Optimized Aerobic Prescription

Most of the amateur bike racers I know are limited by time available to train. I think this is a relatable limitation to all of us… So wouldn’t it be nice if an amateur endurance athlete could optimize the time they do have available to train, by establishing a minimum effective dose for eliciting adaptations.

How to the Pros Spend their Time?

We know how elite athletes spend their time, when time is not as much of a limiting factor.

Interestingly, maximizing recovery time in between training sessions becomes the limiting factor at high training volumes.

Stoggl & Sperlich in a 2015 Review article established that “the majority of studies [of elite endurance athletes] present a ‘pyramidal’ Training Intensity Distribution (TID) with a high proportion of high volume, low intensity training (HVLT).”

Stoggl & Sperlich, 2015
The trainingintensity distribution (i.e., percentage time spent in zone 1: < first ventilatory threshold or steady-state lactate at ~2 mM; zone 2: at or near lactate threshold (~4 mM) or second ventilatory threshold; zone 3: high-intensity training above lactate or second ventilatory threshold) in welltrained to elite endurance athletes in retrospective analyses during (A) preparation phase, (B) pre-competition phase, (C) competition phase, and (D) seasonal analysis.
The training intensity distribution among welltrained and elite endurance athletes
Front Physiol. 2015;6:295.

This means that many elite athletes spend the majority of time at low intensities, with decreasing amounts of time spent at increasingly higher intensities.

However we also know that Polarizing training between high and low intensities, and avoiding ‘moderate’ or Threshold intensity seems to offer greater potential benefits (Hydren & Cohen, 2015 & Seiler, 2010).

So we can we smarter than the Pros in how we spend our limited time by avoiding time in the moderate/threshold zone. But there’s a reason why even the Pros can’t spend hours at high intensity.

Limited Volume at High Intensity

We can understand intuitively that we are limited in how much work we can do at high intensity, either in a single exercise bout or during a training block. So we can quickly establish a maximum effective dose for the high intensity portion of our training plan.

In a Review article, Seiler (2010) established that “about two HIT [High Intensity Training] sessions per week seems to be sufficient for inducing physiological adaptations and performance gains without inducing excessive stress over the long term”. The studies he looked at found only equivocal benefits and clear signs of overtraining resulting from 3 or more HIT sessions per week.

Seiler, 2010

There are a few specific cases in which more than 2/wk HIT workouts can be beneficial, but these cases require very specific planning, adherence, and monitoring and so I’ll leave them out of the current discussion for now..

Otherwise, this seems to concur with typical popular training protocol, and I’m happy to limit my training plan to two HIT workouts per week for logistical convenience.

How much Aerobic is Enough?

The more indeterminate prescriptive element is the minimum effective dose for Aerobic training, to fill out the ‘easy’ portion of our Polarized training plan around our two HIT workouts per week. When time is limited, how do we know whether we’re accumulating enough Aerobic training load to elicit positive adaptations?

One simple answer would be: after I’ve accounted for my two HIT workouts, I should just spend as much time as possible training under my Aerobic Threshold!.. That would probably suffice, but we can try to optimize our time further.

Despite the idea of long slow distance as the “traditional” Base training structure, it was surprisingly difficult to find conclusive literature investigating adaptations to low intensity Aerobic training..

(although I’m not claiming to have done a comprehensive review of the past 60+ years of endurance physiology research, so I’m sure I’ve missed things)

One article I encountered on post-exercise hormonal response to low intensity continuous running (Tremblay et al, 2005) found that changes seemed to occur only beyond 80-minutes of steady activity.

Although the implications of these hormonal changes were unclear, with the study concluding that “Beyond 80-min of running there is a shift to a more catabolic hormonal environment, although whether this will ultimately have negative or positive consequences is debatable”. So something seems to be happening after 80-minutes of low intensity.

Tremblay et al, 2005

These and other findings were called back on by Seiler (2010) to reaffirm the descriptive findings that elite endurance athletes “achieve excellent results when accumulating a high training volume by emphasizing frequent exposure to 60-180min bouts performed at [low intensity]…”

best practice prescriptive summary
Seiler, 2010

How Frequent is Frequent?

One of the remaining questions to the recommendation for low intensity Aerobic training focused around the ~2-hr duration is that, many sports have shorter and more frequent training bouts than cycling:

Rowers, swimmers, triathletes and other endurance athletes often train twice a day, or as Seiler (2010) notes “Numerous descriptive studies of [elite] endurance athletes [converges on] training 10 to 13 times per week…”

Seiler, 2010

With more frequent training bouts, again recovery between bouts becomes more important in facilitating continued quality of training. This might help explain why pure cyclists, who typically train with a single extended training bout on the bike per day, commonly exceed the 2-hr duration recommendation.

As to the question of minimum frequency, Hydren & Cohen in their 2015 review of the literature on Polarized Training provided a “sample” pre-season Polarized training plan consisting of 2-3/7 (per week) HIIT workouts, and 3/7 Aerobic rides of 2-hrs or less, for  5-6/7 total rides and a net total 7-8 hrs/wk.

