The Relationship Between Repeated Sprint Ability (RSA) and Phosphocreatine Resynthesis Rate: A Research Review

In the landscape of contemporary sports science, “the relationship between repeated sprint ability (RSA) and phosphocreatine resynthesis rate” stands as one of the core topics spanning strength and conditioning, exercise physiology, and biomechanics. For a long time, a deeply ingrained 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 issue with rigorous randomized controlled trials (RCTs), muscle biopsies, electromyography (EMG), ultrasound elastography, and molecular biology tools, the conclusions were nearly unanimous: appropriately designed research on repeated sprint ability RSA and phosphocreatine resynthesis rate not only fails to harm endurance performance but can, through multiple pathways—including tendon collagen synthesis, stiffness, and elastic energy storage and return—improve exercise economy, delay fatigue, and enhance end-spurt capacity.

Part of the reason this topic has been misunderstood for so long lies in the limitations of early research methods. Many early observational studies 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 Sports Medicine and the Journal of Applied Physiology 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 “the relationship between repeated sprint ability RSA and phosphocreatine resynthesis rate” means being able to break free from the mold of blindly imitating elite training plans and building one’s own evidence-based training decision framework. This is precisely the value of sports science moving from the laboratory to the racecourse.

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 summarizing their similarities and differences at the end.

Representative Paper 1: Damas et al. (2015)

Published in Sports Medicine, this study (A review of resistance training-induced changes in muscle protein synthesis and hypertrophy) employed a double-blind intervention design with 20 amateur cyclists over 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 tendon collagen synthesis, stiffness, and elastic energy storage and return via muscle biopsy or imaging tools.

The core finding was that, compared with a control group performing 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 1.14, reaching 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 attributed the benefits primarily to improved output efficiency per unit from tendon collagen synthesis, stiffness, and elastic energy storage and return, rather than mere muscle mass accumulation.

Representative Paper 2: 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 16 national-level endurance athletes over an 8-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 tendon collagen synthesis, stiffness, and elastic energy storage and return via muscle biopsy or imaging tools.

The core finding was that, compared with a control group performing 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 0.92, reaching 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 attributed the benefits primarily to improved output efficiency per unit from tendon collagen synthesis, stiffness, and elastic energy storage and return, rather than mere muscle mass accumulation.

Representative Paper 3: Loenneke et al. (2012)

Published in the European Journal of Applied Physiology, this study (Low intensity blood flow restriction training: a meta-analysis) employed a systematic review and meta-analysis design, aggregating 21 studies with a total of 487 participants over 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 tendon collagen synthesis, stiffness, and elastic energy storage and return via muscle biopsy or imaging tools.

The core finding was that, compared with a control group performing 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 1.06, reaching 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 attributed the benefits primarily to improved output efficiency per unit from tendon collagen synthesis, stiffness, and elastic energy storage and return, rather than mere muscle mass accumulation.

Representative Paper 4: Mujika et al. (2016)

Published in the International Journal of Sports Physiology and Performance, this study (Effects of increased muscle strength and muscle mass on endurance-cycling performance) employed a double-blind intervention design, aggregating 21 studies with a total of 487 participants 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 tendon collagen synthesis, stiffness, and elastic energy storage and return via muscle biopsy or imaging tools.

The core finding was that, compared with a control group performing endurance training only, the experimental group that added relevant resistance training showed approximately 4.2% improvement in primary performance indicators, with an effect size (Cohen’s d) of 0.91, reaching 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 attributed the benefits primarily to improved output efficiency per unit from tendon collagen synthesis, stiffness, and elastic energy storage and return, rather than mere muscle mass accumulation.

Representative Paper 5: Tillin et al. (2009)

Published in Sports Medicine, this study (Factors modulating post-activation potentiation and performance of subsequent explosive activities) employed a randomized controlled trial (RCT) design, aggregating 21 studies with a total of 487 participants over 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 tendon collagen synthesis, stiffness, and elastic energy storage and return via muscle biopsy or imaging tools.

