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Professional Strength Hydration Mix

When redesigning EFS-PRO, we discarded tradition to establish a new tier of endurance technology that meets the unique requirements of the most driven athletes on the hottest days in the most demanding races.

✓Promotes mental toughness
✓Engineered for unparalleled performance
✓Prevents cramping & dehydration



Give your all, all the time


Races are won and lost in the moments when you’re so crushed that even the thought of maintaining your target pace or throwing a shift lever can make you want to stop running or climb off the bike. But unless you’ve completely bonked, that’s just a thought, so EFS-PRO includes Suntheanine® (also in EFS) and PharmaGABA® (unique to EFS-PRO) to silence that pain-induced panic. In clinical research, both ingredients have been shown to boost alpha brainwaves and promote whole-body antistress, relaxation, and calming effects while maintaining cognitive functions under stress.

Outside of the clinic, we call that mental toughness, and anyone who’s suffered in competition knows that it’s often the difference between either digging deeper through the pain to find a response or watching the gap grow as the race leaves you behind. Our precise dosing of Suntheanine® and PharmaGABA® make EFS-PRO the most advanced endurance nutrition and hydration mix available. They help you get the most out of every stride or pedal stroke, even—or especially—when your legs are screaming at your brain to stop.

Karl Meltzer
Winningest Ultra runner in history (44 Victories)

“First Endurance is constantly working to make better products. The new EFS-PRO reflects their commitment, it takes things to another level. It gives me the sustained energy I need for a great workout, plus the balance of electrolytes and carbohydrates are perfect for extra-long runs.”

Karl Meltzer

Winningest Ultra runner in history (44 one-hundred mile Victories, 69 entered)


The brain plays an essential role in endurance and performance. Mental toughness and presence of mind are equally as important as fitness. You have to be able to suffer and handle stress when your body is begging you to stop.

That’s why the reimagined EFS includes Suntheanine ®, a patented innovation that gives you the mental toughness you need to push further and find a gear you didn’t know you had.

Suntheanine® is protected by over 40 U.S. and international patents for its various physiological efficacies and L-isomer specific production processes.
PharmaGABA® is a registered trademark of Pharma Foods International, ltd.

You’re Better Than You Think

EFS-PRO now contains Pharma GABA®, a patented form of the amino acid GABA, to help you get the most out of every stride or pedal stroke when suffering ramps up and things get serious.

The GABA supplied by PharmaGABA® is a major neurotransmitter that your brain uses to balance out stress and—in the context of endurance sports—it allows you to push past your perceived maximal exertion and closer to your true maximum exertion for longer periods of time.

Unparalleled Innovation

EFS-PRO’s primary carbohydrate is a special high-glycemic branched-chain cyclic cluster dextrin (CCD) that stimulates fat oxidation for energy, preserving glycogen stores so you’ll have reserves to capitalize when others are hitting the wall.

Cyclic cluster dextrin is one of the lowest-osmolality carbohydrate sources available and is 100% soluble in water, so it can be mixed at stronger concentrations and still be absorbed quickly and easily, making EFS-PRO all you need to see you through anything from an 80-mile road race to a marathon or even a full 140.6-mile triathlon.

‘I’ve had issues with drink mix in the heat before, but not a single issue with the EFS-PRO.”
Nate Brown

Rally Professional Cyclist

Performance benefits

  • PROFESSIONAL STRENGTH HYDRATION MIX provides more electrolytes, calories, and key nutrients for unparalleled performance on the hottest days and most demanding races
  • SUPPORTS MENTAL TOUGHNESS so you can get the most out every stride, every pedal stroke, and every watt, helping you dig deeper when everyone else is falling apart
  • REFUELS WORKING MUSCLES faster than ever before
  • UNRIVALED ELECTROLYTE CONTENT prevents cramping & helps you hydrate fast
  • NEW TASTE PROFILE eliminates the flavor vs function compromise
  • THE INDUSTRY’S MOST ADVANCED CARBS to keep you fueled without GI distress



EFS-PRO provides more fuel, electrolytes, and support for physical performance and mental toughness—all without the corresponding mid-race gut punch that typically accompanies overly ambitious race nutrition.

Adding “PRO” to EFS-PRO isn’t just a rhetorical gesture; nothing else comes close in terms of performance support without GI distress. It’s actually formulated for the best of the best. Regardless of your level of competition, if your goal is to win, then you can’t afford to not have EFS-PRO in your bottles.

Push your limits in good taste

We make a big deal about how EFS more than doubles the cramp-preventing electrolyte content of competing mixes, so it’s significant that EFS-PRO provides even more. EFS-PRO’s 1,400mg of electrolytes per serving are unrivaled across the industry, ensuring untimely cramps aren’t the weak link in your training and racing.

