Part 17: 30-30 Intervals

by Shawn Burke, Ph.D.

SUMMARY

In this installment of The Science of Paddling we’ll investigate Billat’s “30-30” workout as a way to improve VO2max. We’ll use a teeny bit of physics to adapt her workout protocol to paddling.

INTRODUCTION

The most competitive paddlers have great biomechanics, a high lactate threshold and lactate threshold pace, the ability to “get power in the water,” and a high physiological capacity to process oxygen during races (usually characterized by VO2max, or the maximum volume of oxygen uptake one can process during a particular aerobic activity). All of these are trainable. And while it’s tempting to consider each in isolation, these factors play off each other. For example, an improvement in biomechanical efficiency can lead to improvements in VO2max without increasing the number and density of mitochondria (the little cellular engines that process oxygen to produce energy) in the working muscles.

For a given level of fitness, paddling VO2max is inherently tied to pace since the maximal oxygen consumption threshold occurs at a certain pace/speed.[1] Consequently, one predictor of racing performance is velocity at VO2max,[2] commonly written as “vVO2max,” which is the lowest sustainable speed at which you perform at maximum oxygen consumption. For example, if during testing your rate of maximal oxygen consumption is first achieved at a paddling speed of 7 mph, and then shows no increase at higher speeds, then your paddling vVO2max is 7 mph.

An improvement in VO2max will increase your vVO2 max, as well as the time you can maintain this pace. Since VO2max is trainable, what is the best way to increase it? Since VO2max depends upon improvements in both biomechanics and aerobic capacity, one obvious way is paddle more (and use good form!). Another way is to train at vVO2max. But since performing at vVO2max is usually sustainable for somewhere between 6 and 11 minutes (depending on which publication you read!), and this type of workout is really taxing, is there a way to bank more time at VO2max without undue recovery time, or possibly overtraining?

At this point many readers will be saying, “Do intervals!” And they’re right. But is there an optimal type of interval workout to maximize time at VO2max? And since this is a Science of Paddling article, can it be adapted to paddlers?

In this installment of The Science of Paddling we’ll consider “Billat’s 30-30” workout as a way to achieve this. Since the Billat 30-30 was initially developed for runners we’ll use a bit of physics to adapt it so as to match her protocol, which is based on percentages of vVO2max. In doing so we’ll see why paddlers may wish to take into account the difference in the relationship between power and speed for running vs. paddling in order to reap the full metabolic benefit of Billat’s 30-30.

WHAT’S A 30-30 WORKOUT?

The Billat 30-30 is named after its creator, Veronique Billat, an exercise physiologist at the University of Ille. Billat studied and compared various workouts that allow runners to spend the greatest total amount of time at VO2max, and presumably produce the greatest increase in VO2max. She and her colleagues found that runners seeking to improve VO2max should run no faster than vVO2max since they fatigued more quickly at faster speeds. Then, they found that a runner’s rate of oxygen consumption remains at or near VO2max for as much as 15-20 seconds after they stop running at vVO2 max pace. A workout designed to exploit this “lag” phenomenon would allow a runner’s body to spend more time at VO2max while spending less time running at vVO2max.

This prescription naturally lends itself to intervals performed at vVO2 max with short recoveries at a slower speed. Billat and her colleagues set this recovery pace at 50% of vVO2 max. The protocol they settled on consists of 30-second bursts at vVO2 max separated by 30-second recoveries. This workout is repeated to failure, e.g., until vVO2 max can no longer be sustained for 30 seconds over a given interval. Keeping the interval work phases short delays muscle fatigue; keeping the recoveries short keeps the body effectively working at or near VO2max while operating at a slower and more muscle-friendly pace.

Using this format some runners were able to spend more than 18 total minutes at VO2max in a single workout, with up to 1/3 of that total time accrued during 50% vVO2max recoveries. A group of moderately fit runners increased their VO2max by 10 percent in 8-10 weeks after undertaking twice weekly 30-30 sessions. For competitive athletes, a 10% increase in VO2max is huge!

NOW, TIME FOR PHYSICS & STUFF

A 30-30 interval workout sounds like a pretty productive use of one’s workout time; I know a member of the US Wildwater team who uses them to good effect. And as I write this, most of us in the Northern Hemisphere are in or about to enter our offseason aerobic base-building phase; workouts that improve VO2max fit the bill. So… go! Do them now… or soon!

Or, if you’re like me, you might ask the question, “Is half of vVO2max the same for runners and paddlers?” In other words, if I perform a paddling interval workout with work phases done at vVO2max,[3] if I halve my paddling speed during the recovery phase will I get the same effect as a runner who halves their running speed during recovery? In other words, will I match Billat’s 30-30 protocol physiologically if I just halve my speed on the paddle erg?[4]

What follows is a “modest proposal,” based on a syllogism and a little bit of physics since the Science of Paddling’s world headquarters doesn’t have a gas analyzer (or funding).

