If you are looking to build muscle it should be used to help keep your fat gains to a minimum whilst you are gaining muscular bodyweight.
And if you are trying to lose fat it can be used to increase your calorie deficit, alongside a good fat loss diet plan.
But when should you do your cardio for 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 the formation of lactic acid), 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 whilst 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 skipping 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 personally 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. You could however do a more moderate session if you felt up to it. But you should be able to do whatever type of cardio you wish after any upper body workout. 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.
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 it 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 a good 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.