The Latest Word on Working Out
A major study published in the British Journal of Sports Medicine in June 2026 provided a powerful new data point. After tracking over 147,000 adults for up to three decades, researchers found that while both strength training and aerobic exercise individually
reduced mortality risk, combining them delivered the strongest survival benefits. Specifically, the longevity sweet spot seemed to be around 90-120 minutes of strength training per week, paired with robust aerobic activity. This large-scale observational study reinforces what many in the fitness world have come to accept: a combination of both modalities is likely best for overall health and a longer life. But this study focused on longevity, not the nitty-gritty performance questions that gym-goers often ask, like whether cardio will sabotage their muscle-building efforts.
The Old Debate: The 'Interference Effect'
For decades, the conversation around mixed exercise has been dominated by a concept called the "interference effect." First documented in the 1980s, this theory posits that the adaptations triggered by endurance exercise can actively interfere with the body's ability to build maximum strength and muscle size. At a molecular level, the two activities send competing signals. Strength training activates pathways like mTOR to build muscle, while endurance training activates pathways like AMPK for better energy efficiency. The fear was that by doing both, you were telling your body to go in two different directions at once, leading to compromised results in both. This created a generation of advice that often urged people to pick a lane: either focus on getting strong or focus on building endurance, but don't try to be elite at both.
Context is Everything: It's Not 'If,' but 'How'
More recent research has profoundly reshaped our understanding of the interference effect. A wave of modern analyses has shown that for most people, the interference is minimal, if it exists at all. One 2022 meta-analysis found essentially zero difference in muscle growth between groups that did only strength training and those that combined it with cardio. The interference effect isn't a myth, but it's highly dependent on context. It primarily becomes a significant factor for elite athletes or when programming is sloppy. Variables like the type of cardio (running, which has a high eccentric load, causes more interference than cycling), the timing (performing them back-to-back is worse than separating them by a few hours), and the volume are what truly matter. For the average person aiming for general health and fitness, the effect is largely negligible.
So, What Should You Do?
The practical takeaway from the latest science is one of strategic flexibility. If your primary goal is maximizing strength and muscle growth, the evidence suggests performing your strength training first in a workout session. A 2025 study found that participants who lifted before doing cardio gained significantly more strength and lean mass than those who did cardio first. The reason is that cardio can create central fatigue, which can then reduce your performance in the weight room. However, if your main goal is improving cardiovascular health, the order matters less. The most crucial factor, as reinforced by the 2026 longevity study, is consistency. The best program is one you can stick with. For most people, that means combining strength and cardio in a way that fits your schedule and goals, whether in the same session with lifting first, or on separate days entirely.
