Here is a closer look at an old but new, alternative interval workout that satisfies many of the criteria for improving endurance performance and has been scientifically proven effective over and over again for the past 20 years (and in practice for decades before).  This workout is less mentally challenging than traditional intervals while spending a similar amount of time at VO_2max, and at VO_2max pace/intensity.

What is VO_2max?

VO_2max, or your aerobic capacity, is defined as an individual’s highest rate of oxygen consumption (milliliters of oxygen per kilogram of body weight per minute). Most athletes can work at VO_2max for only about 5 to 9 minutes in a competitive environment, so the velocity at VO_2max for many runners is close to their all out 1 mile race pace.  Logically, interval lengths to use in training to target VO_2max need to be shorter than 5 minutes. If the interval is too short and rest too long, then the anaerobic contribution is big, but there is not enough time to actually get to VO_2max. Conversely, if the interval length is too long, the pace is not sustainable or repeatable.  We suggested that ideal interval lengths (when using 1:1 work:rest ratio) should be 1.5-4  minutes, and we narrowed that ideal range to 2-3 minutes so it is both tolerable and effective.  However, what if we told you there was another way?

The Workout

A workout that has been around for decades and has been apart of my arsenal since college, is called “Billat Intervals” or the “Billat 30-30 workout”.  I use the term “VO₂ Float” intervals because it describes the physiological process that is happening. You end up floating your oxygen uptake near 90-100% of maximum for much of the workout.  This is an intermittent interval workout with short work intervals and short rest intervals.  During the first couple bouts, heart rate lags and you do most of the hard work anaerobically.  But with a short recovery, your body has no choice but to ramp up oxygen uptake to near maximum for most of the rest of the workout.

How to do it

In the study from 2000, the subjects performed the 30-30 workout until they could no longer maintain their pace at VO_2maxvelocity.  On average, the subjects completed 19 minutes until exhaustion set, or 9 minutes, 30 seconds at VO_2max pace.  So a simple way to perform would be to alternate 30 seconds hard, 30 seconds easy for 15-20 minutes.   The workout I use most often is 3 sets of 10 x 30 sec hard/30 sec easy.

The finer points

For a runner, it is critical to be at your VO_2max velocity or about your 1 mile race pace.  Often this is done on a track.  Recovery is active and somewhere around 50% of your VO_2max velocity.  So if you are running at 6 min/mi pace for the hard effort, the easy effort is around 12 min per mile pace.  It seems that the recovery intensity is not as important as long as it is active and you can continue to hit the proper intensity for the hard efforts.  One variation I like to use for the runner is a workout I call “straight-aways”.  I like to use this early season as an introduction to track workouts.  The idea is that you run the straights fast and the curves easy, continuously for about 3 miles.  This works best on the older style track where the straights are longer and the curves shorter.  If you are running on a track build in the last 20 years, likely the curves are longer so you might need to run part way into the curve to keep about a 1:1 time ratio of work to recovery (2:1 ratio if you measure distance).

For cyclists familiar with power training, the intensity that corresponds with VO_2max is about 120% of threshold power.  The standard VO₂ Float workout I like to use is 3 sets of 10 x 30 seconds.  I build these workouts in ergometer mode so there is no toggling up and down to try to hit the right intensity.

Why do it?

The main reason to do this workout is because it is tolerated well since work intervals are short, and demonstrated extremely effective.  Recovery is incomplete so you end up spending a majority of time at 90-100% of VO_2max and half of time at 100% of VO2 max pace or power.  In the original study, three of the individuals were able to complete 22-27 of these efforts and spend 18+ minutes near VO2 max.  The reason is that after a few bouts, you end up spending much of your recovery near maximum oxygen uptake.  This workout is of particular interest to me since VO_2max velocity/power is challenging to sustain for long periods at moderate to high altitude.

When to implement

One way to use this workout is as a precursor to standard VO_2max intervals.  It can be done early season as a prep for harder track workouts to come.  They can also be progressed to a 2:1 work to rest ratio.  That could be 40 seconds work to 20 sec rest, or 30 sec work to 15 sec rest.  I also like easier versions of this workout during a taper because it seems less stressful but good for sharpening.

