The debate over whether to perform cardio or weight training first is one of the most common questions in fitness. The optimal sequence is not a universal rule but is determined entirely by the individual’s primary fitness objective. Combining both forms of exercise in a single session, known as concurrent training, requires strategic planning to prevent one modality from negatively impacting the results of the other. Understanding the specific goal—whether it is maximal strength, muscle size, or endurance—is the necessary starting point for structuring a combined workout.
When Muscle Gain is the Primary Goal
When the main objective is to increase muscular strength, power, or size, resistance training must be prioritized by performing it first in the session. Maximal strength gains and muscle hypertrophy rely heavily on the ability to produce maximum force and mechanical tension on the muscle fibers. This requires the central nervous system (CNS) to be completely rested and the muscles to be fully energized at the start of the lifting session. Studies indicate that subjects who perform high-intensity cardio before a strength workout experience a compromise in their strength endurance and power output.
The goal of lifting is to apply sufficient overload to stimulate muscle growth, which is achieved by recruiting the highest-threshold motor units. When a person engages in strenuous cardio first, the subsequent weightlifting performance is diminished, making it impossible to lift the heaviest weights necessary for progressive overload. This reduction in lifting capacity limits the mechanical tension placed on the muscle. By placing weight training first, the body is primed to maximize the quality and intensity of the lifts.
When Endurance is the Primary Goal
In scenarios where the main fitness goal is to improve cardiovascular fitness or train specifically for an endurance event, the order of activities should be reversed. Endurance athletes may benefit from performing their cardio first, sometimes even training in a state of pre-fatigue. This approach helps the body adapt to utilizing fuel sources more efficiently over long periods for sustained performance.
Low-Intensity Steady State (LISS) cardio typically has a minimal negative impact on subsequent weightlifting performance compared to high-intensity interval training (HIIT). If the goal is general health and cardiovascular conditioning, starting with LISS cardio is an acceptable strategy, especially if the following resistance work is moderate and not focused on maximal strength.
The Physiological Impact of Sequencing
The preference for one workout order is rooted in how the body’s energy systems are taxed and how the nervous system responds to fatigue. High-intensity resistance training primarily relies on the anaerobic energy systems, specifically the phosphagen system and anaerobic glycolysis. These systems provide rapid bursts of energy and depend heavily on readily available stores of ATP and muscle glycogen. Intense cardio, particularly HIIT, also draws heavily on these same limited resources.
Performing intense cardio first significantly depletes muscle glycogen and other immediate energy substrates, leaving less fuel for the high-force demands of weightlifting. This metabolic fatigue is compounded by Central Nervous System (CNS) fatigue. CNS fatigue is a temporary decline in the brain’s ability to maximally recruit motor units, compromising the effectiveness of the strength workout.
Structuring the Combined Workout
Regardless of the chosen workout order, a properly structured session begins with a dynamic warm-up to prepare the muscles and joints for movement. This phase should include light activity and movement-specific drills to increase blood flow and reduce the risk of injury.
Optimizing Recovery and Timing
Ideally, separating the resistance and endurance workouts by six to eight hours, or even 24 hours, allows for optimal recovery and performance in both disciplines. If they must be performed consecutively, a rest of at least 20 to 30 minutes between the two main activities can help mitigate some of the fatigue effects. Proper hydration and the timing of nutrient intake are also beneficial for maximizing recovery. A final cool-down, including static stretching, should be incorporated to aid in the transition back to a resting state.