I don’t think most of us would question the benefit of a good exercise program.  However, we see a few of our patients’ injuries and illness likely occurring as a direct result of training error.  Even with the best of intentions, our exercise intensity often doesn’t match up with our health goals.  From an elite athlete to someone just getting started in an exercise program, it’s easy to fall into the trap of ‘the harder we work out, the better the result’.  Unfortunately, this is often not the case.

Our exercise intensity often doesn’t match up with our health goals.

As always, it’s important to realize that we are all an experiment an one and recommendations can vary significantly based on an individuals health and goals.  This article looks at exercise predominantly from an ideal health perspective.  For a competitive athlete who might be dealing with injury or burnout, this might offer some insight for getting health back (and at the same time potentially improving performance).  For someone just starting into a new exercise program, hopefully this helps to provide some suggestions on how to start the right way and not fall into the trap of starting out too hard and too often.

Low intensity, varied exercise is key

Low intensity movement (easy jogging, biking, or hiking) should not elevate our heart rate into the range that kicks in our ‘fight or flight’ mode. This is an exercise level we are designed to do for long amounts of time. The benefits are wide ranging and can include improved cardio vascular function, enhanced fat metabolism, increased brain activity, stress management and improved general health.  However with sedentary jobs and busy lives, most individuals have very limited exposure to low intensity, varied movement and often try to ‘make up for it’ with training intensely.  This has recently been termed the ‘exercising couch potato’ where the individual’s ratio of sedentary time versus movement time remains quite lopsided. This does not offer balance to protecting against the dangers associated to unnatural stress versus rest.  Unfortunately, with good intentions many individuals train intensely too often with not enough low level movement. This can cause an excess amount of stress response that ends up becoming chronic (for a deeper look at the physiological implications of high vs low intensity training, check out this scientific paper.)

With good intentions many individuals train intensely too often with not enough low level movement.


Low intensity, aerobic exercise walking

Low intensity, aerobic exercise can have numerous health benefits such as improved cardio vascular function, enhanced fat metabolism, increased brain activity, stress management and improved general health.

When our bodies go into ‘fight or flight’ mode, stress hormones like cortisol and adrenaline are produced, glucose is released into the bloodstream, blood pressure increases all to get our body ready to…well, fight or run away!   Small amounts of this type of stress is great for our body and where we make many our gains by adaptation (and to help us run away from a chasing lion).  This would be ideally be a pattern of occasional brief, intense, strength or speed training interspersed with adequate recovery time.  By doing so, our genes which have adapted to react and thrive upon this short but acute stressor, can help to build lean muscle, enhance metabolism, and potentially improve critical organ functions.  We can also see improved cellular function in our mitochondria (our cells ‘power houses’).   As such, brief bursts of intense exercise can protect us more against oxidative damage than overly frequent moderate intensity training. In small amounts, stress helps build us to be more resilient. However, in high amounts we quickly see diminishing returns.

Excessive high stress can wear us down

Excessive stress or ‘chronic stress’ can, over time, really start to wear us down in a whole number of ways which can lead to systemic inflammation, fatigue, and potential weight gain. Stress can come from training too intensely too much of the time, but often also accumulates from stress at work, bad or insufficient sleep, and poor nutrition.  Prolonged release of stress hormones can  begin to work against us and create a catabolizing (breakdown) effect.  Most exercisers don’t make this connection and as injuries accumulate, their ability to recovery is drastically diminished (this article asks the question of whether or not we’re ‘fit but unhealthy?’).  It’s really important to realize that physiologically speaking, your body doesn’t know the difference between good stress like a high intensity workout and bad stress like an upcoming work deadline or an argument with a friend.  We have enough stress to deal with in our lives that we don’t want our exercise intensity to be working against us!

Crossfit benefits

Small amounts of high intensity anaerobic training (such as sprinting, lifting etc) at any age can help to build lean muscle, enhance metabolism, and potentially improve critical organ functions.  However, it’s critical that we closely monitor the amount of this type of exercise we do as it can quickly lead to diminishing returns.

In order to understand and differentiate low intensity versus high intensity training and balancing the ‘ideal’ amount of each, it’s important to know the difference between aerobic and anaerobic training.

