I’ve discovered the ultimate, magical, fitness-boosting super-workout several times over the past few decades. Usually it came after switching to a new coach or training regimen. In high school, for example, I generally did either long intervals with short rest or short intervals with long rest. My university track coach, on the other hand, gave us long intervals with long rest, like 4 x 1,000 meters with three or five or even seven minutes of rest. It took me a while to adjust, but once I did, my race times dropped. A few years later, I discovered short, steep hills; after the next coaching switch, it was long progression runs of up to 16 miles.
Eventually, I saw the pattern. Any given training program, no matter how balanced and well thought-out, emphasizes some aspects of fitness and deemphasizes others. Every time I switched to a different program, there’d be at least one new ingredient that pushed an aspect of my physiology that I’d been neglecting for a few years. The “magic” workout, in other words, was specific to me at that moment in time, not a universal elixir begging to be copyrighted and sold to the masses.
It’s with this caveat in mind that I present the results of an interesting new study from Bent Rønnestad and his colleagues at Inland Norway University of Applied Sciences, in the Scandinavian Journal of Medicine and Science in Sports. In a group of 18 elite cyclists with an impressive average VO2 max of 73 ml/min/kg (a value in the 50s would be considered “excellent” for typical adults), they demonstrated that very short (30-second) intervals with even shorter (15-second) recoveries produce bigger performance gains than a longer bread-and-butter session of 5-minute intervals with 2.5 minutes of rest. It’s not a magic workout—but the results are worth considering.
The training program involved three weeks of thrice-weekly workouts: either 4 x 5 minutes with 2.5 minutes of recovery, or three sets of 13 x 30 seconds with 15 seconds of recovery and three minutes between sets. The cyclists were all fit, and had all been training 16 to 17 hours a week in the period leading up to the study.
Crucially, the workouts were “effort-matched”—that is, the subjects were instructed to go as hard as they could sustain for each workout. In a lot of interval studies, the power output is controlled to ensure subjects burn the same amount of energy in both workouts. But that’s misleading, because it’s not how we pace workouts and plan training weeks in the real world: what matters is how hard it feels.
The key result is that the short-interval group improved mean power in a 20-minute cycling test by 4.7 percent after three weeks of training, while the long-interval group improved by only 1.4 percent. They also had a 3-percent increase in power output at a blood lactate concentration of 4 mmol/L, which is a standard benchmark approximating lactate threshold; the long-interval group had a 3.5-percent decrease. Several other measures also suggested that the short-interval group had gotten fitter while the other group stagnated.
The new findings back up a previous study by the same group, which found essentially the same thing with less-trained (but still decent!) cyclists who had an average VO2 max of around 65 ml/min/kg. In that case, both groups improved. Extending training findings to elite athletes is always tricky, because they’re already so optimized, so it’s not surprising that the long-interval group didn’t improve in the new study—but that makes it all the more impressive that the short-interval group did.
In terms of why the short intervals worked, there was no improvement in VO2 max. But tellingly, average lactate levels during the 20-minute time trial increased from 5.4 to 7.5 mmol/L in the short-interval group; there was no change in the long-interval group. Doing all those short intervals with tiny snippets of rest seems to have improved their ability to tolerate high levels of lactate, perhaps by improving the capacity of the muscles themselves to buffer lactate. In contrast, a long interval with no rest forces you to start more slowly and spend less time overall in that high-lactate zone.
So should we all be doing short 30-second intervals instead of the more common 3- to 5-minute VO2 max intervals? Not quite. As I suggested at the top, I think the benefits of any given workout depend heavily on the context. These cyclists were already super-fit, and had just completed a training block that emphasized high volume and low intensity. They were already strong on VO2 max and weak on lactate—so it makes sense that they responded to the shorter intervals.
On the other hand, the VO2 max-heavy focus of the cyclists in the study is, I suspect, pretty representative of how most endurance athletes train. While lots of people (including me) pay lip service to the importance of sprinting, the truth is that most of us are out there racking up mileage and threshold sessions and long intervals. So, like the athletes in the study, we might benefit from this new magic workout—but probably not three times a week, every week. That’s the real failing of the “magic workout” mindset: the idea that the new thing should replace all the old things, instead of just adding to them.
For more Sweat Science, join me on Twitter and Facebook, sign up for the email newsletter, and check out my book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance.
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