With weight lifting, it is often questioned whether to do cardio before or after? The answer depends on what your goals are. If you want to increase the efficiency of your weight training, then do cardio before. If you want to increase the efficiency of your cardio, then it should be after weight training. As a whole complete work out, it is best to do cardio work before and after your weight training.
By doing cardio work before your weight training, you are increasing the effectiveness of your strength work. Cardio work, such as running or jumping rope, gets your blood rate flowing to all your muscles. Your goal is to work your muscles as much as possible. If they are not working at full capacity, they are not going to be able to lift their maximum weight or do as many reps, and this won't cause the tissue to tear as much.
Therefore, by doing 10-15 minutes of cardio work before weights, you can fill your muscles with blood and get them warmed up. By doing this, they will be ready to go and can lift their maximum weight and do the maximum reps. This will cause more need to for tissue repair, creating larger and stronger muscles.
By doing cardio work after your weight training, you are increasing the effectiveness of your cardio work out. This is due to your heart rate already being elevated by the time you start your cardio work. If you wish to make a new record time on your run, this is the wrong idea as you will be exhausted and not able to perform with as much energy or stamina as you would be starting from rest.
If the purpose of your cardio is strictly burning calories, this is the way to go. Think of it this way, if you run for 20 minutes straight, the first 5 minutes you are getting your heart rate up and the level of calories your are burning increases over time. But if you start with your heart rate up, you are burning more calories for the whole 20 minutes. For this reason, it is recommended that you lift weights for 15 minutes before you do cardio work. This can almost double the amount of calories you burn while doing cardio work.
Where you place your cardio in your weight lifting work out is completely based on your goals. Whatever you decide, by having both weights and cardio, you are burning more calories and toning more muscles than you would if you were only doing one. Keep it up and find a routine that works for you and your goals.