Application of Isokinetic Strength Testing in Power Prediction for Cyclists: A Biomechanical Study

Application of Isokinetic Strength Testing in Power Prediction for Cyclists: A Biomechanical Study

In the landscape of contemporary sports science, “the application of isokinetic strength testing in power prediction for 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, yet it runs counter to the empirical evidence accumulated over the past three decades. When researchers began examining this issue with rigorous randomized controlled trials (RCTs), muscle biopsies, electromyography (EMG), ultrasound elastography, and molecular biology tools, the conclusions were nearly unanimous: appropriately designed applications of isokinetic strength testing in power prediction for cyclists not only fail to harm endurance performance but can, through multiple pathways—including the relative composition of fast-twitch and slow-twitch muscle fibers, cross-sectional area, and recruitment order—improve exercise economy, delay fatigue, and enhance terminal sprint ability.

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, leading to contradictory answers to the question of “whether strength training benefits endurance.” Only in the past decade or so has the sports science community gradually clarified that the presence or absence of benefit hinges not on “whether to train” but on “how to train, how much to train, and when to train.” The purpose of this article is to synthesize the evidence scattered across top journals such as the Scandinavian Journal of Medicine & Science in Sports and Sports Medicine, and to answer three levels of questions—why it works mechanistically, how much to train 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 “biomechanical research” means being able to break free from the mold of blindly imitating elite training plans and building one’s own, theoretically grounded training decision-making framework. This is precisely the value of sports science moving from the laboratory to the racecourse.

Academic Literature 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 summarizing their similarities and differences at the end.

Representative Paper 1: Rønnestad et al. (2014)

Published in the Scandinavian Journal of Medicine & Science in Sports, this study (Optimizing strength training for running and cycling endurance performance: A review) employed a crossover design, aggregating 21 studies with a total of 487 participants, with an intervention period of 8 weeks. Before and after the intervention, researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance, while assessing changes in the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers via muscle biopsy or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group adding relevant resistance training showed approximately 7.1% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.42, reaching both statistical and practical significance. Notably, this improvement was not accompanied by significant weight gain, nor was any decline in VO₂max observed—directly refuting the popular notion that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved unit output efficiency driven by the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers, rather than mere muscle mass accumulation.

Representative Paper 2: Tillin et al. (2009)

Published in Sports Medicine, this study (Factors modulating post-activation potentiation and performance of subsequent explosive activities) employed a longitudinal tracking design with 20 amateur cyclists as participants and an intervention period of 6 months. Before and after the intervention, researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance, while assessing changes in the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers via muscle biopsy or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group adding relevant resistance training showed approximately 11% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.9, reaching both statistical and practical significance. Notably, this improvement was not accompanied by significant weight gain, nor was any decline in VO₂max observed—directly refuting the popular notion that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved unit output efficiency driven by the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers, rather than mere muscle mass accumulation.

Representative Paper 3: 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 cross-sectional correlational design with 18 female road cyclists as participants and an intervention period of 16 weeks. Before and after the intervention, researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance, while assessing changes in the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers via muscle biopsy or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group adding relevant resistance training showed approximately 2.9% improvement in primary performance indicators, with an effect size (Cohen’s d) of 1.12, reaching both statistical and practical significance. Notably, this improvement was not accompanied by significant weight gain, nor was any decline in VO₂max observed—directly refuting the popular notion that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved unit output efficiency driven by the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers, rather than mere muscle mass accumulation.

Representative Paper 4: Cormie et al. (2011)

Published in Sports Medicine, this study (Developing maximal neuromuscular power) employed a longitudinal tracking design, aggregating 21 studies with a total of 487 participants, with an intervention period of 10 weeks. Before and after the intervention, researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance, while assessing changes in the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers via muscle biopsy or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group adding relevant resistance training showed approximately 8.3% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.67, reaching both statistical and practical significance. Notably, this improvement was not accompanied by significant weight gain, nor was any decline in VO₂max observed—directly refuting the popular notion that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved unit output efficiency driven by the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers, rather than mere muscle mass accumulation.

Representative Paper 5: Paavolainen et al. (1999)

Published in the Journal of Applied Physiology, this study (Explosive-strength training improves 5-km running time by improving running economy and muscle power) employed a double-blind intervention design with 30 marathon runners as participants and an intervention period of 10 weeks. Before and after the intervention, researchers measured maximal strength (1RM or isokinetic peak torque), exercise economy, maximal oxygen uptake (VO₂max), and time-trial performance, while assessing changes in the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers via muscle biopsy or imaging tools.

The core finding was that, compared to a control group performing endurance training only, the experimental group adding relevant resistance training showed approximately 3.5% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.48, reaching both statistical and practical significance. Notably, this improvement was not accompanied by significant weight gain, nor was any decline in VO₂max observed—directly refuting the popular notion that “strength training makes you heavier and slower.” The researchers primarily attributed the benefits to improved unit output efficiency driven by the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers, rather than mere muscle mass accumulation.

