Should You Do Cardio First or Weight Lift First?

When you decide to combine cardio and weightlifting in the same session, the question often arises: which one should you do first? If you've done some research on this, you’ve probably encountered the standard advice of "do whichever order feels right for you" or "start with the one that aligns best with your goals." While there is some truth to these suggestions, a deeper dive into the science and physiology behind the process gives a clearer answer: lift first, then do cardio.

One of the most important factors in this decision is glycogen, which is the stored form of glucose, the body's primary source of quick energy. Both cardio and weightlifting rely on glycogen for fuel. However, lifting demands more of it than cardio does. Resistance training requires short bursts of intense energy, which come primarily from glycogen. If your glycogen stores are depleted, your performance in lifting will suffer significantly. On the other hand, cardio is more of a sustained activity and uses fat as its primary fuel source, which makes it better suited for a longer, slower breakdown of energy. While glycogen is still involved, the body can adapt to cardio with lower glycogen levels, and some research even suggests that performance can improve under these conditions.

Another reason why lifting first might be beneficial lies in the roles of two key enzymes: mTOR and AMPK. mTOR plays a critical role in muscle growth and is elevated after resistance training. AMPK, on the other hand, is activated during lower-intensity activities like cardio and promotes fat breakdown. However, AMPK also inhibits mTOR signaling, which could potentially hinder muscle growth if you perform cardio first. Although the effects of AMPK are still theoretical, it’s believed that this inhibition only lasts for around 15 minutes post-cardio. In contrast, mTOR activation can remain elevated for up to 48 hours after resistance training, supporting muscle growth over a longer period.

Fatigue is perhaps the most significant factor in determining whether you should lift or do cardio first. Many strength training programs aim for progressive overload, where the goal is to gradually increase resistance with each workout. To achieve this, you need to perform at your best. If you start with cardio, the fatigue you accumulate can compromise your lifting performance. Muscle fatigue, heart strain, and mental tiredness can all affect your ability to generate strength, transport energy, and stay focused. The result is less effective lifting.

That said, lifting first isn’t without its drawbacks, especially when it comes to cardio. Lifting can still impact your ability to perform cardio afterward, although this effect is less significant. Steady-state cardio tends to demand less energy than intense lifting, and by the time you transition from weight lifting to cardio, the muscle fibers used for cardio are likely to be sufficiently recovered to perform well.

So, should you always lift first? Not necessarily. If you have the option to separate your workouts into different days or even different times of the day, you'll get better recovery and performance for both activities. It’s all about giving your body enough time to recover between sessions. But if doing cardio first works better for you personally, whether it makes you feel good or helps you with your lifting, there's no need to change what feels right for you.

In conclusion, while the science behind lifting first suggests better overall performance, it ultimately depends on your individual goals and preferences. If you can, splitting your workouts or spacing them out can provide the best of both worlds. Whatever approach you take, remember that the key to success is consistency and making the right choice for your body.

So before you jump into any new routine, it is smart to speak with a health expert who can guide you based on your personal needs. And if you are looking for a custom plan to support your goals in fitness or nutrition, I would be happy to work with you and put together something that fits your lifestyle and helps you stay on track.

Emmanuel Ofori

Your friendly neighbourhood fitness professional