If you are looking to build muscle, it should be used to help keep your fat gains to a minimum while you are gaining muscular bodyweight.
And if you are trying to lose fat, you can use it to increase your calorie deficit, alongside a properly constructed fat loss diet plan.
But when should you do your cardio in order to get the best results? Should you do cardio before or after weights? Or should you do it at a completely different time? Well, let’s take a look at each of these situations.
Cardio Before Weights
Whether you want to build muscle or lose fat, your resistance training should always be your no. 1 priority. Weight training is what provides the stimulus to build (or maintain) muscle, which is crucial in both situations. Therefore, you should always start your weight training in a fresh and focused state. And doing a full cardio session beforehand will not allow you to do this. If you are fatigued from your pre-workout cardio, you will not be able to reach the level of intensity and overload that you would otherwise have reached, and your results will suffer because of this.
Pre-workout cardio will not only fatigue your muscles and lower your mental focus, it will also increase the acidity of your blood (due to an increase in the production of hydrogen ions), which will further inhibit performance.
And apart from reducing the effectiveness of your weight training workout, the increase in fatigue and loss of focus you will experience will also increase your chances of sustaining an injury while you are lifting.
You do need to warm up before training with weights, of course, but a five minute brisk walk on the treadmill, or a few minutes jumping rope, is enough. You can then do a little mobility work for your shoulders (if training upper body) or hips (if training lower body) and you’ll be all set to start your weight training.
So, in view of all that, I would suggest you avoid any sort of pre-workout cardio, and save it for another time.
Cardio After Weights
Many people perform cardio post-workout, in the belief that they will burn off more body fat at this time, due to the fact that their glycogen stores will have been depleted by their weight training. But in reality, this is not really the case, as even a very strenuous weights session will only deplete your overall glycogen stores by about 30%. So you’ll still have plenty left to fuel an intense cardio session.
However, despite the fact that you probably won’t burn any additional fat this way, post-workout cardio is still a viable strategy. Provided you still have the necessary energy and focus left to do it justice that is.
Personally, I would not want to do an intense cardio session straight after training legs. It would just be too much, and would certainly impair your recovery. You could, however, do a more moderate session if you felt up to it. But you should be able to do a longer, or more intense, cardio workout after training your upper body if you wish. And combining your cardio with your weight training in this way is a very time efficient method of getting them both done.
Cardio at a Different Time
The alternative, of course, is to do your cardio at a completely different time to your weight training. That way you will always have peak energy levels and full focus to give to each, and there will also be less of an issue with recovery from your weight training.
So you could do your cardio on completely separate days to your weight training. Or you could do your cardio in the morning, and your weight training in the afternoon or evening. Or you could do your weight training in the morning, and your cardio later in the day. Any of these options will work fine, so just do whichever fits into your schedule in the best way.
One thing I would avoid though, is doing your cardio first thing in the morning before you eat or drink anything. Fasted cardio has become popular in some circles, but not only is this NOT the most effective way to burn fat (as your intensity and performance levels will be decreased), but there is a much greater degree of muscle loss when cardio is performed on an empty stomach. So always make sure you eat something at least a few hours prior to your cardio sessions.
In summary then, cardio before weights is not recommended, because you will be starting your weight training in a fatigued state, so you won’t be able to get as good a workout as you would if you started fresh. Cardio after weights is an acceptable strategy to adopt, but tailor the type and intensity of the cardio according to how tough your weight training was. Or, if you have the time available, and it fits into your schedule well, you could do your cardio and your weights on completely different occasions, and this is, in fact, the best way to do it.