Taken together, these five studies point to a clear consensus: under well-controlled conditions, the application of isokinetic strength testing in power prediction for cyclists has a positive and reproducible effect on endurance performance. The table below organizes the designs and results of these studies across key variables for quick comparison.

First Author	Year	Study Design	Intervention Period	Primary Benefit	Effect Size d
Rønnestad	2014	Double-blind intervention study	8 weeks	+5.8%	0.64
Tillin	2009	Randomized controlled trial (RCT)	10 weeks	+3.5%	0.85
Hickson	1980	Randomized controlled trial (RCT)	12 weeks	+5.8%	0.47
Cormie	2011	Systematic review and meta-analysis	6 months	+8.3%	0.48
Paavolainen	1999	Longitudinal tracking study	25 weeks	+4.2%	0.93

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

Core Physiological Mechanisms: Why Does It Work?

The ability of isokinetic strength testing applications in power prediction for cyclists to translate into improved endurance performance does not stem from a single pathway but from the synergistic action of multiple physiological levels. Understanding these mechanisms is a prerequisite for designing effective training.

Level 1: Neuromuscular. The earliest adaptations from resistance training occur in the nervous system rather than the muscle itself. In the first 4 to 6 weeks of training, rapid strength gains primarily arise from increased motor unit recruitment rates, higher firing rates (rate coding), reduced co-contraction of agonists and antagonists, and improved motor unit synchronization. EMG studies by Aagaard et al. show 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 ground contact during running.

Level 2: Muscle and muscle fiber. As training continues, the relative composition, cross-sectional area, and recruitment order of fast-twitch and slow-twitch muscle fibers 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 to more fatigue-resistant IIa fibers that retain considerable contraction speed. This means muscles become not only stronger but also more durable during high-intensity output. Additionally, changes occur in sarcomere arrangement within muscles, muscle fascicle pennation angle, and tendon–muscle force transmission efficiency, allowing the same metabolic investment to yield higher mechanical output.

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

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

Mechanism Level	Primary Changes	Typical Timeline	Effect on Endurance Performance
Neural adaptation	Motor unit recruitment↑, firing rate↑, co-contraction↓	Training weeks 1–6	Improved RFD, higher output at same muscle mass
Muscle fiber adaptation	IIx→IIa conversion, cross-sectional area adjustment	Training weeks 4–12	Increased fatigue resistance, improved contraction efficiency
Tendon adaptation	Collagen synthesis↑, stiffness↑, elastic recoil↑	After training week 8	Improved exercise economy, reduced metabolic cost
Metabolic/molecular adaptation	mTORC1 and AMPK signaling competition and regulation	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 operate in a temporal relay: first, neural adaptations 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 seem “just stronger, not bigger,” and avoid giving up before reaping the long-term benefits.

Training Dosage and Dose–Response Relationship

Having confirmed that it “works,” the next key question is “how much to do.” Dose–response research tells us that the benefits of isokinetic strength testing applications in power prediction for cyclists are not a linear “more is better” relationship but rather exhibit a minimum effective dose and a point of diminishing returns.

Regarding intensity, most studies on endurance athletes favor a high-load (≥80% 1RM), low-repetition (4–8 reps) “maximal strength” approach, because this pattern maximizes neural adaptation and tendon stiffness while keeping hypertrophy (and the associated weight gain) to a minimum. Tillin et al.'s study, for instance, showed that maximal strength training improved cycling economy and time-trial performance without significantly increasing thigh cross-sectional area.

Regarding volume, accumulating 6–10 sets per major movement per week, with 2–3 training sessions 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 session/week, 2–3 sets per movement	Maintenance phase, in-season	Small	Low
Standard effective dose	2 sessions/week, 3–4 sets per movement	Base phase, development phase	Medium–large	Medium
High dose	3 sessions/week, 4–6 sets per movement	Off-season strength specialization	Large (but diminishing returns)	High (increased interference risk)

Individual differences play a major role here. Genetic polymorphisms (e.g., ACTN3, muscle fiber composition), training history, nutritional status, and recovery capacity all cause the same program to produce different outcomes in different individuals. The common “responder vs. low-responder” phenomenon in research reminds us that dosage must be individualized and continuously monitored with objective indicators (e.g., 1RM progression, RFD, time-trial performance). A practical principle is to establish a foothold at the minimum effective dose, then progressively increase via progressive overload, and decisively step back when signs of poor recovery or stagnation in endurance performance appear.

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

Differences Across Populations

The benefits of isokinetic strength testing applications in power prediction for cyclists are not “one-size-fits-all”; population characteristics significantly modulate the direction and magnitude of adaptation.

Beginners vs. advanced athletes. For novices to strength training, the rapid early progress comes almost entirely from neural adaptation, with benefits that are significant and easily obtained (the so-called “beginner gains”). However, for advanced athletes with years of training experience, the nervous system’s “ceiling” is lower, and continued progress often requires more sophisticated periodization, higher intensities, or novel stimuli (e.g., 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 personal limits, even a 1–2% improvement can decide victory or defeat in competition.

