
Tried. Tested. Loved.
World's #1 Endurance Supplement
Recover Faster
Fights Free Radical Damage & supports crucial cellular functions.
Stamina Increase
Proven increase in VO2 max (heart-lung function)*
Deeper Breaths
Increase VO2 Max & Aerobic Threshold. Perform better for longer.
Increase Power
Increase power output by 10-25% with a similar heart rate.
Age Slower
Promotes anti-aging by reducing damaging oxidative stress.
Reduce Lactic
Reduces lactic build up for a healthier more energetic you*
Proven by Clinical Studies since 2008
Trusted by 450,000 Athletes
Trust is everything. That's why world-class athletes choose Extreme Endurance to maximize their chances of standing on top of the podium.*
Josh Bridges
I've been using this for 12 years. When I stop taking it, I notice increased muscle soreness. Many top CrossFit athletes rely on this to reach the podium.
Danielle Brandon
I've been using this since 2017 and consider it my secret recovery weapon. It's the best recovery supplement available.
Jacob Heppner
Started using this in 2016 while preparing for CrossFit Games. My endurance and recovery improved significantly, and muscle soreness decreased dramatically.
One Week Challenge
See proven results in 7 days
Day 1
Record a workout before taking Extreme Endurance.
Day 2-7
Start taking Extreme Endurance and don't skip any days.
Day 8
Retest workout from Day 1 and see your performance increase.
Day 8+
Maintain daily dosage for compounding benefits.
Clinically tested in over 14 studies, with proven performance since 2008.
Extreme Endurance has been proven effective under rigorous clinical trials. See the results below.
Lactic Acid Reduction of 26%
In a 2010 German clinical study, 22 professional athletes showed an average 15% reduction in lactic acid levels and significant improvements in aerobic threshold over a 10-day period.
VO2 Max Increases by 15%
This second study follows the published clinical study conducted in Germany in 2010, which showed the average lactic acid reduction was 15% in 22 elite athletes with an increase in aerobic threshold by double digits in a short, ten-day period.
Reduce Oxidative Stress by 39%
This second study follows the published clinical study conducted in Germany in 2010, which showed the average lactic acid reduction was 15% in 22 elite athletes with an increase in aerobic threshold by double digits in a short, ten-day period.
Muscle Damage Decreases by 6X
This second study follows the published clinical study conducted in Germany in 2010, which showed the average lactic acid reduction was 15% in 22 elite athletes with an increase in aerobic threshold by double digits in a short, ten-day period.
Extreme Endurance vs the Competition
Channel your inner titan. Recover like a champion. Extreme Endurance delivers results that are simply unmatched.*
| BENEFITS | XND | OTHERS |
|---|---|---|
| Since 2008, Extreme Endurance has been the trusted choice of world champions and medalists chasing the top of the podium* | ||
| Proven by over 14 clinical studies, including 2 published Gold Standard trials and open-label testing—trusted for real results since 2008.* | ||
| Clinically proven to reduce lactic acid by 26%, oxidative stress by 39%, creatine kinase by 6X, and increase VO2 max.* | ||
| The first US sports nutrition supplement to achieve Informed Sport certification, starting in 2008.* |
Getting the most out of Extreme Endurance
Frequently Asked Questions
Extreme Endurance stands out as superior to beta-alanine for many athletes due to its faster action, broader benefits, and lack of side effects. While beta-alanine requires 4–10 weeks of loading (often 4–6g/day) to raise muscle carnosine levels and buffer acid—sometimes causing tingling (paresthesia)—Extreme Endurance delivers results in just 48–72 hours. Clinically tested to reduce lactic acid by 26%, oxidative stress by 39%, and creatine kinase (muscle damage marker) by 6X, it also boosts VO2 max and supports faster recovery—benefits beta-alanine doesn't provide, as it primarily targets acid buffering via carnosine without impacting muscle trauma, soreness, or VO2 max. In short, Extreme Endurance offers quicker, more comprehensive support for endurance, recovery, and performance without the wait or drawbacks of beta-alanine.*
Extreme Endurance begins working in your system within 48-72 hours, as confirmed by over 14 years of clinical testing. Testing shows that the longer you are on Extreme Endurance, the greater the benefits. Elite athletes have used Extreme Endurance for 12+ years straight.
