces central fatigue, slows muscle contractions, and reduces motivation. Supplementing with EAAs—especially those high in BCAAs—can counteract this effect and delay both mental and muscular fatigue.
Why Swolverine INTRA Is the Best Intra-Workout Supplement for Endurance Athletes
Swolverine’s INTRA isn’t just another sports drink—it’s a scientifically formulated performance booster built for real athletes with real demands. It addresses all the key variables that impact endurance performance:
✅ Hydration – Complete electrolyte profile with Himalayan pink salt, potassium, and coconut water
✅ Energy – Natural energy support from B vitamins and ginseng
✅ Recovery – EAAs and superfoods that reduce inflammation and support tissue repair
✅ Performance – Enhanced endurance, better focus, and reduced fatigue
Whether you're grinding through an ultra, prepping for a triathlon, or hitting a 2-hour CrossFit session, Swolverine’s INTRA helps you push through walls, recover quicker, and train stronger.
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Best Supplements for Endurance Athletes: Final Takeaway
If your goal is to go farther, last longer, and perform better, then optimizing your training with the best supplements for endurance athletes is not optional—it’s essential. Endurance sports place a tremendous demand on the body’s energy systems, hydration, and recovery processes. Incorporating targeted supplements into your nutrition strategy can make a measurable difference in your performance, recovery, and longevity in sport.
From muscle-buffering agents like beta-alanine and citrulline malate, to recovery-accelerating nutrients like L-glutamine, essential amino acids (EAAs), and electrolytes, the right intra- and post-workout support can help you:
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Delay fatigue and improve time to exhaustion
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Maintain peak output over longer sessions
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Recover faster between workouts and competitions
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Protect lean muscle from catabolism
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Support immune health and hydration
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Fuel longer durations with real food-based carbohydrate sources like Clean Carbs
Whether you're training for a marathon, competing in CrossFit, cycling across states, or just aiming to crush your next PR, your body needs more than just grit—it needs fuel, hydration, and recovery tools to keep pushing.
Supplements are not meant to replace a solid diet, but when used strategically, they fill critical performance gaps, help you train smarter, and make your nutrition work for your athletic goals.
Start with the basics—hydration, amino acids, quality carbs, and proven endurance boosters—and you’ll set yourself up for faster times, stronger finishes, and better results all around.
Looking For The Best Supplements To Refuel Your Endurance?
Swolverine's INTRA-workout powder features an advanced supplement formula to maximize hydration and improve training performance during your workout. INTRA is a vegan EAA powder made with proven sports performance ingredients, antioxidant-rich superfoods, and electrolytes. INTRA-workout powder combines essential amino acids, tart cherry extract, pomegranate, spirulina, coconut water, and Panax ginseng for maximum endurance, mental focus, muscle growth, hydration, and recovery.
SWOLVERINE is an endurance athlete and active lifestyle brand. Made for the elite athlete, and the strong-willed our products were designed to fuel your athletic performance. We perform when you perform.
We believe that everyone can optimize not only their athletic performance but their human potential. The way we believe we can optimize performance is through transparency, clinically effective doses, and clinically proven ingredients with evidence-based outcomes. We provide the nutrients you need to power your active lifestyle.
