A quick scan of the web reveals multiple zone systems, from three to seven and with HR variations between bike and run (more muscles are used when you run as opposed to cycling, hence the discrepancies). Here we detail the five-zone system and highlight the benefits of training in each.
ZONE 1 % of max heart rate (range)
Swim: 50-60% Bike: 60-65% Run: 50-60% Perceived exertion: RPE 2-4, easy to moderate Performance benefit(s): Training at this aerobic intensity will boost your recovery and get you ready to train in the higher heart rate zones.
Swim: 60-70% Bike: 65-75% Run: 60-70% Perceived exertion: RPE 4-5, moderate Performance benefit(s): Basic cardiovascular training at a good recovery pace. This is the intensity to improve aerobic capacity; i.e. stamina. Your body will get better at oxidising – burning – fat and your muscular fitness will increase along with your capillary density.
Swim: 70-80% Bike: 75-82% Run: 70-80% Perceived exertion: RPE 5-7, moderately hard Performance benefit(s): Running in zone 3 is especially effective for improving the efficiency of blood circulation in the heart and skeletal muscles. This is the zone in which lactic acid starts building up in your bloodstream. Training in this zone will make moderate efforts easier and improve your efficiency.
Swim: 80-90% Bike: 82-89% Run: 80-90% Perceived exertion: RPE 7-9, very difficult Performance benefit(s): This zone will improve your anaerobic capacity, threshold and speed endurance. Your body will get better at using carbohydrates for energy and you’ll be able to withstand higher levels of lactic acid in your blood for longer.
Swim: 90-100% Bike: 90-100% Run: 90-100% Perceived exertion: RPE 9-10, maximal Performance benefit(s): Training at maximum (i.e. interval training) will increase your anaerobic and muscular endurance, power and cardiovascular levels.