Identifying Overtraining in Adolescent Trail Runners: A Study on Training Load Monitoring During Growth Periods

Based on the Journal of Applied Physiology, Medicine & Science in Sports & Exercise, Sports Medicine, British Journal of Sports Medicine, and other international peer-reviewed journals, this article provides an in-depth analysis of the scientific evidence on “Overtraining and Load Monitoring in Adolescents” within the field of youth athletic development. It also incorporates Taiwan’s local climate, competition, and sports culture contexts to offer evidence-based training and health strategies.

In the realm of youth athletic development, “Overtraining and Load Monitoring in Adolescents” is a topic that carries both academic depth and practical value, yet it has long been misunderstood or overlooked. Over the past decades, knowledge accumulated in sports science has largely focused on healthy adult males, meaning that many of the unique physiological characteristics and needs of youth athletic development have only recently received systematic attention and research. In fact, adolescents, females, and special populations (such as older adults, pregnant and postpartum women, and those with chronic diseases) differ fundamentally from the “standard young male athlete” in terms of physiological structure, hormonal environment, developmental stage, and health context. Directly applying adult male training principles and physiological data to these groups can at best reduce effectiveness and at worst cause health damage. This is precisely why understanding “Overtraining and Load Monitoring in Adolescents” is so important—it allows us to move beyond the myth of a “one-size-fits-all” approach and provide scientific guidance that truly aligns with the physiology and needs of different populations. Taiwan is moving toward an aged society, gender equality awareness is rising, and youth sports participation is becoming increasingly common—trends that make the local application of youth athletic development particularly valuable. This article will take you from the cellular and systemic physiological mechanisms, through empirical research in top international journals, the quantitative dose-response relationships, and differences in responses across populations, to directly actionable training applications and Taiwan’s local context. Finally, it will debunk long-standing myths, ensuring your understanding of “Overtraining and Load Monitoring in Adolescents” is truly built on science rather than hearsay or outdated stereotypes.

Academic Research Review

Regarding the scientific exploration of “Overtraining and Load Monitoring in Adolescents,” the field of youth athletic development has accumulated rigorous and rich evidence in recent years. 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. Brenner (2016). Pediatrics AAP Clinical Report, addressing the identification, prevention, and risks of early specialization in relation to overtraining and burnout in children and adolescents.

2. Matos et al. (2011). Medicine & Science in Sports & Exercise, investigating the prevalence and risk factors of overtraining syndrome in adolescent athletes.

3. Difiori et al. (2014). British Journal of Sports Medicine AMSSM Position Statement, reviewing overuse injuries and training load management in children and adolescents.

4. Bell et al. (2018). Journal of Athletic Training, confirming that highly specialized adolescent athletes have a significantly higher risk of overuse injuries.

Looking across these studies, it is clear that the scientific picture of “Overtraining and Load Monitoring in Adolescents” has deepened with advances in research methods and a growing awareness of “population specificity.” Early research often interpreted data from adolescents, females, or special populations directly through the framework of adult males, ignoring the fundamental differences brought by developmental stage, hormonal cycles, aging processes, or disease contexts. In contrast, recent high-quality research increasingly emphasizes “tailored research methods for specific populations”—analyzing adolescents by biological maturity rather than chronological age, incorporating menstrual cycle and energy availability as control variables in female studies, and conducting stratified assessments of resistance training and cardiovascular risk in older adults. This methodological evolution has allowed us to progress from “treating differences as noise” to “treating differences as the core of research.” It is worth noting that this field still faces several challenges: research on females and special populations remains relatively scarce compared to males, with sample sizes often limited; longitudinal tracking (especially long-term development in adolescents) is costly; and ethical considerations prevent certain interventions in vulnerable populations. Therefore, when interpreting conclusions, we must both value the population-specific insights these studies reveal and remain mindful of the level of evidence and scope of applicability—a conclusion drawn from a specific age, sex, or health status group may not be generalizable to other populations. This dual caution regarding population differences and evidence quality forms the foundation for the scientific application of youth athletic development and is the consistent stance of this article.

