Bulking is a structured period of intentionally consuming a caloric surplus alongside resistance training to maximize muscle tissue gain. This approach provides the body with the excess energy and building blocks required for muscle hypertrophy. Incorporating running makes the process significantly more complex due to the competing demands placed on the body. Success requires precise management of the energy equation and strategic scheduling to minimize the physiological conflict between endurance and strength adaptation.
Managing the Caloric Surplus
Running significantly increases your Total Daily Energy Expenditure (TDEE). To maintain the anabolic state required for muscle gain, every calorie burned during a run must be added back to your food intake to preserve the necessary surplus. A typical muscle-building surplus is modest, often aiming for an extra 250 to 500 calories per day above maintenance levels.
Adding a run, which can easily burn several hundred calories, means the required daily food intake must increase proportionally. Failing to compensate for the calories expended will negate the surplus, stalling or preventing muscle gain. Accurate tracking of both food intake and exercise expenditure is a fundamental requirement for bulking while running.
Carbohydrates are important for individuals combining these two training types, serving as the primary fuel source for both resistance training and endurance running. Adequate carbohydrate intake ensures muscle glycogen stores are replenished, allowing for high-quality workouts that stimulate muscle growth. Protein intake must also be prioritized to supply the amino acids needed for muscle repair and to counteract potential muscle breakdown signaled by endurance exercise. A protein target of 1.7 to 2.2 grams per kilogram of body weight is recommended to support recovery and hypertrophy during high-volume training.
The Physiological Conflict: Interference Between Running and Muscle Gain
The most significant challenge when combining running and muscle gain is the “interference effect”—the blunting of muscle-building adaptations when endurance and resistance training are performed concurrently. The conflict occurs at a cellular level through two distinct energy-sensing pathways.
Resistance training stimulates the Mammalian Target of Rapamycin (mTOR) pathway, signaling the body to synthesize new muscle protein and promote hypertrophy. Conversely, prolonged or intense endurance exercise, like running, activates the Adenosine Monophosphate-Activated Protein Kinase (AMPK) pathway. AMPK is activated in response to low cellular energy and signals the body to conserve fuel and adapt for endurance.
The activation of the AMPK pathway can suppress the mTOR pathway, sending a mixed signal to the muscle cell. This suppression interferes with the muscle’s ability to process growth signals from resistance training. When this occurs, the rate of muscle protein synthesis is reduced, making the hypertrophic response less efficient compared to resistance training performed alone.
This interference is most pronounced with long-duration, high-volume, or high-intensity running sessions. Extended periods of muscle contraction and energy depletion inherent in long runs maximize AMPK activation. Therefore, the frequency and duration of running must be controlled to minimize its negative cross-talk with muscle-building signals.
Structuring Your Combined Training Schedule
Practical scheduling is the most effective way to minimize the interference effect and maximize muscle gain while running. The timing of your sessions is paramount, as the physiological conflict between the two types of exercise is time-dependent. It is recommended to separate your resistance training and running sessions by a minimum of six to eight hours.
This temporal separation allows molecular signaling pathways, particularly AMPK activation from the run, to return to baseline levels before the subsequent lifting session. If both must be done on the same day, prioritize resistance training first, as muscle growth is the primary goal during a bulk. Performing the run afterward ensures the muscle-building stimulus is delivered while the muscles are fresh and signaling pathways are optimal.
Prioritize low-intensity steady state (LISS) cardio over high-intensity interval training (HIIT) runs. LISS running, such as a moderate jog, places less metabolic stress on the muscle fibers and minimizes the duration of AMPK activation compared to high-intensity work. Running should be viewed as a supplemental activity for fitness during a bulk, not a primary focus.
Structure your weekly schedule so that lower body lifting days and running days are separated, ideally by a full day of rest or a dedicated upper-body lifting session. If separation is not possible, ensure the run is light and performed at least eight hours after a strenuous leg workout, preventing residual fatigue from compromising the quality of the lifting session.