If you've ever done p90x or Insanity you've probably heard trainers say stuff like "check your heart rate" and "make sure you are in the right zone."  If you are a runner, you have heard terms like "aerobic run," "tempo pace," and "VO2 Max" most likely.  Well, this blog post is just a quick guide to what the simplest things you need to know about your heart rate are, and how knowing them can affect the way you exercise.

Your Max Heart Rate

For ages, people have used a very inaccurate formula to calculate your max heart rate (literally, the fastest your heart can pump). Simply take the number 220, and subtract your age.  So if you are 35, your MHR is approximately 185.  Some people modify the formula so that when you are over 30, you take 190 then subtract (your age - 30)/2.  This would make your heart rate at 35, 190 - 2.5 = 187.5.  However, people that have been working out their whole life or are professional athletes may still have a higher heart rate than that at age 35, so just please keep in mind that it is just an estimate.  A slightly more accurate way you can figure out your max heart rate is to do some work on the track (this is primarily for runners).  This might sound ridiculous, but it's what we did in High School Cross-Country to calculate max heart rate.  Have a heart rate monitor on - do a warm up run for 2 miles or so.  Run a 1600 (approx. 1 mile) at full out race pace. Rest for 4 minutes, and then run another 1600 at full out pace!  At the end of the second 1600, take your heart rate immediately and you should be pretty close to max heart rate.  You can also go to a sports medicine specialist and they can calculate by monitoring oxygen levels while you run on a treadmill.

The reason you need a number in your head for your max heart rate is so you can figure out what percentage you are at, at any given point.

Aerobic vs. Anaerobic

Your aerobic training zone, where you body transports oxygen efficiently to the muscles, is generally when you are working between 70-80% of your max heart rate (even as low as 60%).  This might include a run or jog, or light cardio.  When you are between 80-90% of your max heart rate, you are in the anaerobic zone, when you body begins burning glycogen as its main source of energy instead of stored fat.  Glycogen is a renewable source of stored carbohydrates, stored in the muscles and liver.  Weight training and interval training where you have short bursts of intense activity are examples of common anaerobic exercises.  To learn a little bit more about how your body uses energy in both your anaerobic and aerobic zones, read this article.

If you are above 90% heart rate, you have most likely passed your "anaerobic threshold" where your body can no longer keep up with the build up of lactic acid it is creating while burning glycogen.  It isn't safe to be in this zone for too long, so listen to your body.  Some people call this area the "red zone" or the "red line."

What do I look for in my workout?

If you are doing Insanity or p90x Plyo, or any other interval workout, you want to try to get into the anaerobic zone for as much as the interval as possible, and then make sure you recover during the rest period.  So to reiterate, you must be within 80-90% MHR when working, and it is ideal to get back around 60-70% during your rest period to recover.  If you are above 90, you might have to tone it back a bit.  If you are below, you aren't working hard enough!  When you are doing weight training, you don't really have to check heart rate, as the focus of the exercise is not necessarily where your heart rate lies.

Using a "Heart Rate Maximizer" to Test Your Cardiovascular Strength

As part of the p90x fitness test, there is a "Heart Rate Maximizer" that tests your cardiovascular strength.  The more anaerobic exercise you do, the higher your anaerobic threshold will be, and also the faster you will recover after anaerobic activity.  In a Heart Rate Maximizer test, you do 2 full minutes of intense cardio (like jumping jacks) and go at sprint pace for the last 30 seconds.  Measure your heart rate immediately, and then measure after 1, 2, 3, and 4 minutes of standing still.  You should aim to be able to get down to about 60% MHR by maybe the 1st and definitely the 2nd minute.  This is a great way to use a heart rate monitor to test your cardiovascular strength!

Tips for Runners

As a runner, pace and heart rate monitoring (at least by "feel") is incredibly important.  One of the great ways to build up your lactic acid tolerance is to go for a "tempo" run when you go at about 80% MHR for a decent amount of time (start with 20 minutes for 5k training, and add time for longer distance training).  A lot of runners call this "comfortable hurt" or a similar term because you are working, but aren't gasping for air like you might be during a race.  When going on your LSD (long slow distance) runs it is important that you stay below your anaerobic zone. Aerobic training accesses the slow twitch muscles, and very simply put, this helps you build endurance, while anaerobic work tends to help you with speed and strength.