Probiotics for Endurance Training: What Lab4 and TWK10 Can Actually Do For You

When designing the MARCHON endurance range I knew we needed something to support gut health as it plays such a central role and a huge number of people suffer with stomach issues.

I had used Lab4 probiotics before but went digging in the science and came across TWK10. If you're serious about endurance performance, recovery, or body composition, these are worth understanding.

Lab4 is not a single strain — it's a four-strain consortium of 

• Lactobacillus acidophilus CUL60
• Lactobacillus acidophilus CUL21
• Bifidobacterium animalis subsp. lactis CUL34
• Bifidobacterium bifidum CUL20. 

Developed in the UK, it's the most clinically studied group of probiotic strains for athletes in Britain, backed by over 35 trials.

Much of the sport-specific work has come from Dr Jamie Pugh and the team at Liverpool John Moores University, who have consistently used Lab4 in well-designed randomised controlled trials with endurance athletes.

1. Fewer Gut Symptoms During Racing

GI distress is one of the most common performance limiters in endurance sport. Around 27% of recreational marathon runners report moderate to serious gut symptoms during a race, bloating, cramping, nausea, the urgent need to stop. Lab4 directly addresses this.

In a randomised, double-blind, placebo-controlled trial by Pugh et al. (2019), 24 recreational marathon runners supplemented with the Lab4 consortium for four weeks. The number of moderate GI symptoms and the number of days experiencing those symptoms were significantly reduced in the final two weeks of supplementation compared to the first two weeks and compared to placebo. Athletes taking Lab4 probiotics for endurance tended to maintain their running pace in the later stages of the race, where gut symptoms typically compound fatigue.

The mechanism is well understood: hard training and racing reduces blood flow to the gut, disrupting the intestinal barrier and triggering an immune response. Lab4 helps reinforce that barrier, keeping endotoxins where they belong.

2. Better Carbohydrate Utilisation

This one is under appreciated. Pugh's work showed that four weeks of Lab4 supplementation increased peak oxidation rates of ingested carbohydrate and increased total carbohydrate oxidation during two hours of exercise at moderate intensity, while also reducing fat oxidation. In plain terms: you get more usable energy from the carbs you consume during exercise.

This is particularly relevant for anyone taking on gels, sports drinks, or high-carbohydrate fuelling strategies. If the gut can't absorb the fuel efficiently, you get GI distress and energy deficits at the same time. Lab4 appears to improve the absorption side of that equation.

3. Marathon des Sables: 12% Faster Completion Time

Runners competing in the Marathon des Sables, a 250km, multi-day ultra across the Sahara, showed a 12% reduction in completion time after supplementing with Lab4 probiotics (Marshall et al., 2017). That's a reduction of 5 hours and 36 minutes. 

A separate study in Ironman triathletes showed a 10% faster overall race time in the probiotic group compared to placebo, alongside fewer and less severe GI symptoms during training.

These are not trivial effect sizes for a single supplement. The most likely explanation isn't that Lab4 made athletes fitter, it's that it kept them healthier, reduced GI disruption, and allowed them to sustain pace when gut issues would otherwise have forced them to slow down. This is why I think these are the best probiotics for endurance.

4. Reduced Metabolic Disruption After Racing

A marathon creates significant metabolic stress, causing major shifts in circulating blood metabolites. Lab4 supplementation has been shown to attenuate this disruption, lessening the metabolomic impact of marathon running. Whether this translates to faster recovery remains an active area of research, but the data is promising for athletes stacking multiple events or training blocks.

Lactiplantibacillus plantarum TWK10 (formerly Lactobacillus plantarum TWK10) is a strain isolated from Taiwanese fermented pickled cabbage. It operates through a distinct mechanism from Lab4, rather than focusing primarily on gut integrity and GI symptoms, TWK10 appears to directly influence body composition, glycogen storage, fatigue markers, and exercise capacity.

It won Sports Nutrition Ingredient of the Year at the NutraIngredients-USA Awards in 2021 and recently the same award at the Nutraingredients Europe 2026 awards.