Despite its high electrolyte content, EFS-PRO still tastes good, which—we admit—is something we couldn’t always say about our previous mixes. There’s no need to lighten the concentration and substitute with electrolyte tabs just to make it palatable or stave off sweetness fatigue. Like many of you, we came to enjoy and even crave the salty flavor of previous endurance mixes; however, the new EFS-PRO’s reworked flavor profile eliminates the need to acquire a taste for it—it just tastes good, with a light sweetness that isn’t so cloyingly saccharine that ingesting it for several hours in a row becomes yet another race-day obstacle.

“The electrolyte content of EFS-PRO is industry-leading, with an emphasis on replenishing nearly all of the sodium lost through sweat.”

“THE ELECTROLYTE KING…EFS-PRO adds up to 10 times what some other leading mixes provide.”


Bioavailability is the best ability

EFS-PRO utilizes Optimal Absorption Technology, which means every ingredient is selected and portioned to deliver more carbs, electrolytes and other essential nutrients without causing GI distress. We insist on ingredients like Cyclic Cluster Dextrin (CCD) carbs, which prevent distress even at high concentration, and DiCalcium malate and DiMagnesium malate, two unique mineral sources that boost absorption rates by 20 to 100%.

EFS-PRO also includes sodium citrate, which reduces stomach acidity to further ease absorption, and citric and malic acids to encourage oxygen uptake and production of ATP (the body’s energy source), helping your cells use the fuel once it’s delivered.

Premium ingredients for purity and purpose

We prioritize purity across the rest of EFS-PRO’s ingredients list by using only Suntheanine® (the original and cleanest L-theanine), free-form instantized amino acids (which have a purity level of 99-100%), and PharmaGABA® (supported by clinical studies and free of chemical impurities).

We also omit ingredients with no value—even the ubiquitous vitamin C, which features in virtually every other mix despite research that shows it reduces endurance when taken during exercise. The inclusion of Suntheanine® still provides immune system support, which is necessary when training and racing is already pushing your body to its limits, just without impacting performance.

No respect for the status quo

Our approach to product design eschews unexamined ingredients, traditional processes, and trendy minimalism in favor of research-based innovation, premium ingredient sourcing, and exceeding the uncompromising expectations of elite athletes. We’re always ready to show our work and support our products with the scientific literature that informs our design choices, but we also know what virtually every athlete and publication using or reviewing our products learns firsthand: First Endurance products speak for themselves, and you can feel the difference right away.

A system that puts endurance first

EFS-PRO is for use during exercise to prevent cramps, maintain fuel levels, and support mental toughness. It can be supplemented with Liquid Shots before and during an event. For recovery, Ultragen helps consolidate gains between sessions, and a daily dose of MultiV and Optygen help you lay a foundation to achieve your goals.


Q: How is EFS different than EFS-PRO?

 A: Compared to EFS, EFS-PRO has a more premium ingredients list, delivers more carbs and electrolytes, and includes PharmaGABA® for added mental toughness support. Though EFS is itself a step above the competition, EFS-PRO supports the most demanding efforts in the most extreme conditions by providing even more fuel and cramp prevention while doubling down on First Endurance’s revolutionary approach to supporting your brain like it’s a key muscle for endurance athletics.

Q: Are there other benefits to drinking EFS or EFS-PRO, besides for training and racing?

A: Absolutely. EFS and EFS-PRO can be used to top off electrolytes and help you calm down so you can get a good night’s sleep the night before (or two nights before) an event or race. When you’ve invested an entire season’s prep in peaking for a specific day, the calming effects of EFS or EFS-PRO can help ensure restless nights leading up to that day don’t undercut your form.

Q: Do EFS or EFS-PRO have any artificial flavors or colors?

A: No, but it tastes so good you’d be forgiven for thinking we were cheating.

Q: Do I need to take a full serving of EFS or EFS-PRO to get a benefit? 

A: No. A higher concentration increases calories and electrolytes. While our recommended serving concentration is designed to maximize theanine’s effects in a steady dose, ingesting reduced amounts will still produce a proportionally scaled effect in terms of promoting calm focus. In other words, if you are a smaller person and normally consume a somewhat reduced amount, you will still get the same benefits.

Q: Do EFS or EFS-PRO have any stimulants in it?

No. In fact, it does the opposite, calming you down and maintaining a cool, collected approach to whatever you’re doing, whether that’s racing, training, or resting up the night before an event.

Q: Can I use EFS and EFS-PRO with caffeine?

Yes. The calming effects of EFS and EFS-PRO affect you according to the baseline for caffeine consumption that you’ve established through your daily caffeine habit—err, intake. Keep drinking tea or coffee as usual. 

Q: Why doesn’t EFS-PRO contain Vitamin C?

A: EFS-PRO doesn’t contain Vitamin C because the latest research shows that Vitamin C can have a negative effect on endurance and performance when consumed during exercise. Click here for more info.

Q: What electrolyte can we find in the new EFS-PRO?

A: There is 500mg of sodium per serving in the new EFS-PRO drink (EFS has 300mg). This represents the highest sodium content in any electrolyte drink on the market. The EFS-PRO formula now offers over 1,500mg of electrolytes coming from all 5 electrolytes, per serving.

