The challenge for most triathletes is to find the balance between training and the rest of the great things in life (family, work, non-active recreation, and chores). It makes sense to maximize the training effects specific to competition while minimizing the time invested in the training.
Thus the “80/20 rule” – Research has shown that world class endurance athletes do approx. 80% of their training at low intensity (referred to as zone 2) and the remaining 20 percent at moderate and high intensities (referred to as zone 4). Further research has shown that most people automatically selected a pace that places them at a moderate intensity (zone 3). Thus leaving a void in the adaptation, and no maxing out the gains that can only be made at these lower and higher intensities.
Here’s the deal
80% of training should be at a low intensity – low being 60-77percent of max heart rate or 73-80% of FTP (Functional Threshold Power). While 20% of training should be at a high intensity that being above 93% of max heart rate or 102-110% of FTP.
There are a variety of zone training structures. Most share the common intensity concepts
Zone 1 is a recovery intensity
Zone 2 is a base training zone as noted above
Zone 3 is a racing zone – more about this below
Zone 4 is an interval of above FTP, anaerobic intensity (also noted above)
There are other sub zones (such as zone X, zone y and zone 5) that all have a place, but not a big place in endurance training.
Zone 3 is interesting – its best used closer to the competition phase of training (late base phase through the build phase and into the taper phase).
A well structured periodized program can use these zone targets to maximize gains and stratify the training phases based on the priority races in your season.