How do the best endurance athletes train to reach the highest level? Off course they train a lot - getting in many moderate hours and doing hard intervals. But how much time do they spend just 'coasting' at lower intensities, and how much time is allocated to demanding high intensity training?
This questions has been central in a lot of scientific work in the last 15-20 years.
One of the most interesting and clarifying scientific studies is the one by Selier and Tønnesen from 2009 called 'Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training', which looked deeply into how some of the worlds best endurance athletes train.
The study came up with 'The 80-20 rule Rule for Intensity', as one of the main findings was, that among highly successful endurance athletes the general rule was that they did spend about 80 % of their training time at lower intensities, and 20 % of the training time at higher intensities.
But what is lower intensities and what is higher intensities? To keep it simple this was defined by a 3 intensity zone model based on the ventilatory thresholds VT1 and VT2, which corresponds to blood lactate levels around 2 and 4 mmol. The 2 mmol threshold is also called the 'the first lactate threshold' (LT1) and the 4 mmol threshold 'the second lactate threshold' (LT2).
LT1 is defined as the lowest intensity where there is a sustained increase in blood lactate concentration. LT2 is defined as the intensity where there is a rapid increase in blood lactate concentration. The latter is also know as the anaerobic threshold (AT) or maximal lactate steady state (MLSS).
Below you will find the 3 zone model. The low intensity zone (zone 1) was set as being intensities below 2 mmol lactate and the high intensity zone (zone 3) as intensities above 4 mmol lactate. Intensities in-between 2 and 4 mmol was defined as zone 2.
Model adopted from : Seiler S, Tønnesen E (2009). Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Sportscience 13, 32-53.
Comparing the 3 intensity zone model to a more typical intensity scale used in cycling, which are often based on 5-7 zones (e.g. Coggan's Power Zones), zone 1 will correspond roughly to zone 1 and 2 (recovery and endurance), zone 2 to zone 3 (tempo/sub-threshold) and zone 3 to zone 4 and above (lactate threshold, VO2max and anaerobic power).
So the best endurance athletes spend around 80 % of their training time at fairly easy intensities (zone 1) and the remaining 20 % in zone 2 and zone 3. How the 20 % training time is allocated between zone 2 and 3 varies between athletes, and is dependent on the sport and specific performance demands. Further individual strengths and limiters might influence the training time in zone 2 and 3, in order to optimize individual needs for training.
It has been suggested that the optimal intensity distribution looks a bit like this. A distribution that would be referred to as polarized training.
Zone 1: 75-80 % of total training time.
Zone 2: 5 % of total training time.
Zone 3: 15-20 % of total training time.
So, how will a 80-20 intensity distribution affect your training?
Paying attention to training time distribution is crucial for the outcome of a training process. Many athletes tends to spend to much time in zone 2 (i.e. in between LT1 and LT2), and would benefit from allocating more time in zone 1, as it will allow for greater endurance related adaptations needed for optimal endurance performance.
A better endurance foundation, as a result of an appropriate amount of zone 1 training, will prime the body to be more ready to perform the crucial high intensity workouts needed to optimize performance.
Less time in zone 2, will leave the body more fresh for the hard interval efforts. Thus, most likely resulting in a higher quality of the workout.
Least but not last, the longer endurance rides might be more enjoyable, as you don't need to push as hard as you think, to reaps the benefits of the training!
Reference: Seiler S, Tønnesen E (2009). Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Sportscience 13, 32-53.