It is important to know your heart rate while exercising because it indicates your effort level and available work capacity, and also provides information about how close you are working to your aerobic and anaerobic thresholds.
Your heart rate is also the primary indicator of which energy system you are using to fuel your exercise – be it fat, stored glycogen or amino acids.
The main heart rate zones measured in terms of maximum heart rate (MHR – roughly calculated as 220 – age) include:
- 50-60% of MHR:
Suitable for performing light cardio to improve blood flow and circulation. It is therefore ideal for warming up and cooling down and is the base zone used to target fat stores as a primary source of energy.
- 60-70% of MHR:
Ideal for developing general fitness and is the ideal range for utilising fat stores as an energy source, as fat stores can be efficiently mobilised for energy at this intensity.
- 70-80% of MHR:
This is the aerobic zone and is ideal for developing endurance and improving lactate thresholds. Due to the energy demands in this zone your body will rely more on stored glycogen and digested carbs for energy, but around half of your energy will still be supplied from fat stores.
- 80-90% of MHR:
This is the anaerobic threshold limit, where your body is producing massive amounts of lactic acid, so it is only able to maintain this level for a short period of time. This is the best zone to increase your VO2 max to improve your body’s ability to utilise oxygen. This heart rate zone relies predominantly on your ATP-PC system for energy, with some reliance on glycogen.
- 90-100% of MHR:
This zone is the upper limit of your physical capacity and should only ever be reached during HIIT for a short period of time, if at all.
Knowing and understanding these zones will ensure that you work at the right level to achieve your goals, and it will make your training more accurate. You will also notice that there are a number of zones that preferentially use fat stores as a primary energy source, namely 50-75% of MHR.
Author: Tanja Schmitz
Founder and Editor of Fitness Magazine. You’ll find her behind her computer or on her bike, dreaming up new ways to improve or create content for you.