Heart rate and exercise: everything you need to know.
Hello and welcome back. I hope after reading my last blog I have motivated you to start exercising or improving your current exercise regiment. So now that you have started let's take it one step further and get into some detail on how to become a more educated athlete. One of the most basic tools you can use to enhance your exercising experience is heart rate. Your heart rate tells you a lot about what kind of exercise you are doing: aerobic, threshold or anaerobic. Each with its own benefits and limitations. And most of you probably already have a smart watch that measures your heart rate, so let's learn how to put it in use. But first I am going to teach you a little physiology, I think once you learn the science it all becomes much more exciting and easier to understand. Easy stuff, I promise.
Here it goes:
When you exercise you essentially move a certain body part by bending and extending a joint. The joint is moved by the bones that make the joint. The bones in turn are moved by the muscles that are anchored to them: Muscles move the bones, the bones move the joint.
I wish I was good enough to make a video for this, but I am not. So, instead let's use a more graphic example:
Imagine a boat, a paddle and you holding the paddle.
The boat is the joint
the paddle is the bone
and you are the muscle attached to the paddle.
In order for the boat to move the muscle (you) pulls and pushes the bone (paddle) which in turn moves the joint (boat). It all starts from you, the muscle. The faster the boat has to go, or the more upstream it has to go, the harder you have to push and pull the paddle. In other words, the faster you exercise, or the more resistance you have to overcome, the harder your muscles have to push and pull.
The muscles use oxygen and glucose (simplest form of carbohydrate) to generate the energy that contracts and relaxes the muscle. In turn they generate carbon dioxide as a byproduct that has to be removed and expelled from the body.
Glucose + Oxygen ---> energy + waste (carbon Dioxide).
Who delivers oxygen and nutrition to the muscles and removes the waste?
The heart pumps blood to the lungs where they get oxygen, the heart then pumps the oxygenated blood to the muscles, in return the heart pumps the blood with waste products from the muscles to the lungs, where carbon dioxide is exhaled and oxygen is picked up. The cycle keeps going.
So, to make sense of it all: The muscles generate the power to move you during exercise. The heart, lung and blood vessels deliver the necessary ingredients to the muscles and remove the waste. The harder or faster you exercise the more energy the muscles need, you have to breath faster and deeper, and your heart has to pump faster and harder to meet the demand of the working muscles. You can maintain this level of activity for a long time (think marathon) as long as you have enough nutrition stored. This is referred to as aerobic exercise, meaning oxygen dependent: the muscle cells use oxygen to generate energy.
Ok, you got all of that right? Excellent. Now let's throw in one more twist.
There is a limit as to how fast the heart and lungs can deliver oxygen and remove waste products. If you are exercising so hard that you exceed this capacity then your muscles run out of oxygen. At this point the muscles start using an alternative fueling system, but this is an inefficient process and it generate lactic acid as its byproduct. As lactic acid builds in your muscle (because your heart can not pump fast enough to remove it) it starts burning your muscle. You have all experienced that burn before; whether it being from a sprint run or weight lifting. This is only a last resort and the muscles can only do this for a very short time.
This is called anaerobic exercise (aerobic refers to oxygen dependent, anaerobic means oxygen independent). Exercises at anaerobic intensity can only be maintained for seconds to minutes depending on how well trained you are. They burn a lot of calories and improve your cardiovascular capacity, but they are very demanding on your joints, bones, muscles and heart. Think of 100 meter sprinters.
So, you have learned about aerobic and anaerobic state. But in reality there is no one particular point at which you switch from one system to another. As you exercise harder you enter into a gray area, where there is enough oxygen to meet most of the demand but not all. This is called the Lactic threshold capacity, or the maximum effort you can sustain before becoming completely anaerobic. At this stage you do generate a small amount of lactic acid, but it's small enough that it can gradually be removed, so you won't feel an immediate burn. You can maintain a threshold pace from few minutes to an hour depending on how fit you are. Think of professional 10k races, they are not sprinting, but they are also not comfortable like a marathoner.
