Cardio or weights first? It depends!

A very common question that comes up, whether it’s from clients or from family and friends, is “What should I be doing first, cardio or weights?” The response is always the same: “it depends.” This normally annoys people, as I then need to explain what it depends on and why (and in the case of family and friends boring them in the process), and it usually doesn’t end with the answer they were actually fishing for! So let’s have a look at what it depends on.

Whenever you perform any kind of training at all, you are providing a set of stimuli for the body, for example: a reduction of muscle and liver glycogen (fuel which has been used up during the exercise); a change in the pH levels of the muscles and the blood (your body using fuel makes the muscles and blood slightly more acidic); structural ‘damage’ to the muscle cells and protein degradation (by force being applied to them by increasingly forceful contractions), as well as many others. Each of these stimuli cause inflammation in the affected tissues, which despite what the anti-oxidant marketeers and holistic health quacks keep spouting, is not a bad thing. Indeed, this inflammation is a key element of the adaptive process and is what causes our bodily systems to get better and adapt after exercise.

Now in order for the body to respond to these stimuli and adapt, it can follow two pathways, both of which lead to very different results, and it cannot do both at the same time. Let’s say you’ve gone to the gym and completed a typical weights session, where you’ve completed two compound exercises (mulitjoint movements i.e., squat, deadlift) with 4 sets of 4-6 reps each with 3-5 minutes rest, followed by two assistance exercises (single joint exercises i.e., straight leg deadlifts, banded side steps) of 3 sets of 8-12 reps each with 45-90 s rest. This session will have caused a relatively small reduction in glycogen, a small change in the blood and muscle pH, but will have caused a significant amount of structural muscle ‘damage’ and protein degradation. Each of these elements will activate what is known as the mTOR signalling pathwayIn the simplest of terms, this pathway is the process by which protein is synthesised by the body to repair and build muscle tissue. Without this pathway being activated, your muscles would not be able to adapt to the work you’ve just completed – you would not get the massive gainz you were aiming for!

On the other hand, if you have just completed a cardio session, such as a 5K run, or a HIIT session, then your body will have experienced a large change in the pH of the blood, a large reduction in glycogen content of the muscle and the liver, but a relatively low amount of structural ‘damage’ to the muscles (unless this is the first cardio session you’ve ever done, which is a different story entirely!). In this instance, the stimuli placed on your physiology causes the activation of the AMPK signalling pathway. Again, without getting into details, the AMPK pathway is responsible for the adaptations required for better cardio performance – more red blood cells, greater fat usage as energy, increased stroke volume, etc. All of these are good and are needed by the athlete and recreational trainer alike……


…..and this is the kicker. If the AMPK pathway is activated, it blocks the mTOR pathway, preventing protein synthesis, which in turn prevents optimal benefits to the muscular system being achieved. Your body is physiologically unable to improve the cardiovascular and muscular systems at the same time. It cannot do it. Imagine being in a nice restaurant with your significant other, trying to have a conversation, but Slipknot are playing full volume on the table next to you. In this instance, your conversation is mTOR, Slipknot is AMPK.

Ever wondered why marathons runners and Tour cyclists are very skinny in comparison to strength based athletes? This is a key reason why – their training does not allow the muscular system to physiologically grow. Another key aspect is that the mTOR pathway can only operate optimally in the presence of glycogen, which has been used up by the cardio sessions being completed, further inhibiting muscle adaptation.

Related image

No-one is mistaking Mo Farah for an NFL player any time soon.

Now, when training a competitive athlete, the solution is simple: make sure you’re training strength on a different day to when you train cardio, ideally separated by about 36 hours. But what if you’re a normal person just looking to stay in shape? Well let’s a have look at a couple of different scenarios.

1 – “I can train a few times a week”

This is fairly straight forward. Start your week with cardio on the Monday morning, and make sure you refill your glycogen stores over the next 36 hours by eating normally (as long as your normal is a good healthy diet!).  Tuesday evening, hit the weights. Complete heavy compound exercises with nice long rests. Get it done in a hour or so, go home, get the protein in. Repeat the same pattern Thursday and Friday. Boom – strength and size improvements to go with your healthy cardiovascular system!

2 – “I can only do once/twice a week”

This is standard, due to time and cost restrictions. It’s not ideal, but it can still be worked with, and this is where “it depends” really comes into it. If your main aim is to lose fat and get a bit healthier without making your muscles bigger, then it could be beneficial to lift weights first, but still going heavy with long rests. Follow this with some cardio work (a HIIT session or 20-30 minutes at a fast pace – don’t be that person walking on a treadmill, there are parks for that!). With this set up,  you will be blocking the mTOR pathway, so you will not get a significant amount of muscle growth, but you will still get some strength improvements for at least 6-8 weeks through adaptations to your nervous system (this is why going heavy is key! Anything more than 4-6 heavy reps per set is a waste of time and energy here), and you will get the fat loss and health benefits brought about by the AMPK pathway. After 6-8 weeks, your strength improvements will stop, so this is very much a short term option.

If your aim is to build muscle and get bigger, but still keep your heart healthy then you will have to perform a small amount of cardio first (20 minutes or so of moderate intensity), followed immediately by refueling. An energy bar or gel would be useful here, because remember the mTOR pathway can only work in the presence of glycogen. Then, you complete your weights session (still going heavy with compound movements). Again, this is not optimal, but it gets you a bit of both, with the mTOR pathway not being completely shutdown by the AMPK pathway.

In an ideal world, we would all be option number 1, but this is the real world, and you have to decide what’s more important to you – muscular improvements or cardiovascular improvements. My advice here (if you’re recreationally training for health) would be to aim for a bit of both by changing your training program every 4 weeks to target each pathway separately. If you’re a competitive athlete then you should be prioritising your training and getting in there with a qualified S&C coach at least 4 times a week anyway!

Either way, next time your trainer is discussing the structure of your session, ask them if they considered the AMPK-mTOR system. If they haven’t, or they can’t answer it, then it may be worthwhile considering the advice of one of my previous posts and walking away from them to get a trainer who knows what they’re doing.

So there you have it, the reason why “it depends”, and another reason why you need to make sure your trainer has the required knowledge to help you achieve your goals, whatever they are.

If you want more information, or you’re in the Lancashire area and in need of strength and conditioning or sport science support, then contact me via the website, or leave a comment at the bottom of this post.

Until next time, have fun everyone!



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