The decision of whether to perform cardio before or after resistance training is a common dilemma for individuals combining these two types of exercise. The answer depends entirely on your primary fitness goal, as the sequence significantly influences physiological adaptations. Structuring a workout where both modalities are performed in the same session requires understanding your main objective to prevent one form of training from compromising the other.
Maximizing Strength and Hypertrophy
If your main goal is to build muscle size (hypertrophy) or maximize lifting capacity, you should always perform resistance training first. Starting with vigorous cardio depletes glycogen, the muscle’s primary energy source essential for high-intensity, repeated efforts like weightlifting. The quality of your resistance workout is paramount for muscle growth, requiring maximum force production and high training volume.
Pre-fatiguing muscles with cardio compromises your ability to lift heavy weights for the necessary repetitions. This reduction in intensity and volume limits the mechanical tension required to signal muscle growth. Research consistently shows that performing resistance training first leads to superior improvements in muscular strength and explosive power. Furthermore, lifting weights when fresh minimizes the risk of injury that can occur when attempting heavy lifts with fatigued pathways. A resistance-first approach ensures muscles are primed to handle the load and volume needed to stimulate the greatest anabolic response.
Prioritizing Endurance and Conditioning
When the goal is to improve cardiovascular fitness, such as increasing aerobic capacity or preparing for a running event, prioritizing endurance activity is the logical choice. The objective of an endurance workout is to challenge the cardiorespiratory system and push the body to resist fatigue over a sustained period. Performing a maximal-effort resistance session beforehand can leave the muscles and lungs fatigued, compromising the quality of the subsequent cardio.
Studies indicate that completing a heavy weightlifting session before endurance work can reduce time-to-exhaustion during the cardio. If you are training for a specific distance or aiming for a personal best time, you need your freshest energy stores for that primary effort. The resistance training that follows can then focus on muscular endurance using lighter weights and higher repetitions. If cardiovascular fitness is the main focus, the order matters less for low-intensity steady-state cardio, but for high-intensity interval training (HIIT), the cardio should come first.
The Physiological Basis Why Order Matters
The reason for the differing outcomes is rooted in a molecular conflict known as the “interference effect” in concurrent training. Resistance exercise activates the mechanistic target of rapamycin (mTOR) signaling pathway, the primary driver of muscle protein synthesis and hypertrophy. Endurance exercise, especially high-volume or high-intensity cardio, activates a different pathway: adenosine monophosphate-activated protein kinase (AMPK).
The activation of AMPK by aerobic exercise is believed to inhibit the mTOR pathway, essentially halting muscle-building signals. This molecular crosstalk suggests that the signaling for endurance adaptation can suppress the signaling for strength and size adaptation. When both types of exercise are performed too closely, the dominance of the endurance signal blunts the hypertrophic response to resistance training. The order of exercise determines which pathway receives the strongest signal. Performing resistance training first ensures the mTOR signal is maximally activated before the AMPK signal from subsequent cardio has the chance to interfere.
The Optimal Solution Separating Your Training
For individuals who want to maximize gains in both strength and endurance, the most effective strategy is to separate the training sessions by time. This approach minimizes the interference effect and allows the body to fully recover energy stores and signaling pathways between efforts. The recommended time separation is a minimum of six hours, with eight to twelve hours being ideal for optimal results.
This separation allows the AMPK pathway, activated by cardio, to return to baseline levels before the resistance training session begins. By the time weightlifting starts, the mTOR pathway can be fully engaged without inhibition. Practical scheduling options include performing resistance training in the morning and cardio in the evening, or alternating the two types of workouts on different days. This strategic spacing ensures the body’s adaptive response to each stimulus is maximized, allowing for simultaneous gains in both muscular strength and cardiovascular fitness.