You arrive at the gym pumped to get moving, but can’t seem to figure out where to start. Should you head to the weights, the treadmill, or split them into separate sessions like your gym buddy swears by?
The short answer: It doesn’t really matter – but not for the reason you might think.
Blending strength and cardio in one program can be tricky. Both are great for your health, but they ask your body to adapt in different ways. Knowing when and how to incorporate the two can help you get more out of each workout.
“It’s easy to think that a combined training session would be the best of both worlds, but it unfortunately decreases the effects of each modality,” says Kyle Costello, a Future performance coach with a Ph.D. in exercise and sports studies. “As a general rule of thumb, it’s best practice to separate cardio and lifting into different days.”
The order you train in can impact your results due to the interference effect. This happens when the body’s competing signals for endurance and strength training overlap, limiting the progress you might see from one or both.
Cardio and weight training ask your body to adapt in very different ways. Endurance workouts, like running or cycling, boost your ability to use oxygen efficiently by enhancing cardiovascular and mitochondrial function. Strength training, on the other hand, relies on the mammalian target of rapamycin (mTOR) pathway — a cellular signal that promotes muscle growth and repair.
When you stack these workouts too closely, especially in the same session, the endurance signals can dampen the muscle-building effects of your lift.
“Your nervous system controls training adaptation, so if you are working on several different adaptations in one session, the nervous system can’t focus on just one area,” explains Costello. “Therefore, the results will be worse than if you did them separately.”
It’s important to note that the interference effect isn’t something you need to worry about every time you exercise. When your workout is around 45–60 minutes, your body can typically handle both cardio and strength work in the same session without significant overlap in those competing pathways.
Whether it’s due to time constraints or personal preference, it’s totally fine to do both cardio and strength training in a single gym session.
For shorter, low-intensity cardio sessions (10-30 minutes), the order isn’t as crucial. Before or after weights is fine, but starting with cardio can serve as a solid warm-up without affecting your strength training session.
“Many people prefer this approach. It’s an effective way to get the heart pumping and get a little sweat going,” says Costello.
For longer cardio sessions (60+ minutes) or high-intensity interval training (HIIT), it's recommended to do cardio after strength training because this helps avoid the aforementioned "interference effect.”
Additionally, cardio causes vasodilation of the blood vessels, which is one of the main acute responses that cardio achieves, while strength training triggers vasoconstriction, the temporary restricting of those vessels.
If you do your strength training after cardio, you lose all of the cardiovascular benefits that the cardio triggered. By doing cardio second, you still get all of the muscular impacts from the strength training and still have the vasodilation occur.
For most healthy adults, the best kind of cardio is the one you’ll actually enjoy and stick with, says Costello. The key is tuning into how your body feels from one workout to the next, especially if you notice lingering soreness or fatigue.
“If you have a history of knees feeling tender after squats, for example, you might want to avoid running post-workout, or the following day,” says Costello.
If joint pain is a concern, opt for a lower-impact option that still keeps your heart rate elevated. Cycling, swimming, or using the elliptical are great choices because they minimize joint stress while still supporting endurance and recovery. Brisk walking or incline treadmill work can pair nicely with lifting, especially on days you want to prioritize muscle preservation without overdoing it.
