Intermittent Intervals for Threshold/VO2 Development

I’ve been trying intermittent high-intensity intervals (30/15s; 40/20s, etc) at a lower than all-out intensity to replace steady 5x5s or 4x8s.
Honestly, I do them because as an adult with ADHD, it’s really challenging to hold my attention for eight minutes!!
I do the hard part at a few percent over my target. For example, if I’m targeting threshold work, I work a few watts over the usual range.
My concern is that the intermittent part of the effort decreases the effectiveness of the threshold adaptations.
Any thoughts?

Get yourself a tool to keep your focus.
That could a bike computer, watch, app or human coach.

The difference in adaption between the two approaches has been researched, but not necessarily in a group that compares to your fitness level.
So just give it a try for a few weeks and see what happens. The learning experience is worth a lot.
And you don’t have to be afraid that your VO2max or FTP will drop 50%.


@SimpleEndurance, what kind of wattage or % are you targeting for your rest periods of 15, 20 sec, etc. when you come off the high-intensity portion?

Hi Ryan,
That’s a really good question. I was doing them by just turning the pedals over with recovery or about 50 to 60 percent of FTP. Otherwise, they’d be kind of like over/unders.
My thought centers on whether doing these about 105 percent works for building FTP power. Does the short rest “negate” the adaptation effects?
We do them at 120-130 percent and that works to build anaerobic capacity, correct? So does the same hold for threshold power?

Thanks @SimpleEndurance, for the clarification. I took a look back at some of my 30/30 sessions over the seasons to see how closely they relate to what you’re describing. By the way, I totally get what your saying in your original post about holding attention for 8 minutes, so I historically had a tendency to approach threshold intervals from a similar perspective.

Not exactly the same as your 30/15 or 40/20s, but in many of my sessions I would do 30/30. Even with 10-15s additional rest, it still worked to stay around threshold on average. I would hit around 85-92% of HRmax, 104% FTP, and average HR for the entire set is about 96% HR threshold. The difference among 90-100% FTP, 105% FTP, and 120-130% FTP is W’ balance. How much you tap into that will affect the rest the body needs. As you increase the intensity, it’s going to take somewhat less time to realize the benefits paired with more recovery, so this would be an approach I might save for closer to a competition or the season. Leading up to that point, I would aim to keep your effort just below FTP to maintain as much strain as possible on the aerobic system. If you do go with an over/under approach, I would just try to minimize the change in power necessary while keeping HR as steady as possible in that sub-threshold range. (e.g., 30s @104% // 15s @89% FTP)

From personal experience, I’ve realized positive gains from the 30/30 type of approach, but those gains were shorter lived. When I was able to be steady with the efforts, the gains were longer lasting. So I’m not sure that I’d say that short rest necessarily “negates” the adaptation effects; just that those effects may be “different.” Still positive, but different.

I hope that’s helpful!