Furthermore, these superior minerals also offer a buffering of stomach acids. DiCalcium and DiMagnesium malate lower stomach acids significantly helping to reduce the unwanted gastric distress that can be associated with other minerals.

Q: Are there any changes to the amino acids?

A: The amino acids in the EFS-PRO drinks are AjiPure amino acids, the purest, most- bioavailable source of free-form amino acids available. AjiPure amino acids have purity levels of 99%-100%. This results in faster and more complete absorption.

Q: What is the osmolality of the EFS-PRO drink mix?

A: EFS-PRO has an osmolality around 250 when mixed at full concentration (32 grams in 12 ounces of water).

Q: How should I mix EFS-PRO?

SMALL BOTTLE: Mix 3 scoops with 21-22oz water

LARGE BOTTLE: Mix 4 scoops with 24-26oz water

BEFORE: Consume 1 bottle 30 minutes before exercise.

DURING: Alternate 1 serving of EFS-PRO and 1 bottle of water every 30 minutes.

TIP: For additional calories and electrolytes, double the concentration or supplement with Liquid Shot.

Q: Is there any way to get too much Theanine from EFS or EFS-PRO?

A: Only if you macro-dose (200mg or more in a single or repeated shot). Even if theanine is administered in a single macro-dose, the effect is just a too-calm calm that fades as the theanine leaves your body—Nothing serious or harmful. Click here to learn more about dosing and uptake. Since our EFS or EFS-PRO serving is limited to a gradually administered 80g every hour, you won’t hit that dose of theanine, even with continued use as directed. That’s because theanine is water-soluble, it metabolizes fast and doesn’t accumulate . Once ingested, it’s half gone after 60-90 minutes, and it’s gone completely in 24 hours. 

 Q: Does EFS or EFS-PRO help me hydrate better than water?

A: We won’t name them, but there’s a growing list of competitors in the sports hydration game making the claim that their product hydrates better or faster than water alone. This is a so-what claim predicated on evidence that not only doesn’t apply to endurance athletics, but actually hampers performance during long-term endurance events. For their rationale and claims support these companies cite WHO and other medical guidelines for treating serious dehydration in disease and severe exposure conditions, not the sports nutrition guidelines for healthy athletes in endurance competitions. Also important is the need for more fuel, and these drinks fall short in the fuel department. Check out Dr. Bucci’s extended consideration of these claims here.

 Q: I’ve heard that there are benefits to having protein during exercise. Why doesn’t EFS contain protein?

A: EFS contains 2g free form amino acids per serving which is the equivalent in BCAA and glutamine profile to 9g whey protein. Protein naturally contains BCAAs and glutamine.

Clinical evidence supporting the use of BCAAs and glutamine during exercise dates back to 1991. These clinical studies clearly indicate supplementing with as little as 1g free form amino acids improved performance, reduced post-exercise muscle damage, improved muscle glycogen resynthesis, reduced central fatigue and improved rate of perceived exertion. These are the same claims made by the most recent protein study and clearly support a mechanism for improved performance.

In addition to the clinical support, other factors lead to a decision to use these free form amino acids over complete proteins.

  • Proteins are more difficult to digest than amino acids during exercise
  • Proteins don’t taste very good during exercise
  • Proteins can reduce the glycemic index of a drink, further reducing its ability to be quickly absorbed
  • There is considerably more evidence supporting free form amino acids than complete proteins 

 Q: Are EFS and EFS-PRO safe for kids?

Yes. Just make sure they pay it back during their turns at the front.

Q: What is L-Alanyl L-Glutamine? 

A: The EFS-PRO is also fortified with L-Alanyl L-Glutamine which is a highly soluble water stable source of glutamine with some very unique features. This amino acid has been clinically proven to significantly improve the absorption of water and electrolytes in the intestinal tract.

Q: What is malic acid used for in the EFS-PRO drinks? Why is this important? 

A: The new EFS-PRO drink contains 700mg of malic acid. Malic acid stimulates oxygen consumption by increasing mitochondrial uptake, improving mitochondrial respiration and increasing energy production. Malic acid is essential in the formation of ATP, the body’s energy source. Malic acid allows the body to make ATP more efficiently, even under low oxygen, or hypoxic conditions. During anaerobic conditions, malic acid has an ability to remove the accumulation of reducing equivalents. Human studies have shown that after endurance training, athletes’ muscles were characterized by a 50% increase in the malate-aspartate redox shuttle enzymes.

Q: How is the flavor? 

A: The new EFS-PRO formula went through extensive flavor testing in the most demanding races in the world. We used this extensive feedback to create a flavor profile that mimics flavored water. With practically no sweetness this formula is ideal for those long, hot workouts where sweet drinks simply do not cut it. All formula uses 100% natural flavors and contains NO color. This allows athletes to use EFS not having to worry about staining water bottles.



First Endurance offers a complete endurance system—everything an endurance athlete needs to maximize performance. Each product has a specific purpose and complements the others. No guesswork and no missing components—First Endurance provides the comprehensive building blocks for an endurance training lifestyle.