Wooh, that was a lot of physiology. But now you understand what aerobic, anaerobic and threshold mean. And I know now you are pondering how do you find out what is your heart rate for each stage. And that is a loaded question that depends on your age, sex and fitness level.
There are many tests you can do to find out your heart rate zones. It can be as simple as a field test to as sophisticated as in lab testing. If you have the money, access and desire to get the most accurate measurements, then by all means, schedule yourself with an exercise lab. But for the rest of us, here are two simpler measures to find out your numbers:
The first one is by feel:
Zone 1: aerobic. very very easy. think of a walk slightly faster than your casual walk, you are not sweating.
Zone 2: aerobic: easy, but you feel like you are exercising. You can keep this pace for a long time, it's comfortable but you are sweating. You can talk in small sentences but get a little winded as you talk. This is the zone for long duration exercises.
Zone 3: Lactic threshold: this is when you are pushing your aerobic capacity to the limits. You feel like you are working out hard, but its sustainable for at least 5 minutes if you are a beginner athlete or up to an hour if you are an experienced athlete. You are sweating, you can talk but in 1-3 word sentences. You are feeling the pain but it's moderate and you can keep at it for sometime.
Zone 4: you are mostly anaerobic: you are pushing, you are sweating. You are working. You are not talking, but you are also not pushing to your maximum limit. You can maintain this for 1-5 minutes.
Zone 5: anaerobic: you are all out. You can maintain anywhere from few seconds to a minute max. If you are pushing past 1 minute you are in zone 4.
The second method is by field test using a smart watch:
This is specific for every exercise. Your test for running, biking, swimming, rowing or whatever else will have different results.
Pick a day that you are rested, slept well, hydrated and well fueled. Go to a place where you dont have to stop (for example a track for running or a indoor bike for cycling). Do a good warm up, at least 20 minutes.
A little stretching. Psych yourself up. Get ready and: do your exercise for 20 minutes, going as fast as you can. Record your heart rate. Its important that you pace yourself. Start a little slower and pick up the pae every 3-4 minutes if you can. Going to fast and then having to stop or slow down will make the test inaccurate. This is a very challenging test. I failed to finish it the first couple of times. But with experience you will get better. Once you are done look at your average heart rate for the 20 minutes. That is your threshold heart rate: a stage where you are transitioning from aerobic to anaerobic. Use the formals below to calculate your exact heart rate zones:
(THR: threshold heart rate, its the average heart rate of your 20 minute test)
Zone 1 Less than 85% of THR Zone 2 85% to 89% of THR Zone 3 90% to 94% of THR Zone 4 95% to 99% of THR Zone 5 100% to 106% of THR
One last word about using these numbers. Heart rate works great for aerobic and threshold exercises. You can use them to make sure you are going easy enough for your aerobic workout or hard enough for your threshold workouts. In fact you will be shocked to see that a lot of times you need to slow down if you are trying to remain in Z1,2 for an aerobic workout. I found out I was working out too hard when I really thought I am going easy. But for sprints (zone 4, 5) workouts just go by feel. Push as hard as you can, don't look at your heart rate. It takes your heart rate few seconds to a minute to adjust and respond, so if you are sprinting for less than a minute your heart rate may not reflect your level of effort. This is called a heart rate lag. For the same reason, after you slow down for recovery, your heart rate may take a few seconds or minutes to slow down as it tries to remove all the waste from your sprint all out exercise. So, utilize your heart rate to improve your easy and moderate exercises, but not your all out sprints.
Ok, this was the nerdiest post. But now you are an exercise heart rate guru. In the next post I will show you how to use the heart rate zones to improve your exercise experience. Until then try to pay more attention to your feel or heart rate next time you go out for an exercise and if you feel like it, do a field test. Stay tuned.