Cardio or Weights First?

I was recently asked about whether or not it is beneficial to do strength training before doing a cardiovascular exercise session.  The person who approached me about this was under the impression that if you do strength training before cardiovascular exercise you could increase the amount of fat used during the cardiovascular exercise because the strength training session would have depleted the muscle glycogen.

While this is possible, the average person has enough glycogen in their muscle to last for about 2 hours of sustained, moderate intensity exercise.  Most strength training workout sessions aren’t long enough or intense enough to deplete this store.  Remember, there is usually a decent amount of rest taking place between sets of a strength training session. Even if the strength training session was long enough and intense enough, depleting our glycogen does have some negative consequences:  low blood insulin, more amino acid  metabolism, etc.  In addition, there is not a body of research evidence that shows that strength training right before a cardiovascular workout increases the amount of fat used during that cardiovascular workout.

We have to remember that exercise intensity determines which substrates are used.  It’s also important to consider that if we have a really intense strength training session, how will that affect the intensity of our cardiovascular portion of our workout?  It really comes down to our goals and what we want to achieve.  If weight loss or improved fitness are the goal, then cardiovascular exercise should come first.  If we want to build muscular strength and/or muscular endurance, strength training should be performed first.