Environmental and Physiological Challenges of Taiwan's Manyueyuan Ultramarathon: A Study on Thermoregulation During Night Running

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 of “nocturnal ultradistance thermoregulation,” and combines Taiwan’s subtropical climate, mountainous terrain, and local race scenarios to offer evidence-based training and race preparation strategies.

Within the field of environmental physiology, “nocturnal ultradistance thermoregulation” is one of the key variables determining whether endurance athletes can perform at their best on a real racecourse. Many amateur and elite athletes focus their training on power output, pacing, and equipment, yet underestimate the enormous physiological impact of the environment—heat, cold, high altitude, humidity, and air quality. In fact, when two athletes have similar fitness and equipment, the one who better understands how to adjust their 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 altitude differences from sea level to Wuling at 3,275 meters, plus urban air pollution and typhoon season, making environmental physiology especially valuable in practical terms for the local sports community. This article will guide you from cellular and systemic physiological mechanisms, through empirical research in top international journals, quantitative dose-response relationships, differences in responses across populations, to directly actionable training applications and Taiwan-specific scenarios, and finally debunk long-circulated myths, so that your understanding of “nocturnal ultradistance thermoregulation” is truly built on science rather than hearsay.

Academic Research Review

Regarding the scientific exploration of “nocturnal ultradistance thermoregulation,” the field of environmental physiology has accumulated rigorous and rich evidence. Below are several representative studies selected for their value in methodological design, study populations, and strength of conclusions, which together form our current understanding:

1. Millet & Millet (2012). BMC Medicine review of the physiological demands and fatigue mechanisms of ultramarathons.

2. Costa et al. (2013). Extreme Physiology & Medicine examining the thermoregulatory, fluid, and gastrointestinal challenges of ultra-endurance events.

3. Bongers et al. (2015). British Journal of Sports Medicine review of cooling strategies in endurance exercise.

4. Knechtle & Nikolaidis (2018). Frontiers in Physiology review of environmental and physiological performance determinants in ultramarathons.

Taken together, these studies show that the scientific picture of “nocturnal ultradistance thermoregulation” has deepened with advances in measurement technology. 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 “phenomenological observation” to “mechanistic explanation.” Notably, most high-quality studies employ randomized crossover designs, where each subject serves as their own control, greatly reducing noise from individual differences. However, extrapolation of research findings must remain cautious: a single environmental variable controlled in the laboratory does not necessarily equate to the complex combination of heat, humidity, wind, radiation, and fatigue on a real racecourse; nor do responses from well-trained subjects necessarily apply to general amateurs. When interpreting “statistical significance” and “effect sizes,” we must also distinguish between average trends in the laboratory and practical meaning on the individual racecourse—a 3% performance difference may determine rankings in elite competition, while its significance for recreational riders is relatively limited. It is precisely this careful attention to evidence quality and scope of applicability that forms the foundation of scientific training.

Core Mechanisms

Nocturnal ultradistance running faces unique environmental physiological challenges. At night, ambient temperature drops and solar radiation disappears, improving heat dissipation conditions and helping to avoid daytime heat—this is why summer ultramarathons are often held at night. However, prolonged, low-intensity, extremely long-duration exercise introduces new thermoregulatory challenges: on one hand, continuous heat production is relatively easy to dissipate on a cool night; on the other hand, if temperatures drop significantly in the deep night, athletes are exhausted, and metabolic heat production decreases (especially during rest stops at aid stations), there is instead a risk of hypothermia and cold injury—particularly in mountain ultramarathons (such as around Manyueyuan). Additionally, limited nighttime visibility increases the risk of falls and navigation errors, the circadian low point (3–5 a.m.) brings drowsiness and cognitive decline that affect pacing and safety, and prolonged duration brings compounded challenges of gastrointestinal issues, electrolyte imbalance, and sleep deprivation. The strategy involves dynamic regulation balancing heat dissipation and warmth retention, headlamp use and course familiarity, and pacing and alertness management during the physiological low point.

