Combining resistance and endurance work is known as concurrent training, which requires a carefully constructed approach. The body’s physiological response to these two distinct stimuli is not always cooperative, meaning gains in one area may compromise progress in the other. Achieving both muscle growth (hypertrophy) and aerobic fitness is possible, but it depends on strategically managing the molecular signals, timing, and nutritional support. The answer to whether you should run while trying to build muscle is yes, provided you manage the biological trade-offs involved.
The Physiological Trade-Off
The primary challenge of combining running and resistance training stems from the “Interference Effect,” where the two types of exercise activate opposing molecular pathways. Resistance training activates the mammalian Target of Rapamycin (mTOR), which signals the cell to increase protein synthesis for muscle growth.
Prolonged endurance exercise, such as running, activates AMP-activated protein kinase (AMPK). AMPK is activated when muscle energy stores are depleted, signaling the body to conserve energy and increase mitochondrial biogenesis for endurance. When AMPK is active, it can inhibit the mTOR pathway, meaning the endurance stimulus from running can blunt the muscle-building signal from weightlifting.
The degree of interference depends on the volume and proximity of the running session to resistance training. High volume endurance work pushes the body toward an energy-conservation state, hindering muscle growth. Minimizing the duration and intensity of the AMPK signal is necessary to successfully pursue both goals.
Running Intensity and Duration
The type of running significantly influences the interference effect. Long-distance running (LSD or LISS cardio) is most likely to interfere with muscle gains. The prolonged nature of these runs activates the AMPK pathway for an extended period, sustaining the signal that opposes muscle building.
To reduce this conflict, focus on shorter, more intense running protocols. High-Intensity Interval Training (HIIT) or short-burst sprints are less detrimental to hypertrophy. These intense, short bouts do not maintain the AMPK signal as long as distance running.
When running is performed at a lower volume, such as 20 to 30 minutes, the impact on muscle gains is reduced. Avoid excessive running volume, defined by the cumulative duration of the endurance stimulus. Prioritize short, intense bursts or moderate-duration runs to maintain cardiovascular health without prioritizing endurance over muscle building.
Strategic Workout Scheduling
Timing is a powerful tool for minimizing the Interference Effect. If exercising on the same day, prioritize weightlifting first. Starting with resistance training ensures maximum energy to lift with high intensity, triggering the mTOR pathway. Running first can deplete energy and pre-fatigue muscles, compromising lifting performance.
To allow opposing molecular signals to dissipate, separate a significant running session from resistance training by several hours. A separation of six to eight hours is recommended between the two training modes.
Scheduling running and lifting on completely separate days is the simplest and most effective strategy. This allows for full recovery and ensures the signaling pathways operate independently. Avoid placing a long, high-volume run immediately before or after a lower body lifting day to prevent excessive fatigue.
Fueling for Concurrent Goals
Proper nutrition is a significant factor when pursuing both running and muscle-building goals. Since your body is subjected to two demanding stimuli, total caloric expenditure will be higher. To support muscle growth, consume enough total calories, often requiring a caloric surplus, to meet both training demands. A consistent caloric deficit makes it nearly impossible to sustain the energy needed for running and provide the building blocks for hypertrophy.
Adequate protein intake is necessary for muscle repair and synthesis, especially since running increases muscle breakdown. A daily protein intake of 1.2 to 2.0 grams per kilogram of body weight is recommended to support concurrent training. This protein should be distributed evenly across multiple meals throughout the day to maximize the anabolic signal.
Carbohydrates are the primary fuel source for running and for replenishing glycogen stores. Timing carbohydrate intake is important after a running session to quickly restore glycogen needed to fuel the next muscle-building workout. Sufficient carbohydrate intake, especially following a demanding run, helps maintain a positive energy balance that supports both recovery and muscle growth.