-by Master Coach Sam Naney
Many athletes I work with throughout the year target long-duration events: high-altitude climbs, ultramarathons and big ski tours. As avid readers of Uphill Athlete literature know, the biggest bang for these athletes’ buck will be aerobic capacity-building training in the form of low-intensity, long duration work. Multi-hour climbs, weighted pack carries, long aerobic runs: the bread-and-butter of the diligent endurance athlete.
But for others there are competitions on the horizon. The 50km ultrarunner, the skimo racer with an eye on Patroille des Glaciers or the road runner-turned-Vertical-K aficionado all need to pay attention to their speed potential, and ability to prolong a higher pace output for longer duration in their events. Traditionally this means interval training, but what type? There are myriad flavors out there and perhaps more than any other form of exercise (with the exception of strength training), high-intensity interval training causes more ripples on the pond and more debate over correct protocol. None of these recipes for success are (or should be) secret, and there are only a few I employ across the spectrum of athletes I train. When I’m looking to build speed, particularly on varied terrain? I turn to 30/30s. (Interestingly and arrived at completely independently, Kilian Jornet uses 30/30s and says they are his preferred way of introducing intensity in his training program.)
I first heard of the :30sec on, :30sec off interval workout when Scott coached me and several other Nordic racers over a decade ago. He had read of a professor of Sport Sciences at the University of Lille in France named Veronique Billat who tested several different methods of increasing an athlete’s velocity at VO2max (vVO2max) with the aim of finding the one that gave the best results with the least stress to the athlete. The optimal protocol she arrived at was a :30sec fast, at around 90-95% of max speed with an 30 second recovery interval which we dubbed “30/30s”. Lacking a reliable vVO2max pace in Nordic skiing due to the varied nature of our race terrain, we targeted around 92-95% of max HR and during the equal rest portion we’d only allow the HR to drop about 5bpm. The effect of this was that we’d be skiing at a very high speed during the on-time, but not decreasing our speed that much during the recovery interval, despite the fact the perception of recovery was quite positive given the equal time on and off. In our early iterations of this workout I recall striding up a very steep road grade on roller skis, with Scott behind me in his car, honking the horn every 30 seconds to signal the intervals.
Why These Work:
The 30sec recovery interval allows the myoglobin in the muscle cell to recharge its small oxygen store which in turn allows a higher power output (and better engagement of Fast Twitch muscle fibers) for the next 30 second work bout. Fast Twitch fibers have poor endurance and will fatigue during longer work repetitions, therefore the short repeats with equal rest intervals allow more endurance training effect for them.
Fast-forward to present day: the 30/30 interval protocol remains an incredibly effective means of improving an athlete’s high-end speed without overly taxing them metabolically. Why? Because the :30sec on-time is not long enough to develop a high blood lactate concentration, which has the effect of decreasing power output by increasing the concentration of hydrogen ions and therefore acidity in the working muscles. Instead, the :30sec is just long enough to accelerate up to a high speed, hold it for 15-20sec and then decelerate into the rest. The cardiac demand stays relatively high with only a ~5bpm decrease during the rest interval so as far as your heart is concerned, you’re working quite continuously at or near your VO2max.
Perception-wise, athletes report leaving a 30/30 interval workout feeling invigorated and not overly wiped-out, often in stark contrast to sensations after finishing a more traditional VO2max interval workout with long-duration repeats. For the athlete in a technique-focused sport or one requiring high cadence such as Nordic skiing, skimo or running, these intervals allow you to maximize those efficient movements but then recover before fatigue sets in.
The best way to incorporate some 30/30s into your diet is to (surprise, surprise) build them on a foundation of good aerobic base capacity and some moderate Z3 intensity first. This readiness varies by individual so getting some outside input can be very helpful. When you’re ready to try the 30/30s out, start with one or two sets of 8-10min apiece, separating the sets by at least 5min of very easy movement. Use terrain which mimics your sport requirements and prioritize precision movement – both cadence and technique – to get the most out of the intervals.
A tip to get you started: let the first 4-5 intervals of the first set be part of your warmup: don’t try and peg the target intensity right from the start or you’ll blow up by the 5th 30/30; instead build gradually upward to the heart rate or pace you want to reach with an aim to get there midway through your first set. In this manner, you’ll be able to complete the subsequent intervals and sets with greatest efficiency and power.
Example 30/30 workout for Uphill Athletes:
- Warmup 20min easily, building up to your Aerobic Threshold on mellow terrain
- Complete 2x 2min in low-mid Z3, approaching your Anaerobic Threshold, taking 1 min rest between each
- Do 2x 8-10min of :30sec on, :30sec off, with the “on-time” at around 92-95% of your max heart rate and the “off-time” only allowing the heart rate to drop about 5bpm. Build the intensity gradually so you’re not reaching the target heart rate until interval #4.
- Take 5-10min easy recovery between sets, and cooldown with 15min easy (sub-AeT) movement when done
NOTE: The real benefits of this workout come from the volume of hard work so we typically build to where an athlete is eventually doing 1x 30min of 30/30s. Repeating the warning above: DON’T START TOO FAST.
Let the 30/30 workout be part of the finishing touches of your training leading into a speed-focused event, keeping in mind the timeless words of Uphill Athlete co-founder Scott Johnston, “Speed Kills…Those Who Don’t Have It!”