To truly understand how “nocturnal ultradistance thermoregulation” affects 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, interfering with heat dissipation and fluid balance, or altering central fatigue perception and exercise 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 and Metabolism | Alters substrate utilization, enzyme activity, and contractile function | Determines sustainable power output and timing of fatigue onset |

| Central Nervous System | Regulates fatigue perception, exercise drive, and cognitive decision-making | Affects “how tired it feels” and the ability to persist and make safe judgments |

Special emphasis should be placed on the two dimensions of “dose-response” and “temporal dynamics.” The same environmental exposure, under different intensities, durations, and acclimatization states, 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-duration, high-intensity efforts, limitations mostly arise from anaerobic energy supply and local metabolism; for multi-hour endurance events, the focus shifts to the combined effects of rising core temperature, fluid imbalance, glycogen depletion, and central fatigue. “Nocturnal ultradistance thermoregulation” deserves in-depth exploration precisely because it can specifically influence some of these limiting factors. Only by understanding the mechanisms can we determine “how to adjust for a given environment, by how much, and when,” rather than being led by the environment on the racecourse. The more thoroughly you understand the mechanisms, the more flexibly you can respond across different situations such as 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 low fail to reach physiological thresholds, producing no adaptation or effect; excessive exposure can exceed the body’s compensatory capacity, leading to risks such as heat injury, hypothermia, or altitude sickness. The table below summarizes the dose-response relationships for “nocturnal ultradistance thermoregulation” and serves as the most important quantitative reference for developing training and race preparation plans:

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

|—|—|—|

| Early night | Improved heat dissipation | Avoids daytime heat |

| Deep night cooling + exhaustion | Decreased heat production | Hypothermia risk (mountainous areas) |

| 3–5 a.m. | Circadian low point | Drowsiness, cognitive decline |

| Prolonged stay at aid stations | Body heat loss | Warmth retention required |

From the table above, it is clear that 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, not only is there no additional benefit, but risks and costs rise sharply. This means that “finding your own optimal exposure” is far more important than “blindly pursuing extremes.” Whether it is the daily heat dose for heat acclimation, the altitude and duration for altitude training, or the exposure time in cold environments, there exists a sweet spot that balances benefit and safety. It is recommended to progressively test responses under different environmental conditions during training (rather than on race day), recording core temperature or heart rate, perceived exertion, power data, and recovery status to build your own environmental response profile. Remember: laboratory averages are a starting point, not an endpoint; each person’s body type, sweat rate, acclimatization level, and genetic background will cause individual shifts in the optimal dose. Only by calibrating with your own data can you translate population science into a personal prescription.

Differences Across Populations

The impact of “nocturnal ultradistance thermoregulation” is not equal for everyone. Age, sex, training status, body composition, acclimatization state, and genetic background all significantly modulate individual responses to the environment. Ignoring these differences and applying a one-size-fits-all recommendation is one of the most common errors in the application of 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 be conservative and progressive, building basic tolerance before increasing load |

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

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

| Body Composition Differences | Body surface area, body fat, and muscle mass affect heat dissipation and heat production | Larger individuals have more difficulty dissipating heat; smaller individuals cool faster—each has its own risks |

When interpreting individual differences, one must also be wary of a statistical pitfall: 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 particular environmental strategy (such as pre-cooling or heat acclimation), compare power, core temperature, heart rate, and subjective feelings, and repeat several times before drawing conclusions.

Taking Taiwan’s common amateur endurance population as an example, many are cyclists and runners over 35 years old who train around work commitments. This group’s thermoregulatory and recovery capacities are already somewhat inferior to young elites, and when facing hot-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 should 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 that 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 be translated into training plans and the racecourse. Below is a practical framework for converting “nocturnal ultradistance thermoregulation” into concrete training and race operations:

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

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

• Progressive exposure: Start with mild environmental stimuli and gradually increase load based on bodily responses, establishing 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 component of training, sleep, recovery, and nutrition; no single strategy can compensate for sleep deprivation, dehydration, or flaws in training design.

