The Interference Effect of Aerobic and Anaerobic Training: A Latest Meta-Analysis of Concurrent Training

Many athletes pursue both endurance and strength simultaneously, but “concurrent training” may produce an interference effect—endurance training blunts strength and muscle hypertrophy adaptations. Understanding the mechanisms and conditions of this interference can help design programs that accommodate both goals.

Based on research published in leading international academic journals, this article systematically unpacks the scientific underpinnings of the interference effect in concurrent training. We will start from the methods and findings of key papers, delve into the underlying physiological mechanisms, quantify the relationship between training dose and outcomes, compare differences across populations, and ultimately translate these academic insights into actionable training recommendations for endurance athletes in Taiwan. This is not merely a compilation of knowledge—it is a practical map leading from the laboratory to the training ground. In an era where information authenticity is hard to discern, returning to rigorous scientific evidence is the most worthwhile investment for any athlete who takes training seriously.

Review of Academic Research

The most effective way to understand this topic is to directly examine representative studies from top international journals. Below are several landmark or methodologically rigorous papers that, from different angles, collectively construct our current scientific understanding.

1. Hickson (1980, EJAP)

This study employed the classic discovery of the interference effect. Concurrent training blunted strength gains. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

2. Wilson et al. (2012, JSCR)

This study employed a meta-analysis of concurrent training. The mode, frequency, and timing of endurance training influence the degree of interference. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

3. Coffey and Hawley (2017, Sports Medicine)

This study employed a review of molecular interference mechanisms. Potential antagonism between the AMPK and mTOR pathways. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

4. Fyfe et al. (2014, Sports Medicine)

This study employed a review of concurrent training adaptations. Interference primarily affects strength/power, while endurance is minimally impacted. The value of this study lies in its systematic approach to testing hypotheses, providing a quantifiable basis for subsequent training prescriptions, and allowing us to move beyond the ambiguity of rule-of-thumb practices.

Looking across the literature above, a common trend emerges: contemporary sports science increasingly emphasizes replacing intuition with objective data and rigorous experimental design. These studies echo and reinforce one another, converging on consistent core conclusions that give us greater confidence when formulating training strategies. The next section will delve into the physiological mechanisms behind these phenomena.

Synthesis of Core Findings

The interference effect primarily blunts strength and power adaptations, while endurance adaptations are less affected. The mechanisms involve potential antagonism between AMPK (endurance signaling) and mTOR (hypertrophy signaling), as well as residual fatigue. The degree of interference depends on the volume and intensity of endurance training (running interferes more than cycling) and the time interval between the two training modes.

It is worth emphasizing that these findings are not isolated laboratory numbers but robust conclusions repeatedly validated across different populations and study designs. Precisely for this reason, they can serve as the scientific foundation for training prescriptions. However, between “research findings” and “training application” lies a layer of mechanistic understanding—only by clarifying the “why” can we make correct adjustments in the face of individual differences and on-the-ground variables, rather than rigidly applying numbers. This is also the key dividing line between “executors who follow a set plan” and “athletes who truly understand training”—the former merely replicates programs, while the latter can flexibly modify every training decision based on their own condition, environmental changes, and race demands, maximizing the benefit of limited time and energy.

Core Physiological Mechanisms

Behind every training adaptation lies a cascade of physiological changes operating from the molecular, cellular, to organ-system levels. Understanding these mechanisms helps us determine which training methods truly target the limiting factors of performance and which merely add fatigue with limited benefit. The table below summarizes the key physiological mechanisms closely related to this topic and their effects:

Mechanism/Adaptation	Physiological Change	Impact on Performance
AMPK vs mTOR	Signaling antagonism	Suppresses hypertrophic synthesis
Residual fatigue	↓ Strength training quality	Limited adaptations
Muscle damage	Running eccentric	Interferes more than cycling

These mechanisms do not operate independently but are interwoven into an integrated network that influences one another. For example, without a simultaneous improvement in peripheral muscle metabolic capacity, the increased oxygen delivery from central cardiovascular adaptations cannot be effectively utilized; and vice versa. This “barrel effect” reminds us that comprehensive and balanced training stimuli often yield more lasting progress than extreme focus on a single point.

More importantly, the “timing” of these adaptations varies. Some changes (such as plasma volume expansion, neural coordination) manifest within days to weeks, while others (such as cardiac structural remodeling, skeletal adaptations) require months or even years of accumulation. Understanding this temporal dimension helps us maintain reasonable expectations for training outcomes, avoiding the mistake of declaring a method ineffective before giving it sufficient time—a key reason why many people give up halfway.

