Gut Microbiota Effects in Endurance Sports: New Research on Lactobacillus and Athletic Performance

Gut microbiota is a new frontier in sports science in recent years. Research has found that athletes have a unique microbiota composition, with certain bacterial species associated with performance, recovery, and immunity. The concept of “sports probiotics” has even emerged, opening new pathways for performance enhancement.

Based on research from top international academic journals, this article systematically analyzes the science of exercise and the gut microbiota. Starting from the methods and findings of key papers, we will delve into the underlying physiological mechanisms, quantify the relationship between training dose and effects, compare differences across populations, and ultimately translate these academic findings into actionable training recommendations for Taiwanese endurance athletes. This is not merely a compilation of knowledge, but a practical map from the laboratory to the training ground. In an era where it is difficult to distinguish truth from falsehood, returning to rigorous scientific evidence is the most worthwhile investment for any athlete who takes their training seriously.

Review of Academic Research

The most effective way to understand this topic is to directly examine representative studies from top international journals. Below is a compilation of several landmark or methodologically rigorous papers that, from different perspectives, collectively build our current scientific understanding.

1. Scheiman et al. (2019, Nat Med)

This study used the microbiota of marathon runners. Veillonella increased after the race and can metabolize lactate to produce short-chain fatty acids. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

2. Clarke et al. (2014, Gut)

This study examined the microbiota diversity of athletes. Rugby players had higher microbiota diversity than controls. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

3. Mohr et al. (2020, JISSN)

This study examined the consensus on exercise and the microbiota. Exercise positively influences microbiota composition and function. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

4. Allen et al. (2018, MSSE)

This study examined how exercise alters the microbiota. Six weeks of exercise altered the microbiota and short-chain fatty acids. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

Looking across the above literature, a common trend emerges: contemporary sports science increasingly emphasizes replacing intuition with objective data and rigorous experimental design. These studies echo and reinforce each other, all pointing toward consistent core conclusions, giving us greater confidence when formulating training strategies. The next section will delve into the physiological mechanisms behind these phenomena.

Synthesis of Key Findings

Athletes have higher gut microbiota diversity and harbor specific bacterial species associated with performance. Scheiman’s groundbreaking study found that Veillonella increased in marathon runners after a race; this bacterium can metabolize lactate into propionate (a short-chain fatty acid), potentially enhancing endurance. Exercise itself can also positively reshape the microbiota and increase the production of beneficial short-chain fatty acids.

It is worth emphasizing that these findings are not isolated laboratory numbers, but robust conclusions repeatedly validated across different populations and study designs. Precisely for this reason, they can serve as the scientific cornerstone of training prescriptions. However, between “research findings” and “training application” lies a layer of mechanistic understanding—only by figuring out the “why” can we make correct adjustments when facing individual differences and on-the-ground variables, rather than rigidly applying numbers. This is also the key dividing line that distinguishes “executors who follow a set plan” from “athletes who truly understand training”—the former merely copy workout schedules, while the latter can flexibly adjust every training decision based on their own condition, environmental changes, and race demands, maximizing the benefit of limited time and energy.

Core Physiological Mechanisms

Behind any training adaptation, a cascade of physiological changes operates from the molecular and cellular levels to the organ-system level. Understanding these mechanisms helps us judge which training methods truly address the limiting factors of performance and which merely add fatigue with limited benefit. The table below summarizes the key physiological mechanisms closely related to this topic and their effects:

Mechanism/Adaptation	Physiological Change	Effect on Performance
Veillonella↑	Metabolizes lactate	Produces propionate for energy
Short-chain fatty acids↑	Microbial fermentation	Anti-inflammatory and energy
Microbiota diversity↑	Exercise-induced	Metabolic and immune benefits

These mechanisms do not operate independently but are intertwined, influencing each other as a holistic network. For example, without a simultaneous improvement in peripheral muscle metabolic capacity, the increased oxygen delivery from central cardiovascular adaptations cannot be effectively utilized; and vice versa. This “barrel effect” reminds us that comprehensive and balanced training stimuli often lead to more lasting progress than extreme focus on a single point.

More importantly, the “timing” of these adaptations varies. Some changes (such as plasma volume expansion and neural coordination) can manifest within days to weeks, while others (such as cardiac structural remodeling and bone adaptations) require months or even years of accumulation. Understanding this temporal dimension helps us maintain reasonable expectations for training outcomes, avoiding the mistake of declaring a method ineffective before giving it sufficient time—a key reason why many people give up halfway.

