The Latest Science on Working Out
A large-scale study published in the British Journal of Sports Medicine has provided powerful new evidence on the benefits of mixing exercise types. Researchers tracked nearly 150,000 adults over a long period and found that combining both strength training
and aerobic exercise delivered the strongest survival benefits. Individuals who performed both activities enjoyed a staggering 45% lower risk of death from all causes compared to those who did neither. The study suggests a 'sweet spot' for resistance training of about 90 to 120 minutes per week, after which the additional benefits appeared to plateau. This implies that for general health, endlessly adding more time in the weight room isn't necessary, and that time might be well-spent on cardiovascular work.
The Old Debate: What is the 'Interference Effect'?
For decades, the conventional wisdom in many gyms was that 'cardio kills your gains.' This idea stems from a real, but often misunderstood, scientific concept called the 'interference effect'. The theory originates from early research in the 1980s that suggested that the endurance adaptations from cardio could send competing signals to the body, potentially blunting the development of maximal strength and muscle size from weightlifting. At a cellular level, the fear was that the pathways activated by endurance exercise (like the AMPK pathway, which regulates energy) could inhibit the pathways responsible for muscle growth (like mTOR). This created a belief that you had to choose one priority over the other: be strong, or have stamina.
Has the Interference Effect Been Overstated?
While the interference effect is a real phenomenon, a growing body of modern research, including several large-scale analyses, suggests its impact is minimal for most people. A meta-analysis covering 43 studies found that adding cardio to a strength program had virtually zero negative effect on muscle growth or maximal strength for the average person. The main area where interference was noticeable was in explosive power (like jumping or sprinting), particularly when cardio and lifting were done in the exact same session. For elite athletes or highly trained lifters, the effect can be more pronounced, but for the majority of people seeking general health and fitness, the fear of cardio wiping out their progress in the weight room appears to be largely unfounded.
Your Goal Should Dictate Your Strategy
So, how should you apply this to your own routine? The answer depends on your primary goal. If your main objective is general health, fat loss, or cardiovascular fitness, combining cardio and strength training is unequivocally the best approach. The order in which you do them is less critical than simply getting both done. If your primary goal is to maximize muscle size and strength, you might want to be more strategic. The science suggests separating your strength and cardio sessions by at least a few hours can minimize any potential interference. Furthermore, some research indicates that lower-impact cardio like cycling may interfere less with strength gains than high-impact running. But for most people, the best workout is the one you will consistently do.