Training Dose-Response Relationship

“How much should I train?” is the question every athlete cares about most. Sports science answers this through the concept of “dose-response”—a quantifiable relationship exists between training variables (intensity, frequency, duration, volume) and the magnitude of adaptation, but this relationship is almost never a simple linear one. Understanding the shape of the dose-response curve helps us find the “sweet spot” with the highest return on investment, avoiding undertraining or overtraining.

The table below summarizes dose recommendations and expected outcomes under different scenarios as a reference for practical planning:

Population/Scenario	Recommended Dose	Expected Outcome
Separate sessions	Several hours apart/next day	Reduced interference
Control endurance volume	Moderate	Preserved strength adaptations
Choose mode	Cycling < Running	Lower interference

Several general principles can be drawn from the table. First, diminishing marginal returns: as fitness levels rise, the training stimulus required to achieve the same improvement becomes increasingly larger—which is why elite athletes often measure progress in “fractions of a percent.” Second, ceiling effect: beyond a certain threshold, additional training volume not only yields sharply diminishing benefits but may even backfire due to fatigue accumulation. Third, individual threshold: the minimum effective dose required to trigger adaptation differs from person to person, which explains why the same program produces vastly different results across individuals.

Therefore, the smartest training strategy is not blindly pursuing “more” but pursuing “just right”—providing sufficient stimulus to trigger adaptation, paired with adequate recovery to allow the adaptation to actually occur. Periodization is designed precisely to achieve this goal: through planned fluctuations in load, it avoids linear fatigue accumulation and allows the body to peak at critical moments.

Differences Across Populations

A recurring and unavoidable theme in research on the interference effect of concurrent training is “individual and population differences.” Applying the same conclusions indiscriminately to everyone is one of the most common mistakes in training prescription. Below, we analyze these differences from several key dimensions.

Beginners vs. Advanced Athletes: Because beginners are far from their physiological ceiling, they respond significantly to almost any regular stimulus—this is the so-called “beginner’s bonus.” Advanced athletes, on the other hand, have limited adaptive capacity and require more precise, higher-intensity, or more varied stimuli to keep progressing. This means the optimal training strategies for the two groups are fundamentally different. Advanced athletes especially need to prioritize training “quality” and “specificity” rather than simply stacking “volume.”

Men vs. Women: In absolute values (such as absolute VO₂max, muscle mass, and hemoglobin concentration), men generally exceed women, largely due to differences in body size, hormones, and body composition. However, in “relative training responses” (percentage improvements), the differences between sexes are often insignificant—women benefit fully from all types of training as well. Notably, women’s menstrual cycles, hormonal fluctuations, and energy availability (RED-S risk) need special consideration in training planning.

Age Differences: With advancing age, maximal heart rate, muscle mass, recovery speed, and the hormonal environment all change. However, extensive research confirms that even middle-aged and older populations retain the capacity to adapt to training—adaptation may simply be slower and require more adequate recovery. In other words, “it’s useless to train when you’re old” is a complete myth. Older adults, in fact, need regular training even more to combat sarcopenia, bone loss, and cardiorespiratory decline.

Genetic Factors: Don’t forget the “responder–non-responder” phenomenon. Large family studies indicate that a considerable proportion of training response can be explained by genetics. This means that given the same training plan, some people improve rapidly while others progress slowly—often not due to insufficient effort, but to innate differences in response potential. Recognizing this helps athletes maintain a healthier mindset about their own and others’ rate of progress, and makes them more willing to experiment with different training modes to find the stimulus that suits them.

Practical Training Application

The value of theory lies in guiding practice. Translating research findings on the interference effect of concurrent training into executable daily training requires grasping three core principles: “specificity,” “progression,” and “monitorability.”

Principle of Specificity: Training must target the energy systems and physiological adaptations required by your goals. If the goal is long-distance endurance, you need substantial aerobic base training; if you want to break through your VO₂max ceiling, you need targeted high-intensity interval stimuli. The most common problem with indiscriminate training is falling into the “moderate-intensity black hole”—every session leaves you somewhat breathless but not intense enough, failing to effectively accumulate aerobic base while also missing the key high-intensity stimulus, ultimately leading to stagnation.

Principle of Progression: The body only adapts when faced with loads slightly above its current capacity, but load increases must be gradual. A practical guideline is to keep weekly training volume increases within about 10%, and schedule a deload week every 3–4 weeks to allow accumulated fatigue to dissipate and adaptations to consolidate. Rushing progress is the number one culprit behind injuries and overtraining in amateur athletes.

