XEndurance Extreme Endurance is a Supplement for Battling Fatigue

XEndurance Extreme Endurance is a Supplement for Battling Fatigue

By: Mark Barroso, NSCA-CPT


Supplements are not a substitute for hard work in the gym and they never will be. That said, the right combination of supplements can make up for a lack of training and enable you to get through tough workouts. I tried XEndurance Extreme Endurance between May and September during which I ran 10 obstacle course races (OCRs) and while I didn’t follow a strict scientific protocol like researchers at the University of Louisiana did when studying the product, I still know it had a beneficial effect. Before we get it into how I used Extreme Endurance, let’s dive into how it’s been clinically studied.

Small studies in 2010, 2013, 2015 found that using Extreme Endurance for a week resulted in decreased lactate levels and creatine kinase levels. In November 2016, a University of Louisiana Lafayette study found that 10 days of supplementing with Extreme Endurance resulted in significantly lower (26%) lactate accumulation compared to a placebo. In this small study, the fourth done on Extreme Endurance, 16 healthy male recreational athletes supplemented with either a placebo pill or Extreme Endurance pills where they took four tablets in the morning and evening (eight tablets total) for the first four days followed by six days of three tablets in the morning and evening (six tablets total).

After 10 days of supp-taking, the participants had their blood drawn, exhaled gases collected and performed exercise tests on a cycle ergometer (machine bike that measures power). The test consisted of cycling to exhaustion at work rate of 25 watts per minute during which lactate was measured before the test and every two minutes via finger pricking (puncturing) with a needle. I’ve seen a lactate threshold test conducted before during a graded exercise test on a treadmill: the participant gets their finger pricked every few minutes and the lactate from each blood sample is measured. After the cycling test, a post-exercise blood sample was collected. Let’s explore what lactate is and why lowering it can be beneficial for performance.



Pyruvate is a precursor to lactate in the final step of glycolysis, the breakdown of carbohydrate (either glycogen stored in the muscle or glucose delivered in the blood) to resynthesize ATP. The formation of lactate is catalyzed by the enzyme lactate dehydrogenase. Contrary to popular belief, lactate is not the cause of muscular fatigue: it’s just the biomarker fatigue. According to the NSCA Essentials of Strength & Conditioning (Fourth Edition), it’s the decrease in muscle pH that causes the cell’s energy systems to work in a diminished state which contributes to muscle fatigue. So, that burning sensation in your quads during high-intensity is NOT PYRUVATE CONVERTING TO LACTATE OR LACTIC ACID. It’s actually the effect of the hydrolysis (breakdown) of one molecule of ATP into a hydrogen ion, inorganic phosphate and ADP. Even though lactate isn’t the direct cause of fatigue, it’s important for people to train at their lactate threshold, which is generally 70-80% of VO2 max in aerobically trained athletes and 50-60% in untrained athletes.

The normal range of lactate, an organic compound, is 0.5 to 2.2 mmol/L at rest. Lactate production increases with exercise intensity and appears to depend on muscle fiber type, specifically, type II muscle fibers are more suited for lactate production. Blood lactate concentrations reflect the net balance of lactate production and clearance as a result of bicarbonate buffering, in other words, keeping your muscle pH levels ideal for performance. Blood lactate returns to pre-exercise activity within an hour after activity, depending on the duration and intensity of exercise, training status and type of recovery. The onset of blood lactate accumulation occurs when blood lactate reaches 4mmol/L. Things get interesting because by training at levels of 4mmol/L of blood lactate or more, you can condition your body to be able to train at higher percentages of your VO2 max without as much lactate accumulation in the blood since your body essentially gets more efficient at stabilizing pH levels. Here’s where the ingredients in Extreme Endurance come into play.



Calcium carbonate is the first ingredient and the recommended daily dietary allowance for calcium is 700-1,300mg for both males and females. The calcium carbonate version of calcium has been reported to be less bioavailable than calcium citrate. Those reports don’t account for that fact Extreme Endurance also includes black pepper, which has been shown to increase bioavailability of curcumin and other compounds. The next ingredient is papain, an enzyme that can only be found in the papaya fruit that improves digestion and fights inflammation by producing cytokines/immune cells. Magnesium and potassium are minerals whose benefits span from anti-spasmodic to improved rehydration. Catechins are polyphenols found in green tea which have been shown to yield favorable improvements in body composition in humans as well as possible have some lowering effects on cholesterol. It would be nice to know exactly what type of tea (green vs white) these catechins come from as white tea has the highest catechin content. Selenium and chromium have been studied for their longevity and weight loss benefits respectively but neither has conclusive evidence on significant fat loss or anti-disease properties. Overall, Extreme Endurance’s most telling ingredients are the calcium, magnesium, potassium, papain and black pepper to speed up the absorption.

Another finding of the 2016 study was a decrease in creatine kinase after the cycling test in Extreme Endurance users compared to placebo pill eaters. Creatine kinase is a biomarker for muscular damage that get elevated during unusually high aerobic training volumes. Like lactic acid, the ability to keep creatine kinase quantity down after intense exercise will only lead to improved performance throughout an athletic season as metabolic demands increase.


In my case, I took 3-4 Extreme Endurance tablets the night before and the morning of OCRs of distances ranging from 3-12 miles. Some mornings I also took beet root powder mixed with water, Cellucor Alpha Amino Xtreme, and GLUKOS energy gels. The combination of these electrolytes, BCCAs, nitrate, and glucose kept me moving in hot weather on mountains. Some weeks, I would load the Extreme Endurance, taking 2-3 pills in the morning and evening the week before a Saturday race. I never once cramped during an OCR while on the Extreme Endurance nor was I unable to complete any events. The Extreme Endurance gave me a mental and likely physical safety net for not having prepared the way I would’ve liked for these races, since I had a bunch of micronutrients in my body ready to be spent for hours. I’m looking forward to experimenting with this product more, especially prior to cardio workouts.


Next time I take Extreme Endurance, I will use a more calculated approach, syncing it up with a training plan and logging my results. Even when I used it sporadically, the thought was that my body could use this unique blend of minerals and micronutrients. If you’re looking for even the slightest edge over your competition or if you just like experimenting with endurance supplements, Extreme Endurance is worth a shot.

For more information about XEndurance visit xendurance.com.

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