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Endurance Training Science 101

Our Perspective on Human Performance

Endurance Training Science 101

Endurance Training Science 101

Following on from the Training Peaks University I attended, I wrote up a synopsis of the Endurance Coaching Summit where real-world practitioners, i.e ‘coaches’ working with sub-elite receational athletes, get to learn some of the evidence of research and schools of thought from professionals and experts in both commercial and academics setting working with elite athletes. Even though the time-crunched athlete is a different type of project compared to elites in terms of management, there are many relevant studies which have focused on important aspects of performance, observational (i.e. looking at data sets from athletes in retrospect), or gathering data on interventions moving forward (prospective), and evidence-based which are more pertinent to the real-world than current guess work, anecdotes or misinformed schools of thought from controversial headlines. I have previously called the latter pseudo-journalism where the outcomes aren’t really put in context and just pushed out into the public endurance sports sphere just to ‘impress’ recreational athletes, or even polarise their own beliefs…it is all too common.

Many of the headline speakers at the Endurance Coaching Summit (and even at the ESP) have shared my frustrations, even though…or especially because they are working with athletes at the pinnacle of their sport, but have also had to reach that position from somewhere (a starting point)…So, rather than just ranting about it, I like to put my time into productive criticism, and appraising good science that applies to the general endurance sport population, because that should be the role of a coach, a translator from good scientific observation to real world practice, where an athlete needs have answers that translate to results asap. Unfortunately, that is not always the case.

Much like the TPU, we were spoilt by some really well delivered presentations, and as you will probably never get to listen to these people for the amount of time that respects their credentials, I’ll take the pleasure of providing what I feel are the most useful ‘snippets’ in my own interpretation that can help morph your training into what it deserves to be, progressive and fruitful for the time you put in.

I’m not into eye-catching headlines or controversy, but we can say that much of the misinformation has tuned into myths which is just another way of saying what someone has stated as ‘fact’ probably doesn’t apply to your situation and is taken out of context for other agenda reasons. So perhaps the following info will explain some of these myths, or at least set some sound, yet often misinterpreted info into more clarity….namely the two most important aspects to ALL athletes, how to train, and what to eat…but I’m not making infinitives rather than making explanations, as we approach personalised everything…we need to apply the right principles to ourselves at the right time, not what people ‘think’ is relevant, as we get caught up in subjectivity…even coaches. This post is probably a long over-due addition, as finding a chance to put it all together should give the reader insight into my coaching methods but this comes at a time when I have finally appreciated that coaching is more than just designing a programme to fit someones schedule, but actually steering or collaborating with an individual from A to B on what is always a non-linear path. If it was a straight-line to success, then more of us would become elite athletes, much more quickly…

Interval training, or more importantly training distribution which this falls under is plagued with so called ‘experts’…..as the concept and practice of interval training has been around since the 1930’s and 40’s, it’s not a recent thing, although you may have recently discovered it. As Dr. Seiler stated ‘We must be careful as coaches to apply the highest intensity work in careful, infrequent doses’.

Interval training boils down to the non-linear relationship between sustainable duration and intensity, and is defined by the curvi-linear response of lactate accumulation and clearance. Stephens endurance hierarchy bases the fact that volume, hence duration and frequency can have the most significant effect on performance preparation over just high intensity training alone….”duration matters and doesnt live in it’s own vacuum”, long duration intervals win over short duration intervals, and I will explain why.

But further to this, the human body needs variation in anything it does to elicit adaptation and thrive as opposed to crash. The effectiveness of the 80/20% rule of polarised session training is probably accounted for by biological variation. That is to say that in high-performing athletes, 90% of training time is below Lactate Threshold, which is all well and good for steady-state athletes in cross-county skiing or ironman etc, but they still perform a small fraction of time in higher zones, and where events are raced at longer duration in those higher zones.

We know that when a lot of time is spent in Zone 2 and 3 training this translates up the energy system pyramid and pushes lactate threshold up from below, but shorter interval durations which are conducive of 80-100% Vo2max are able to both increase the total size of the performance engine as well as pull lactate threshold from above. Purely just accumulating time in this range as an interval session is beneficial as there is less overall stress on the body, and energy demands of oxygen cost is low on the muscle, i.e. lactate values tend to remain relatively low so more intervals can be conducted. This can be referred to as the ‘first wave of change’, aerobic capacity which plateaus and undulates seasonally.

The second wave of change can be related to the longer term cardio to skeletal adaptations of lactate threshold (the effectively utilised fraction of aerobic capacity) increase over months and years. You are right in thinking that this is all well and good for elite athletes or even well-trained ones, as we know that their training programmes incorporates a large amount of racing at the high intensities, threshold and above, depending on discipline, and so it would suggest that variation and interval training would be even more important for recreational athletes, and why sweet-spot training (Zone 3/ low Zone 4) is commonly misperceived to give the most bang-for-buck. There supposedly is at the moment no evidence to suggest it provides any significant improvements in race performance.

We realise that the race intensity, training and racing history may explain why sweet-spot training works for some athletes as a maintenance tool, and not for others. In contrast, when I see recreationally well-trained athletes riding at this sort of intensity for far too much of their expendable training time we see a ‘step’ or a ‘dead-zone’ in the lactate curve usually just below the second lactate turning point or MLSS. Basically, too much lactate buffering of acid in the muscles starts to breakdown the lactate shuttles (Mono Carboxylate Transporters in aerobic fibers) for rapid recycling between muscle cells. Anaerobic conditioning is repressed also at this lower aerobic intensity. Luckily this is temporary and reversible so that threshold can continue to rise rather than plateau, think saturated ‘training’, quite literally…the analogy is that you can’t get any more water out of the bath as there are fewer plug-holes. Everyone else trying to build threshold or VO2max capacity could be polarising efforts across their energy systems in the little time they have and distributes the stress much more evenly for the duration and is in-keeping with Dr. Seilers postulates of aerobic interval conditioning, and these will translate to race or event demands when the time comes….So avoid the dead-zone!

