This is a question that many of us ask ourselves. In general, we tend to think that you have to start with cardio to warm up and then work your muscles when warm. Be careful, however, not to confuse cardio and warm-up. A cardio exercise itself requires a warm-up!
When it comes to fitness we each have our own preferences, some prefer their training to start with cardio and others with strength training. There are also those who only practice one or the other. Obviously, the combination of the two will give you results more quickly since the efforts will be multiplied.
Doing these two in a workout will achieve the same goal of building muscle and losing calories. However, if you particularly want to build muscle, tone, and burn more fat, you'll need to go for weight training first. Here are some good reasons to do so:
You will be more focused in the first part of your workout. If you are already fatigued from your cardio workout, you will be performing much less well on your muscle building routine. However, you seek to be to the maximum of your capacities and to make the most of your efforts.
It makes more sense to lift weight (for example) when energy is at its peak, so at the start of training. A cardio session requires a lot of energy, which means that when you do weight training after cardio, you tend to destroy muscle fiber rather than build up.
Starting with cardio tends to strain the muscles you need for weight training. This means that you will not be able to get the maximum benefit from your muscle building exercises. In addition, you are more likely to injure yourself.
Your weight training session will draw on your carbohydrate reserves and release fat into the blood. Cardio will burn these famous released fats. A loss of fat would therefore be visible if you organize your sessions in this way over the long term.
Remember, above all, you need to target your goal. Do you want to lose weight, build endurance, strengthen your muscles or have more energy instead? Once you have set this goal, you can best define the organization of your sessions. All this while listening to your body!