Fast, Slow or Combo?

Last time we were talking about activity (exercise) and making sure to change it on a regular basis.   This brings up an interesting question that again has multiple 'Opinions' and actual real science.  Speaking of just cardiovascular exercise (also know as aerobic or endurance exercise) is it better to do prolonged exercise at a lower heart rate or aggressive exercise that really gets your heart rate up there?  The first question is 'What is your goal?'  and the second is 'what is your current fitness level?'  Due to the statistics we have already talked about we can guess that most adults want to lose weight (actually lose body fat) so then the question of fitness level comes into play.  Remember, gradual progressive increases are the way to go, so where is the best place for you to start.  Simple, you start where you are (I know Genius Right?!?!) Actually you start with what you have been doing for the last couple of months.  If you haven't been doing anything, then start walking.  Remember we want early success and no pain. So start with a 10 minute walk.  One of the best ways to evoke change is not to plan to go out for a 30 or 60 minute walk, just go out for a 5 minute walk then once you are out there it will be much easier to keep going.  If we 'decide' to do a 60 minute walk, that little voice inside our head starts telling us all the reasons why this is not a good day or time (I'm to busy, we have a lot of things we need to get done today, what if I get to tired, what if its to hot or cold).  Trick the little voice by going out for a short walk and once your moving keep moving (Newton's law works the other way as well-A body in motion tends to stay in motion!)  I can hear it already, but my 'friend/trainer/video/biggest loser program' said you burn more calories running. To that I say, you are correct but is your body ready for that level of exercise?  Here is where the science comes in...ready...ok, when we start any exercise we start in anaerobic state (meaning we are burning carbohydrates and not utilizing oxygen) this is the way our energy systems work.  Have you ever notices that the first 2-3 minutes of cardio seem hard and it doesn't feel very good, but then around 3-4 minutes you start feeling better?  That is because of science, we burn carbohydrates to get started and then (based on how hard we are going and how high our heart rate goes) we switch to aerobic exercise where we are utilizing a different energy system and utilizing oxygen.  Now that we are in this state we can keep going until we hit the anaerobic threshold on the other side.  Remember the anaerobic system utilizes carbohydrates, actually technically it utilizes glucose (simple sugar).  We have some glucose in our blood, and we store some in our muscles and organs as Glycogen and that's it.  Once we burn up our glucose and glycogen stores we are done.  This is known as "hitting the wall" that feeling when you are doing something when your body says.."That's it I'm done!!"  and you have to sit down.  So, if you push your cardio too hard you will blow through the aerobic phase back into anaerobic and then you are done. Because of this for years it was reported that if you want to burn fat, which occurs in the aerobic phase that you should do exercise around 50% of your max heart rate, no higher than 70% or basically the level where you can still talk but couldn't sing.  (called the Talk/Sing test).  The problem is that while this is true, you will burn calories from fat stores during the length of exercise once you stop exercising you go back to your normal metabolic rate and burn calories at that level.  So if you burned 300 calories then that was your net amount burned in addition to your resting metabolic rate.  But, if you do intervals of exercise where you get your heart rate up and then recover (allow it to come down) and do this several times you will actually increase your Metabolic Rate for several hours after you finish exercising burning more calories for HOURS!  But let's cover that and how to figure your your heart rate in the next blog.