These are exciting times to be an endurance training geek. We seem to have entered a new period in which exercise scientists are taking the lead in coming up with innovative new workout formats. It makes sense. For many decades, humanity knew so little about how to train optimally for endurance performance that the majority of innovations simply had to come from folks in the trenches—namely coaches and athletes—throwing stuff against the wall and seeing what stuck. The role of scientists was to come along afterward and confirm that what seemed to work best in the real world really did, and to explain why.
In the past several decades, however, the pace of innovation has slowed greatly, a sure sign that we’ve gotten pretty close to the point where training methods cannot be improved any further. Being close to this point is not the same thing as being at this point, however. There’s still room to innovate, but it’s more a matter of fine-tuning now; the days of radical tacking are gone for good. A different sort of expertise is required for this task—a sort that scientists are showing themselves to be well suited for.
Specifically, exercise scientists have lately been using their knowledge of why some training methods work better than others to create workout formats that work better still. True to their nature as scientists, they are very focused on measurable fitness variables such as VO2max, Their way of innovating, therefore, is to in seek out ways to enhance he fitness benefits of training without simply making workouts harder. Most of the new workout formats I’ve seen in the past few months have been designed specifically to boost the amount of time an athlete spends above 90 percent of VO2max in an individual session—known to be an especially potent fitness-boosting stimulus—as compared to a traditionally formatted workout of equal workload and/or perceived difficulty.
The latest offering comes from a trio of researchers working at the University of Udine, Italy. Their idea was to design an interval session featuring high-intensity work bouts that steadily decreased in length throughout the session. The rationale behind this design, as noted in a study published in the European Journal of Applied Physiology, was that past research had shown that longer intervals at high intensity allow athletes to reach VO2max quickly, whereas short intervals allow them to continue longer before reaching exhaustion. Would a set of decreasing intervals offer the best of both worlds, comparing favorably to a set of long intervals and a set of short intervals in these respects?
To find out, the researchers had 12 cyclists complete the following three workouts:
| Short Intervals | Long Intervals | Decreasing Intervals |
| 0:30 @ high intensity/0:20 @ low intensity repeated to exhaustion | 3:00 high/2:00 low repeated to exhaustion | 3:00 high/2:00 low 2:00 high/1:20 low 1:00 high/0:40 low 0:45 high/0:30 low 0:30 high/0:20 low repeated to exhaustion |
In all three workouts, the high-intensity efforts were performed at the highest power output each individual cyclist could sustain for 5 minutes and were repeated to exhaustion. Each subject completed all three workouts in random order on separate occasions. On average, the cyclists lasted 13 minutes and 20 seconds and spent 5 minutes and 12 seconds above 90 percent of VO2max in the decreasing intervals workout, compared to 11:54/3:02 in the short intervals workout and 11:04/2:59 in the long intervals workout.
The researchers concluded that “despite the higher stimulation of VO2, the rate of perceived exertion and the other physiological parameters at the end of the exercise were not different compared with long- or short-interval HIIT, suggesting that [the decreasing intervals format] was not more demanding. In light of the favorable or similar physiological and/or perceptual
responses to [decreasing intervals] compared to the other protocols and given the improved capability to prolong the time close to VO2 peak, it could be used as a preferable method to elicit similar or greater physiological adaptations.”
Sound like decreasing intervals are simply better, right? And if so, they should completely displace short- and long-interval VO2max sessions in the training process, right? Not so fast. As interesting as it is, this study falls far short of constituting a total contextual evaluation of these three interval formats. It’s important not to lose sight of the fact that doing five 3-minute intervals at your 5-minute maximum power is a different experience from doing decreasing intervals. The suck that you feel toward the end of the former is more similar to the suck you’re going to experience in races, and I think there’s a lot to be said for that. Therefore I have no intention of expunging traditional VO2max interval workout formats from the training I prescribe for the athletes I coach or for myself.
Still, I’m excited about decreasing intervals, and indeed I’ve already begun to prescribe them to athletes I coach and to practice them in my own training. They can be done either on a bike, as originally designed, or as a run. If you do them on a bike, complete the high-intensity intervals at 117 percent of the average power output you achieved in your most recent 20-minute FTP test. So, if your 20-minute power is 293 watts, do the high-intensity intervals at (293 x 1.17 =) 342 watts. If you choose to do decreasing intervals as a run, complete the high-intensity intervals at maximal aerobic speed (MAS), which is the fastest pace you could sustain for about 6 minutes.
Note that the subjects in the study I described performed decreasing intervals to the point of exhaustion solely for the sake of determining which of the three formats allowed them to continue the longest. When doing decreasing intervals as a part of your normal training, you may want to stop short of exhaustion. Specifically, I suggest you complete the sequence just once on your first try to get a feel for it. If you’re game for a tougher challenge, the next time you do decreasing intervals, go back to the top of the sequence immediately after the 20-second recovery and continue until you can no longer hold power on the bike or until you’ve “had enough,” if you’re running. On average, the study participants were able to complete only one full circuit plus part of a second 3-minute effort, so don’t expect the fun/suffering to last too terribly long.