Core Mechanisms

Adolescents are in a unique stage where growth, development, and training adaptation occur simultaneously, making the identification of overtraining significantly different from that in adults. Growth itself consumes substantial energy and metabolic resources; when combined with excessively high training loads and insufficient recovery, adolescents are more likely to slide into overtraining and overuse injuries. At the physiological level, overtraining disrupts autonomic nervous system balance and endocrine function (such as elevated cortisol and decreased testosterone), and in adolescents it may also delay growth and suppress menstruation (in females). Overuse injuries are more common at growth plates and apophyses because these areas are not yet mature. Key monitoring indicators include: unexplained performance plateaus or declines, persistent fatigue and deteriorating sleep quality, elevated resting heart rate, loss of interest in training and low mood, recurrent minor injuries and illnesses, and changes in appetite and body weight. Training load can be quantified using the “Acute:Chronic Workload Ratio” (ACWR) concept—when short-term load suddenly spikes relative to the long-term baseline, injury risk rises significantly. Compared to adults, adolescents require greater vigilance against “monotonous training volume with insufficient recovery” patterns, as well as the repetitive stress caused by early high specialization. Effective prevention lies in: gradual progression, ensuring recovery days and sleep, encouraging multi-sport participation, regularly monitoring with subjective health questionnaires and simple physiological indicators, and fostering an environment that values enjoyment rather than results alone.

To truly understand “Overtraining and Load Monitoring in Adolescents,” one must return to the physiological context unique to youth athletic development: how the developing body, fluctuating hormones, aging systems, or disease effects alter exercise responses at the cellular, tissue, and systemic levels. The table below organizes the key mechanisms of this topic across different physiological levels, helping you build a complete mechanistic picture:

| Physiological Level | Key Mechanisms | Implications for Training and Health |

|—|—|—|

| Endocrine/Hormonal | Population differences in sex, growth, and metabolic hormones | Affects adaptation direction, energy regulation, and reproductive/skeletal health |

| Bone and Muscle | Bone mass accumulation/loss, muscle fiber composition, and protein synthesis | Determines bone density, strength development, and injury risk |

| Cardiovascular and Metabolic | Population-specific characteristics of cardiac remodeling, VO₂max, and substrate utilization | Affects endurance performance, recovery, and long-term health |

| Neural and Psychological | Neuromuscular control, motivation, and psychosocial needs | Determines skill development, injury prevention, and sustained participation |

Two dimensions deserve particular emphasis: “developmental stage” and “individual variability.” The same intervention can produce vastly different or even opposite effects depending on maturity, age, sex, hormonal status, or health conditions—this is precisely where youth athletic development is most easily misled by oversimplified recommendations. For adolescents, the effects, risks, and optimal timing of a training stimulus differ before and after PHV; for females, energy availability and menstrual function are key regulators behind many physiological responses; for older adults, anabolic resistance and the rate of decline give “stimulus intensity” a different meaning than in younger individuals. “Overtraining and Load Monitoring in Adolescents” deserves in-depth exploration precisely because it can target specific key aspects of youth athletic development. The more thoroughly you understand the mechanisms, the better you can judge “for whom, at what stage, what to do, and how much,” rather than blindly applying unsuitable general rules. This ability to adjust according to population and individual context is the dividing line between those who truly understand youth athletic development and those who train blindly.

Dose-Response Relationship

In youth athletic development, “the dose determines the effect” is a core principle, but this dose often needs to be recalibrated according to population characteristics. Stimuli that are too low fail to reach the adaptation threshold and produce no benefit; loads that are too high may exceed the compensatory capacity of vulnerable populations, causing injury, developmental disruption, or health damage. The table below outlines the dose-response relationships for “Overtraining and Load Monitoring in Adolescents” and serves as the most important quantitative reference when designing training and health plans for specific populations:

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

|—|—|—|

| Functional Overreaching | Short-term fatigue, recovery within days | Normal training response; performance rebounds with adequate recovery |

| Non-Functional Overreaching | Performance plateau lasting weeks | Requires significant load reduction; warning sign |

| Overtraining Syndrome | Months of underperformance plus physical and psychological symptoms | Requires prolonged rest and medical intervention |

| Monitoring Tools | Sleep, mood, resting heart rate, interest | Subjective questionnaires are more sensitive than single physiological markers |