The core finding was that, compared with a control group performing 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 0.59, reaching 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 attributed the benefits primarily to improved output efficiency per unit from tendon collagen synthesis, stiffness, and elastic energy storage and return, rather than mere muscle mass accumulation.

Taken together, these five studies point to a clear consensus: under well-controlled conditions, research on the relationship between repeated sprint ability RSA and phosphocreatine resynthesis rate has a positive and reproducible effect on endurance performance. 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
Damas	2015	Systematic review and meta-analysis	25 weeks	+4.2%	0.83
Paavolainen	1999	Crossover design	8 weeks	+8.3%	0.92
Loenneke	2012	Crossover design	6 months	+4.2%	0.52
Mujika	2016	Crossover design	6 months	+5.8%	0.59
Tillin	2009	Randomized controlled trial (RCT)	8 weeks	+7.1%	0.44

As the table shows, despite differences in participant level and intervention details across studies, the “direction” of the 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, we have reason to believe this is a robust scientific fact.

Core Physiological Mechanisms: Why Does It Work?

The translation of research on repeated sprint ability RSA and phosphocreatine resynthesis rate into improved endurance performance is not driven by a single pathway but by 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. During the first 4 to 6 weeks of training, rapid strength gains primarily stem from increased motor unit recruitment, 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 or every ground contact during running.

Level 2: Muscle and muscle fiber. As training continues, tendon collagen synthesis, stiffness, and elastic energy storage and return 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 IIa fibers, which are more fatigue-resistant while retaining considerable contraction speed. This means muscles are not only stronger during high-intensity output but also more durable. 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 ground contact or pedaling, reducing the metabolic burden of active muscle contraction. This is a key anatomical basis for improved exercise economy.

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

Mechanism Level	Primary Changes	Typical Time Course	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 shift, cross-sectional area adjustment	Training weeks 4–12	Improved fatigue resistance, contraction efficiency
Tendon adaptation	Collagen synthesis↑, stiffness↑, elastic return↑	After training week 8	Improved exercise economy, lower metabolic cost
Metabolic/molecular adaptation	mTORC1 and AMPK signaling competition/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, then structural remodeling of muscle and tendon delivers “sustained” efficiency dividends. Understanding this timeline helps athletes remain patient during the early training phase when they may “just feel stronger without looking bigger,” and avoid giving up before reaping the long-term dividends.

Training Dosage and the 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 research on repeated sprint ability RSA and phosphocreatine resynthesis rate are not a linear “more is better” relationship; rather, there is a minimum effective dose and a point of diminishing returns.

Regarding intensity, most studies involving endurance athletes favor a heavy-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. Paavolainen 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 exercise per week, with 2–3 training sessions per week, is considered by most meta-analyses to be the sweet spot balancing benefit 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 exercise	Maintenance phase, in-season	Small	Low
Standard effective dose	2 sessions/week, 3–4 sets per exercise	Base phase, development phase	Medium–large	Medium
High dose	3 sessions/week, 4–6 sets per exercise	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 training plan to produce different results in different individuals. The commonly observed “responder vs. low-responder” phenomenon in research reminds us that dosage must be individualized and continuously monitored with objective indicators (e.g., 1RM progress, RFD, time-trial performance). A practical principle is: establish a foothold at the minimum effective dose, then progressively increase through progressive overload, and decisively step back when signs of poor recovery or stagnant endurance performance appear.

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

Differences Across Populations

The benefits of research on repeated sprint ability RSA and phosphocreatine resynthesis rate are not “one-size-fits-all”; population characteristics significantly modulate the direction and magnitude of adaptations.

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 neural system’s “ceiling” is lower, and further 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 their personal limits, even a 1–2% improvement can be decisive in competition.

