Base & Aerobic Threshold Training

By Alex Price

With the New Year here and the first part of the season behind us, there is a break with regards to long course and ironman racing. That means a lot of us will, and perhaps should look at this period as a mid season break and go back to developing our aerobic systems. This is especially important this year with Ironman Australia and Huskisson Long Course moving back a month and Cairns still six months away!

To help to understand “Base” training, I like compare it to a house….

Everywhere below the ceiling is your Aerobic zone. This is an area of the house where there is a lot of space and where we can train and race for a longer period of time.

The actual ceiling represents the Aerobic Threshold (AeT) and the roof of the house represents your Anaerobic Threshold (AnT) or the point where we ‘blow up’.  In between the ceiling and the roof is a grey area in which athletes are working too hard for their aerobic zones and not hard enough for their AnT. In the ‘training house’ the ceiling height can be lifted slightly and so can the roof with the correct training. The size of the house or the aerobic zone is an area which can get bigger, also with the right training.

There are two mistakes that
athletes often make with this
aspect of their training…

  1. They spend too much time in the area above the ceiling (anaerobic zone) where they are working too hard to lift the ceiling (AeT). In this area they are purely adding to their fatigue levels without stressing any specific area of the house.
  2. They spend too much time just above the floor of the house (cruising mode). In this area they are not getting the full benefits of training. They are just going through the motions

So often this is done when people ride in a group and push into the grey zone when they are on the front of the pack and then just cruise when they are sitting back.

Very little racing, even at an elite level, is done above the ceiling or your aerobic threshold, most of it takes place within the house.

With this is mind, the development of our aerobic system or the house is the most important factor of performance. For peak performance a fit athlete races a Half Ironman at or around their Aerobic threshold (AeT) and an Ironman just below this level.

For most of us the easiest way to gauge our AeT or AnT for that matter, is by monitoring Heart Rate (HR).

Improving your AeT will mean 2 things:

  • Your AeT HR will increase – ‘the ceiling will lift’
  • You will become more efficient, stronger and have better technique at this HR – ‘your house will get bigger’

Both of these factors will mean that you will be able to go faster when it counts, on race day.

Many athletes fall into the trap of peaking too early in training, usually due to cutting their ‘base’ period of training too short. This is done by feeling they need to incorporate higher intensity Anaerobic workouts too early, racing their friends in training or feeling they need to get home from a session absolutely ‘had it’ to make it feel like they have gained something. Make sure your Base Period is at least half to two thirds of your training plan, which if you are working towards Ironman Oz, gives you PLENTY of time!

During this Base period, it is important to not just do Long Slow Distance (LSD) workouts where you could have a cup of tea while riding along. By incorporating some Aerobic Threshold work within this, you will be stressing all the parts of your aerobic system. This will ensure you will make the physiological changes necessary to your body, which is what training is all about, not feeling like a hero as you beat your training buddy – leave that for the race!

The easiest way for most of us to measure our Aerobic Threshold is with a HR monitor. This will differ for everyone, but a good estimate is 20 beats below your Anaerobic threshold.

  • If you don’t know your Anaerobic Threshold, a good way to test it is to do a max 40km bike time trial or a 10-15km run, with your average heart rate for these being your AnT. Remembering it will typically be slightly higher for running than riding.

Therefore by working at a HR about 20 beats below your AnT, you will be working strongly, but still should be feeling in control, ideally how you would feel when racing Long Course.  Athletes would typically aim to work this hard for sections of their sessions, as it is still quite a stressful form of training.

As with any training, it is very important to maintain good form and technique when doing these efforts. This is an area that many triathletes are not conscious of, but separates the good and great athletes. This will ensure that you are not wasting energy and that you are minimising the risk of injury, both of which are essential elements of making it to that finish line!

The trick is to determine how long to do these sessions for. This will obviously vary for everyone depending on their fitness levels, stage of training, age and goals. However, remember that specificity in all training, whether it is triathlon or chess, is of utmost importance. Therefore if you are training for Ironman, the goal should be to build these sessions up to longer distances and times (but perhaps slightly lower intensity) than Half Ironman athletes.

Examples two athletes key sessions may be:

Athlete 1:

Megan (Half Ironman focus)

Megan is a keen runner, turned triathlete. She has competed in several Olympic distance races, but is yet to race a Half Ironman.


CYCLE: 30min easy warm up

6 x 5min @ AeT, with 5min spin recovery.

30min easy warm down

RUN: 5min @ AeT x 4, with a 2min easy jog recovery in between

As Megan is new to longer racing you would be more inclined to make the rep’s slightly shorter in time, but more of them. You could progress this by increasing the time for each followed by the number of rep’s. She should make sure each rep is at AeT and not losing focus during it. In this session she is spending a shorter amount of time just below the ‘ceiling of the house’ but as she gains experience would increase the time in each rep.

Athlete 2:

Craig (Ironman focus)

Craig is an experienced triathlete, who has done several Ironman’s. In the past Craig has ridden mostly with a group, either riding hard or really easy.


CYCLE: 90min easy warm up

4 x 20min @ AeT, with 5min easy recovery.

30min easy warm down

RUN: 4 x 15min @ AeT, with a 5min easy recovery jog.

Craig could potentially spend a little longer training at the ‘ceiling’ given his training history. With this he could both increase the number of rep’s and the time near the ceiling.

As per any progression in training, it is very important to do so slowly and make sure that good form and technique is kept when doing all training!

Where possible it is also a good idea to try to do these key sessions on terrain which resembles the race you will do. This may mean that you have to occasionally change your ritual Saturday ride or run, especially if you are used to riding with a large group. This will not only give your body and mind time to adjust to what it will encounter on race day; it may also mean some renewed enthusiasm by going somewhere different!

Alex Price

Bach. App. Sc. (Physio)NSWIS Accredited Physio
F.I.S.T. Cert. Bike Fitter

Triathlon Level 1 Coach

E: [email protected]
W: 02 4225 2233


Alex Price Twitter 

Alex_Price_ap10_nepean_2010Alex is a New South Wales Institute of Sport (NSWIS) Physiotherapist in Wollongong. He is the current NSWIS triathlon Physio, working with elite and age group athletes. He has worked across the globe, including the Olympics, the Tour de France and several U.S. college athletic departments. He has also studied the gold standard F.I.S.T. Slowtwitch Bike Fitting  course in California. Alex has also been racing for many years and is currently racing in the Open or Pro categories, with a long course focus.







Karl Hayes

Karl is a keen age group triathlete who races more than he trains. Good life balance! Karl works in the media industry in Australia and is passionate about the sport of triathlon.