What’s old is new again

In 2018 a new study was published with a slightly different twist. Rønnestad (2018) described a “new” workout regimen with intermittent cycling intervals with 30 seconds on, 15 seconds off.  The main workout described was three sets of 13 x 30/15. Results were astonishing, but not if you have been following the research.  What’s old is new again.

VO2max, or your aerobic capacity, is defined as an individual’s highest rate of oxygen consumption (milliliters of oxygen per kilogram of body weight per minute). Most athletes can work at VO2max for only about 5 to 9 minutes in a competitive environment, so the velocity at VO2max for many runners is close to their all out 1 mile race pace.  Logically, interval lengths to use in training to target VO2max need to be shorter than 5 minutes. If the interval is too short and rest too long, then the anaerobic contribution is big, but there is not enough time to actually get to VO2max. Conversely, if the interval length is too long, the pace is not sustainable or repeatable.  We suggested that ideal interval lengths (when using 1:1 work:rest ratio) should be 1.5-4  minutes, and we narrowed that ideal range to 2-3 minutes so it is both tolerable and effective.  However, what if we told you there was another way?

The Workout

A workout that has been around for decades and has been apart of my arsenal since college, is called “Billat Intervals” or the “Billat 30-30 workout”.  I use the term “VO2 Float” intervals because it describes the physiological process that is happening.  You end up floating your oxygen uptake near 90-100% of maximum for much of the workout.  This is an intermittent interval workout with short work intervals and short rest intervals.  During the first couple bouts, heart rate lags and you do most of the hard work anaerobically.  But with a short recovery, your body has no choice but to ramp up oxygen uptake to near maximum for most of the rest of the workout.

How to do it

In the study from 2000, the subjects performed the 30-30 workout until they could no longer maintain their pace at VO2max velocity.  On average, the subjects completed 19 minutes until exhaustion set, or 9 minutes, 30 seconds at VO2max pace.  So a simple way to perform would be to alternate 30 seconds hard, 30 seconds easy for 15-20 minutes.   The workout I use most often is 3 sets of 10 x 30 sec hard/30 sec easy.

The finer points

For a runner, it is critical to be at your VO2max velocity or about your 1 mile race pace.  Often this is done on a track.  Recovery is active and somewhere around 50% of your VO2max velocity.  So if you are running at 6 min/mi pace for the hard effort, the easy effort is around 12 min per mile pace.  It seems that the recovery intensity is not as important as long as it is active and you can continue to hit the proper intensity for the hard efforts.  One variation I like to use for the runner is a workout I call “straight-aways”.  I like to use this early season as an introduction to track workouts.  The idea is that you run the straights fast and the curves easy, continuously for about 3 miles.  This works best on the older style track where the straights are longer and the curves shorter.  If you are running on a track build in the last 20 years, likely the curves are longer so you might need to run part way into the curve to keep about a 1:1 time ratio of work to recovery (2:1 ratio if you measure distance).

For cyclists familiar with power training, the intensity that corresponds with VO2max is about 120% of threshold power.  The standard VO2 Float workout I like to use is 3 sets of 10 x 30 seconds.  I build these workouts in ergometer mode so there is no toggling up and down to try to hit the right intensity.

Why do it?

The main reason to do this workout is because it is tolerated well since work intervals are short, and demonstrated extremely effective.  Recovery is incomplete so you end up spending a majority of time at 90-100% of VO2max and half of time at 100% of VO2 max pace or power.  In the original study, three of the individuals were able to complete 22-27 of these efforts and spend 18+ minutes near VO2 max.  The reason is that after a few bouts, you end up spending much of your recovery near maximum oxygen uptake.  This workout is of particular interest to me since VO2max velocity/power is challenging to sustain for long periods at moderate to high altitude.

When to implement

One way to use this workout is as a precursor to standard VO2max intervals.  It can be done early season as a prep for harder track workouts to come.  They can also be progressed to a 2:1 work to rest ratio.  That could be 40 seconds work to 20 sec rest, or 30 sec work to 15 sec rest.  I also like easier versions of this workout during a taper because it seems less stressful but good for sharpening.

What’s old is new again

In 2018 a new study was published with a slightly different twist. Rønnestad (2018) described a “new” workout regimen with intermittent cycling intervals with 30 seconds on, 15 seconds off.  The main workout described was three sets of 13 x 30/15.  Results were astonishing, but not if you have been following the research.  What’s old is new again.