Youth Endurance Training and Growth & Development: Training Considerations and Injury Risks During the Peak Height Velocity Period

Why Teenagers Can’t Simply Follow Adult Training Plans

In cycling and running clubs, it’s common to see coaches or parents take an adult athlete’s training volume and intensity distribution, scale it down proportionally, and apply it to teenagers, thinking “less volume should be safe enough.” This approach overlooks a critical fact: a teenager’s body is not a miniature version of an adult body—it is a system undergoing rapid remodeling. Bones, tendons, ligaments, muscles, and neuromuscular coordination all develop at different rates, and this period of developmental mismatch is precisely when sports injuries are most likely to occur.

The core concept this article addresses is the so-called “Peak Height Velocity” (commonly abbreviated as PHV)—the period during which a teenager’s height growth rate is at its fastest. This concept is frequently discussed in youth sports science because it influences how training loads should be structured, which injury risks are elevated, and what mindset parents and coaches should adopt. The article will explain the mechanisms as clearly and conservatively as possible, while repeatedly emphasizing: each child’s developmental timeline varies greatly, and any training arrangement should be evaluated by a qualified coach, with input from medical professionals (such as pediatric orthopedics or sports medicine) when necessary. This article provides only a general knowledge framework and cannot replace individualized professional assessment.

What Is Actually Happening During the Growth Spurt

Bones Grow First; Tendons and Muscles Lag Behind

During the period of rapid height gain in adolescence, long bones (such as the femur and tibia) grow rapidly through the epiphyseal plates (growth plates). This is generally accepted physiological knowledge: the longitudinal growth of bones occurs primarily at the growth plates, and until these areas are fully ossified (growth plate closure), their mechanical strength is weaker than that of mature bone. Meanwhile, the tendons and ligaments attached to the ends of the bones do not lengthen “proportionally” with the bones, and muscle flexibility and strength development often cannot keep pace with the rate of bone lengthening. This mismatch is widely referred to in sports science as “asynchronous growth”—in simple terms: bones surge ahead first, muscles and tendons haven’t caught up, and the tension distribution around joints becomes uneven as a result.

This is also why many adolescent athletes, during the year or two of rapid growth, suddenly feel they have become “clumsy,” with coordination appearing worse than when they were younger—they trip easily, their balance deteriorates, and previously familiar movement patterns (such as running form or pedaling rhythm) suddenly feel off. This is not regression; it is a normal process of the body recalibrating its proportions. However, this process also makes the body more sensitive and more susceptible to injury from high-intensity, high-repetition training stimuli.

Cardiopulmonary and Musculoskeletal Development Are Not Necessarily Synchronized

Beyond the mismatch between bones and soft tissues, the developmental trajectory of the cardiopulmonary system (heart size, maximal cardiac output, lung capacity) in adolescents does not necessarily align perfectly with height and weight growth curves. Some children may already look like adults, but their cardiopulmonary “engine” is still developing; others may be smaller in stature but already have relatively mature cardiorespiratory fitness. This means using height, weight, or appearance to judge how much training load a teenager can handle is unreliable. A more practical approach is to adjust training progressively based on coach observation (recovery status, subjective fatigue, movement quality) rather than applying a fixed formula.

Neuromuscular Control Changes Around Puberty

Another often-overlooked aspect is neural control of muscles. From childhood to early puberty, the nervous system has high plasticity, which is why many coaches consider childhood the golden period for developing fundamental movement skills (running, jumping, throwing, pedaling coordination). However, once the growth spurt begins, the rapid change in limb length disrupts previously established motor memory, requiring the body to relearn control. During this “recalibration” period, if training emphasizes high-intensity, high-impact, repetitive single movement patterns (such as excessive high-intensity interval running too early), the risk of adverse stress on joints and soft tissues increases.

Common Injury Patterns During the Growth Spurt

The following summarizes injury patterns that adolescents are more prone to during the growth spurt and are frequently mentioned in cycling and running populations. These are conceptual generalizations; actual diagnosis must be made by medical professionals.

Important reminder: The table above is only a conceptual summary of general patterns and is not a basis for diagnosis. If a teenager experiences persistent pain (not relieved after several days of rest), localized swelling, limping, waking at night due to pain, or obvious unilateral asymmetry, these are warning signs requiring medical evaluation. Do not self-diagnose as “growing pains” and delay seeking care, and do not force the athlete to continue training through pain.

