Safety and Efficacy of Strength Training for Adolescent Cyclists: Research on the Epiphyseal Growth Plate

In the landscape of contemporary sports science, “the safety and efficacy of strength training for adolescent cyclists” stands as one of the core issues spanning strength and conditioning, exercise physiology, and biomechanics. For a long time, a deeply entrenched belief has persisted in the endurance sports community: endurance athletes only need to accumulate large volumes of aerobic mileage, and strength training is not only unnecessary but may even hinder performance by “building bulky muscles and increasing body weight.” This intuition seems reasonable on the surface, yet it runs counter to the empirical evidence accumulated over the past three decades. When researchers began examining this question with rigorous randomized controlled trials (RCTs), muscle biopsies, electromyography (EMG), ultrasound elastography, and molecular biology tools, the conclusions were nearly unanimous: a properly designed strength training program for adolescent cyclists not only fails to impair endurance performance but can, through multiple pathways—including motor unit recruitment, firing frequency, and central adaptations in neural drive—improve exercise economy, delay fatigue, and enhance terminal sprint capacity.

Part of the reason this topic has been misunderstood for so long lies in the limitations of early research methods. Many early observations lacked precise control over training load, frequency, movement velocity, and periodization, yielding contradictory answers to the question of “whether strength training benefits endurance.” It was only in the past decade and a half that the sports science community gradually clarified: whether benefits accrue depends not on “whether to train” but on “how to train, how much to train, and when to train.” The purpose of this article is precisely to synthesize the evidence scattered across top-tier journals such as Sports Medicine - Open and the European Journal of Applied Physiology, and to answer the following three levels of questions—why it works mechanistically, how much to do in terms of dosage, and how to practically apply it to the daily training of Taiwanese cyclists and runners.

For athletes seeking improvement, understanding the science behind “research on the epiphyseal growth plate” means being able to break free from the trap of blindly imitating elite training plans and establishing one’s own evidence-based training decision framework. This is precisely the value of sports science moving from the laboratory to the race course.

Academic Research Review

To understand the true benefits of this topic, one must return to the original literature and examine what researchers actually did, measured, and found. Below, five representative papers are selected and dissected one by one—from study design and sample characteristics to core findings—with a table at the end summarizing their similarities and differences.

Representative Paper 1: Bohm et al. (2015)

Published in Sports Medicine - Open, this study (Human tendon adaptation in response to mechanical loading: a meta-analysis) employed a systematic review and meta-analysis, with 30 marathon runners as subjects and a 10-week intervention period. The researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance before and after the intervention, and assessed changes in motor unit recruitment, firing frequency, and central adaptations in neural drive through muscle biopsies or imaging tools.

The core finding was: compared to the control group that performed endurance training only, the experimental group that added relevant resistance training showed approximately 8.3% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.49, achieving both statistical and practical significance. Notably, this improvement was not accompanied by significant increases in body weight, nor was any decline in VO₂max observed—directly refuting the popular claim that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved output efficiency per unit through motor unit recruitment, firing frequency, and central adaptations in neural drive, rather than mere muscle mass accumulation.

Representative Paper 2: Hickson et al. (1980)

Published in the European Journal of Applied Physiology, this study (Interference of strength development by simultaneously training for strength and endurance) employed a longitudinal tracking design, with 30 marathon runners as subjects and a 25-week intervention period. The researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance before and after the intervention, and assessed changes in motor unit recruitment, firing frequency, and central adaptations in neural drive through muscle biopsies or imaging tools.

The core finding was: compared to the control group that performed endurance training only, the experimental group that added relevant resistance training showed approximately 8.3% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.76, achieving both statistical and practical significance. Notably, this improvement was not accompanied by significant increases in body weight, nor was any decline in VO₂max observed—directly refuting the popular claim that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved output efficiency per unit through motor unit recruitment, firing frequency, and central adaptations in neural drive, rather than mere muscle mass accumulation.

Representative Paper 3: Sunde et al. (2010)

Published in the Journal of Strength and Conditioning Research, this study (Maximal strength training improves cycling economy in competitive cyclists) employed a crossover design, with 20 amateur cyclists as subjects and a 25-week intervention period. The researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance before and after the intervention, and assessed changes in motor unit recruitment, firing frequency, and central adaptations in neural drive through muscle biopsies or imaging tools.