Like-wise in lesser trained or beginner athletes, they tend to have a linear lactate accumulation much like sprinters, once they go beyond their first turning point (LT1, aerobic threshold) then they are soon on the irreversible path to total exhaustion (if they try to maintain what they are doing) to lactate accumulation and exhaustion, either at slightly greater intensity or duration, because the muscles are flooded by acid. This is probably what many mean by ‘low lactate tolerance’, another public myth. The best strategy in this case is to use this turning-point (easily measureable in the lab), and start to build the base below, and increase the duration slightly above…in almost interval style process, but longer durations, so that they start to learn how to spread efforts. Then they may flip-flop this increasingly as the lactate/ heart rate/ power curve improves, and will ultimately become curvi-linear over months/ couple of years…and switch to anchoring zones to lactate threshold and they will be able to tolerate more pertinent intervals of greater intensity, as well as build threshold duration and intensity. Prior to this, less conditioned athletes would benefit from an easy/ moderate and severe intensity (anchored around both lactate turn-points) approach to training rather than defined zones, which also works well with younger competitors looking to get the basics right. Dr. Seiler touched on this during his keynote speech at the recent TPU.


We know that there are recommended durations of training time for each zone intensity, although these have been defined discretely it is actually a continuum of 3 separate energy pathways and muscle type recruitment. With respect to interval training above VO2max, this tends to reduce maximum O2 consumption, initiates effects of lactate acidosis and results in decreased training volume. Whereas working at 75-100% VO2max increases the tolerance for exercise at submaximal intensities. Accumulating time at VO2max is most effectively done at shorter intervals 4-8min for optimally 3-8 intervals, with no significant benefit at longer intervals at that intensity because of the cardiac drift effect, although again this is individually dependent. Longer steady-state session of 40-60 minutes, or less 20-40min work effectively for lactate threshold improvement. That’s not to say starting on the popular 5 x 5min isn’t a good means to reaching 20 minute efforts where aerobic capacity is improved the longer session improves lactate threshold duration and hence why the 2 x 20min session has become a ‘go-to’ workout for many. I have finally be able to publish my own proprietary interval session generator CPS-Gen which provides personalised interval sessions for each zone and combination of zones for specific preprartion…physiologically based, and downloadable….no guess work involved. Learn more and access the trial period here.

Ultimately, if the intensity is appropriate for a given interval session – an athlete should be able to complete all the intervals at the same speed/ power, and even the last one or two being faster with much greater effort. This would suggest that excessive lactic acid isn’t accummulated (which inhibits both oxygen utilisation and decreases fatty acid metabolism) during the session. Otherwise the athlete isn’t at the right intensity to optimise training stimulus. A prematurely abandoned session would leave the athlete exhausted and under stimulated.

Higher intensity interval sessions can work well as ‘triggers’ for race form closer to an event when lager volumes have been implemented and may be reduced to allow some freshness. Although sprint and anaerobic style workouts should be conducted more infrequently as they can leave an athlete physiologically stale and detracts from the overall volume of aerobic adaptations.

Of course as previously mentioned the caveats for this, I personally believe, are that these observations may be more relevant to steady-state athletes for than variable road cyclists which need an array of maximal intensity for different durations, but the same principle applies, developing aerobic capacity takes priority. Plus, as we see for beginner athletes, a layering of intervals will help condition the lactate curve to become more ‘mature’ when a bigger aerobic engine can sustain greater volumes of work at greater intensities.

Dr. Seiler continued on to suggest that consistency and volume of exercise at 70-90% VO2max in a training programme provides the biggest long term impact on progress, where this is more intuitive for marathon runners who target a variety of paces, this may not be so for other athletes involved in shorter or highly erratic racing. Training at near LT speed increases distance at LT rather than LT speed so long as the number of sessions ae kept low, as studies have shown that one threshold session (2 x 20min or 4 x 10min) can be more beneficial than two per week, probably because of the reasons I explained above, about ‘the dead-zone’. However, this also suggests that a maximal 20 minute effort is more worthwhile than a series of short duration 1-3min itnterval session, if that is the only time available.

Another aspect of training that was picked out Dr. Seilers hierarchy was how the type of periodisation probably doesn’t play as much of a role in an optimal conditioning as everyone likes to believe. This is pretty refreshing to hear even though I’m quite sold on the idea of periodisation as a form of variation I have come to realise, and see in practice this type of training distribution format of volume and intensity actually fits quite well with someone’s schedule, and the seasons they may be training. So perhaps the use of periodisation came after variation rather than precede or dictate it? At the end of the day, complexity and sophistication of training prescription isn’t necessary…but extemes of randomness of workouts may suggest other issues are afoot. Consistency and variation are the two main elements which everyone should include in their training, and that IS my professional recommendation…hopefully I have given you some tools to interpret that.

With such a long post, I will publish a separate one (here) about the components of nutrition Dr. Jeukendrup spoke about, which deserves an equal amount of time teasing out some of the misinformation that has pervaded the endurance sports scene.

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