As the table shows, the dose-response relationship in youth athletic development often follows a threshold or inverted U-shaped curve: before reaching an effective dose, benefits increase with dose; but beyond a certain critical point, not only are there no additional benefits, but risk and cost rise sharply—this is especially critical for vulnerable populations (developing adolescents, females prone to energy imbalance, and older adults with reduced compensatory capacity). This means that “finding the optimal dose for the specific population and individual” matters far more than “relentlessly pursuing more and stronger.” In practical application, it is recommended to continuously monitor responses using objective indicators (such as performance, recovery, health markers, and subjective feelings) and calibrate according to population characteristics and individual data. Remember: the group average reported in research is a starting point, not an endpoint; each person’s maturity, hormonal status, health background, and genetics will cause individual shifts in the optimal dose. Only by calibrating with your own data and professional assessment can you safely translate group science into a personal prescription.

Differences Across Populations

The impact of “Overtraining and Load Monitoring in Adolescents” is not equal for everyone. Age and maturity, sex, training status, hormonal state, health conditions, and genetic background all significantly modulate the magnitude of individual responses. Ignoring these differences and applying a single recommendation is one of the most common and dangerous mistakes in the application of youth athletic development.

| Population Dimension | Response Characteristics | Practical Recommendations |

|—|—|—|

| Beginners vs. Advanced | Advanced individuals have mature adaptations and better tolerance but less room for marginal gains | Beginners should progress conservatively, building a foundation before increasing load |

| Male vs. Female | Differences in hormones, body composition, bone, and metabolic characteristics | Females need individualized assessment of energy, iron, and bone health |

| Young vs. Older | Older individuals recover more slowly, have anabolic resistance, and accelerated decline | Older adults need sufficient stimulus intensity but longer recovery and screening |

| Developmental Stage | Maturity affects adaptation direction, risk, and timing | Arrange training by biological maturity rather than chronological age |

Regarding population-specific considerations for this topic: overtraining in females is often accompanied by menstrual dysfunction and RED-S; in males, decreased testosterone is common. Early and late maturers tolerate the same load differently and require individualization.

When interpreting individual differences, one must also be wary of a statistical trap: research reports mostly “group average responses,” but beneath the average often lies enormous individual variability. In the same intervention, some may be strong responders while others barely respond. This is why even when a study shows “average effectiveness,” you still need to combine professional assessment and your own response to confirm applicability. Taking common athletic populations in Taiwan as an example—whether it’s adolescents burdened with heavy academic workloads, women balancing family and training, or middle-aged and older adults pursuing healthy aging—correctly understanding the physiological characteristics of your own population group is the only way to avoid the ineffective or even harmful consequences of “copying someone else’s training plan.” After understanding population differences, you will realize: truly professional youth athletic development advice is always an individualized prescription that varies “by person and by stage,” never a one-size-fits-all slogan.

Practical Training Applications

Theory must ultimately translate into concrete training and health practices. Below is a practical framework for turning “Overtraining and Load Monitoring in Adolescents” into specific applications:

• Population Matching: All training and health recommendations must first ask, “Is this suitable for this population?”—adolescents prioritize development and protection, females prioritize energy and bone health, and older adults prioritize safety and functional maintenance. The starting points are all different.

• Progression and Monitoring: Progress gradually from an appropriate starting point, continuously monitor responses with objective indicators (performance, recovery, health markers) and subjective feelings, and adjust dynamically based on individual conditions.

• Health Over Performance: For vulnerable populations, long-term health (development, bone, endocrine, cardiovascular) always takes precedence over short-term performance. Never sacrifice health for a temporary number.

• Holistic Context: Training is just one piece of the puzzle; sleep, nutrition (especially energy availability), recovery, psychological, and social support are equally critical. A single intervention cannot compensate for overall imbalance.

• Professional Collaboration: When dealing with growing adolescents, female-specific health issues, or older adults and those with chronic diseases, seeking collaborative assessment from coaches, medical professionals, nutritionists, and psychologists is a safeguard for safety and effectiveness.

For practical planning as an example, when designing a program, you should first clarify the population characteristics and health context of the individual, then set reasonable goals, doses, and monitoring indicators accordingly. The most common mistake many people make is directly applying practices seen on social media or in adult elite athletes to adolescents, women, or older adults, ignoring the underlying physiological differences—this is precisely what youth athletic development seeks to avoid. Daily training and life serve as the best laboratory for observing population and individual responses and building personalized data.