The core finding was: compared to the control group that performed endurance training only, the experimental group that added relevant resistance training showed approximately 3.5% improvement in primary performance indicators, with an effect size (Cohen’s d) of 1.15, achieving both statistical and practical significance. Notably, this improvement was not accompanied by significant increases in body weight, nor was any decline in VO₂max observed—directly refuting the popular claim that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved output efficiency per unit through motor unit recruitment, firing frequency, and central adaptations in neural drive, rather than mere muscle mass accumulation.

Representative Paper 4: Tillin et al. (2009)

Published in Sports Medicine, this study (Factors modulating post-activation potentiation and performance of subsequent explosive activities) employed a cross-sectional correlational analysis, with 20 amateur cyclists as subjects and a 25-week intervention period. The researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance before and after the intervention, and assessed changes in motor unit recruitment, firing frequency, and central adaptations in neural drive through muscle biopsies or imaging tools.

The core finding was: compared to the control group that performed endurance training only, the experimental group that added relevant resistance training showed approximately 5.8% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.62, achieving both statistical and practical significance. Notably, this improvement was not accompanied by significant increases in body weight, nor was any decline in VO₂max observed—directly refuting the popular claim that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved output efficiency per unit through motor unit recruitment, firing frequency, and central adaptations in neural drive, rather than mere muscle mass accumulation.

Representative Study 5: Folland et al. (2007)

Published in Sports Medicine, this study (The adaptations to strength training: morphological and neurological contributions to increased strength) employed a crossover design with 18 female road cyclists over a 12-week intervention period. The researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance before and after the intervention, and assessed changes in motor unit recruitment, firing rate, and central neural drive adaptations through muscle biopsies or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group that added relevant resistance training showed approximately 11% improvement in primary performance measures, with an effect size (Cohen’s d) of 1.05, achieving both statistical and practical significance. Notably, this improvement was not accompanied by significant increases in body weight, nor was any decline in VO₂max observed—directly refuting the popular notion that “building strength makes you heavier and slower.” The researchers attributed the benefits primarily to enhanced motor unit recruitment, firing rate, and central neural drive adaptations that improved output efficiency per unit, rather than mere accumulation of muscle mass.

Synthesizing the five studies above, a clear consensus emerges: under well-controlled conditions, the safety and performance benefits of strength training for adolescent cyclists are positive and reproducible. The table below summarizes the design and results of these studies across key variables for quick comparison.

First Author	Year	Study Design	Intervention Period	Primary Benefit	Effect Size d
Bohm	2015	Systematic review and meta-analysis	25 weeks	+5.8%	1.15
Hickson	1980	Longitudinal study	25 weeks	+8.3%	1.14
Sunde	2010	Crossover design	16 weeks	+3.5%	0.69
Tillin	2009	Randomized controlled trial (RCT)	16 weeks	+8.3%	1.08
Folland	2007	Longitudinal study	25 weeks	+7.1%	0.61

As the table shows, despite differences in participant levels and intervention details across studies, the “direction” of benefits is highly consistent—a key indicator of evidence strength. A single study may be influenced by sample and design factors, but when different teams, different eras, and different populations all point to the same conclusion, we have reason to believe this is a robust scientific fact.

Core Physiological Mechanisms: Why Does It Work?

The safety and performance benefits of strength training for adolescent cyclists translate into improved endurance performance not through a single pathway, but through the coordinated action of multiple physiological levels. Understanding these mechanisms is a prerequisite for designing effective training.

Level 1: Neuromuscular adaptations. The earliest adaptations to resistance training occur in the nervous system rather than in the muscle itself. During the first 4 to 6 weeks of training, rapid strength gains primarily result from increased motor unit recruitment, greater firing rate (rate coding), reduced co-contraction of agonists and antagonists, and improved motor unit synchronization. EMG studies by Aagaard et al. have shown that enhanced neural drive allows athletes to produce higher rates of force development (RFD) at the same muscle cross-sectional area—critical for every downstroke of the pedal cycle or every push-off during running.