Hydren & Cohen’s (2015) sample pre-season Polarized training week, based on at least 5 key studies demonstrating consistent superiority of Polarized training for athletes of all training levels across multiple endurance sports

That may be achievable for time-constrained athletes and demonstrates that you don’t need to devote massive hours to gain the benefits of Polarized training. The priority is the two weekly HIIT workouts, then filling in whatever your remaining time is with steady Aerobic riding.

Coming to a Conclusion… For Now

Despite the questions remaining as to minimum effective dose for Aerobic adaptations, at this point I would recommend the following features to consider as part of your time-constrained training plan:

Optimized Aerobic Training Plan

    • Polarize your training: Spend most of your time at low intensity, under Aerobic Threshold, and a small but important amount of time way above FTP, around VO2max or ANaerobic intensities. Minimize moderate intensity, including Tempo, Sweet Spot & Threshold.
    • Aerobic training bouts should last at least 80-min to accumulate enough training load for significant adaptations.
    • Two high intensity interval workouts per week is sufficient to optimize adaptations. More than two often results in fatigue and overtraining, and diminishes training quality for very little benefit
    • More frequent Aerobic training bouts are better: there doesn’t seem to be a minimum frequency, but more frequent may be more beneficial than fewer longer bouts (although see why I still think including a long Stamina Ride in your training can give you an adaptive edge)



References (not comprehensive)

6 thoughts on “Optimized Aerobic Prescription

  1. Hello Jem,
    A perfect review as usual.
    I will start base period next week. I plan on practicing polarized training this year even if I applied the pramid training plan last year. And I think that it is absolutely necessary to study weight. How can weight studies be planned? Before or after HITT training? Or should I definitely put a day between the HITT workouts and weight training?


    1. Thanks Sefa, and great question! I haven’t done as much research into weight training, but what I have come across suggests Lifting should be part of every Endurance athlete’s routine at least at some point during the training cycle. Might be a topic for a future post 🙂

      The Prep and Base phases are the perfect time to include some kind of Lifting. For the most part, Lifts should be considered high intensity, so they will contribute to fatigue. For that reason I wouldn’t recommend Lifting on “recovery days”, as I used to do!

      I personally prioritize my bike workouts – my VO2max & HIIT workouts, so I want to ensure I’m fresh for those days. For that reason I tend to schedule my own Lift workouts *after* my HIIT workouts, either on the same day or the following day. The downside is that I’m fatigued for the Lift workout, but that’s a sacrifice I have to make to ensure maximal quality on the bike. Then I’ll give myself one or two days of low intensity Aerobic riding to recover before going into my next bike HIIT workout as fresh as possible.

      Just my opinion for now, but hopefully that gives you somewhere to start!


  2. Where does aerobic threshold sit in relation to FTP, or is it measured with HR? I’m new to cycling and this idea is intriguing. It seems simple. 2 HIIT per week, the rest below aerobic threshold? No more crazy SST complicated plans? Just 80/20? I keep hearing that those low intensity miles are called “junk miles”. Thanks for the references, and especially for a fantastic blog!


    1. Thanks Cory! There are a lot of different ways to get fast, and the body definitely isn’t simple! But the literature I’ve encountered seems to be trending toward consensus around Polarized training and a certain minimum volume of Aerobic work for Physiological Training. But yeah, Polarized training is basically just a little bit of very very hard work, and a lot of very easy worK!

      ‘Junk miles’ usually refers to riding in the ‘tempo’ zone or moderate intensity, eg. 75-95% FTP. It’s the kind of intensity that feels “just hard enough” but doesn’t really give you much training benefit. I do think there’s a time and place for Tempo rides, and SST falls at the high end of Tempo.. Actually, I’ve written before about the value of SST as I see it, and I do think SST belongs in Performance Training, but that’s for a future blog post 🙂

      Aerobic Threshold (AeT) and ANaerobic Threshold (AnT, or FTP) are represented as *both* Power and HR thresholds:

      Power reflects ‘energy out’ or how much Work you produce
      HR reflects ‘energy in’ or how hard your body is working to produce that output workload

      So the relationship between both is critical to understand. Joe Friel has a good summary of the different and overlapping terms

      AeT & AnT are measured precisely by lab tests via gas exchange or blood lactate, but they are fairly predictable and AeT can be reliably estimated if you know your FTP. AeT HR usually occurs anywhere from 75-85% of LTHR, and AeT Pwr is a bit tighter, usually right around 75% FTP.

      Hope that helps!

      Liked by 1 person

  3. Hey Jem

    The information provided is valuable and I want to give you a thumbs up for it. I want to say that Aerobic exercises today is recognized is the absolute necessity of healthy living. It is also fit for someone who is trying to lose weight or tone their muscles. The simplicity of an aerobics exercise program extends in its flexibility. It can be done almost everywhere, indoors or outdoors, and almost anytime.


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