Training Dose and Effect Relationship

“How much should I train?” is the question every athlete cares about most. Sports science answers this with the concept of “dose-response”—there is a quantifiable relationship between training variables (intensity, frequency, duration, volume) and the magnitude of adaptation, but this relationship is almost never simply linear. Understanding the shape of the dose-response curve helps us find the “sweet spot” with the highest return on investment, avoiding undertraining or overtraining.

The table below summarizes dose recommendations and expected effects under different scenarios as a reference for practical planning:

Population/Scenario	Recommended Dose	Expected Effect
Regular exercise	Microbiota remodeling	Diversity↑
Dietary fiber	Prebiotics	Supports beneficial bacteria
Fermented foods	Probiotics	Microbiota supplementation

Several general principles can be drawn from the table. First, diminishing marginal returns: as fitness levels rise, the training stimulus required to achieve the same magnitude of improvement becomes increasingly larger, which is why elite athletes often measure progress in “fractions of a percent.” Second, ceiling effect: beyond a certain threshold, additional training volume not only yields sharply diminishing benefits but may even backfire due to fatigue accumulation. Third, individual thresholds: the minimum effective dose required to trigger adaptation differs for each person, which explains why the same training plan produces vastly different results in different individuals.

Therefore, the smartest training strategy is not to blindly pursue “more,” but to pursue “just right”—providing sufficient stimulus to trigger adaptation, paired with adequate recovery to allow the adaptation to actually occur. Periodization is designed precisely to achieve this goal: through planned fluctuations in load, it avoids linear fatigue accumulation and allows the body to peak at critical moments.

Differences Across Populations

A recurring and unavoidable theme in research on exercise and the gut microbiome is “individual and population differences.” Applying the same conclusions indiscriminately to everyone is one of the most common mistakes in training prescription. Below, we analyze these differences across several key dimensions.

Beginners vs. Advanced Athletes: Because beginners are still far from their physiological ceiling, they respond significantly to almost any regular stimulus—this is the so-called “beginner’s bonus.” Advanced athletes, on the other hand, have limited adaptive capacity and require more precise, higher-intensity, or more varied stimuli to keep improving. This means the optimal training strategies for the two groups are fundamentally different. Advanced athletes especially need to prioritize training “quality” and “specificity” rather than simply stacking “volume.”

Men vs. Women: In absolute values (such as absolute VO₂max, muscle mass, and hemoglobin concentration), men generally exceed women, largely due to differences in body size, hormones, and body composition. However, in terms of “relative training response” (percentage improvement), the differences between sexes are often insignificant—women benefit just as fully from various types of training. Notably, women’s menstrual cycles, hormonal fluctuations, and energy availability (RED-S risk) need special consideration in training planning.

Age Differences: With aging, maximal heart rate, muscle mass, recovery speed, and hormonal environment all change. Yet extensive research confirms that even middle-aged and older populations retain the capacity to adapt to training—adaptation may simply be slower and require more recovery. In other words, “it’s useless to train when you’re old” is a complete myth. Older adults, in fact, need regular training even more to combat sarcopenia, bone loss, and declines in cardiorespiratory function.

Genetic Factors: Don’t forget the “responder–non-responder” phenomenon. Large family studies indicate that a considerable proportion of training response can be explained by genetics. This means that given the same training plan, some people improve rapidly while others progress slowly—often not due to insufficient effort, but to inherent differences in response potential. Recognizing this helps athletes view their own and others’ progress with a healthier mindset and become more willing to experiment with training modifications to find the stimulus that suits them.

Practical Training Applications

The value of theory lies in guiding practice. Translating research findings on exercise and the gut microbiome into daily executable training requires grasping three core principles: “specificity,” “progression,” and “monitorability.”

Principle of Specificity: Training must target the energy systems and physiological adaptations required by the goal. If the goal is long-distance endurance, substantial aerobic base training is needed; if the goal is to break through VO₂max limits, high-intensity interval training provides the targeted stimulus. The most common problem with indiscriminate training is falling into the “moderate-intensity black hole”—every session leaves you somewhat breathless but not intense enough, failing to accumulate an effective aerobic base while also missing the critical high-intensity stimulus, ultimately leading to stagnation.

Principle of Progression: The body adapts only when faced with loads slightly above current capacity, but load increases must be gradual. A practical guideline is to keep weekly training volume increases within about 10%, and schedule a deload week every 3–4 weeks to allow accumulated fatigue to dissipate and adaptations to consolidate. Rushing progress is the number one cause of injury and overtraining in amateur athletes.