In order to motivate the syllogism we’ll first examine the relationship between walking / running speed and oxygen consumption, depicted in Fig. 1 for a 70kg athlete based on an ACSM model:

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Fig. 1: Model of running O2 consumption rate vs. speed (mph).

Note that there is a breakpoint in O2 consumption between walking and running since the biomechanics and muscle engagement differ between these two modes of movement.[5] Also, this model doesn’t incorporate the plateau in O2 consumption that occurs at vVO2max. The relevant takeaway here is that the relationship between O2 consumption and speed for running over a range of running speeds is linear.

Next, consider the relationship between walking / running speed and power, depicted in Fig. 2 for a 70kg athlete based on the same ACSM model:

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Fig. 2: Model of running Power vs. speed (mph).

Note again that there is a breakpoint in this power plot between walking and running since the biomechanics and muscle engagement differ between these two modes of movement. The relevant takeaway here is that, like in Fig. 1’s plot of running O2 consumption vs. speed, the relationship between power and speed for running over a range of running speeds is linear. This model is supported by field test data; see the References for more info. So, if I go out on a limb I can contend that for running there is a correlation between O2 consumption and power expenditure in that both linearly depend on running speed.

Now those of you who have read Part 1 in the Science of Paddling series will know that, for paddling, the proportionality between paddling power and hull speed is cubic, not linear:

{{v}_{hull}}\propto \sqrt[3]{P}\to P\propto v_{hull}^{3}

where “\propto ” means “is proportional to.” Since paddling power is produced metabolically, I will again go out on a limb and contend that paddling O2 consumption will have this same cubic relationship to paddling speed in light of the correlative dependence of running O2 consumption and running power expenditure vs. speed noted above.[6] So if you wish to determine the speed that will halve the power expended (which should also halve O2 consumption using the running analogy), for paddling you need to take into account the cubic relationship between power and speed. In mathematical terms,

\sqrt[3]{\frac{P}{2}}\propto 0.794\cdot {{v}_{hull}}

where 0.794 is the cube root of one half rounded to three digits[7]. Consequently, in light of the relevant physics Billat’s “50% vVO2max” for paddling is instead 79.4% vVO2max. To perform a paddling Billat 30-30 interval workout, one alternates between 30 second work phases at vVO2max and 30 second recovery phases at 79.4% vVO2max. Or if you like round numbers, 80% vVO2max; it’s close enough!

For those of you who have done intervals on the water this is plausible since going from a work phase at (for example) 7mph to a recovery phase at 3.5mph (50% of 7mph) feels like you’re hardly working at all. The goal of Billat’s 30-30 is to allow the muscles to recover enough while keeping the body metabolically working at or near VO2max. By contrast, going from 7mph to 5.6mph (80% of 7mph) feels qualitatively about “half as hard.”

If you are ready to take the leap (or… do the intervals) I’ve compiled a table of possible vVO2max speeds / paces and their corresponding 80% speeds and paces. Paces for those who train on Concept 2 ergometers – or who prefer MKS units – are included since these commonly display pace in units of min/500m.

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Table 1: Speed, pace, and 80%.

A 30-30 INTERVAL PROTOCOL FOR PADDLERS

Before we go any further, a message from our friends at Dewey, Cheatem & Howe:

This article is provided for your personal enjoyment and educational use. While best efforts have been used, the author is not offering medical or any other professional services advice and makes no representations or warranties of any kind and assumes no liabilities of any kind with respect to the accuracy or completeness of the contents, and specifically disclaims any liability of any kind with respect to the fitness for use for any particular purpose, nor shall the author be held liable or responsible to any person or entity with respect to any loss or accidental or consequential damages caused, or alleged to have caused, directly or indirectly, by the information contained herein. The discomfort described herein relates to the normal range of stress reactions. If you believe for any reason that you have physical (or mental) symptoms that require medical attention, get proper help immediately.

Now that we have that out of the way, what is the 30-30 workout protocol, and how to you determine your vVO2max? First, the only sure way to determine VO2max and vVO2max is in a properly-outfitted lab with a gas analyzer. Lacking that, you can get a good approximation by paddling a time trial of between 6 and 8 minutes (after a thorough warmup, of course. And don’t forget to cool down afterwards!) The speed you are able to sustain over that time trial will be reasonably close to vVO2max. You’ll get feedback from the 30-30 interval workout itself that will help you tune your vVO2max speed going forward

Billat’s 30-30 workout for paddlers is then:

  1. Do a thorough warmup of at least 10 minutes of easy paddling;
  2. Paddle at vVO@max for 30 seconds (work phase)
  3. Paddle at 80% of vVO2max for 30 seconds (recovery phase)
  4. Repeat steps 2 and 3 until you can no longer maintain vVO2max during the work phase.
  5. Cool down with easy paddling for at least 10 minutes

Modern sports watches can be programmed to provide timed alerts at 30 second intervals. A GPS sports watch will help you set pace if you’re doing the workout on the water; a performance monitor will help if you’re using a paddling ergometer.

