Zones

One of the main things I get questions on related to turbo training and training with power is about what ‘zones’ I use and what % of threshold I train and race at.

The gold standard for setting training zones on the bike is to do an incremental power test where effort is increased by a set amount of watts every 4 minutes. A measurement of blood lactate and heart rate are taken at the end of each step and the data plotted on a graph. Here we have a good age group male athlete with a nice profile so you can see blood lactate is stable at lower power outputs before rising steeply.

The best known landmark is where lactate starts to rocket at around 4mmol^-1 lactate which is the ANAEROBIC threshold (AT) which most people are more familiar with. This is close to race effort for anything up to an hour so will be very uncomfortable. Taking 95% of a 30min time trial effort can be a good estimate of threshold power and is known as the functional threshold, which is still useful in setting zones.

The key landmark on this graph however is where the lactate first starts to rise at about 75% of the AT watts which is the AEROBIC threshold and is the level where you will first start noticing your breathing a bit more and where you really start to stimulate aerobic training adaptations. The bulk of aerobic training as well as Ironman racing is done in the A1 zone just above this threshold between 75-85% AT.

The closer you get to the AT the more the fatigue increases for little more aerobic benefit so I limit training in the A2 zone between 85-95% AT for specific intervals where possible. It is important because a lot of triathlon racing at Olympic,  ½ Ironman and for advanced athletes Ironman will be in this zone.

Training in the threshold zone is very fatiguing and limited to specific workouts. It’s very important however in conditioning you physically and mentally for racing by improving lactate clearance and tolerance and should be a key part of your weekly training approaching race season.

Training in the VO2 max zone, 105%+ AT has limited use for endurance racing but can improve power, efficiency and VO2Max so is used more in training especially swimming and biking where the impact is not so great.

What about heart rate? In my view heart rate is extremely variable and of limited use in setting bike training zones so should be used in conjunction with perceived effort. Typically anaerobic threshold is around 85% or 80-90% of maximum with the key A1 training zone being around 75-80%. You should look for cues though with increased breathing and perspiration and try and focus on even effort not even heart rate!

Any other questions leave me a comment or drop me an e-mail.

G