Cognitive Function Impairment in High-Temperature Environments: A Study on the Effects of Heat Stress on Decision-Making Ability

Based on the Journal of Applied Physiology, Medicine & Science in Sports & Exercise, Sports Medicine, and other international peer-reviewed journals, this article provides an in-depth analysis of the environmental physiology mechanisms behind “the effects of heat on cognition and decision-making.” It also integrates Taiwan’s subtropical climate, mountainous terrain, and local race scenarios to offer evidence-based training and race preparation strategies.

In the field of environmental physiology, “the effects of heat on cognition and decision-making” is one of the key variables determining whether endurance athletes can perform at their true level on race day. Many amateur and elite athletes focus their training on power, pacing, and equipment, yet underestimate the immense physiological impact of the environment—heat, cold, high altitude, humidity, and air quality. In fact, when two athletes have similar fitness and gear, the one who better understands how to adjust strategy in response to the environment is often the one who can maintain pace in the latter stages of a race, avoiding collapse and accidents. Taiwan’s geography is particularly unique: hot and humid summers, cold and damp winters, extreme elevation gains from sea level to Wuling at 3,275 meters, plus urban air pollution and typhoon season—all of which make environmental physiology especially valuable in the local sports community. This article will guide you from cellular and systemic physiological mechanisms, through empirical research in top international journals, dose-response relationships, differences across populations, and then to directly applicable training strategies and Taiwan-specific scenarios. Finally, we will debunk long-standing myths, so that your understanding of “the effects of heat on cognition and decision-making” is truly built on science, not hearsay.

Review of Academic Research

The scientific exploration of “the effects of heat on cognition and decision-making” has accumulated rigorous and rich evidence in the field of environmental physiology. Below are several representative studies, each valuable in its methodological design, subject population, and strength of conclusions, collectively forming our current understanding:

1. Hancock, Ross & Szalma (2007). Human Factors used meta-analysis to quantify the overall impact of heat stress on cognitive task performance.

2. Gaoua et al. (2011). Journal of Thermal Biology confirmed that elevated core and brain temperatures impair complex cognition and working memory.

3. Schmit et al. (2017). Sports Medicine reviewed the effects of heat on athletes’ decision-making, focus, and psychological performance.

4. Taylor et al. (2016). Frontiers in Physiology integrated the interaction between cognitive and physical performance under heat stress.

Taken together, these studies show that the scientific picture of “the effects of heat on cognition and decision-making” has deepened as measurement techniques have advanced. Early studies typically manipulated temperature, humidity, or partial pressure of oxygen in environmental chambers, observing changes in VO₂max, time to exhaustion, or time-trial performance. Subsequent research introduced ingestible core temperature capsules, near-infrared spectroscopy, stable isotope tracers, muscle biopsies, and molecular markers, allowing us to move from “observing phenomena” to “explaining mechanisms.” Notably, most high-quality studies employed randomized crossover designs, where each subject served as their own control, greatly reducing noise from individual differences. However, extrapolation of research findings requires caution: a single controlled environmental variable in the lab does not necessarily replicate the complex combination of heat, humidity, wind, radiation, and fatigue on a real race course; nor do responses from well-trained subjects necessarily apply to the average amateur. When interpreting “statistical significance” and “effect sizes,” we must also distinguish between average trends in the lab and practical meaning on the individual race course—a 3% performance difference may determine rankings in elite competition, but its significance for a recreational rider is relatively limited. This careful attention to evidence quality and applicability is precisely the foundation of scientific training.

Core Mechanisms

Heat affects not only muscles and the cardiovascular system but also the brain. As core and brain temperatures rise, higher-order cognitive functions governed by the prefrontal cortex—attention, working memory, complex decision-making, risk assessment—are the first to be affected, while simple reactions and over-learned automatic movements are relatively more tolerant. Mechanisms include direct effects of brain temperature on neural transmission, changes in cerebral blood flow and oxygenation, neurotransmitter imbalances, and the occupation of cognitive resources by thermal discomfort. For endurance athletes, this means that in the latter stages of a hot-weather race, beyond declining physical capacity, pacing judgment, fueling decisions, hazard response, and tactical thinking may all deteriorate, increasing the risk of errors and accidents. This is why, in long hot-weather events, having a simple, pre-planned fueling and pacing protocol that can be executed automatically is more reliable than complex in-the-moment judgment.