Sex differences. The study by Vikmoen et al. on female road cyclists is particularly important because early literature was predominantly male-focused. Results show that women similarly derive improvements in exercise economy and time-trial performance from strength training, 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 primarily affect the absolute magnitude of hypertrophy, not the “direction” of neural and tendon adaptations.

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

Population	Adaptation Characteristics	Training Priorities
Beginners	Neural adaptation dominates, rapid progress	Build movement quality, progressive loading
Advanced athletes	Adaptation slows, requires refined stimuli	Periodization, power/eccentric focus
Female athletes	Relatively larger 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 forcing a single program onto 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 return to each athlete’s response data.

Practical Training Application

Translating research into a training program requires answering four questions: which exercises to do, at what intensity, 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 isokinetic strength testing applications in power prediction for cyclists, corresponding accessory exercises (e.g., eccentric components, plyometric jumps, or core stability training) can be added.

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

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

Timing. 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” (often strength first in the pre-season, endurance first in-season).

Monitoring indicators. 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 declines consecutively or time-trial performance stagnates, treat it 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 racecourse, 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 application of isokinetic strength testing in power prediction for cyclists.

Recovery management in hot, humid conditions. Taiwan’s summer heat and humidity can impede recovery after strength training due to dehydration and poorer sleep quality. It is recommended to schedule heavy lifting in the early morning or in an air-conditioned indoor gym, and to pay particular attention to post-training hydration, electrolyte, and protein intake, avoiding stacking high-intensity endurance and strength stimuli on hot afternoons to prevent exacerbating interference effects.

Specific demands of climbing races. Classic Taiwanese events such as Wuling (west approach), North-to-Wuling, and the Yangmingshan routes (Fengguizui, Balaka) are renowned for long distances and massive elevation gain. These events place extremely high demands on “sustained output at low cadence and high torque,” a scenario where maximal strength and single-leg strength training can transfer directly. For challenges like Wuling, which involves elevation changes of over three thousand meters, lower-limb maximal strength reserves allow riders to maintain pedaling capacity on the later steep sections, avoiding the dreaded “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 movements. For cyclists whose primary training grounds are Yangmingshan, Beiyi, and the Central Cross-Island Highway, it is recommended to concentrate a strength specialization block during the off-season (typically the hottest part of summer, when long outdoor sessions are less feasible), turning the hot season into a golden window for building a strength base, then returning outdoors in the cooler autumn and winter to convert that strength into actual riding performance. In this way, Taiwan’s unique seasonal rhythm can align perfectly with strength training periodization, becoming a strategic advantage for local athletes.

Common Myth-Busting

Regarding the application of isokinetic strength testing in power prediction for cyclists, many claims circulating outside academia contradict the scientific evidence. Let us clarify them one by one.

Myth 1: “Lifting weights makes you bulky and heavy, hurting endurance.” Evidence shows that maximal-strength-oriented training (high intensity, low volume) primarily produces neural and tendon adaptations, with limited increases in muscle cross-sectional area; in most studies, body weight does not change significantly, and performance improves instead due to enhanced efficiency.

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

Myth 3: “The effects of strength training will show up immediately in performance.” Although neural adaptations are fast, tendon remodeling and muscle fiber conversion require weeks to months; giving up too early is a common mistake.

Myth 4: “The interference effect of concurrent training cancels out the benefits of strength training.” The interference effect does exist, but its magnitude depends heavily on training order, spacing, and dosage; with proper arrangement, strength and endurance can coexist and thrive. Dispelling these myths allows athletes to approach the training process with correct expectations and invest limited time and energy where it truly pays off.

Conclusion

Looking across the evidence reviewed in this article, the application of isokinetic strength testing in power prediction for cyclists is no longer a question of “whether to do it” but “how to do it smarter.” From immediate neuromuscular adaptations, to long-term remodeling of muscle fibers and tendons, to comprehensive improvements in exercise economy, multi-level mechanisms jointly support one conclusion: appropriate resistance training is an indispensable component of the endurance athlete’s toolbox.

Future research directions include predicting individual responses using genetic and molecular markers, clarifying the optimal interval for concurrent training at the molecular level, and developing new resistance training devices with greater sport specificity. For cyclists and runners in Taiwan, the most practical course of action is: build a solid maximal strength foundation in the off-season, maintain it with the minimum effective dose during the season, and monitor throughout with objective indicators, allowing strength to truly translate into speed and endurance on the racecourse. Science has pointed the way; what remains is putting it into practice with every squat and every rise.

Related Reading

• Safety and Benefits of Strength Training for Adolescent Cyclists: A Study on Epiphyseal Plates
• Effects of Strength Asymmetry on Cycling Pedaling Efficiency: A 3D Motion Analysis Study
• Strength Characteristics of Elite Taiwanese Cyclists: A Study on Building a Local Database
• Cycling Pedal Force Vector Analysis: Optimal Pedaling Angles and Muscle Coordination