Synergy in Sweat: Strength and Endurance
StrengthEndurance

Synergy in Sweat: Strength and Endurance

For decades, athletes and fitness enthusiasts have often viewed peak neuromuscular power and endurance as distinct, even antagonistic, training goals. However, recent scientific evidence challenges this deeply ingrained belief, revealing that these seemingly disparate qualities are, in fact, willing partners in enhancing performance, health, and resilience across the lifespan.

Published: November 28, 2025

The Traditional Training Divide

The widely accepted assumption that explosive power and endurance capacity are fundamentally incompatible goals has shaped training programs, athlete development, and our fundamental understanding of human performance capabilities; You're either built for power or for endurance, but not both. The concept of the interference effect, popularized by seminal work from Hickson (1980) [1], proposed that simultaneously training for endurance and resistance could hinder gains in peak neuromuscular power from resistance training. The initial molecular explanation suggested that resistance training primarily activates the Akt-mTORC1 pathway, crucial for muscle growth (hypertrophy), while endurance training activates the AMPK-PGC-1α axis, promoting oxidative capacity. It was theorized that endurance exercise-induced AMPK activation could inhibit mTORC1 signaling, thus "interfering" with strength adaptations. This widely accepted assumption has shaped training programs into segregated disciplines: resistance training and aerobic training.

However, Ferguson et al. (2025) [2] suggest a more nuanced perspective, based on recent findings that the physiological response to exercise is far more intricate than these early models suggested. For example, both resistance and endurance exercise acutely induce remarkably similar signals within the body, including elevated cortisol and catecholamine hormone levels, mechanical stress, and changes in intracellular calcium levels, showing a significant overlap in immediate molecular response. Moreover, extensive human studies have shown the positive practical implications of concurrent training. Meta-analyses by Murach and Bagley (2016) [3] and Schumann et al. (2022) [4] largely found no evidence that endurance training interferes with muscle hypertrophy or strength gains in response to resistance training, particularly in untrained or moderately trained individuals. In many cases, concurrent training even augmented whole muscle hypertrophy. A nuance is in place for specific scenarios; In well-trained individual, explosive power development shows the highest susceptibility to interference. And also training proximity matters for advanced athletes—interference primarily occurs when resistance and endurance exercise are performed within the same session, but not when separated.

In essence, while the interference effect may hold some truth for highly specific adaptations like explosive peak neuromuscular power in elite athletes, it largely appears to be a myth for general fitness goals. The two modalities, rather than being polar opposites, often work as willing partners, especially when it comes to broader health and performance benefits.

Aging and Muscle Function

Another hint for the strong positive correlation between strength and endurance can be found in aging. As we age, the decline in muscle strength and endurance capacity follows remarkably similar trajectories, whereas traditionally they were considered to deteriorate independently. Studies of hindlimb muscles in rats, and the fibre types within those muscle, found that both slow oxidative muscles and fast-twitch muscles exhibit nearly identical patterns of decline, with modest atrophy (muscle loss) in middle age that becomes severely pronounced in very old age. Strong parallel declines with age were found in peak muscle force, maximum oxygen uptake (VO₂ max) and lactate efflux - the rate at which lactate produced inside muscle cells is transported out of the cell into surrounding tissue.

These findings suggest that a common biological mechanism drives both power and endurance losses with aging. The like culprit appears to be dysfunction of mitochondria, the "powerhouses" that convert nutrients into energy, primarily in the form of adenosine triphosphase (ATP). Mitochondria are enriched in the neuromuscular junction, hence their decline affects not only ATP production for muscle contractions, but also contributes to denervation of the muscles which can lead to loss of motor function.

The practical implications are significant. Rather than targeting strength and endurance separately in older adults, exercise interventions addressing the underlying mitochondrial biology may prove more effective. This explains why endurance training in older individuals can notably improve muscle strength, and why resistance training produces adaptations typically associated with endurance exercise, including increased mitochondrial enzyme activity and blood flow in the muscles.

How to Train Both Strength and Endurance?

The traditional approach of separating power and endurance training into distinct phases may be unnecessarily limiting your athletic potential. Concurrent training protocols offer a practical solution for athletes seeking to develop both qualities simultaneously.

For untrained and moderately trained individuals, the implementation is straightforward. They can perform resistance and endurance training in the same session without experiencing limitations in strength, power, or endurance adaptations. The traditional concern about interference effects simply doesn't manifest at these training levels, making concurrent training an ideal approach for general fitness goals.

Elite and well-trained athletes require more nuanced programming strategies:

  • Session separation: Perform resistance and endurance training in separate sessions with at least 6 hours recovery, preferably 24 hours.
  • Exercise order: When same-session training is necessary, resistance exercise should precede endurance exercise to maintain training quality.
  • Avoid training to failure: While this is often associated to greater gains in peak neuromuscular power, it is not a prerequisite, and instead it does increase stress and impair recovery.
  • For endurance runners: Adding resistance training sessions to approximately 25% of total sessions was found to significantly improve running economy without comproming VO₂ max adaptations.
In conclusion, the review by Ferguson et al. [2] challenges the notion that endurance training automatically diminishes power output. Instead, aerobic capacity improvements can enhance recovery between power efforts, while neuromuscular power development can improve movement efficiency during endurance activities. Rather than choosing one quality over another, strategic programming allows for simultaneous development of both systems.

References

  1. Hickson RC. "Interference of strength development by simultaneously training for strength and endurance", European Journal of Applied Physiology and Occupational Physiology 45 (1980) 255–263. https://doi.org/10.1007/BF00421333
  2. Ferguson C, Furrer R, Murach KA, Hepple RT, Rossiter HB. "Power and Endurance: Polar Opposites or Willing Partners?", Med Sci Sports Exerc 57 (2025) 2480-2495. https://doi.org/10.1249/mss.0000000000003793
  3. Murach KA, Bagley JR. "Skeletal Muscle Hypertrophy with Concurrent Exercise Training: Contrary Evidence for an Interference Effect", Sports Med 46 (2016) 1029–1039. https://doi.org/10.1007/s40279-016-0496-y
  4. Schumann M et al. "Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis", Sports Med 52 (2022) 601–612. https://doi.org/10.1007/s40279-021-01587-7