Combining cardiovascular and resistance training in the same session requires a strategic choice regarding the sequence of activities. The sequence is not merely a matter of preference but a strategic choice that directly impacts the specific adaptations your body makes. The order affects the quality of your workout, influences energy systems, and ultimately determines how effectively you move toward your fitness objectives. Understanding the physiological trade-offs allows you to structure your routine to prioritize your desired training outcome, whether that is increased muscle size, improved endurance, or better body composition.
The Impact of Running Before Lifting
Beginning a workout with a long or intense run can compromise the subsequent resistance training session. Running first depletes muscle glycogen stores, which are the primary fuel source for high-intensity activities like weightlifting sets. This energy deficit can lead to a reduced power output and diminished strength endurance during lifting.
Starting with cardio also introduces a degree of fatigue that can compromise form and technique during compound lifts. As the stabilizing muscles become tired, the risk of improper movement patterns increases, which may elevate the potential for injury while handling heavy loads. This sequence is generally counterproductive if your main goal is to maximize muscle strength or size, as the quality of the strength stimulus is blunted by pre-existing fatigue. Training in this order effectively prioritizes the adaptations related to endurance.
The Impact of Lifting Before Running
Performing resistance training before running ensures that your muscles are fresh for the most demanding part of your strength workout. Lifting first allows you to recruit the maximum number of muscle fibers and maintain the necessary intensity to stimulate muscle growth (hypertrophy) and strength gains. This sequence provides the optimal mechanical tension and metabolic stress required for resistance-based adaptations.
However, the fatigue accrued from an intense lifting session, especially one targeting the legs, will negatively affect your running performance. Muscle damage and neurological fatigue from lifting can impair running mechanics and gait efficiency. Exhausted stabilizing muscles, such as the glutes and core, struggle to maintain proper alignment and posture, which can increase the perceived exertion during the run. While this order prioritizes strength adaptation, the subsequent run may be slower or shorter than a run performed on fresh legs.
Understanding the Interference Effect
The conflict between concurrent strength and endurance training is known as the interference effect. This phenomenon occurs because the two types of exercise send opposing signals to the muscle cells, often leading to a compromise in adaptation for both strength and endurance. The conflict centers on two molecular signaling pathways: the mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK).
Resistance training stimulates the mTOR pathway, which is the primary signaling hub that promotes muscle protein synthesis and muscle hypertrophy. Conversely, prolonged endurance exercise, like running, activates the AMPK pathway, which senses low cellular energy and promotes mitochondrial biogenesis for improved aerobic capacity. Activation of AMPK can suppress the mTOR pathway. This means that doing both types of exercise together, particularly at high intensity, can result in suboptimal gains when compared to performing either training mode in isolation.
Determining Your Optimal Sequence Based on Fitness Goals
Your primary fitness goal should be the deciding factor in workout sequencing, as the order determines which adaptation pathway receives the strongest signal.
Maximizing Strength and Hypertrophy
For an individual focused on maximizing strength and muscle size (hypertrophy), always lift first. This ensures the resistance training stimulus is performed with maximal effort. The run should be kept to a low-to-moderate intensity to minimize the inhibitory effect on muscle growth signaling.
Improving Endurance Performance
If your objective is to improve endurance performance, the run should be prioritized and performed first. Placing the endurance work at the beginning allows you to run at the desired speed and volume with an unfatigued cardiovascular system.
Body Composition and Fat Loss
For those aiming for body composition improvements or fat loss, either order can be effective. Lifting first may be beneficial due to the greater excess post-exercise oxygen consumption (EPOC) response associated with intense resistance training. This elevated metabolic rate continues to burn calories for an extended period after the workout concludes.
Minimizing Interference
The most effective strategy to minimize the interference effect is to separate the two workout types by at least six hours, if possible. This time separation allows the molecular signaling from the first workout to become dominant before the opposing signal is introduced. If same-day scheduling is unavoidable, prioritize the activity that aligns with your goal by performing it first.