Renowned exercise physiologist Stephen Seiler has created waves amongst the endurance training community broadly, with many coaches and athletes attesting to his research and subsequent findings, which have become well documented and commonplace on numerous podcasts and social media.
The aforementioned is a consequence of his contrarian views relative to peers, namely Andrew Coggan and co of Peaks Group, commonly known as Training Peaks, proponents of a pyramidal philosophy and attesting to the value of accumulating time at intensities close to, but below FTP, an extrapolation of sorts of the anaerobic threshold.
Here, we take the original research paper (see below) from Seiler himself, titled unambiguously ‘Training Intensity Distribution’, and delve into the methods used, analysis and subsequent findings, to understand the practical applications for coaches and athletes alike.
The paper is summarised, giving a broad overview of the following topics, which are summarized below:
Training zones- how many and why?
Seiler first acknowledges that there are numerous methodologies for measuring intensity. Broadly speaking, a trade-off here is present, namely the fact that the generalised scales that many of us use (myself included!) are an approximation, which by nature is therefore subject to error. An approximation of what? The relationship between heart rate/power output, and blood lactate. This will vary from individual to individual, thus applying a standard ‘one-size fits all’ percentage of upper and lower bounds, is imperfect.
Given the errors associated with the upper and lower bounds of these zones, it makes attempting to train at those boundaries, under the assumption they are concrete, potentially detrimental, with the belief you are training one energy system, when in fact you are doing the other.
Thus, practically, training in the middle of the prescribed zones and taking the approach of seeing it as a ‘range’ rather than an exact number, is likely to deliver the best outcomes.
However, assuming you are using a well-informed model (see below) which is interpreted correctly, Seiler describes the trade-off as positive, given the improved communication between athlete and coach. In other words, prescribing training without zones, and executing with quality and consistency, could be challenging!
Figure 1
Adapted from Seiler (2012)
Three zones- but there are five! (or seven, or eight…)
Also addressed is a common point of confusion, with Seiler describing the much-discussed three-zone model.
This is demarcated by an upper bound for zone one, being the first ventilatory turn point, commonly referred to as the aerobic threshold. While acknowledged as imperfect, for practical purposes, it can be interpreted as the following, regarding the table above:
Z1 & 2 = Z1 (on the three-zone model)
Z3 & Z4 = Z2
Z5 = Z3
So how many is the right number? As always, it depends, but practical advice is offered. For young or inexperienced athletes, a three-zone model can offer simplicity as well as allow a broader application until an athlete becomes more nuanced in monitoring and ‘feeling’ their effort, without riding around with their eyes glued to their stem!
Intensity- how much is too much?
A broader note to ‘how good endurance athletes train’ is given notable consideration in the paper, with a focus on reviewing the literature on elite athletes and the intensity distribution of their training.
With a focus on elite endurance athletes in rowing, running and cycling, a broad theme emerges- that only 5-15% of the total training time (in duration, not a percentage of the number of sessions), was completed at ‘intensity’ – ie. race pace, or an intensity above VT1, or zone one on the three-zone model (green band in the table above).
Notably, the polarised nature of training increased in the studies which measured the intensity distribution as a time series, as well as intensity broadly, increasing as competition became closer. In the case of the paper referenced regarding Spanish U23 cyclists (Zapico et al, 2007), sometime between VT1 and VT2 (Zone 2 on the three-zone model, or ‘tempo’ work) was noted, however, this was still below 20% of total training volume, with 80+% of training volume across all studies comprising of time in zone one, around 65% of max heart rate (Z1 on the five-zone model, and three-zone model) - easy, but not excessively so.
Figure. 2
Zapico et al (2007)
Another interesting note from this paper was that they found no increases in V02 max in the final test, despite the training completed in the cycle previous as the most intense, begging the question, why do it? It is likely, as noted, that the focus was not on improving a variable which is notoriously ‘sticky’, but instead to bolster the sustainable time at such an intensity.
Therefore, think ‘more efforts’ (4* 8 at same intensity), rather than ‘harder efforts’ (3* 8 at higher intensity), often a determining factor in road races.
A final point here is regarding the impact of high-intensity training, noting an empirically supported benefit of 2-4% to performance (Khort et al, 1991; Lindsay et al, 1996; Weston et al, 1997). Yes, you read it right, between TWO and FOUR PERCENT.
So, the next time you skip your four-hour ride for a ‘quality’ one hour
turbo session, think about where the quality truly lies.
Intervals- how hard, how many, how long
Addressed in this section of the paper is the question of how hard the ‘high-intensity'
portion of the distribution should be. Given that intensity moves inversely to duration, the question here is whether intervals should be longer, in this case 3x 16mins at ~85-90% of VO2 max, 4x 8mins at ~90-95% of VO2 max, or 4x 4mins at ~95+% of VO2Max. In other words, will more volume, or more intensity give me more ‘bang for my buck’?
Findings here concluded that the 4*8min prescription was shown to deliver the largest effect, with every subject in question seeing improvements in the average change in their power at 4mM blood lactate (Anaerobic threshold/FTP) or VO2 max, greater than or equal to 4%, with over half the subjects seeing ‘large’ effects, over 9%.
The distribution of the gains between the anaerobic threshold and VO2 max is not disclosed, however, given the findings outlined by Zapico et al (2007), it is reasonable to assume that these improvements were derived mainly from improvements in the anaerobic threshold.
How does this fit with a periodised training plan?
Discussed next is how the distribution of training intensity and the classic ‘80/20’ model fits into a periodised training plan. Stemming back to the 1960s, the training structure in endurance sports has tended to focus on an approach which focuses on a volume first, followed by intensity, framework. While physiologically sensical, Seiler notes that the evidence to either support,
or discount this is limited.
Of the literature available however, the key takeaway focuses on the fact that ‘low intensity
, or time below the aerobic threshold, is a key component of training regardless of the time of year in which elite athletes are competing, noting that greater than 80% of training volume is spent within ‘Zone 1’ (three-zone model), independent of the time of year (see Fig. 3).
Figure 3
Source: Seiler (2012)
Takeaways in this regard should focus on the importance of ensuring that training volume is maintained throughout the year. In turn, discipline should be enforced, relating to the intensity of that time, emphasizing the importance of aerobically focused, longer rides during the competition phase, emphasizing the importance of ensuring a contrast between the easy and hard days.
Finally, regarding the distribution of interval, or high-intensity work, across the season, at first glance, the recommendation, as is commonly misunderstood, is not merely to complete between one and two 4*8 sessions per week, year-round.
Zapico et al (2007) highlight in their findings that there was a significantly greater amount of time spent in the sub-threshold range (zone 2 on the three-zone model), suggesting that there was an intensification of the work carried out within the ‘high-intensity category, however that zone one time remained >80% total volume, while the total volume, and thus total training load, increased.
Succinctly, the ‘amount’ of intensity in the pre-competition phase did not change, just the type.
References:
Seiler, S. (2012), Endurance Training: Science and Practice (pp. 31-39) Edition: 1st, Chapter: 4.
Zapico, A.G., Calderon, F.J., Benito, P.J., Gonzalez, C.B., Parisi, A., Pigozzi, F. & Di Salvo, V. (2007). Evolution of physiological and haematological parameters with training load in elite male road cyclists: a longitudinal study. Journal of Sports Medicine and Physical Fitness, 47, 191-196.