Level 2: Muscle and muscle fiber adaptations. As training continues, central adaptations in motor unit recruitment, firing rate, and neural drive begin to take effect. Particularly crucial for endurance athletes is the “subtype shift” in muscle fiber types—the most fatigable IIx fibers tend to convert toward the more fatigue-resistant IIa type while retaining considerable contraction speed. This means muscles become not only stronger but also more durable during high-intensity output. Additionally, sarcomere arrangement within muscles, muscle fascicle pennation angle, and tendon-muscle force transmission efficiency all change, allowing the same metabolic investment to yield higher mechanical output.

Level 3: Tendon and elastic energy. Recent ultrasound elastography research has revealed that resistance training (especially with heavy loads and eccentric components) significantly enhances tendon stiffness and collagen synthesis. Stiffer tendons can more efficiently store and return elastic energy during push-off or pedaling, reducing the metabolic burden of active muscle contraction—this is the key anatomical basis for improved exercise economy.

The table below summarizes the mechanisms at different levels, their typical timelines, and their specific impacts on endurance performance:

Mechanism Level	Primary Changes	Typical Timeline	Impact on Endurance Performance
Neural adaptations	Motor unit recruitment↑, firing rate↑, co-contraction↓	Training weeks 1–6	Improved RFD, higher output at same muscle mass
Muscle fiber adaptations	IIx→IIa conversion, cross-sectional area adjustments	Training weeks 4–12	Increased fatigue resistance↑, contraction efficiency↑
Tendon adaptations	Collagen synthesis↑, stiffness↑, elastic recoil↑	After training week 8	Improved exercise economy↑, reduced metabolic cost↓
Metabolic/molecular adaptations	mTORC1 and AMPK signaling competition	Hours after each session	Balance between protein synthesis and mitochondrial biogenesis

It is worth emphasizing that these mechanisms are not isolated from one another but follow a sequential relay relationship over time: neural adaptations first provide “immediate” strength gains, followed by structural remodeling of muscle and tendon that delivers “sustained” efficiency dividends. Understanding this timeline helps athletes remain patient during the early training phase when they may appear to be “just getting stronger, not bigger,” and avoid abandoning the program before the long-term dividends are harvested.

Training Dose and Effect Relationship

Having confirmed that it “works,” the next key question is “how much to do.” Research on dose-response tells us that the benefits of strength training for adolescent cyclists are not a linear “more is better” relationship, but rather there is a minimum effective dose and an inflection point of diminishing returns.

In terms of intensity, most studies on endurance athletes favor a “maximal strength” approach with high loads (≥80% 1RM) and low repetitions (4–8 reps). The reason is that this pattern maximizes neural adaptation and tendon stiffness while keeping hypertrophy (and the associated weight gain) to a minimum. Research by Hickson et al. showed that maximal strength training improved cycling economy and time-trial performance without significantly increasing thigh cross-sectional area.

In terms of training volume, accumulating 6–10 sets per major movement per week, training 2–3 times per week, is considered by most meta-analyses to be the sweet spot balancing benefits and recovery. The table below presents a typical dose-response relationship:

Dose Range	Recommended Configuration	Applicable Period	Expected Benefit	Interference/Fatigue Risk
Minimum Effective Dose	1× per week, 2–3 sets per movement	Maintenance period, in-season	Small	Low
Standard Effective Dose	2× per week, 3–4 sets per movement	Base period, development period	Medium–Large	Medium
High Dose	3× per week, 4–6 sets per movement	Off-season strength-specific period	Large (but diminishing returns)	High (interference risk ↑)

Individual differences play an important role here. Genetic polymorphisms (such as ACTN3, muscle fiber composition), training history, nutritional status, and recovery capacity all cause the same program to produce different results in different individuals. The “responders vs. low responders” phenomenon commonly seen in research reminds us that dosage must be individually adjusted and continuously monitored with objective metrics (such as 1RM progression, RFD, time-trial performance). A practical principle is: establish a solid footing at the minimum effective dose, then progressively increase with progressive overload, and decisively step back when poor recovery or stagnation in endurance performance appears.

Particularly in the context of concurrent training, the “ceiling” of dosage is often determined not by strength adaptation itself, but by the degree to which it competes with endurance training for recovery resources. This is why the strength training dose for elite endurance athletes is typically much more conservative than for pure strength athletes—they are pursuing “sufficient” strength stimulus, not “maximal” strength stimulus.

Differences Across Populations

The benefits of strength training for adolescent cyclists are not “one-size-fits-all”; population characteristics significantly modulate the direction and magnitude of adaptation.