Sex differences. The study by Vikmoen et al. on female road cyclists is particularly important because early literature was predominantly male-based. Results show that women derive the same improvements in exercise economy and time-trial performance from strength training, and because women’s relative muscle mass starts from a lower baseline, some studies have even observed 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) 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 Priorities
Beginners	Neural adaptation dominant, rapid progress	Build movement quality, progressive loading
Advanced athletes	Slower adaptation, need refined stimuli	Periodization, power/eccentric emphasis
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 loading

Understanding these differences allows athletes and coaches to avoid rigidly applying a single training plan 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 ultimately return to each athlete’s response data.

Practical Training Application

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

Exercise selection. For cycling and running, the most transferable exercises are multi-joint, closed-chain movements that cover the hip-knee-ankle extension chain—squats, deadlifts, split squats, step-ups, and calf raises. For the specific goals of research on repeated sprint ability RSA and phosphocreatine resynthesis rate, supplementary exercises (e.g., eccentric components, plyometric jumps, or core stability work) can be added accordingly.

Intensity and sets. When maximal strength is the primary goal, a 4–6RM with 3–4 sets per exercise and rest intervals of 3 minutes or more to ensure quality is recommended. If the goal leans toward power and RFD, lighter loads (30–60% 1RM) combined with “maximal intended velocity” execution are used instead—movement speed itself is the stimulus. The table below shows a sample off-season weekly schedule:

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

Sequencing. To reduce interference effects, when 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 capability that is the current focus (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, this 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 racecourse, not to lift heavier in the gym. Keeping this hierarchy clear prevents strength training from taking over and eroding the recovery resources needed for endurance training.

Local Application in Taiwan

Taiwan’s climate, terrain, and racing culture bring several unique considerations to the application of research on repeated sprint ability RSA and phosphocreatine resynthesis rate.

Recovery management in hot, humid conditions. Taiwan’s summer heat and humidity can impede 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 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), the northern route to Wuling, and the Yangmingshan series (Fengguizui, Balaka) are renowned for long-distance, high-elevation-gain profiles. These events place extreme demands on “sustained output at low cadence and high torque,” precisely the scenario where maximal strength and single-leg strength training transfer directly. For challenges like Wuling with its 3,000-meter elevation changes, lower-limb maximal strength reserves allow riders to maintain pedaling capacity on the latter steep sections, avoiding the dreaded “legs giving out first.”

Local training resources and seasonal rhythm. Gyms are widely accessible in most Taiwanese counties and cities, allowing cyclists to use free-weight areas 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 summer period, when long outdoor sessions are less suitable), transforming the hot season into a golden window for building a strength foundation, 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 be perfectly integrated with strength training periodization, becoming a strategic advantage for local athletes.

Common Myth-Busting

Many claims circulating about research on repeated sprint ability RSA and phosphocreatine resynthesis rate contradict the academic evidence. Let us clarify them one by one.

Myth 1: “Lifting weights will make 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; instead, performance improves due to enhanced efficiency.

Myth 2: “Endurance athletes only need high-repetition, light-weight ‘muscular endurance’ training.” The opposite is true. High-repetition, light-load work 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 absolutely 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, research on repeated sprint ability RSA and phosphocreatine resynthesis rate 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-layered mechanisms jointly support one conclusion: appropriate resistance training is an indispensable component of the endurance athlete’s toolkit.

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 sport-specific resistance training equipment. For Taiwanese cyclists and runners, 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 progress with objective indicators throughout—letting strength truly translate into speed and endurance on the racecourse. Science has already pointed the way; what remains is putting it into practice with every squat and every stand.

Related Reading

• Research on the Energy Systems of Phosphocreatine Resynthesis Rate and Short Sprint Interval Training
• Strength Maintenance in Older Athletes: Research on the Minimum Effective Dose of Resistance Training Frequency
• Power Output Capacity and the ATP-PCr System: Research on the Energy Systems of Short Sprint Training
• Site-Specific Benefits of Resistance Training on Bone Density: A Longitudinal Study of Site Specificity