If you missed the introduction to Training Zones click here.
While training in Zone 5 worked on our ability to use oxygen for energy, training in Zone 6 works on our ability to create energy in the absence of oxygen. In this zone you are going so hard that you need energy quicker than it could be produced with the use of oxygen. Energy is produced through anaerobic (without oxygen) glycolysis which can produce energy quicker but in shorter supply, meaning you can only rely on this energy system for up to 3 min. Thus, intervals in Zone 6 which targets improving your Anaerobic Capacity are 30 seconds to 3 min in length. Since these intervals are even shorter, the percentages of FTP continue to be a guide, but you should rely on feel as well. Like Zone 5, if you are going as hard as you can for 30s-3min you are likely in Zone 6. Watching your power or pace too much during these intervals could distract from giving your hardest effort. Instead, if on early intervals of your workout you fade too much by the end of the interval then you know you are going a bit too hard and should go a bit easier on the upcoming intervals. Heart rate will not respond quick enough to be an accurate gauge of effort on this short of an interval so shouldn’t be used. If heart rate is the only metric you have to gauge effort, then use Rate of Percieved (RPE) instead.
The intensity range for Zone 6 is bigger than other ranges as you can clearly go a lot harder for a 30 sec interval compared to 2.5min intervals. Hence the shorter the interval, the higher in Zone 6 you will be and vice versa. Inversely, the recovery between these intervals will be longer for shorter (harder) intervals and vice versa. In general recovery should be 3-5min between Zone 6 intervals with a 1:2+ Work:Recovery ratio i.e., at least twice the duration of the interval. For example, 2min intervals in Zone 6 should require at least 4min of Zone 1 recovery between them. We say at least twice the length of the interval because these should be a little more based on feel. By that I mean that you should feel fully recovered between these intervals and able to go just as hard for each interval so if you need to recover a little longer to make this happen than you should.
Just like previous intervals you should pick a route free of stop signs/lights, but now it’s more imperative that the route doesn’t involve any downhill sections, since they should be intense and a downhill section wouldn’t allow you to get every last bit of intensity out of the interval. Short and even somewhat steep hills would suit these intervals well. In fact, I like the combination of Zone 6 and hill workouts. The hills help you make them even more difficult (which they should be) and a lot of races have short punchy hills that usually require a little spike in effort. This could be performed on a single hill with recovery being on the way back to the bottom. Picking a route with a variety of short to medium length hills along the way that take 30s-3min to get up and going up them hard is another way I love to implement a Zone 6 work out as it gives you a bit of variety and would be more similar to real world races. Just make sure to fit some recover in between the hills so you can maintain intensity during your intervals. Lastly, for running these could be 200, 400, or 800 meter repeats on a track with an equal or distance walk/jog for a recovery.
Running >109% of FTP >106% of FTHR 8-9 RPE
Cycling 121-150% of FTP N/A % of FTHR 8-9 RPE
Swimming FTP - 5sec/100yds(m)+ 10 RPE
Interval Duration: 30sec-3min w/ 3-5min Recoveries (shorter, harder intervals require longer end of recovery range and vice versa; 1:2+ Work:Recovery)
Continue reading about Zone 7 here.