Aerobic vs anaerobic training

Aerobic exercise means we’re training with oxygen and are able to use fat primarily as fuel.  Oxygen is plentiful in this form of exercise and is the critical component of converting fat into fuel for the cells. This is a low exertion activity like walking, easy running/biking/swimming, gardening etc that ideally makes up about 80% of our activity time.  Aerobic training offers improved circulation as your heart and muscles’ cells become especially efficient at using energy from fat with minimal damage.  This intensity is generally regarded as heart rate ranges between 40-75% of your maximum.  A conservative yet accurate measure of maximum aerobic function (heart rate) is to subtract your age from 180 (180-age = MAF).  

A conservative yet accurate measure of maximum aerobic function (MAF) is to subtract your age from 180.

Anaerobic exercise means we’re exercising without oxygen and only able to burn stored sugar (glycogen). Anaerobic exercise causes the body’s stress response that we talked about earlier.  This can cause oxidative damage which then requires time to repair and recover from. This intensity of exercise can be very beneficial as we talked about earlier but ideally makes up only 20% of our activity time assuming we’re recovering appropriately.  Many people that believe they’re exercising aerobically are actually anaerobic if their heart rate is too high.  Anaerobic intensity is generally regarded as heart rate ranges above 75 – 80% of your maximum and lasts for approximately 3 minutes or less in duration (like a short sprint, heavy lift or carry).  The body’s collective response is to build resilience to the stress to perform better against it the next time.  However, recovery is crucial.

Black hole training

So you can imagine if someone is stressed at work, stressed at home, AND doing excessive amounts of high intensity anaerobic training, it can lead to all kinds of problems.  Entering into a pattern of too much intense work has been referred to as ‘black hole training.’ Black hole training would mean you’re not training easy enough to take advantage of the benefits of aerobic training and because of this, you’re often not recovered enough to gain the full benefits of the occasional harder, anaerobic sessions.  Check here for more.

The goal is to find your ‘sweet spot’ where the intense demands are easily met, the body is recovering well and your performances improve while you easily conduct plentiful amounts of low intensity.

Methods to track our intensity levels

So now that we have a bit of insight into why we might want to track our activity intensity, let’s look at a few ways to ensure your activity levels are matching your health goals.

Heart Rate.  It certainly doesn't need to be an expensive heart rate monitor (even your fingers on your pulse will do) but heart rate is a great indicator of workout intensity.  For aerobic workouts, try to keep a heart rate below 180 - age.  This can be very hard for some as it will feel like you're going really slow!

Heart Rate Variability.  We talked about the benefits of HRV in the past and really see this as being one of the best metrics to let you know how well your body is recovering.

Be inconsistent with your intense training. Consider doing your 20% of harder work when the body feels right. Honour your recovery by listening to when to go easy by using the first two strategies. If pain or poor energy is present, and when life is throwing many other stressful variables your way, best to stick to the aerobic exercise.

Prioritize easy movement above and beyond your actual 'workouts'. Walking the dog, a local hike, a relaxed commute to work by bike, a FitBit walking challenge may all help you to enjoy the long lasting benefits of a strong aerobic base.

Measuring exercise intensity with heart rate

Heart rate monitors like the FITBIT and Apple watch (and many others) can track your heart rate through your wrist while exercising.  However, you don’t necessarily need to buy anything to check your heart rate.  Using your fingers on your pulse and counting beats can be just as effective!

measuring HRV to track recovery

Heart rate variability (HRV) is a great way to track your recovery.  You do need a device to be able to determine your HRV score but it only requires a bluetooth HR chest strap and a mobile app (SweetBeats App used here).  There are now even rings that can be worn that will track your HRV score!


Many of us fall into the trap of training that little bit too hard when we really should be training easier.  Because your body doesn’t know the difference between good stress and bad stress, overdoing the stress from anaerobic training (even if it ‘feels’ easy) can potentially lead to the injury, illness, and burnout. Try to make an effort to spend about 80% of your time training aerobically (MAF Heart rate = 180 – age).   For those that are starting into an exercise program, try to prioritize low intensity exercise in most cases.  For those that are training for upcoming events, pay particular attention to things like heart rate variability (HRV) to track recovery and ensure you’re getting the most benefit from your more intense anaerobic workouts.


As always, we’d love to hear from you if you have any questions/comments.  To keep up with blog posts, health tips, and upcoming events be sure to sign up for our monthly newsletter!

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