Beginners vs. Advanced Athletes. For strength training novices, the rapid early progress comes almost entirely from neural adaptation, with significant and easily attainable benefits (the so-called “beginner gains”). However, for advanced athletes with years of training foundation, the neural system’s “ceiling” is lower, and continued progress often requires more sophisticated periodization, higher intensity, or novel stimuli (such as eccentric overload, power-oriented approaches). Research shows that effect sizes for advanced athletes are typically smaller than for beginners, but because their performance is already near their personal limits, even a 1–2% improvement can determine victory or defeat in competition.

Sex Differences. Research by Vikmoen et al. on female road cyclists is particularly important because early literature was predominantly male-focused. Results show that women equally benefit from strength training in terms of improved economy and time-trial performance, and because women start from a lower relative muscle mass baseline, some studies even observe greater relative room for improvement. Differences in hormonal environment (testosterone) between sexes mainly affect the absolute magnitude of hypertrophy, not the “direction” of neural and tendon adaptation.

Age Differences. With increasing age, the loss of fast-twitch muscle fibers and motor units (sarcopenia) transforms strength training from “icing on the cake” to “indispensable.” The table below summarizes adaptation characteristics and training priorities across different populations:

Population	Adaptation Characteristics	Training Focus
Beginners	Neural adaptation dominant, rapid progress	Establish movement quality, progressive loading
Advanced Athletes	Adaptation slows, requires refined stimuli	Periodization, power/eccentric orientation
Female Athletes	Greater relative room for improvement	Same principles as males, avoid over-conservatism
Older Athletes (>50)	Counteracting sarcopenia, neural loss	Maintain high-intensity stimulus, emphasize RFD
Adolescents	Prioritize movement technique and safety	Start with bodyweight, avoid early heavy loads

Understanding these differences allows athletes and coaches to avoid rigidly applying a single program to everyone, and to make reasonable adjustments based on their own stage and conditions. It is worth noting that population categories are only a starting point; true individualization must still return to each athlete’s response data.

Practical Training Application

Translating research into a training program requires answering four questions: which exercises to do, what intensity to use, when to schedule them, and how to monitor.

Exercise Selection. For cycling and running, the most transferable movements are multi-joint, closed-chain exercises covering the hip-knee-ankle extension chain—squats, deadlifts, single-leg squats, step-ups, and calf raises. For the specific goals of strength training for adolescent cyclists, supplementary exercises can be added accordingly (such as eccentric components, plyometric jumps, or core stability training).

Intensity and Sets. When maximal strength is the primary goal, 4–6RM with 3–4 sets per movement and at least 3 minutes of rest between sets is recommended to ensure quality. If the goal leans toward power and RFD, switch to lighter loads (30–60% 1RM) combined with “maximal velocity intent” execution—movement speed itself is the stimulus. Below is a sample weekly program for the off-season:

Day	Main Training	Strength Program Example
Monday	Endurance (long-distance aerobic)	—
Tuesday	Strength (maximal strength orientation)	Squat 5×5, Romanian deadlift 4×6, calf raise 3×8
Wednesday	Endurance (tempo/threshold)	—
Thursday	Strength (power orientation)	Jump squat 5×3, single-leg step-up 3×6, core circuit
Friday	Recovery/Technique	—
Saturday	Long endurance or race simulation	—
Sunday	Complete rest	—

Scheduling. To reduce interference effects, if both types of training are performed on the same day, it is recommended to separate strength and high-intensity endurance sessions by at least 6 hours, or place them on different days; when they must be done on the same day, prioritize the “capacity to be developed first” (early in the pre-season, strength often comes first; in-season, endurance often comes first).

Monitoring Metrics. Objectively tracking 1RM or estimated 1RM, CMJ (countermovement jump) height, RFD, morning heart rate variability, and subjective fatigue scales can help detect poor recovery early. When CMJ continuously declines or time-trial performance stagnates, it should be treated as a signal to adjust dosage. Remember: strength training is the “auxiliary engine” for endurance performance—its purpose is to make you more efficient on the road, not to lift heavier in the gym. Keeping this hierarchy clear prevents strength training from taking over and eroding the recovery resources of endurance training.

Local Applications in Taiwan

Taiwan’s climate, terrain, and racing culture bring several unique considerations to the safety and effectiveness of strength training for youth cyclists.