How many intervals should you be able to perform? Somewhere between 12 and 20. If you can do more than this your vVO2max is too slow; you should increase it a bit until you can do around 12-16 intervals, and no more. And if you can only do less than 12, no problem; just dial back your vVO2max a bit for the next 30-30 workout. Over time the number of intervals you can do will increase, as will your vVO2max. You can adjust the protocol accordingly. Since this is a High Intensity Interval Training (HIIT) workout most of us will do it no more than once per week after we’ve completed our Winter/Spring aerobic base training. Continue doing the paddling Billat 30-30 workout once a week for, say, 3-4 months, or until you hit your transition phase and race season.

Experiment! You can tweak the recovery time to as short as 20 seconds and increase the work interval to 40 seconds. Or, if your sights are set on long distance (marathon and ultra-marathon) races consider adding 10-30 minutes of aerobic paddling after you’ve recovered from your last 30-30 interval, but before the cool down. This type of workout addition is advocated by the Hanson brothers (no; not those Hanson brothers) in their book Hanson’s Marathon Method as a way to increase weekly mileage without lumping most of your overdistance time into a single, very long workout – you’re already working out anyway, plus adding aerobic mileage right after a hard effort acclimates you to working through the “tiredness” of a long race. So… get creative, have fun, and go get some more VO2max.

FINAL THOUGHTS

In previous Science of Paddling articles we’ve considered lactate threshold and lactate threshold pace (see Part 12: The Deflection Point), getting “power in the water” (see Part 1: Tandem vs. Solo, as well as Part 9: Power to the Paddlers), matters of exercise physiology (see Part 6: What Fuels You), and touched a bit on biomechanics (see Part 11: About the Bend). So it was inevitable that we would take a look at VO2max, another factor that plays a role in race performance.  What I enjoy about writing these particular articles is that they present something actionable that is motivated by understanding.  That’s where the fun is.

The Billat 30-30 interval workout offers the promise of improving VO2max with less risk of overtraining. For that reason alone it’s worth adding it to your off-season workout program. The tweak here is to offer a recovery speed for paddlers that reflects the protocol Billat and her colleagues developed, motivated by parallels and differences between running and paddling. We’re all looking for ways to get the most out of our paddling workouts. I hope this helps you in getting the most out of yours.

I also encourage you to read Billat’s articles, which are listed in the References section. They’re accessible to most readers and can give further insight into the workout protocol and its physiological basis.

And finally, if you want to endow a lab here at the Science of Paddling world headquarters to validate this protocol, send me an e-mail. I already have the erg.

REFERENCES

https://www.topendsports.com/testing/running-power.htm

F. García-Pinillos et al, “Prediction of power output at different running velocities through the two-point method with the Stryd™ power meter,” Gait & Posture 68, pp. 238-243 (2019).

S. DeMarie, J.P. Koralsztein, and V.L. Billat, “Time limit at time at VO2max during a continuous and intermittent run,” J. Sports Med. Phys. Fitness 40, pp. 96-102 (2000).

V.L. Billat et al, “Interval training at VO2max: effects on aerobic performance and overtraining markers,” Medicine & Science in Sports and Exercise, pp. 156-163 (1997).

V.L. Billat et al, “Intermittent runs at the velocity associated with maximal oxygen uptake enables subjects to remain at maximal oxygen uptake for a longer time than intense but submaximal runs,” Eur J Appl Physiol 81, pp. 188-196 (2000).

© 2019, Shawn Burke. All rights reserved.

v1.0

  1. We consume oxygen (O2) as part of our metabolism. While there is a certain amount of oxygen processed while we’re at rest – our so-called basal metabolism – we process more oxygen as we become more active. Oxygen uptake depends upon which muscles are engaged in an activity, and the degree to which they are working. Paddling will engage some different musculature than, say, running. As you paddle faster you consume a greater volume of oxygen, until you reach a level of effort and hence speed where your body cannot process more; this is your VO2max for paddling. Hence VO2max’ dependence on pace (or speed, which is the inverse of pace) as well as the type of activity (paddling vs. running vs…).
  2. Yes, velocity is a vector, and what is really meant here is speed, which is a scalar. But vVO2max is a term of art, so we’ll use it.
  3. We’ll suggest ways to approximate vVO2max based on a simple time trail. Or you can go to a sports testing lab.
  4. Note that this question is different than, “Will I get the same improvement in VO2max if I just halve my speed?” To this, I have no answer; not enough data. In this article we’ll limit ourselves to looking for ways to match Billat’s protocol. This is an important distinction.
  5. There is a similar breakpoint in the relationship between foot contact time and pace between walking and running. In each mode of movement the relationship is linear, but the slopes of these relationships are different.
  6. I know; it’s a Christmas miracle. But work with me here…
  7. And for you completists out there I’ve neglected the complex-valued roots since I’m not sure what imaginary time means.