• AB


Welcome to the first of several posts on cycling zones. The who, what, where, when of the intensity and duration curve.

First up, we are going to look at the Anaerobic Capacity (AC), also known as Zone 6 or 5b (depending on what zones you're using!), which comprises maximal efforts from around 30sec-90sec, of 120-150% of FTP. Heart Rate is difficult to use for these efforts due to the short nature of them.

What is it?

Anaerobic Capacity is the zone you'll hit at the fast start of an XC race, at the start of an aggressive attacking move on or offroad, or on a single lap flyer of a criterium race. You'll be working in this zone frequently in Gravity Enduro and Downhill. By training this zone you can increase the power you can produce in the zone, amount of time you can spend in the Anaerobic zone (ie: 'on the rivet') and improves repeatability and recovery when hitting this zone in racing. All winning things!

How do I do it?

There are many ways of training in this zone, but a few easy ones are below:

Session 1: Intensive Anaerobic Intervals: Warm up 30min, then complete 6x1min maximal intervals with 5min recovery between efforts (!), Warm down 30min. These can develop out to 8 or 9 intervals in total.

Session 2: Extensive Anaerobic Intervals: Warm up 30min, then complete 3x 45sec maximal intervals, 90sec recovery followed by 3min recovery, repeated 3x.

What does it feel like?

Vomit, mainly. No, just kidding. But these are HARD. These are the type of effort where you're watching your computer and praying for the seconds to tick by. From my experience, those who have a weakness in their Anaerobic Capacity fine the whole session harder and more difficult to complete than those who naturally have more top end, which makes sense. Though they're hard at the time, with all the time you have NOT pushing hard on the pedals it's really an easy session RIGHT? (I'm joking, it's hard).

For self-pacing without power, usually the start of the effort feels fine until around 20-30seconds in, when the burn hits. The 'cycling life-choices' regret often only starts around that 40+ second mark, and the final part of the efforts will take a heck of mental resolve.

When do I do it?

This depends on your goals and events, and even rider type. If using a reverse periodisation approach (for example, for very long endurance events) I would look to build the anaerobic engine and work backwards towards the goal race. Likewise, for the rider that is very aerobically strong but has higher intensity and power outputs as a weakness (a rider with a pure time-trialler phenotype that will not budge throughout a season with accurate maximal profile testing) I may introduce these efforts earlier in order to work on this limiter.

For the majority of riders though, these efforts are a bit of the cherry on the top for athletes in mainly aerobic disciplines (XC, CX, XCM), and due to the taxing nature of them should be dispersed carefully with attention to adequate freshness to complete them, and recovery to reap the benefits of them!

How do I measure this?

Power metres are the gold standard for these efforts, especially tracking between sessions. Alternatively, using a section of road or trail where you can benchmark your performance (ie: 60second efforts this week vs next week: aim for the next tree!) can be handy to monitor progress. Unfortunately, heart rate is pretty unhelpful for these guys.

For example, I had an athlete recently complete a 6x 1min AC session, which was quite intensive with a 1:5 work:rest interval. His power numbers were through the roof, yet their heart rate topped out at subthreshold, a whole 8 beats under threshold! If we were to use HR based training stress to validate our training stress, it would be seriously underestimating the workload. However, when using power, doing AC efforts is a great way to break the system, as it generates a training stress score far greater than your legs would have you believe!

So get out there and get pedalling!

Next up: VO2 Max.


  • Instagram Social Icon
  • Facebook Social Icon
  • LinkedIn Social Icon