MPA Doesn't drop during interval training

Recently I did a workout featuring over/unders, on the last interval I blew up and took some time backpedalling. When looking at my ride summary, the MPA line doesn’t drop very far at all. However on a recent FTP test it dropped at the end of my hard effort. Why does the MPA remain high despite the fact my legs were flooded with lactate? It seems like xert thinks I could maintain that power (physically) where psychologically I failed…but what’s the difference? A failed interval is the max you could put out at that time, isn’t it? Thanks

Brent, Thank you. Great question.

There are a couple of things I would look at when answering the question “Why doesn’t my MPA drop when I feel like I’m at my max?”.

  1. Check your numbers. One of things we see quite often is where the athlete uses one power meter to obtain their signature and another power meter during other hard efforts. This can throw off your efforts and can make them feel like they are impossible. Even a 5-10W difference, when doing intervals near FTP will make a huge difference to how much MPA will come down and how difficult the interval will be. Pay close attention to this.
  2. Lowering MPA hurts. Sometimes it hurts more than others. One of things we’re working on for the new year is a way to measure a new dynamic in fitness. We are calling it “hardness” which is a measure of how much strain an athlete is able to bear. One may never come close to reaching MPA but yet feel like they are at their limit. There are many aspects to fatigue and MPA doesn’t measure every one. It is, however, the main factor governing your best efforts, like those that define your power-duration curve. But when other factors get in the way of achieving your best - such as heat accumulation or carbohydrate depletion - MPA doesn’t capture those (at least not yet!). Look at how much strain you had accumulated when you were having trouble bringing MPA down and more often than not, there would have been a number of harder efforts beforehand.