Hard start VO2max intervals

I’ve had a few requests to share some hard start VO2max workouts I created.

I created the following team that has four workouts to start with.


The workouts are a variant on the one below - with 6 x 2.5 minute, 3.0 minute , 3.5 minute and 4.0 minute VO2max intervals.


The goal of these workouts is to get your heart rate up quickly to ~90% of maximum early in the interval, and then maintain it for the remainder of the interval at 90%+.

The first interval has the highest power target, and the power target declines slightly in subsequent intervals. The goal of this is to try keep RPE similar across the intervals, vs. having the first feel too easy and the last feel to hard (which can happen with a workout like Kaiser where all intervals have the same power target).

You can play around with the power targets for the initial spike during the first portion of each interval, as well as the steady power target during the second portion of each interval.

I used Kaiser as the base workout to modify - so don’t pay attention to the workout text as it doesn’t match these modified workouts.



VO2 work, made harder!! :exploding_head:

‘This looks like fun!’ said nobody, ever.


I actually find these easier than Kaiser. In Kaiser, the first two intervals felt “easy”, but I was barely able to get through the last two intervals, and sometimes “failed” them. And in the last two intervals, the first minute would feel “easy”, and it was the last 1.5-2 minutes that really destroyed me.

These workouts / intervals with gradually declining power work well for me.

1 Like

When I was doing POL in the summer, HS intervals were no problem. In the fall I did a few weeks of anaerobic training; I don’t know how long that carries overs but it can take me 2-3 intervals just to blow out the AN contribution, which means I’m really cooked by the last couple of intervals.

I think I need to do a different type of warm-up to counteract this.

1 Like

Yep - I have high anaerobic contribution also. Even with higher power intervals to start, and then declining, my HR rises as the intervals go by.

I’m going to try a version with higher power in initial intervals, and a bigger decline in subsequent.


Just read this:

Hunter Allen and Andrew Coggan in Training and Racing with a Power Meter recommend using the third interval of a VO2max-interval workout as your benchmark. They recommend stopping if your power output in subsequent intervals drops to more than 15 percent below that level.

Kinda works in the same prescription as HS – use the first couple to clear AN contributions; then, if you’re shooting for the standard 120% (e.g. 360w), allowable power could drop to near-threshold levels (~305w).

1 Like

And this (from a running article, so still leggy):

The contribution of the fast glycolytic system increases rapidly after the initial 10 seconds of exercise. This also coincides with a drop in maximal power output as the immediately available phosphogens, ATP and especially PCr begin to run out. By about 30 seconds of sustained activity the majority of energy comes from fast glycolysis (2). At 45 seconds of sustained activity there is a second decline in power output (the first decline being after about 10 seconds). Activity beyond this point corresponds with a growing reliance on the oxidative energy system.

Funnily enough, looking at my ilevels chart thingy, for the season, my Ae/An cross-over is exactly 1:00; for the last month it’s ~0:45…which lines up nicely with interval results. Damn science!

1 Like

Some possible ideas for further individualization:

  • A more ‘aerobic-dominant’ athlete can probably have a lower workload and/or shorter hard-start segment, and a longer work segment above FTP.

  • A more ‘anaerobic-dominant’ athlete may need to start harder/longer, but may have to allow work segment power to taper lower/shorter, but still above FTP.

  • The hard-start should probably not exceed MAP, ie. your peak power from a ramp test protocol. And the tapered power target MUST be above FTP. But otherwise in my opinion the precise workloads are less important than just doing the full duration of work, and can be adjusted day to day to optimize for RPE and completion, as @DaveWh mentioned.

  • Hard-starts can be less hard/shorter on each subsequent rep, which your workout example have built in. Rest intervals can be longer between subsequent reps.

  • If your HR is decreasing during the work segments after the initial hard-start, you might want to make your hard-start easier/shorter, and/or your tapered power target harder.


Could you explain that a bit more please, ie why? I’d have a hard time keeping it to MAP tbh.

1 Like

Yeah, I don’t understand the rationale behind that at all.

Not a firm rule, definitely just speculation right now based on VO2 kinetics (how quickly VO2 rises) with increasing intensity above FTP. Kinetics may actually get slower, or at least plateau at MAP. Meaning no further or diminishing benefit gained to speeding VO2 response, at the cost of expending more energy & substrate resources to get there.


I thought this was another good option for when you’re trying to get these adaptions when you are using erg mode (even though I’d recommend resistance mode)

1 Like

Great ideas. I think dialing these in to get the HR response you want is pretty individualized.

In my next iteration, I’m going to make the steady work portions of the initial intervals higher, and lower in later intervals. I’m looking at dialing in to a similar HR across each of the intervals. With the workout above, my HR and RPE rise with each interval.

Good video. The first half had a succinct overview on VO2max.

I don’t get the reason to decrease power after the hard start, then increase it again half way through the VO2max intervals however. If the goal is to keep HR elevated, then you don’t want to let HR drop too much in the first place - so why drop power only to raise it again? Seems unnecessary vs keeping a constant power.

But that’s splitting hairs. At the end of the day, time at high HR is what counts.

It might not be a physiological outcome they’re chasing; maybe a psychological one. E.g. an end of race scenario where you’ve buried yourself but need to dig for those extra watts to pull it out. Just a thought.

1 Like

Did some hard-start & cadence testing today; weird because I’ve been doing them for well over a year now, but this block is different somehow, not smooth at all. I think I’m just out of VO2max shape! :tired_face:

I need to do more short hard efforts (45s) in warm-up to hopefully burn off more anaerobic cont. (and get the heart fired up!). Too much work to “waste” those first couple of intervals.

Doing the intervals w/o hard starts, and with “normal” cadence and steady power, esp the early ones, it can take my HR up to 2min to reach VO2 speed.

What seems to work best is a very high cadence (~130) hard start (130-140%) for the 45-60s and then dropping to 100-110 to finish.

Structuring the workout, just like @DaveWh did, w/ harder, faster hard starts earlier (if I don’t alter the warm-up); might even get away with doing the last 2/3s w/ steady-state cadence and power.

Just some thoughts. :man_shrugging:t2:

sure, I’ve been doing a lot of endurance training and on Saturday did a 7+ minute vo2 effort and after a while followed up with one max effort 2 minute effort. Even without a) hard start, b) high cadence (averaged ~80rpm), and c) high HR (4bpm under LTHR), the legs were fine but lungs/brain gave out. This type of conditioning comes back quick.

These things all factored into my thinking when I created the hard start workouts. My response to VO2 max is very similar to yours.

Wicked. Thanks, not that I’ll need these until March

I applied this approach to 30/15 intervals. I do not know if there are any negative correlations to this approach, but it is the one workout that pushes my heart rate up nicely and keeps it there. It is my favourite VO2 max workout.

I think the ranges are quite individual, but in my case they range from 150-145% (initial 30sec intervals) to 120%, whereas the last intervals are just to delay the drop in heart rate. They are not really “hard” anymore.

I often struggle to keep my HR up with VO2 work and mostly my legs are the limiting factor, while for this workout my HR is also highly elevated and stays there. I think I am more of an fast twitch guy with a very high anaerobic contribution.