To truly understand how “the effects of heat on cognition and decision-making” impacts athletic performance, one must return to the systemic integration of thermoregulation, cardiovascular, respiratory, metabolic, and central nervous systems. Environmental factors translate into measurable performance differences precisely because they act on one or more key links in this physiological chain—either limiting oxygen and fuel delivery, disrupting heat dissipation and fluid balance, or altering central perceptions of fatigue and motor drive. The table below summarizes the key effects of this topic at different physiological levels, helping you build a complete mechanistic picture:

| Physiological Level | Key Mechanisms | Significance for Athletic Performance |

|—|—|—|

| Cardiovascular System | Affects blood flow distribution, stroke volume, and circulatory capacity | Determines oxygen delivery and stability during prolonged exercise |

| Thermoregulation / Fluid Balance | Regulates heat dissipation pathways, sweat rate, and electrolyte balance | Affects rate of core temperature rise and dehydration risk |

| Muscle & Metabolism | Alters substrate utilization, enzyme activity, and contractile function | Determines sustainable power output and timing of fatigue onset |

| Central Nervous System | Modulates perception of fatigue, motor drive, and cognitive decision-making | Influences “how tired it feels” and the ability to persevere and judge safety |

Two dimensions deserve special emphasis: “dose-response” and “temporal dynamics.” The same environmental exposure, at different intensities, durations, and states of acclimatization, can produce vastly different or even opposite effects—this is precisely why many popular recommendations are one-sided. The limiting factors of athletic performance also shift dynamically with context: for short, high-intensity efforts, limitations come primarily from anaerobic energy supply and local metabolism; for multi-hour endurance events, the limiting factors shift to the combined effects of rising core temperature, fluid imbalance, glycogen depletion, and central fatigue. “The effects of heat on cognition and decision-making” deserves in-depth exploration precisely because it can selectively affect some of these limiting factors. Only by understanding the mechanisms can we determine “what adjustments to make in which environment, how much, and when,” rather than being led by the environment on race day. The more thoroughly you understand the mechanisms, the more flexibly you can respond across different situations—heat, cold, high altitude, or pollution. This ability to adapt to context is the dividing line between those who understand environmental physiology and those who train blindly.

Dose-Response Relationships

In environmental physiology, “the dose determines the effect” is a core principle. Environmental stimuli that are too mild fail to reach physiological thresholds, producing no adaptation or effect; excessive exposure can exceed the body’s compensatory capacity, leading to heat injury, hypothermia, altitude sickness, and other risks. The table below outlines the dose-response correspondence for “the effects of heat on cognition and decision-making” and serves as the most important quantitative reference when developing training and race preparation plans:

| Dose / Condition | Physiological State | Effects & Key Points |

|—|—|—|

| Core <38°C | Cognition largely normal | Judgment maintained |

| 38–39°C | Complex cognition slightly impaired | Working memory affected |

| >39°C + elevated brain temperature | Higher-order decision-making clearly impaired | Increased errors |

| Fatigue + dehydration叠加 | Cognition further deteriorates | Elevated risk |

As the table shows, the effects of environmental exposure often follow a threshold or inverted U-shaped curve: before reaching an effective dose, adaptation or effects increase with dose; but beyond a certain critical point, there are no additional benefits, and risks and costs rise sharply. This means “finding your optimal exposure” matters far more than “chasing extremes.” Whether it’s the daily heat dose for heat acclimation, the altitude and duration for altitude training, or exposure time in cold environments, there exists a sweet spot that balances benefit and safety. It is recommended to progressively test your responses under different environmental conditions during training (not on race day), recording core temperature or heart rate, perceived exertion, power data, and recovery status to build your own environmental response profile. Remember: the lab average is a starting point, not the finish line; everyone’s body type, sweat rate, acclimatization status, and genetic background will shift the optimal dose individually. Only by calibrating with your own data can you translate population science into a personal prescription.