What TWK10 Does For Exercise Performance

1. Significantly Improves Endurance Capacity

In a double-blind, placebo-controlled clinical study, six weeks of TWK10 supplementation significantly elevated exercise performance in a dose-dependent manner in healthy adults. A 2025 study combining data from C. elegans, mouse, and human models confirmed improvements in exhaustion time of 1.27-fold and grip strength of 1.1-fold compared to controls, alongside significant reductions in circulating lactate and ammonia levels during exercise. 

This is meaningful: lactate and ammonia accumulation are key contributors to peripheral fatigue, and blunting their rise means sustaining effort for longer.

2. Muscle Mass and Body Composition

TWK10 is particularly notable for its effects on body composition, an area where most probiotics have no meaningful data at all. In human trials, the high-dose TWK10 group showed a significant increase in muscle mass and a significant decrease in body fat. Grip strength improved on both hands in placebo-controlled trials (p < 0.001 and p < 0.014).

The likely mechanism runs through the gut-muscle axis: TWK10 promotes greater muscle glycogen storage, which supports both muscle function and energy availability during training. Short-chain fatty acids produced by TWK10's action in the gut may drive this effect by increasing skeletal muscle glycogen levels and supporting anabolic signalling.

3. Anti-Fatigue Effects

]TWK10 consistently reduces fatigue-associated biomarkers across animal and human models. This includes blood lactate, blood ammonia, creatine kinase (a marker of muscle damage), and blood glucose dysregulation during exercise. These effects suggest TWK10 is helping the body manage the byproducts of hard training more effectively, not simply masking fatigue.

4. Works Even as a Postbiotic

An emerging finding in the TWK10 research is that heat-killed (inactivated) TWK10, technically classified as a postbiotic, retains significant ergogenic properties. 

A 2023 clinical trial found that heat-killed TWK10 significantly improved exercise endurance time, grip strength, and muscle mass after six weeks. This matters for product formulation and shelf stability, and suggests that the bioactive compounds in the cell wall or metabolites, not just live colonisation, are driving the benefits.

These two don't overlap as much as you might think. Lab4 is your gut-health and endurance support. It helps to 

• Reduce GI symptoms
• Improve carbohydrate absorption
• Keeps your gut functioning under the stress of long-distance training and racing. 

TWK10 is more of a performance and body composition ingredient it pushes endurance capacity, supports muscle mass, and blunts fatigue markers directly.

Used together, they represent a uniqe evidence-based probiotics for endurance stack for athletes that addresses both ends of the gut-performance relationship: keeping the gut healthy under duress (Lab4) and using the gut-muscle axis to drive genuine performance adaptation (TWK10).

Alongside Lab4 and TWK10, MARCHON Tri-Biotic formula includes Aquamin, a multi-mineral complex derived from red marine algae (Lithothamnion calcareum), sustainably harvested from the North Atlantic. It's included for three specific reasons.

First, probiotic stability and delivery. Aquamin's unique honeycomb cell structure acts as a natural carrier for probiotic bacteria, protecting the probiotic cargo from the severe acidic conditions of the gastric phase of digestion due to its calcium carbonate superstructure. This means more of the Lab4 and TWK10 bacteria survive the journey through the stomach and reach the intestines where they're needed.

Second, prebiotic-like activity. Calcium supplementation has been shown to exert a prebiotic-like effect on the gut microbiota and has been associated with distinct changes in lactate and short-chain fatty acid (SCFA) production. 

Aquamin's marine-derived calcium drives this effect, helping to feed and support the beneficial bacteria the formula is designed to deliver. Crucially, unlike conventional prebiotics such as FOS or GOS, Aquamin doesn't cause the unpleasant side effects associated with gas production, such as bloating and discomfort — a meaningful advantage in a product aimed at athletes already managing GI sensitivity.

Third, gut wall integrity. Aquamin helps to maintain a healthy digestive barrier, reducing chronic inflammation in the gut and preventing leakage of undigested foods, bacteria, toxins and viruses into the bloodstream — directly complementing the gut barrier work of Lab4.

In short, Aquamin isn't a filler. It's doing real structural work: keeping the probiotics alive long enough to act, feeding them once they arrive, and supporting the gut environment they're trying to protect.

Probiotics have been pitched as everything from an immune booster to a cure for post-run gut rot. Most of that noise is backed by weak evidence and generic strains that have never been tested in athletes or for exercise performance. 

