The heart rate is the speed with which your heart beats. If you have a heart rate of 70, it means your heart pumps blood into your arteries 70 times per minute. There are many things that affect heart rate. For example when you suddenly find yourself in a stressful situation your body goes through series of reactions one of which is to increase your heart rate. Or when you are dehydrated your blood volume decreases and to compensate this, your heart starts beating faster. The moderate zone Your heart rate also changes when you exercise. Knowing the right heart rate zone for the exercise you are doing will help you keep the right intensity. According to Health Harvard a moderate level of intensity is when the exercise feels not too hard or too easy but just right, and your heart rate is between 60% and 75% of its maximum. A simple way to calculate your maximal heart rate is to subtract your age from the number 220. For example if you are 30 years old, your maximal heart rate should be 190 bpm and you will be in the "moderate zone" of intensity during exercise when your heart rate is between 114 bpm and 142.5 bpm. According to Dr. Baggish, director of the Cardiovascular Performance Program at the Massachusetts General Hospital Heart Center, it is best as a beginner to stick around the 60% of your maximal heart rate (MHR) for a few weeks before moving up in the zone.
Aerobic heart rate zone See, your body mainly uses fat, glucose (coming from carbs) and ATP-CP (more on that in another post) as source of energy during exercise. No matter what exercise you are doing your body always uses some combination of these three. It's just that sometimes it uses more fat and sometimes more glucose. To give you simple example: ATP-PC is used when you do a 50 meter sprint, glucose is mainly used when you do a set of 10 repetitions of deadlift, and fat is mainly used as an energy source when you go for a two hour easy walk or do a 45 minute jogging session. The aerobic heart rate zone is called like this because when you are in it your body uses a lot of oxygen. This is the zone you're in when you do your cardio. Your body oxidises fat and uses it as fuel. It also uses glycose as source of energy but the proportion of energy coming from fat is still significant (~45%). The optimal heart rate for cardio workouts such as running or cycling falls between 70% and 80% of your MHR. The benefits of training in this zone are improved circulation and oxygen transport throughout the body. Lung capacity also improves. You might struggle with your breathing in the beginning but as you begin to adapt to this heart rate zone, you will feel it improving.
Anaerobic heart rate zone This is the zone you're in when you are lifting weights for building muscle or are running a 400 meter race. At this point your workout is more intense and the aerobic system can't keep up. Your body switches to higher use of glucose and glycogen found in your blood and muscles respectively to fuel your workout. Because this process happens without the use of oxygen, it is called anaerobic. Your anaerobic heart rate zone falls between 80 and 90% of your MHR. Benefits from training in this zone include building muscle endurance and improving your VO2 max - the maximum amount of oxygen your body can convert to energy.
How to keep track of your heart rate during workout The heart rate monitor on the treadmill in your gym is hardly if at all accurate. You would probably be better off using a commercial heart rate monitor. Their accuracy varies between 92% and 97%. For more accurate measurement you can try a chest strap HR monitor, which accuracy has been estimated at 99.6%. Normally you can estimate that you are in the aerobic heart rate zone if you can keep a conversation while exercising. If you can't, it's more likely that you are in the anaerobic heart rate zone. Considerations Remember to always consult your health care provider before attempting to do something you haven't done before, especially training above 85% of your MHR. Listen to your body and be safe. Thank you for reading! References: Accuracy of Wrist-Worn Heart Rate Monitors | Cardiology | JAMA Cardiology | JAMA Network Feel the beat of heart rate training - Harvard Health Aerobic & Anaerobic Heart Rate Zones (azcentral.com) Exercise Heart Rate Zones Explained – Cleveland Clinic