Benefits of Long-Term Aerobic Training on Cognitive Function: Research on Hippocampal Volume and BDNF

The benefits of exercise are not limited to the body—aerobic training promotes the secretion of brain-derived neurotrophic factor (BDNF), increases hippocampal volume, and improves memory and executive function. “Exercise for a sharper brain” has evolved from a slogan into a science backed by solid evidence.

This article systematically dissects the scientific underpinnings of aerobic exercise and cognitive function, grounded in research from leading international academic journals. We will start from the methods and findings of key papers, delve into the underlying physiological mechanisms, quantify the relationship between training dose and effect, compare differences across populations, and ultimately translate these academic findings into actionable training recommendations for endurance athletes in Taiwan. This is not merely a compilation of knowledge; it is a practical map leading 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 leading international journals. Below is a compilation of several papers that are either landmark studies or methodologically rigorous, collectively constructing our current scientific understanding from different perspectives.

1. Erickson et al. (2011, PNAS)

This study focused on aerobic exercise and the hippocampus. One year of aerobic training increased hippocampal volume by 2%. 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. Cotman et al. (2007, Trends Neurosci)

This study was a review on exercise and BDNF. Exercise upregulates BDNF, promoting neural plasticity. 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. Hillman et al. (2008, Nat Rev Neurosci)

This study was a review on exercise and cognition. Aerobic fitness is positively correlated with cognitive performance. 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. Voss et al. (2013, Trends Cogn Sci)

This study focused on exercise and brain networks. Aerobic training enhances functional brain connectivity. 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 aforementioned literature, a common trend emerges: contemporary exercise science increasingly emphasizes replacing intuition with objective data and rigorous experimental design. These studies echo and reinforce each other, converging on consistent core conclusions, which gives us greater confidence when formulating training strategies. The next section will delve into the physiological mechanisms behind these phenomena.

Integration of Core Findings

One year of regular aerobic training can cause the age-related shrinking hippocampus to “regrow” by approximately 2%, equivalent to reversing 1–2 years of aging. The core mechanism is that exercise upregulates BDNF, promoting neurogenesis, synaptic plasticity, and cerebral blood flow. The benefits encompass memory, attention, and executive function, with particularly notable cognitive protection in older adults.

It is worth emphasizing that these findings are not isolated laboratory numbers but robust conclusions repeatedly validated across different populations and study designs. Precisely because of this, they can serve as the scientific cornerstone for 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 in the face of individual differences and on-the-ground variables, rather than rigidly applying numbers. This is also the critical dividing line between “executors who follow a set plan” and “athletes who truly understand training”—the former merely replicates workout schedules, while the latter can flexibly modify 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 at the molecular, cellular, and organ-system levels. Understanding these mechanisms helps us determine which training methods truly address the limiting factors of performance and which merely add fatigue with limited benefit. The table below organizes the key physiological mechanisms closely related to this topic and their functions:

Mechanism/Adaptation	Physiological Change	Effect on Performance
BDNF↑	Exercise-induced	Neurogenesis and plasticity
Hippocampal volume↑	Neurogenesis	Improved memory
Cerebral blood flow↑	Vascular adaptation	Oxygen and nutrient supply

These mechanisms do not operate independently but are interwoven into an integrated network that influences each other. 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 yield 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, neural coordination) can manifest within days to weeks, while others (such as cardiac structural remodeling, skeletal 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-Response Relationship

“How much should I train?” is the most pressing question for every athlete. Sports science answers this using the concept of “dose-response”—there is a quantifiable relationship between training variables (intensity, frequency, duration, total 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 both undertraining and overtraining.

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

Population/Situation	Recommended Dose	Expected Effect
Aerobic exercise several times a week	Moderate intensity	Cognitive benefits
One year of regular training	Hippocampus +2%	Reversal of aging
Older adults	Significant benefits	Cognitive protection

Several general principles can be drawn from the table. First, diminishing marginal returns: as fitness levels improve, the training stimulus required to achieve the same degree of progress becomes increasingly larger, which is why elite athletes often measure their improvements in “fractions of a percent.” Second, ceiling effect: beyond a certain threshold, additional training volume not only yields sharply diminished benefits but may even backfire due to accumulated fatigue. Third, individual threshold: the minimum effective dose required to trigger adaptation differs for each person, explaining why the same workout 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 enough 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 aerobic exercise and cognitive function 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 progressing. 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 “relative training response” (percentage-based improvements), the differences between sexes are often insignificant—women benefit fully from all types of training as well. 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 adults 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 cardiopulmonary decline.

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 improve rapidly while others progress slowly—often not due to lack of 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 adjust training approaches to find the stimulus that suits them.

Practical Training Application

The value of theory lies in guiding practice. Translating research findings on aerobic exercise and cognitive function 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, targeted high-intensity interval stimuli are required. 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 aerobic base effectively 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 roughly 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. The following monitoring habits are recommended:

• 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 fatigue warning sign.
• Power or pace: Tracking output at the same intensity under standardized conditions is the most objective way to assess fitness progress.
• Subjective fatigue and sleep quality: Simple daily self-ratings 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, a small volume of high-intensity work to raise the ceiling, sufficient recovery to consolidate adaptations, and objective data to guide direction.” 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 Application in Taiwan

With Taiwan’s aging population and the need for dementia prevention, cycling and brisk walking are highly promising “brain-boosting exercises.” Communities can promote regular aerobic activity among middle-aged and older adults, benefiting both body and brain. Incorporating social elements (group rides, walking groups) is recommended to stack cognitive and psychological benefits.

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. By making good use of high-altitude resources such as Hehuan Mountain and Wuling for altitude training, by adapting to heat and managing hydration and electrolyte replacement in humid environments, and by adjusting training focus to the characteristics of Taiwanese races (such as a high climbing proportion), Taiwan’s endurance athletes can turn local conditions into competitive advantages. 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 wisdoms” widely circulated in the sports community do not hold up to empirical scrutiny. Below, we debunk the myths most relevant to this topic:

Myth 1: Exercise only trains the body.

In reality, exercise simultaneously trains the brain—the evidence is solid. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 2: The aging brain cannot change.

In reality, aerobic training promotes neurogenesis and hippocampal growth. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 3: Only vigorous exercise benefits the brain.

In reality, regular moderate-intensity aerobic exercise is effective. 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 “demanding evidence.” Whenever you hear any training claim, ask: “What research supports this? Which population does it apply to?” Only by grounding decisions in evidence can we avoid plausible-sounding traps in an age of information overload and make truly beneficial training decisions.

Conclusion: From Evidence to Action

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

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

For every reader, the most important action recommendation 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, helping you enjoy the purest joy of sport while pursuing your limits.

Related Reading

• Longitudinal Study on Aerobic Exercise, Hippocampal Volume Increase, and Memory Improvement
• Cycling Cardiorespiratory Endurance and Cognitive Performance: The Benefits of Riding for Brain Health
• Cycling and Cognitive Function: The Scientific Impact of Aerobic Exercise on the Brain
• Exercise and Brain Neuroplasticity: Aerobic Training Research on Hippocampal Neurogenesis