Differences Across Populations

The impact of “the effects of heat on cognition and decision-making” is not equal for everyone. Age, sex, training status, body type, acclimatization state, and genetic background all significantly modulate an individual’s response magnitude to the environment. Ignoring these differences and applying a one-size-fits-all recommendation is one of the most common errors in applying environmental physiology.

| Population Aspect | Response Characteristics | Practical Recommendations |

|—|—|—|

| Beginners vs. Advanced | Advanced athletes have more mature environmental adaptation and better tolerance, but less marginal room for adaptation | Beginners should progress conservatively, building baseline tolerance before increasing load |

| Male vs. Female | Differences in surface area-to-mass ratio, hormonal cycles, and sweat composition | Females should individually assess heat dissipation and hydration, and monitor energy availability |

| Young vs. Older | Older individuals have reduced thermoregulation, sweat gland function, and compensatory capacity | Older individuals are more sensitive to extreme environments, requiring greater caution and longer adaptation |

| Body Type Differences | Surface area, body fat, and muscle mass affect heat dissipation and heat production | Larger individuals dissipate heat less efficiently; smaller individuals cool faster—each has its own risks |

When interpreting individual differences, one must also be wary of a statistical trap: studies typically report “group average responses,” but beneath the average often lies enormous individual variability. In the same environmental intervention, some may be strong responders, some may barely respond, and some may even respond in the opposite direction. This is why even when a study shows “average effectiveness,” you still need to confirm through your own testing which category you fall into. It is recommended to conduct personalized controlled tests: in two training sessions with similar conditions, with and without a given environmental strategy (e.g., pre-cooling, heat acclimation), compare power, core temperature, heart rate, and subjective feelings, repeating several times before drawing conclusions.

Take the common amateur endurance population in Taiwan as an example: many are middle-aged cyclists and runners over 35 who train around work schedules. This group’s thermoregulation and recovery capacity are already somewhat inferior to young elites. When facing humid summers and high-altitude challenges, correct environmental strategies (heat acclimation, individualized hydration, gradual ascent) can yield relatively greater safety and performance benefits. Female athletes, meanwhile, need to pay attention to the effects of the menstrual cycle on baseline core temperature and fluid regulation, as well as whether energy availability is sufficient. After understanding population differences, you will realize: truly professional environmental physiology advice is always an individualized prescription that varies from person to person, not a universal slogan.

Practical Training Applications

Theory must ultimately translate to training plans and race courses. Below is a practical framework for converting “the effects of heat on cognition and decision-making” into concrete training and competition operations:

• Pre-race environmental rehearsal: All environmental strategies must be rehearsed in training first. “Never try anything new on race day” is an iron rule. Whether heat acclimation, pre-cooling, or hydration pacing, the body needs time to build tolerance and familiarity.

• Periodized thinking: Align environmental adaptation with the training cycle—build tolerance in the base phase, and conduct sport-specific environmental adaptation for the target race’s temperature, humidity, or altitude in the pre-race phase.

• Progressive exposure: Start with mild environmental stimuli and gradually increase load based on bodily responses, building a personalized exposure dose and timing profile to avoid injury from a single excessive exposure.

• Objective data monitoring: Combine core temperature (or heart rate drift), power, rating of perceived exertion (RPE), and urine/body weight changes to objectively assess whether environmental strategies are truly effective.

• Holistic context: Environmental adaptation is one part of training, sleep, recovery, and nutrition. No single strategy can compensate for sleep deprivation, dehydration, or flawed training design.

Using a one-week training schedule as an example, you can rehearse different environmental scenarios in key midweek sessions and weekend long rides: on high-intensity days, focus on maintaining power quality in the target environment and testing cooling or insulation gear; on long-distance days, focus on hydration and sodium pacing, thermoregulation, and long-duration gear tolerance. Through repeated rehearsal, your body can respond to the environment almost automatically on race day, leaving mental resources for pacing and tactical decisions. The most common mistake many people make is “only seriously dealing with the environment on race day while treating daily training casually”—this is precisely putting the cart before the horse. Daily training is the best laboratory for building heat tolerance, testing hydration doses, familiarizing with gear, and developing environmental coping rhythms.