Principle of Monitorability: Replacing subjective feelings with objective data is the core of modern training. We recommend establishing the following monitoring habits:

• Morning resting heart rate and heart rate variability (HRV): These reflect recovery status and autonomic nervous system balance. An abnormally elevated resting heart rate or a sudden drop in HRV is an early warning sign of fatigue.
• Power or pace: Tracking output at the same intensity under standardized conditions is the most objective way to assess fitness progress.
• Subjective fatigue and sleep quality: Simple daily self-ratings can capture overall status beyond the numbers.
• Periodic testing: Every 6–12 weeks, perform a standardized test (such as threshold power or a time trial) to objectively evaluate training effectiveness and adjust accordingly.

Integrating these principles, a mature training plan should be “building the base with large volumes of low-intensity work, raising the ceiling with small amounts of high-intensity work, consolidating adaptations with adequate recovery, and navigating direction with objective data.” Rather than blindly chasing mileage numbers every day, it is better to execute 1–2 high-quality sessions per week with discipline and truly relax the rest of the time—this is the essence of quality over quantity.

Local Application in Taiwan

Taiwanese triathletes and multi-sport athletes need concurrent training. It is recommended to separate strength and endurance sessions (on alternate days or several hours apart), prioritize the key session of the day, and substitute some running with cycling to reduce eccentric damage and interference.

Taiwan’s unique geography and climate mean that conclusions from international research must be localized before local application. The hot, humid summers, mountainous terrain, and dense, diverse race culture are both challenges and advantages. By knowing how to leverage high-altitude resources such as Hehuan Mountain and Wuling for altitude stimulus, how to do heat acclimatization and proper hydration and electrolyte replacement in hot, humid conditions, and how to adjust training focus based on the characteristics of Taiwanese races (such as a high proportion of climbing), Taiwanese endurance athletes can turn local conditions into a competitive advantage. Remember, any data from laboratories in temperate countries needs to be interpreted and applied against Taiwan’s real training environment—this is the final mile for scientific training to take root locally.

Debunking Common Myths

There is often a considerable gap between scientific findings and popular beliefs. Many “common sense” notions widely circulated in the sports community do not hold up to empirical scrutiny. Below, we debunk the common myths related to this topic one by one:

Myth 1: Endurance training destroys strength.

In reality, with proper scheduling, the interference is limited. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 2: You can’t train both at the same time.

In reality, you can—it’s all about scheduling and dosage. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

Myth 3: The interference effect impacts endurance adaptations.

In reality, the interference mainly affects strength/power. Blindly believing such myths wastes training time and energy at best, and leads to fatigue, stagnation, or even injury at worst.

The key to breaking myths lies in cultivating the habit of “asking for evidence.” Whenever you hear any training claim, ask yourself: “What research supports this? Which population does it apply to?” Only by grounding decisions in evidence can you avoid plausible-sounding traps in an age of information overload and make truly beneficial training decisions.

Conclusion: From Evidence to Action

Looking across the academic research on the interference effect of concurrent training, we can draw several clear conclusions. First, endurance performance is the result of multiple physiological systems working in concert—no single metric or training method holds the exclusive key to success. Second, the essence of training is “precise stress plus adequate recovery,” not merely stacking effort. Third, individual differences are everywhere; the best training plan is always the one “tailored to yourself and continuously adjusted based on data.”

Looking ahead, sports science is rapidly moving toward “precision individualization.” Advances in genomics, metabolomics, and wearable technology will eventually allow us to predict an individual’s response potential before training even begins, and to fine-tune every session in real time based on physiological data. For Taiwanese athletes and coaches, building a local physiological database and developing training models adapted to the local climate and race conditions are crucial steps toward closing the gap with the world’s best.

For every reader, the most important call to action remains the same: First, understand your physiological baseline through objective testing; then design your training using scientific principles; pair it with disciplined recovery and continuous monitoring; and be patient with your progress. There are no shortcuts to building endurance, but there is a right direction. May this science-based analysis serve as a reliable guide on your training journey, accompanying you as you pursue your limits while also enjoying the purest joy of sport.

Related Reading

• The Interference Effect of Concurrent Training: Molecular Conflict Mechanisms When Resistance and Endurance Training Coexist
• Combining Strength Training with Endurance Exercise: Training Strength and Cardiorespiratory Fitness Simultaneously
• The Interference Effect of Concurrent Strength and Endurance Training and How to Resolve It
• The Interference Effect of Weight Training and Endurance Training: How to Schedule Sessions Without Losing Out on Both