Lab4 has more robust human data in endurance athletes than almost any other probiotic consortium in the world, specifically in the UK context. And TWK10 is one of a very small number of probiotic strains to show direct, replicated effects on exercise performance, muscle mass, and fatigue in controlled human trials.

Neither strain is magic. Both work best with consistent supplementation over at least four to six weeks. Individual response will vary, and the broader literature on probiotics in athletes still has significant heterogeneity and gaps, particularly around dosing, sex differences, and long-term use.

If you're spending money on protein, creatine, and electrolytes, and still getting gut issues during training, fading in the back half of races, or struggling to hold muscle mass in a heavy training block, the gut is worth looking at. These two strains are where the evidence points.

Four weeks of probiotic supplementation reduces GI symptoms during a marathon race – 4-week marathon study found probiotics lowered GI symptom severity in the final third of the race and helped maintain running speed.[ pubmed.ncbi.nlm.nih]

Probiotic supplementation increases carbohydrate metabolism in trained male cyclists – 4-week crossover trial found probiotics increased carbohydrate oxidation and reduced fat oxidation during cycling, suggesting improved fuel utilisation.[ provenprobiotics]

Chronic probiotic supplementation with or without glutamine does not influence the eHsp72 response to a multi-day ultra-endurance exercise event – Multi-day ultra-endurance study found no effect on eHsp72, suggesting some probiotic outcomes are context-dependent.[ pubmed.ncbi.nlm.nih]

Four weeks of probiotic supplementation alters the metabolic perturbations induced by marathon running: insight from metabolomics – 4-week study used metabolomics to show probiotic supplementation altered marathon-related metabolic responses and supported GI symptom management around endurance exercise.[ researchonline.ljmu.ac]

Effect of Lactobacillus Plantarum TWK10 on Improving Endurance Performance in Humans – Human trial found TWK10 improved endurance performance and glucose content during maximal treadmill running, suggesting better energy harvest.[ pubmed.ncbi.nlm.nih]

Effect of Lactobacillus plantarum TWK10 on Exercise Physiological Adaptation, Performance, and Body Composition in Healthy Humans – 6-week trial found TWK10 improved endurance performance in a dose-dependent manner and improved fatigue-related features linked to better physiological adaptation.[ pubmed.ncbi.nlm.nih]

Different Impacts of Heat-Killed and Viable Lactiplantibacillus plantarum TWK10 on Exercise Performance, Fatigue, Body Composition, and Gut Microbiota in Humans – Human study found both viable and heat-killed TWK10 improved exercise performance and fatigue markers, with viable TWK10 also improving body composition.[ pubmed.ncbi.nlm.nih]

Effects of heat-killed Lactiplantibacillus plantarum TWK10 on exercise performance, fatigue, and muscle growth in healthy male adults – 6-week clinical trial found heat-killed TWK10 increased exercise endurance time, grip strength, muscle weight, and reduced lactate and ammonia during exercise and recovery.[ pubmed.ncbi.nlm.nih]

Lactobacillus plantarum TWK10 supplementation improves exercise performance and increases muscle mass in mice – Animal study showed TWK10 improved endurance, grip strength, muscle mass, and fatigue markers, supporting the human performance story mechanistically.[ pubmed.ncbi.nlm.nih]

Lactobacillus plantarum TWK10 attenuates aging-associated muscle weakness, bone loss, and cognitive impairment by modulating the gut microbiome in mice – Mouse study showed TWK10 supported muscle, bone, and cognitive outcomes through gut microbiome modulation, useful as mechanistic support rather than direct human proof.[ pubmed.ncbi.nlm.nih]

A comprehensive approach, based on the use of Caenorhabditis elegans, mouse, and human models, elucidates the impact of Lactiplantibacillus plantarum TWK10 on exercise performance and longevity – Human data showed TWK10 improved grip strength, exhaustion time, and reduced lactate and ammonia, reinforcing the ergogenic story.[ pubmed.ncbi.nlm.nih]

Lactobacillus plantarum TWK10 boosts hut microbiota, amino acid uptake – Human study found TWK10 increased amino acid absorption and improved muscle thickness, strength, power, and anaerobic capacity when paired with pea protein and resistance training.[ pubmed.ncbi.nlm.nih]