Medical Warning Signs Checklist (Parents and Coaches Should Memorize)

• Pain persists for more than one week despite rest or reduced training volume
• Obvious swelling, warmth, bruising, or deformity at the painful site
• Pain causes limping or significant limitation of movement
• Waking at night due to pain, or severe pain even at rest
• Obvious asymmetry in appearance or function between one limb and the other
• Pain recurs at a site with a previous fracture history
• Accompanying systemic symptoms such as fever or general fatigue

If any of the above occurs, it is recommended to stop training in that discipline and seek evaluation from a pediatric orthopedic, sports medicine, or rehabilitation physician as soon as possible. The information provided in this article cannot replace professional medical diagnosis and treatment.

How to Think About Training Load: Progression and Individualization Are Key

Why Managing “Volume” Should Take Priority Over “Intensity”

In adult endurance sports, training intensity (heart rate zones, pace, power) is often the focus of discussion; but for adolescents, managing training “volume”—total hours, total distance, training days per week—is often the variable that requires more careful attention. The reason is that overuse injuries are mostly the result of cumulative repetition rather than a single high-intensity stimulus. This also aligns with the FITT principle frequently cited in training science (Frequency, Intensity, Time, Type). For adolescents, when adjusting training load, it is recommended to prioritize the frequency and time variables, while intensity increases should be approached more conservatively and gradually.

A generally accepted principle is: training load adjustments should be progressive, avoiding large increases in mileage, hours, or training days over a short period. There is no universally applicable precise number for this principle (this article does not provide specific percentages because individual variation is enormous), but the direction is clear—rather than chasing “how much improvement this week,” observe the child’s recovery status, sleep quality, subjective fatigue, and whether movement quality remains stable, and use these as references for adjusting training load.

How to Think About Training Focus Before, During, and After the Growth Spurt

The following provides a conceptual framework for training focus directions that may suit different developmental stages in adolescents. This is not a rigid rule but a thinking framework for coaches and parents; actual arrangements should depend on the individual child’s situation and evaluation by a qualified coach.

The Importance of Warm-Up, Cool-Down, and Flexibility Management

Because growth spurts are often accompanied by a temporary decrease in flexibility (bones grow first, while muscles and tendons lag behind), the role of warm-up and cool-down is even more important than in adult training. A proper warm-up should include dynamic stretching and low-intensity activities that gradually raise the heart rate, giving joints and soft tissues time to adapt to the upcoming training stimulus. Post-training cool-down and stretching help maintain flexibility and reduce the next day’s tightness and discomfort. These practices are generally recognized as common training knowledge; they cannot guarantee complete injury prevention, but they represent a reasonable and low-cost approach to risk management.

Recovery and Sleep: The Often Underestimated Training Variable for Adolescents

For adolescents, sleep is not just “rest”—it also involves growth hormone secretion, tissue repair, and nervous system integration. It is generally recognized that adolescents need more sleep than adults. When training volume increases without corresponding sleep support, the risk of inadequate recovery rises, which in turn increases the likelihood of overuse injuries. This is why many sports science discussions treat “training–recovery–sleep” as a whole rather than discussing training programs in isolation.

Sport-Specific Considerations for Youth: Cycling vs. Running

Cycling: Prolonged Fixed Posture and High Repetition of Hip/Knee Angles

Cycling is characterized by a relatively fixed body position, with the knee joint repeatedly flexing and extending during the pedal stroke. If the frame size and saddle height are not regularly adjusted as the child grows, poor joint angles and localized stress concentration can result. Because adolescents grow quickly, the “shelf life” of a properly fitted bike is much shorter than for adults. Parents and coaches are advised to develop a habit of regularly checking whether the bike setup still fits the child’s body, rather than waiting until the child complains of discomfort. Additionally, when adolescents ride on roads or riverside bike paths, traffic safety and environmental risks (e.g., traffic flow, blind spots, weather changes) require adult supervision or clear rules; open-road race-style training is not recommended for adolescents.

Running: Impact Loading and Ground Reaction Forces

Compared to cycling, running is a high-impact activity—every step transmits ground reaction forces through the lower-limb joints and bones. During growth spurts, this repetitive impact theoretically places greater load-management demands on the still-remodeling skeletal and tendon systems. This is why increases in running volume for adolescents should follow a more conservative and gradual pace, combined with cross-training (e.g., swimming, cycling, and other low-impact activities) to distribute the repetitive load of a single movement pattern. This is a practical application of the general training-science principle that “training diversity helps reduce the risk of overuse injuries.”

