It’s not enough to take a walk or a jog–now, you have to track it, too! With all the wearable technology options, strapping on a smartwatch is almost as crucial as lacing up your sneakers if you want to measure your activity level. The heart rate sensors on your watch likely keep track of your pulse and heart rate zones, but what do the numbers mean, and why should you care?
During aerobic activity, your heart pumps blood to give you the energy you need to run, bike, or swim. The harder your heart works, the higher your heart rate. Heart rate zones help determine your heart’s level of effort and are calculated using your age, maximum, and resting heart rates. According to the Centers for Disease Control, you can estimate your maximum heart rate using the following formula:
220 – [your age in years] = maximum heart rate
You can figure out your resting heart rate by timing your pulse for 30 seconds and multiplying it by two. To find your pulse, put one of your hands out, palm facing up. Place the index and middle fingers of your other hand on the inside of your wrist at the base of your thumb. Press lightly, and you will feel your pulse. Set a timer or watch a clock and count the beats for 30 seconds. You can figure out your zones once you know your maximum heart rate.
Here’s an example using me:
Maximum is 220-48=172
Resting is 38*2=76
My zones will fall somewhere from 76 to 172 beats per minute.
Heart Rate Zones
The 5 zones are created based on your maximum heart rate (MHR). Below is a description of each and when you might want to ensure you’re in that zone.
Zone 1
The lowest zone is about 50 to 60 percent of your MHR. Typically, you start in this zone as you warm up and return to it when you recover. My heart rate would be 84 to 103 in this zone.
Zone 2
The second zone is 60 to 70 percent of your MHR. It’s the zone you are in when you take a brisk walk or leisurely bike ride. It’s not too hard, but you know you are working. My heart rate would be 103 to 120 in this zone.
Zone 3
This is the zone most people want to aim for when doing aerobic activity. Known as the “fat-burning zone,” it is the sweet spot where your body burns fat to fuel your activity level. Usually, you will be a little breathless but should be able to hold a conversation. This zone is 70 to 80 percent of your MHR or 120 to 138 for me.
Zone 4
By the time we hit the fourth zone, it’s a pretty intense workout. At 80 to 90 percent of your MHR, you likely are breathless and would find it hard to talk to a friend. Think interval training, where you go all out for a period of time. You can do it, but not forever! My Zone 4 MHR is 138 to 155. This is where your body starts to use carbohydrates and protein to fuel the exercise.
Zone 5
You can’t stay in this zone for long. It’s reserved for intense bursts of activity that you can push your body as hard as possible. It’s 90 to 100 percent of your maximum heart rate, so it’s not sustainable for long. Think high-intensity interval training or HIIT.
Your target zone depends on your goals. If you are looking for a decent workout where you aren’t out of breath but feel like you’re working your heart, zones 1 to 3 are your best bet. You can build endurance here. Some people refer to zones 1 and 2 as “steady state” since you can sustain it for a while. Once you get into zones 4 and 5, you are pushing your body. Intervals and HIIT training fall into this category. Exercise, where you are trying hard for a short time, helps work your heart.
If you want to add muscle, limit your training to the lower zones to preserve muscle and avoid too much stress and inflammation. The upper zones are fine if you are training for a specific goal or want to push your limits. For most people, 85 percent of your workout should be in zones 1 to 3, 10 percent in zone 4, and 5 percent in zone 5.
If you are precise and want to know your exact target heart rate for your age and ability, check out the ACE’s handy calculator.
There are lots of ways to incorporate cardio into your training regimen. To prioritize muscle gain, program your cardio on days you don’t do resistance training and/or do your aerobic activity after you lift. To prioritize cardiovascular training, perform it first, followed by resistance training.