Taking a one-week training schedule as an example, different environmental scenarios can be rehearsed in key midweek sessions and weekend long rides: high-intensity days focus on maintaining power quality in the target environment and testing cooling or insulation gear; long-distance days focus on hydration and sodium intake pacing, thermoregulation, and long-duration tolerance of equipment. Through repeated rehearsal, the body can respond to the environment in a nearly automated way on race day, freeing mental resources for pacing and tactical decisions. The most common mistake many people make is “only seriously confronting 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 yourself with gear, and developing environmental response rhythms.

It is recommended to integrate an environmental log with your training log, recording the day’s 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 general guide. Furthermore, do not overlook the often-underestimated aspect of “recovery in the environment”—heat or high altitude can delay recovery and exacerbate 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 adaptation seriously as part of training, rather than a last-minute accessory before races, and both your progress and safety will be noticeably different.

Taiwan-Specific Applications

Taiwan’s unique climate, terrain, and race culture add a distinctive local flavor to the application of “nocturnal ultradistance thermoregulation.” In summer, high temperature and humidity mean the apparent temperature often exceeds 35°C, with relative humidity frequently above 80%, making evaporative heat dissipation inefficient and sweat and electrolyte losses far greater than in research scenarios from temperate countries—this means 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 low temperatures and hypothermia risk. Meanwhile, the extreme altitude difference 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, the Hualien-Taitung Cycling Tour, Sun Moon Lake Loop, Taroko Marathon, various triathlons, and island-wide cycling challenges as examples, athletes should incorporate local and seasonal environmental factors into their planning: summer races should start early to avoid the high WBGT in the afternoon, and take advantage of the dense convenience store network along routes to enhance water and sodium replenishment; high-altitude sections should allow for gradual acclimatization, with attention to cold protection and signs of altitude sickness; winter cold-damp races should strengthen windproofing, insulation, and hypothermia protection. By making good use of the Central Weather Administration’s forecasts for apparent temperature, humidity, wind speed, and air quality, and converting them into daily environmental risk assessments and strategies, you can balance safety and optimal performance in Taiwan’s varied and demanding environment.

Common Myth Debunking

Myth: “Night running is cool, so you only need to worry about heat, not warmth.” In nighttime mountain ultramarathons, when energy is depleted, metabolic heat production decreases, or during prolonged stays at aid stations, hypothermia may instead occur; thermoregulation is bidirectional, and long runs on cool nights equally require dynamic warmth retention and heat dissipation management.

This type of myth spreads widely because it “sounds reasonable,” is easily passed by word of mouth, or is 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 dose, timing, individual differences, and risks into a single slogan. The next time you hear a categorical environmental recommendation, it is 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 is a key step for athletes toward scientific training and avoiding environmental injury.

Conclusion

“Nocturnal ultradistance thermoregulation” is a topic in environmental physiology that combines theoretical depth with practical value. From the international journal evidence reviewed in this article, it is clear that the environment’s impact on athletic performance is real and profound, but by no means unmanageable—the key lies in understanding mechanisms, mastering dose, 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 altitude, and variable weather, transforming general principles into personalized prescriptions that suit oneself. May every cyclist and runner sweating on Wuling, in the rift valley, or on island-circumnavigation routes protect themselves, push their limits, and enjoy the purest joy of sport through the wisdom of environmental physiology, amid heat, cold, high altitude, and various challenges. Before you next step onto the racecourse, remember—your true opponents are not just the timer, but the entire environment beneath your feet and all around you.

Related Reading

• Body Temperature Differences Between Morning and Evening Cycling in Taiwan: A Study on Circadian Rhythm-Environment Interactions
• The Temperature Difference Effect of Night Cycling in Taiwan: A Study on the Impact of Diurnal Temperature Variation on Recovery
• The Impact of Climate Change on Taiwan’s Cycling Events: A Physiological Prediction Study of Rising Temperatures
• Physiological Responses to Cold-Environment Cycling: A Study on Vasoconstriction, Muscle Metabolism, and the Respiratory Tract