The Latest Science on Mixed Training
Recent findings are challenging the old-school gym wisdom that "cardio kills your gains." A large 2022 meta-analysis covering 43 studies found that combining strength and aerobic training, a method known as concurrent training, did not meaningfully reduce
muscle growth (hypertrophy) for most people. In fact, for overall health, the combination is powerful. A major 2026 study tracking nearly 150,000 adults found that while 90-120 minutes of strength training per week lowered mortality risk, pairing it with aerobic exercise delivered the strongest survival benefits, reducing overall death risk by about 45%. The idea that you must choose one or the other is fading. The more relevant question now is not if you should combine them, but how you should combine them for your specific goals.
Understanding the 'Interference Effect'
The fear of cardio hindering muscle growth comes from a real phenomenon called the 'interference effect,' first described in a 1980 study by Robert C. Hickson. The theory suggests that the body receives competing signals from endurance and strength training. Endurance work signals the body to become more efficient, while strength work signals it to build larger, more powerful muscle fibres. This can create a biological tug-of-war. However, modern research shows this effect is more nuanced than once believed. Interference is most significant when training for explosive power (like sprinting or jumping) and less of a concern for general muscle size and maximal strength. The effect is also more pronounced in highly trained athletes than in beginners and can be influenced by the type and volume of cardio performed.
Order in the Gym: Does It Matter?
For most people, the order in which you perform your exercises should be dictated by your primary goal. If your main objective is to get stronger or build muscle, you should lift weights first. This ensures your muscles are fresh, your nervous system is sharp, and you can generate maximum force without being pre-fatigued from a cardio session. Lifting first has been shown to result in superior strength gains and allows for a higher quality resistance workout. Conversely, if your priority is improving cardiovascular endurance—for instance, if you're training for a 10K race—doing your cardio first makes the most sense. This allows you to dedicate your peak energy to your aerobic performance. For general fitness or fat loss, the order is less critical than consistency and total workout volume.
Training Based on Your Goals
How you structure your mixed workouts should align with what you want to achieve. For muscle gain, prioritize lifting heavy and consider separating your cardio and strength sessions by at least six hours, or doing them on alternate days to minimize interference. If you must do them in the same session, lift first. For fat loss, combining both is highly effective. Strength training builds muscle, which boosts your metabolism, while cardio burns calories. A 2025 study found that doing resistance training before cardio can lead to greater fat loss. For general health and longevity, the key is simply to do both. The combination of improved cardiovascular function from aerobic exercise and the metabolic and functional benefits of strength training provides a comprehensive boost to your well-being.
Beyond the Workout Order
Several other factors can influence the success of your concurrent training. The type of cardio you choose matters; research suggests that high-impact running may cause more interference with leg strength and growth compared to lower-impact options like cycling or rowing. Nutrition and recovery are also paramount. If you're adding cardio to your routine, you're increasing your overall training volume and energy expenditure, which must be supported with adequate calories and protein to facilitate muscle repair and growth. Ultimately, the body is incredibly adaptive. For the average fitness enthusiast, the risk of cardio 'killing gains' is often overstated, whereas the benefits of a well-rounded routine are significant.