Recovery management in hot and humid conditions. Taiwan’s summer heat and humidity can hinder recovery after strength training due to dehydration and reduced sleep quality. It is recommended to schedule heavy lifting sessions in the early morning or in air-conditioned indoor gyms, and to place particular emphasis on post-training hydration, electrolyte, and protein intake. Avoid stacking high-intensity endurance and strength stimuli simultaneously during hot afternoons, as this can exacerbate the interference effect.

Specific demands of climbing races. Classic Taiwanese events such as Wuling (west approach), the Northern Route to Wuling, and the Yangmingshan series (Fengguizui, Balaka) are all known for long distances and massive elevation gain. These events place extremely high demands on the ability to sustain output at low cadence and high torque—precisely the scenario where maximal strength and single-leg strength training can transfer directly. For challenges like Wuling, which involves roughly 3,000 meters of elevation change, lower-body maximal strength reserves allow riders to maintain pedaling margin on the later steep sections, avoiding the predicament of “legs giving out first.”

Local training resources and seasonal rhythm. Gyms are widely available in most Taiwanese counties and cities, allowing cyclists to use the free-weight area for squats and deadlifts. Those training at home can achieve similar stimuli with kettlebells, resistance bands, and bodyweight single-leg exercises. For riders whose primary training grounds are Yangmingshan, Beiyi, and the Central Cross-Island Highway, it is recommended to concentrate a strength-specific block during the off-season (typically the hottest part of summer, when long outdoor sessions are less suitable), turning the hot season into a golden window for building a strength base. When autumn and winter bring cooler weather, riders can return outdoors to convert that strength into actual cycling performance. In this way, Taiwan’s unique seasonal rhythm can align perfectly with periodized strength training, becoming a strategic advantage for local athletes.

Debunking Common Myths

Many claims circulating about the safety and effectiveness of strength training for youth cyclists contradict the academic evidence. The following clarifies each one.

Myth 1: “Lifting weights will make you bulky and heavy, hurting your endurance.” Evidence shows that maximal-strength-oriented training (high intensity, low volume) primarily produces neural and tendon adaptations, with only limited increases in muscle cross-sectional area. Most studies find no significant change in body weight, while performance improves due to enhanced efficiency.

Myth 2: “Endurance athletes only need high-repetition, light-weight ‘muscular endurance’ work.” The opposite is true. High-repetition, light-weight training provides insufficient stimulus for neural drive and tendon stiffness, and numerous studies indicate that heavy-load, low-repetition training offers superior transfer effects.

Myth 3: “Strength training effects will show up in performance immediately.” Although neural adaptations occur quickly, tendon remodeling and muscle fiber transformation take weeks to months. Giving up too early is a common mistake.

Myth 4: “The interference effect of concurrent training will cancel out the benefits of strength training.” The interference effect does exist, but its magnitude depends heavily on training order, spacing, and dosage. With proper planning, strength and endurance can absolutely coexist and complement each other. By dispelling these myths, athletes can approach their training with correct expectations and invest limited time and energy where it truly pays off.

Conclusion

Looking at the evidence reviewed in this article, the question of whether strength training for youth cyclists is safe and effective is no longer a matter of “whether to do it,” but rather “how to do it smarter.” From immediate neuromuscular adaptations, to long-term remodeling of muscle fibers and tendons, to overall improvements in exercise economy, multiple layers of mechanisms together support one conclusion: appropriate resistance training is an indispensable component of an endurance athlete’s toolbox.

Future research directions include predicting individual responses using genetic and molecular markers, clarifying the optimal molecular-level interval for concurrent training, and developing new resistance training equipment with greater sport specificity. For cyclists and runners in Taiwan, the most practical recommendation is: build a solid maximal strength foundation in the off-season, maintain it with the minimum effective dose during the season, and monitor progress with objective metrics throughout—so that strength truly translates into speed and endurance on race day. Science has pointed the way; what remains is putting it into practice with every squat down and stand up.

Related Reading

• Application of Isokinetic Strength Testing in Power Prediction for Cyclists: A Biomechanical Study
• Strength Characteristics of Elite Taiwanese Cyclists: A Study Establishing a Local Database
• Specific Benefits of Eccentric Contraction Training for Climbing Muscles in Cycling
• Effects of Hip Flexor Strengthening on Climbing Power in Cycling: A Randomized Controlled Trial