It is recommended to integrate training logs with health monitoring, recording key indicators (such as growth and injuries in adolescents, menstrual and iron status in women, strength and recovery in older adults) alongside training content and physical responses. After 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 and long-term development”—for vulnerable populations, excessively pursuing short-term progress at the expense of recovery and health often leads to injury, burnout, or health problems, ultimately stalling the engine of long-term progress. Treat population matching and health-first as core training principles, and both your results and safety will be noticeably different.

Local Application in Taiwan

Taiwan’s unique climate, terrain, social structure, and sports culture add a distinct local flavor to the application of “Overtraining and Load Monitoring in Adolescents.” Climatically, the hot and humid summers and cold and damp winters pose additional challenges for different populations (especially adolescents and older adults with different thermoregulatory capacities); topographically, the extreme elevation gain from sea level to Wuling at 3,275 meters provides a rich training environment; socially, Taiwan is moving toward an aged society, academic pressure is heavy, and gender equality awareness is rising—all of which profoundly shape the sporting circumstances of various populations.

Taking local contexts as examples: adolescent athletes often face the dual pressures of academics and training, lacking systematic recovery and long-term development planning; female sports enthusiasts face insufficient attention to energy availability, iron, bone health, and female-specific health issues; and older adults need friendly, safe, and inclusive exercise environments and communities that accommodate different abilities. By leveraging Taiwan’s dense network of convenience stores for refueling, diverse cycling and running routes, and growing sports communities, and by designing activities tailored to different populations (such as multi-sport development for adolescents, female-friendly gear and environments, and group rides for older adults), the science of youth athletic development can truly reach every sports enthusiast in Taiwan, promoting public health and sports participation for all.

Debunking Common Myths

Myth: “Kids recover fast, so the more they train, the faster they improve.” Adolescents simultaneously bear the dual metabolic burden of growth and training; excessive training easily leads to burnout, injury, and growth disruption. Moderate loads, adequate recovery, and multi-sport participation actually lead to more stable long-term progress.

These myths spread widely because they “sound reasonable,” are easily passed by word of mouth, or stem from inappropriately applying adult male concepts to other populations. Yet the value of science lies in testing intuition with rigorous evidence: many seemingly obvious notions fail to hold up under rigorous research on specific populations. The field of youth athletic development is especially rife with outdated stereotypes and oversimplified claims that compress complex population differences, developmental stages, and individual variability into a single slogan. The next time you hear a definitive exercise recommendation aimed at adolescents, women, or special populations, it’s worth asking: “What is the level of evidence for this claim? Was it studied in this population? Or is it a conclusion from another group being directly applied here?” Cultivating this evidence-based, population-specific critical thinking is more valuable than memorizing any single conclusion, and it is a key step toward making youth athletic development more scientific and injury-free.

Conclusion

“Overtraining and Load Monitoring in Adolescents” is a topic in youth athletic development that combines theoretical depth with practical value. As the international journal evidence reviewed in this article shows, adolescents, females, and special populations have unique physiological characteristics and needs in exercise—they are by no means “scaled-down” or “special-case” versions of adult males. Understanding and respecting these differences is the starting point for scientific, individualized training. The key lies in mastering mechanisms, calibrating doses, adjusting by population and individual, and always prioritizing long-term health over short-term performance. For sports enthusiasts in Taiwan, while grasping scientific principles, it is equally important to integrate local climate, environment, and social context, transforming general rules into prescriptions suited to one’s own population and self. May every adolescent, woman, and older adult who sweats through exercise on their growth journey and at every stage of life safely, healthily, and sustainably enjoy the joy and benefits of sport through the wisdom of youth athletic development. The value of exercise has never been limited by age, sex, or condition—let science become a force that benefits everyone.

Related Reading

• Psychological Development and Sports Participation in Adolescents: A Longitudinal Study of Motivational Evolution
• The Dangers of Weight Control in Adolescents: Research on the Effects of Dietary Restriction on Growth and Development
• Eating Disorders and Exercise in Adolescent Females: A Prevalence Survey of Taiwanese High School Students
• Mental Health and Sports Participation in Adolescents: A Longitudinal Study on Depression Prevention