Myth: Do your cardio before your strength training
Fact: There is no “correct” order for cardio and strength training exercises, it depends on your personal goals!
If you are a runner, or any endurance athlete, cardio should be the focus of your work out. That does not mean NOT to strength train, it just means that your focus should be improving your frequency, intensity or duration. You can save your strength training for after your cardio.
If you are trying to gain muscle, an extensive cardio session before resistance training will be detrimental to your gains. Your muscles will already be fatigued and you won’t be able to work them as hard. Instead, give your training everything you have got and save the cardio for after.
For maximum results, you should separate your cardio and resistance sessions by at least 24 hours. Studies show that your glycogen stores are still depleted up to 12 hours after a workout. By waiting a full 24 hours, you will have replenished your fuel sources and have a more effective workout.
Moral of the story: If your primary goal is endurance, do cardio first. If your primary goal is building muscle or gaining strength, do resistance training first. The most important thing is to get enough of both types of exercise every week.