If you missed the introduction to Training Zones click here.
In Zone 5 we switch our focus to a new training stimulus, which is increasing your VO2 Max. Your VO2 Max is the maximum amount of oxygen your body can take in and be used by your working muscles to create energy for work. Past this point you must rely on creating energy without oxygen which is much more limited. Healthy lungs are capable of breathing in way more air (and thus oxygen) than our body could ever need, so the limiter for how much oxygen you can use is determined at the muscular level where oxygen is used in the process of creating energy. The more efficient these working muscles are at using oxygen to create energy, the more energy you have available which is clearly to your benefit.
The workouts for Zone 5 are quite straight forward in that if you are going as hard as you can for the 3-8min intervals, then you should naturally be in Zone 5. If you find yourself able to maintain your intensity for longer than 8 min, then you’re probably in Zone 4. If you find you can’t maintain your intensity for at least 3 min then you probably started out too hard and are actually in Zone 6. The percentages of FTP for Zone 5 are below, and are a good starting point, but as intervals start getting shorter you can rely somewhat more on feel. Like it was said above, if you are going as hard as you can at a steady pace for 3-8min you are likely in Zone 5. These can often be the hardest intervals for people, as anything shorter you can go all out knowing the end is soon and be alright and anything longer you know instinctively you must pace yourself to make it through the interval, so you do. During these intervals you are still working very hard, but you are doing so for just long enough that mentally you have to convince yourself to keep it up.
As stated above the intervals are straight forward; go as hard as you can for 3-8min. Recovery between intervals would be in Zone 1 and be at a 1:1 or 2:1 Work:Rest ratio meaning your interval would be equal or twice as long as your recovery between intervals. For example, if your interval is 6min long then recover for 3-6min before starting the next interval. A good place to start would be 4-6 intervals of 3-5min with equal rest and slowly progress from there building to a total of 30-40min spent in Zone 5 for a given workout (ex. 10x3min, 8x5min, etc.).
There are a few helpful tips I can give you for these workouts. First, pick a route that has fairly consistent terrain and no significant declines as these can really throw off your steady pace. A gradual incline would work too. If training for hilly races, a hill with a medium grade and length could also be used. Also pick a route which doesn’t have any stop signs/lights that would interfere with your intervals. Second, while these efforts are time-based, it is easy to make the distance based so you can keep pushing for a visual landmark. Start by getting an idea of the distance you would cover at this high level of effort. For most people this would be 1-3 miles for cycling and 800 meters to 1 mile for running. Some of my go to workouts for Zone 5 are 1 mile repeats on a slight incline for cycling with an easy ride back to the start line for recovery and 800 meter repeats on the track for running with a 400m jog/walk recovery.
Running ~104% of FTP 102-105% of FTHR 7-8 RPE
Cycling 106-120% of FTP >106% of FTHR 7-8 RPE
Swimming FTP - 1-5sec/100yds(m) 9 RPE
Interval Duration: 3-8min w/ 3-8min Recoveries (1:1 to 2:1 Work:Rest)
Continue reading about Zone 6 here.