How Coaches and Parents Can Observe and Communicate

Establish a Simple Habit of Reporting Fatigue and Pain

Adolescents often struggle to describe their physical condition precisely—they may only say “a bit uncomfortable” without clarifying where it hurts, how much it hurts, or when it hurts. Coaches and parents can establish a simple routine, such as briefly asking before and after training, “Does anything feel off in your body today?” and describing pain levels in terms children can understand (e.g., using a simplified version of the Borg RPE scale, with numbers or emoji to express how they feel). This allows abnormalities to be detected earlier, rather than waiting until the child is visibly limping.

Training Logs Are Not for Comparison—They Are for Observing Trends

The purpose of recording training volume (time, distance, perceived intensity) is not to compare the child with others, but to let coaches and parents observe trends: Is this month’s volume increasing too quickly? Is recovery stable? Is the frequency of pain reports rising? This log can be a simple spreadsheet or a phone memo—the key is observing long-term trends, not the value of any single session.

Questions to Ask When Communicating with the Coach

If parents have concerns about training arrangements, they can communicate with the coach using specific questions, such as: How was the pace of training-volume progression decided for this phase? What is the adjustment principle if the child reports fatigue or pain? Is sufficient rest and cross-training scheduled? This kind of communication helps build a shared understanding among parents, coaches, and the child regarding training plans, and can also help identify unreasonable arrangements early.

Practical Considerations in the Taiwanese Sports Context

The Real-World Limitations of Riverside Bike Paths and School Team Practices

For many young cycling enthusiasts in Taiwan, the training venue is the riverside bike path. Its advantage is that it is relatively enclosed with less traffic, but its drawback is flat terrain and a lack of elevation change. If training is chronically focused on flat cruising, the child’s pedaling pattern tends to become monotonous, and core and hip-joint muscle stimulation is relatively insufficient. Some parents may want to arrange hill-climbing routes for their children, such as Fengguizui or the Beiyi Highway—common training climbs near Taipei. However, it should be noted that these long climbs place considerable stress on the cardiorespiratory system and lower limbs. If adolescents want to try them, a gradual progression is recommended: start with shorter, less steep sections to adapt, with an adult accompanying throughout and paying attention to traffic and refueling needs. Attempting long continuous climbs from the start is not advised, and racing peers on open roads is even less so.

For running, middle-school and high-school cross-country and track teams in Taiwan typically train on track ovals or roads around campus. The advantage is higher safety and the coach’s ability to monitor form and fatigue on site. However, a common culture of “running together as a group” can force children with greater fitness gaps to keep up with paces that do not suit them. If coaches or parents notice a child chronically struggling to keep up and gasping for air during group sessions, it is worth raising the issue proactively so that training intensity returns to a reasonable individual range, rather than letting group dynamics dictate the training load.

The Additional Burden of Hot, Humid Summers for Adolescents

Summer training in Taiwan often faces the challenge of high heat and humidity. Adolescents’ thermoregulation (sweating efficiency, body-surface-area-to-body-weight ratio) differs from adults’, and it is generally recognized that children and adolescents are relatively more prone to inadequate heat adaptation in extreme heat. This means that during outdoor endurance training in midsummer, hydration frequency, the choice of training time (avoiding the midday heat), and recognition of heatstroke warning signs (dizziness, nausea, abnormally dry or clammy skin, confusion) should all be part of the training plan—not just the training program itself. If a child shows any of these heatstroke warning signs during training, activity should stop immediately, the child should be moved to a cool area to cool down, and medical attention should be sought promptly. This also falls under the category of red-flag symptoms requiring medical care.

The Role of Strength Training in Adolescence

Is “Children Shouldn’t Lift Weights” an Outdated Idea?

There has long been a belief that adolescents should not touch weight training, for fear of prematurely “closing” growth plates or stunting height. This idea has been gradually revised within the sports science community: it is now generally recognized that well-designed resistance training, with professional supervision and correct movement quality, is not contraindicated for adolescents. In fact, it may help strengthen tendons, ligaments, and bones, thereby reducing injury risk. But the key words here are “well-designed” and “professional supervision”—this does not mean adolescents can imitate adult gym weight-training programs on their own. Mastery of movement technique and progressive loading both require coaching from someone with expertise in adolescent training, not self-teaching or following trends.

