Before delving into the details (because I love talking about this stuff and I tend to talk too much), I would like to sum up this post in  one sentence:

If you want to raise your results, raise your intensity.

When we exercise, there are many things that we can control.  We call these things variables, because we can vary the amount of each.  Here are four big variables that, for the most part, are within our control.

  1. The type of exercise we are doing
  2. How often we exercise (often referred to as frequency)
  3. The duration of exercise (often referred to as volume)
  4. The intensity of exercise

According to our recent MUS Wellness survey, lack of time was a big concern for our employees.  71% of respondents said that “lack of time” was an obstacle to their optimal health.  If you feel pressed for time, this may affect the frequency and duration of your exercise.  Given that American Heart Association recommends a minimum of 150 minutes of exercise a week, step #1 is making/finding/creating time to exercise.  (See the AHA exercise recommendations here.)

For this post however, I wanted to focus on the intensity variable, because even if we are pressed for time, we can still control the intensity with which we exercise, in order to maximize our time.  Intensity can be measured by heart rate, breathing, and perceived exertion.  Perceived exertion is how hard you feel like you’re working.  One of the original perceived exertion scales, which is still often used in exercise science labs, is called the Borg Scale.  The Borg scale has values from 6-20, which, not coincidentally, match-up nicely with the average 20-year-old’s heart rate range—something like 60 to 200 beats per minute.  This scale, while clinically valuable, is a little hard to remember, especially if you are in the middle of a workout.  Also, unfortunately, not all of us are still 20-years-old.

Therefore, I wanted to share some practical ways to measure intensity.

1.  Heart Rate.  This is the best measure.  Your heart doesn’t lie.  When it’s working hard, you’re working hard.  When it’s taking it easy, you’re taking it easy.  To measure HR you can buy a heart rate monitor, or utilize the HR monitors built into most modern indoor cardio equipment (although this isn’t as reliable as a monitor you wear).  Don’t have access to a HR monitor?  No problem, just do it the old-fashioned way and find your pulse at your wrist or neck.  Count your heartbeat for 15 seconds and multiply the number by 4.  We’ll talk more in-depth about how to utilize HR in the next post.  Step #1 is to become aware of your heart rate values both at rest and during exercise.

2.  A Simple Perceived Exertion Scale.  I usually use a scale of 1-10 with my clients.  1 equals sitting on the sofa—no work.  10 equals MUST STOP NOW OR I WILL COLLAPSE!  A 10 would be maximal effort, like a 100 meter dash.  Under these terms, we’ll spend most of our time exercising somewhere between a 4 and 9.  Values of 4 to 5 can be sustained for a long time (low intensity).  Values of 6 to 7 can be sustained for a moderate amount of time depending on your fitness level (moderate intensity).  Values of 8 and 9 can only be sustained briefly (very intense or hard).

3.  The talk test.  If you are doing cardio exercise with a partner, can you freely hold a conversation?  If so, you are exercising at a light intensity.  If you can communicate, but with shorter sentences and a lot of breathing in between, you are exercising at a moderate to moderately high intensity.  If you cannot hold a conversation because it’s all you can do to breathe, you are exercising at a pretty high intensity.

So what does this matter?  Why all this talk of intensity levels?  Well, there are several reasons, some of which I’ll list in the third and final list of this post:

  1. Raising your intensity level is a great way to get an effective workout if you are pressed for time.  You don’t have to have an hour to workout.  A moderate to high intensity session of 15-30 minutes still yields positive benefits, and is certainly better than not exercising at all because you thought you didn’t have time.
  2. Raising your intensity will yield faster results if your current exercise routine consists of mostly low-intensity work.  For example, if you get on the treadmill and run for 30 minutes at the same speed every time, after a while you will not see many results.  Try changing the intensity by going faster, increasing the incline, or doing an interval style workout with short bouts of higher intensity work followed by an active rest of low intensity work.
  3. Raising the intensity of exercise burns more calories per minute, and after an intense workout, your body continues to burn calories at a higher rate for hours!  This phenomenon is called afterburn.  This is why interval workouts, lifting weights, and higher intensity exercise are phenomenal tools for weight-loss.
  4. From a physiological standpoint, exercising at a higher intensity has different effects on your muscular, skeletal, nervous, and endocrine systems than low intensity exercise.  Adaptations to these systems can lead to more energy, vitality, focus, and better overall health and fitness.

Keep in mind, that intensity is relative!  What is intense to one person will not be intense to someone else.

This is why we can use heart rate, perceived exertion, and the talk test to get feedback about our intensity level.  If you are a walker, you can raise intensity by walking faster, walking uphill or up steps, or doing periodic bouts of light jogging.

There is still a place and purpose to low intensity exercise.

Even Olympians have easy days.  The crux of this post is to let you know that if you only do light exercise, and you are not limited by your health to only light exercise, you can do wonders for your body and mind by adding bouts of higher intensity.  You know your body better than anyone, so raise intensity gradually and don’t overdo it!  If in doubt, talk to your doctor or a fitness professional about strategies for building intensity into your routines.

Here is sample chart referencing intensity levels for a 40-year old with a resting heart rate of 70 bpm.  Again, it is important to remember that heart rate and intensity vary from individual to individual, but this may help give you an idea of what type of heart rate corresponds to certain intensity levels.

  • 40-year-old with resting heart rate of 70 bpm
Heart Rate Percentage of Max Perceived Exertion 1-10 Intensity Description
125 50% 4 to 5 Light/Sustainable for very long durations/indefinitely
136 60% 5 to 6 Moderately Light to Moderate/Sustainable for longer durations
147 70% 6 to 7 Moderate to Moderately Hard/Sustainable for moderate durations
158 80% 7 to 8 Hard/Heavy/Intense/Sustainable for short bouts
169 90% 8 to 9 Very Intense/Very Hard/Sustainable for very short bouts
180 100% 9 to 10 Exhaustive/Not sustainable


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