Extreme Endurance can be taken together with almost every other supplement but you do not need to take any product containing Beta Alanine when taking Extreme Endurance. Most active people and those that train hard get an adequate amount of magnesium with the daily dose of Extreme Endurance.
You do not need to take Extreme Endurance with food.
Extreme Endurance was the very first US sports nutrition supplement certified and tested for banned substances by LGC; Informed Sport. LGC is a world-renowned sports doping control and research laboratory, with over 50 years of expertise in anti-doping in sport. LGC has published over 300 scientific papers on methods for the detection of trace levels of substances that are prohibited in sport and has over 450 man-years of research into doping control. LGC has been testing supplements and ingredients on behalf of reputable manufacturers and suppliers for over 15 years. It has tested tens of thousands of samples during this time and has also carried out a number of research studies to explore the prevalence of contamination with prohibited substances in products and ingredients. LGC's research into supplements and contamination also includes several administration studies to investigate the levels of prohibited substances that could cause an athlete to fail a doping test. These have been published in peer-reviewed scientific journals. As a doping control laboratory, LGC works directly with sports authorities, national anti-doping organizations, and national governing bodies worldwide.
There are no NCAA approved supplements. The NCAA does not approve supplements. Since 2007, Xendurance has had over a million NCAA student-athletes take Xendurance products. These student athletes rely on the Informed Sport certification which is a global testing method for banned substances. Xendurance was the first US sports nutrition company to use Informed Sport for certifications.
Over the years we’ve discovered that some individuals with highly acidic diets may experience interference with the dissolution of Extreme Endurance. However, everyone is unique—one of our athletes drinks 12 cups of coffee a day and thrives on Extreme Endurance with excellent results! For those who drink acidic beverages such as juices and more than one or two cups of coffee per day, we recommend consuming caffeine and juices one or two hours after consumption to help ensure optimal effectiveness.
You do not need to cycle on and off with Extreme Endurance. Clinical studies, since 2008, show the longer you are on Extreme Endurance the greater the benefits. Elite athletes have been using Extreme Endurance for 12+ years.
Doing a baseline test when starting Extreme Endurance offers valuable data to establish a "baseline," allowing you to measure the benefits of this unique supplement. Below are some examples of baseline tests, which can be applied to almost any sport for accurate tracking. Cyclists: Time yourself on a stationary bike measuring wattage and heart rate. Take Extreme Endurance for 10 days and remeasure. Strength and Conditioning: Choose three exercises to do at 80% max and do as many as possible, timing yourself. Go on Extreme Endurance for one week and do as many as you can of these three exercises, again, at 80% max while timing yourself, and you will see the benefits. Ex: bench press to failure at 80% max, then go to squats, and let’s say you squat 200 lbs, do 80% or 160 lb squats to failure, and immediately go to pull-ups and go to failure.
We do not recommend anyone under the age of 14 use Extreme Endurance.
The most important thing to remember when taking Extreme Endurance is to take it consistently like you would a multivitamin. You can split the morning and evening dosage to the time of the day that works best for you. Ex; If you take it at 6 am and 5 pm, we encourage you to try to take it around 6 am and 5 pm everyday. You can take it with or without food.
The normal dose of Extreme Endurance is 6 tablets per day: 3 in the morning and 3 in the evening. For athletes preparing for a significant event, such as an ultra-distance race, a state meet, or any event more intense than usual, we recommend implementing a “load dose.” This involves increasing your dosage to 8 tablets per day—4 in the morning and 4 in the evening—starting 7-10 days before the event. Continue this dosage for one day after the event, then return to the regular dose of 6 tablets per day. It is important to note that Extreme Endurance should be used on a daily basis to see best results. We have had elite athletes on Extreme Endurance for 12+ years. In 2008, our pro-triathletes began using the load dose and reported achieving their best results with this approach. Based on their success, we now recommend the load dose strategy for competitors across all sports.
Since 2008, we've heard from athletes across nearly every sport imaginable—except curling! We're still waiting for a curler to share their experience. So, if you're a curler, we’d love to hear from you! From runners, ultra-distance athletes, marathoners, and triathletes to CrossFit enthusiasts, cyclists, Jiu Jitsu fighters, swimmers, tennis players, golfers, surfers, football players, basketball players, baseball players, motocross riders, paddleboarders, skiers, boxers, rugby players, rock climbers, wrestlers, and hockey players—the list goes on. Just not curling… yet!