For adolescent endurance athletes in cycling and running, the focus of strength training is usually not on chasing maximal strength numbers, but on strengthening core stability and hip musculature, and improving movement quality and left-right symmetry. These directions are generally recognized as helpful for reducing overuse injury risk. The actual training content, load, and frequency still need to be individually designed by a qualified coach based on the child’s developmental stage and training experience.

Avoiding Early Specialization: The Physical Fitness Perspective

This article focuses on growth, development, and injury risk, but one concept is worth highlighting here (and will be discussed more fully in a later article): maintaining a diversity of physical activities during adolescence, rather than devoting all time to a single sport too early, is generally considered beneficial for the balance of overall motor skills and muscular development. The repetitive movement patterns of a single sport can cause certain muscle groups to become overdeveloped while others are relatively weakened, and this imbalance is itself one of the risk factors for overuse injuries.

Monitoring Tools: Simple but Consistent

Load monitoring for adolescent training does not need to rely on expensive wearable devices or complex data analysis. What matters more is consistency and regularity. Below are several monitoring methods that parents and coaches can easily adopt:

The common spirit behind these tools is: use simple, sustainable methods to allow adults to detect abnormalities early, rather than waiting until the child is already visibly injured before noticing that a problem exists.

Clarifying Common Misconceptions

Myth 1: “Train more while young, so you’ll have more to draw on later.” This notion ignores the vulnerability of the musculoskeletal system during the growth spurt. Injuries caused by overtraining may actually affect a child’s long-term athletic career and physical development. Training plans should be viewed from a long-term, sustainable perspective rather than short-term volume chasing.

Myth 2: “It’s just growing pain; push through it.” “Growing pain” is a term that is often overused. In reality, any persistent, localized pain should not be casually dismissed as growing pain and ignored. Any condition on the medical red-flag checklist requires professional evaluation; it is not advisable to self-diagnose and continue training through the pain.

Myth 3: “Other people’s kids train this much, so we should keep up too.” Every child differs in developmental timing, physical condition, and psychological readiness. Training plans should be based on individualized assessment rather than comparing training volume with other children.

Conclusion and Key Action Points

The growth spurt is a special and critical period in adolescent physical development. The developmental timelines of bones, tendons, cardiorespiratory systems, and neuromuscular coordination are not aligned, and this characteristic means that adolescent training plans cannot simply be scaled-down versions of adult programs. Instead, they require more careful consideration of individual differences, progressive principles, and adequate recovery and sleep.

Below are several key points that can be implemented immediately:

• Increases in training volume should be slow and progressive, avoiding sharp jumps in distance, duration, or training days within a short period. The specific pace should be discussed with a qualified coach and adjusted according to the child’s individual recovery status.
• Establish a simple habit of reporting pain and fatigue, so that abnormalities can be detected early rather than waiting until visible limping occurs.
• Keep the medical red-flag checklist in mind: persistent pain, swelling, limping, waking at night due to pain, and unilateral asymmetry should prompt prompt medical attention. Do not self-diagnose as growing pain and delay treatment.
• Prioritize sleep and recovery, which are especially important yet often overlooked variables during the adolescent body remodeling phase.
• Cyclists should regularly check that their bike fit is appropriate, while runners are advised to incorporate cross-training to distribute repetitive impact loads.
• Parents and coaches should maintain open communication, jointly observing the child’s long-term trends rather than short-term performance.

Finally, it must be emphasized again: this article provides a conceptual, general knowledge framework and cannot replace individualized medical evaluation or training plans made by qualified coaches based on the child’s actual condition. If you have any concerns about your child’s training plan or physical condition, it is recommended to seek assistance from a pediatric orthopedic physician, a sports medicine physician, or a coach with professional experience in adolescent training.

Related Reading

• Research on the Optimal Timing of Pubertal Growth Acceleration (PHV) and Athletic Training
• Adolescent Endurance Training: Growth Plates, Training Volume Limits, and the “Early Maturation Trap”
• Adolescent Athletes’ Growth Spurt (PHV) and Training Adjustments: Coordination and Injury Management During Height Spurts
• Adolescent Running Safety: Developmental Training Volume, Intensity, and Long-Term Development