Principle of Monitorability: Replacing subjective feelings with objective data is the core of modern training. We recommend establishing the following monitoring habits:

• Morning resting heart rate and heart rate variability (HRV): These reflect recovery status and autonomic nervous system balance. An abnormally elevated resting heart rate or a sudden drop in HRV is a warning sign of fatigue.
• Power or pace: Tracking output at the same intensity under standardized conditions is the most objective way to assess fitness progression.
• Subjective fatigue and sleep quality: Simple daily self-assessments capture overall status beyond the numbers.
• Periodic testing: Conduct a standardized test (such as threshold power or time trial) every 6–12 weeks to objectively evaluate training effectiveness and adjust accordingly.

Integrating these principles, a mature training plan should be “built on a large volume of low-intensity work to establish a base, driven upward by a small amount of high-intensity work, consolidated by adequate recovery, and navigated by objective data.” Rather than blindly chasing mileage numbers every day, it is better to execute 1–2 high-quality sessions per week with discipline and truly relax the rest of the time—this is the essence of quality over quantity.

Local Applications in Taiwan

The Taiwanese diet is rich in fermented foods (miso, kimchi, yogurt, natto) and fruit and vegetable fiber, which help cultivate a healthy microbiome. Athletes can combine regular training with a high-fiber diet and moderate fermented food intake to support gut health. This field is still emerging, so commercial claims about “sports probiotics” should be viewed rationally.

Taiwan’s unique geography and climate mean that conclusions from international research must be localized before application. The hot, humid summers, mountainous terrain, and dense, diverse race culture are both challenges and advantages. Endurance athletes in Taiwan can turn local conditions into competitive advantages by knowing how to use high-altitude resources such as Hehuan Mountain and Wuling for altitude training, how to adapt to heat and manage hydration and electrolyte replacement in humid environments, and how to adjust training priorities based on the characteristics of Taiwanese races (such as a high proportion of climbing). Remember, any data from laboratories in temperate countries must be interpreted and applied against Taiwan’s real training environment—this is the final mile for scientific training to take root locally.

Debunking Common Myths

There is often a considerable gap between scientific findings and popular beliefs. Many “common sense” notions widely circulated in the sports community do not hold up to empirical scrutiny. Below, we debunk the common myths related to this topic:

Myth 1: The gut microbiome has nothing to do with exercise.

In reality, exercise significantly affects microbiome composition and function. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 2: Taking probiotics will make you stronger.

In reality, the benefits of individual strains still require more evidence. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 3: The gut microbiome is fixed and unchanging.

In reality, exercise and diet can rapidly reshape the microbiome. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

The key to dispelling myths lies in cultivating the habit of “asking for evidence.” Whenever you hear any training claim, ask yourself: “What research supports this? Which population does it apply to?” Only by grounding decisions in evidence can you avoid plausible-but-false traps in an age of information overload and make truly beneficial training decisions.

Conclusion: From Evidence to Action

Looking across the academic research on exercise and the gut microbiome, several clear conclusions emerge. First, endurance performance is the result of multiple physiological systems working in concert—no single indicator or training method holds a monopoly on the key to success. Second, the essence of training is “precise stress plus adequate recovery,” not merely the accumulation of effort. Third, individual differences are everywhere, and the best training plan is always the one “tailored to yourself and continuously adjusted based on data.”

Looking ahead, sports science is rapidly moving toward “precision individualization.” Advances in genomics, metabolomics, and wearable devices will eventually allow us to predict individual response potential before training even begins and fine-tune every session in real time based on physiological data. For Taiwanese athletes and coaches, building a local physiological database and developing training models adapted to the local climate and race conditions are important steps toward closing the gap with the world’s best.

For every reader, the most important action item remains the same: First, understand your physiological baseline through objective testing; then design training based on scientific principles; pair it with disciplined recovery and continuous monitoring; and be patient with progress. There is no shortcut to building endurance, but there is a right direction. May this science-based analysis serve as a reliable guide on your training journey, accompanying you in pursuing your limits while also enjoying the purest joy of sport.

Related Reading

• The Link Between Gut Microbiome Composition and Endurance Performance: Research on Short-Chain Fatty Acid Energy Supply
• Microbiome and Exercise: New Research on Gut Microbiota and Endurance Performance
• Exercise and the Gut Microbiome: An Emerging Performance Factor—The Second Engine from Endurance to Recovery
• Gut Microbiome and Cycling Performance: How Your Microbiota Affects Your Endurance