It is recommended to integrate an environmental log with your training log, recording temperature, humidity, altitude, wind conditions, environmental strategies used, bodily responses, and performance data for each key session. Over weeks to months of accumulation, the value of this personalized database will far exceed any generic guide. Additionally, don’t overlook “recovery under environmental stress”—a frequently underestimated component. Heat or high altitude slows recovery and increases fatigue accumulation. The quality of recovery between consecutive training days often determines whether you can steadily accumulate training volume without injury, and training volume is the most fundamental engine of long-term progress. Treat environmental management as a serious part of training, not a last-minute accessory before race day, and both your progress and safety will be noticeably different.

Taiwan-Specific Applications

Taiwan’s unique climate, terrain, and race culture add a distinct local flavor to the application of “the effects of heat on cognition and decision-making.” In summer, high temperature and humidity mean the apparent temperature often exceeds 35°C, with relative humidity frequently above 80%. Evaporative cooling is inefficient, and sweat and electrolyte losses far exceed those in the temperate-climate research settings, meaning recommendations from foreign literature often need to be adjusted upward. In winter, the northeast monsoon brings cold, damp conditions and strong winds, and mountainous areas may present hypothermia risks. The extreme elevation gain from sea level to Wuling at 3,275 meters brings high-altitude physiological challenges within easy reach.

Taking events such as the Westbound Wuling Challenge, Tour of East Taiwan, Sun Moon Lake Loop, Taroko Marathon, various triathlons, and round-island challenges as examples, athletes should factor local and seasonal environmental conditions into their planning: for summer events, start earlier to avoid high WBGT in the afternoon, and leverage the dense convenience store network along routes to enhance fluid and sodium replenishment; for high-altitude sections, allow for gradual acclimatization, and watch for cold protection and signs of altitude sickness; for cold, damp winter events, strengthen windproofing, insulation, and hypothermia protection. Make good use of the Central Weather Administration’s forecasts for apparent temperature, humidity, wind speed, and air quality, converting them into daily environmental risk assessments and strategies, so that you can balance safety and optimal performance in Taiwan’s varied and demanding environment.

Common Myth-Busting

Myth: “Heat only affects the body, not the brain.” Heat significantly impairs complex decision-making governed by the prefrontal cortex, and fueling and pacing errors in the latter stages of a race often stem from this; simplifying and pre-planning key decisions can reduce cognitive risk in hot environments.

Such myths spread widely because they “sound reasonable,” are easily passed by word of mouth, or are amplified by marketing and anecdotal experience. Yet the value of science lies precisely in testing intuition with rigorous evidence: many seemingly obvious environmental beliefs do not hold up under controlled environmental chamber experiments and epidemiological investigations. The field of environmental physiology is especially rife with oversimplified claims that compress complex doses, timing, individual differences, and risks into a single slogan. The next time you hear a definitive environmental recommendation, it’s worth asking: “What is the evidence level of this claim? Who is the target population? Are the dose, timing, and safety margins clear?” Cultivating this evidence-based critical thinking is more valuable than memorizing any single conclusion, and it is a key step for athletes toward scientific training and avoiding environmental injury.

Conclusion

“The effects of heat on cognition and decision-making” is a topic in environmental physiology that combines theoretical depth with practical value. As the international journal evidence reviewed in this article shows, the environment’s impact on athletic performance is real and profound, but by no means unmanageable—the key lies in understanding mechanisms, mastering doses, individualizing adjustments, and coordinating with overall training, recovery, and nutrition. For endurance sports enthusiasts in Taiwan, while grasping scientific principles, it is equally important to integrate the local hot-humid climate, extreme elevation, and variable weather, transforming general principles into personalized prescriptions that suit you. May every cyclist and runner sweating on Wuling, in the East Rift Valley, or on round-island routes protect themselves, push their limits, and enjoy the purest joy of sport through the wisdom of environmental physiology—whether facing heat, cold, high altitude, or other challenges. Before you next step onto the race course, remember: your true opponents are not just the clock, but the entire environment beneath your feet and all around you.

Related Reading

• Cerebral Hemodynamics in Hot Environments: Research on the Effects of Heat on Brain Oxygenation
• Central Fatigue Under Heat Stress: Neuroscience Research on Elevated Brain Temperature and Exercise Termination
• The Impact of Climate Change on Taiwan’s Cycling Events: Physiological Predictions of Rising Temperatures
• Designing Interval Training in Hot Environments: Research on Thermoregulatory Strategies During Recovery Intervals