The Old Cardio vs. Weights Debate
For decades, the conventional wisdom in many gyms was to keep your cardio and strength training separate. The fear was something called the “interference effect,” a phenomenon first described in a 1980 study where athletes training for both strength and endurance
at high volumes saw their strength gains plateau. The theory suggested that the physiological signals sent by endurance exercise (which are catabolic, or breaking down fuel for energy) could cancel out the anabolic (muscle-building) signals from lifting weights. This led many to believe that you had to choose: do you want to be strong, or do you want to have great stamina? Trying to achieve both at the same time was seen as a compromise that would leave you short on both ends.
What Recent Science Actually Reveals
The good news is that modern research has shown this interference effect is often overstated and highly dependent on how you train. A large 2022 meta-analysis of 43 studies found that for most people, combining cardio and strength training did not significantly reduce gains in either muscle size or maximal strength. The main area where a conflict appears is in explosive power—the ability to generate force quickly. The most recent studies clarify that you absolutely can and should do both; the key is to be smart about the structure and order of your workouts, tailoring them to your primary fitness goal. A 2025 study, for instance, found that while any combination is beneficial, lifters who did resistance training before cardio saw greater improvements in strength and fat loss.
Prioritising Strength and Muscle Growth
If your main goal is to get stronger, build muscle, or improve your physique, the science is becoming quite clear: lift weights first. When you begin your workout with resistance training, your muscles are fresh and your energy stores are full. This allows you to lift heavier with better form, which is the primary stimulus for muscle growth and strength adaptation. A recent study specifically found that participants who followed a resistance-training-first protocol had better results in maximum strength and reductions in body fat compared to those who did cardio first. Performing your cardio session after lifting is still beneficial for heart health, but it's best to keep it to a moderate intensity to avoid sending conflicting signals to your muscles while they are in a prime state for recovery and growth.
When Endurance Is Your Top Goal
On the other hand, if you are training for a 10K, a half-marathon, or simply want to improve your cardiovascular fitness, it makes more sense to do your aerobic activity first. Your legs will be fresh, allowing for a higher quality run, cycle, or swim. Following up with strength training can still provide immense benefits. It strengthens the muscles and connective tissues around your joints, which can improve your running economy and reduce your risk of injury. For endurance-focused athletes, strength training can be seen as a crucial support system for their primary activity. In this case, you might focus on compound movements and core work after your run to build a more resilient body without compromising your main endurance goals.
The General Health and Fitness Approach
For the majority of people whose goal is simply to be fit and healthy, the order is far less critical. The most important thing is that you are consistently doing both. Combining the two types of exercise yields incredible benefits, including better heart health, improved body composition, increased metabolism, and greater overall fitness. If your schedule allows, separating your sessions entirely—such as doing cardio in the morning and lifting in the evening—is an excellent way to get the best of both worlds. Research shows that allowing at least a six-hour recovery window between sessions can nearly eliminate any potential interference. If you must do them in one session, simply choose the order based on what feels best or which goal you want to give a slight edge to that day.
