On Instagram, former Tour de France and Giro d’Italia champion, Egan Bernal posted a video about doing 30-30 intervals.
At it, Bernal is alternating between 30 seconds at high intensity and 30 seconds at low intensity. However, it’s still less discussed at which particular intensity these efforts should be performed. And what these intervals are good for?
We often read that short intervals of alternating intensities improve performance and they’re en vogue nowadays. But we often miss the underlying process that happens and with that in mind, certain caveats of high-intensity intervals are neglected.
What are 30-30 Intervals?
30-30 intervals refer to Tabata-style high-intensity workouts. Their origin goes back to a study done in 1996 by Dr. Tabata where 8×20 seconds of high intensity (170% of VO2max) was alternated with 10 seconds of rest.
The result was an increase in maximum aerobic capacity and anaerobic capacity compared to a control group that performed steady intervals at 70% of VO2max. The very high intensity, however, is an issue that recent research has addressed. A study by Viana and colleagues from 2018 has questioned the practicality of 170% VO2max and found that only 4 bouts were performed by subjects on average. The intensity was just too hard. However, by lowering the intensity to around 115% of VO2max, athletes were able to perform more bouts (Eight) and achieve more time above 90% of VO2max. More on this later…
Different Types of Short Intervals
30-30 intervals are just one type of short interval training with a 1:1 work-rest ratio. These intermittent intervals became famous through the studies of French physiologist Dr. Billat. That’s why people also refer to these as Billat’s 30-30 intervals. Variations include the original 20-10 Tabata’s, 30-15, or 40-20, where a 2:1 work-rest ratio is used.
The Right Intensity for 30-30 Intervals
A major issue with intermittent intervals I see is choosing the right intensity and duration. For example, some riders do 3x5x30/30 at super high intensity with no intensity during the rest period. You might be working hard but ultimately not getting faster. In the endurance disciplines of cycling, we all want to see higher absolute and relative powers. One of the best ways to do so is by increasing our VO2max and anaerobic capacity. To me, anaerobic capacity means lactate removal and buffering capacity at high intensities.
When we look at the original Billat study, the 30s/30s were done at 100% VO2max during the work period and 50% of that intensity in the rest period. Based on this, a review comparing the results of studies on intermittent intervals, including the Billat study, found that keeping work intensity at 100-105% of VO2max and at least 50% of VO2max power during the rest period leads to substantially more time above 90% of VO2max compared to higher “on” power and no “off” power.
As mentioned earlier, this confirms the findings from the study questioning the reliability of the original Tabata 20s/10s. So instead of going overly hard on the hard 30s and just coasting on the easy 30s, try to keep some work during the rest period.
From a practical standpoint, some scientists suggest taking your 5-6 minute best effort as an approximation of your VO2max power. I did it myself and it works well for me and my athletes too. For example, if your 5-minute power is 400 watts, try to alternate between 400 and 200 watts during the 30/30s. A different way I also enjoy is using %FTP. Try to go around 135-145% of your FTP during the work period and go around 50-60% of your FTP during the rest period. You might find yourself gasping in the last few sets.
In terms of total work duration, Dr. Stephen Seiler suggests at least 8 minutes of work per set. This is an important threshold to get your oxygen uptake toward maximum. Remember, our goal for 30-30 intervals and any other short efforts is to accumulate time over 90% of our max heart rate and create a high respiration rate.
An example session could be 3x8x30-30 with 4-8 minutes of rest between sets. You perform 30 seconds on and 30 seconds off and repeat this rhythm till the 8-minute block is over.
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The Benefits of Short Intervals Like 30-30
The benefits of 30-30 workouts reveal themself over time. Our anaerobic system is immediately able to fire. With a power meter, you see the change in speed immediately. As soon as you accelerate you see the power numbers bumping up.
In contrast, our maximum aerobic capacity needs some time to ramp up. But our goal during an endurance event is to be able to utilize as much oxygen as possible, hence we need to increase our maximum oxygen uptake or VO2max. To do that we need very high intensity.
For that reason, we perform 30-30 intervals. It’s an intensity where our aerobic system runs at full speed. And you can see the delay of your aerobic system yourself. As your power numbers are already there, your heart rate needs some 90 seconds or more to increase and so does your oxygen uptake.
The great thing about these alternating intervals is that during the 30-second rest period, your power numbers drop but your oxygen uptake stays high.
Therefore, not only does the 30 seconds high-intensity count as interval length but the whole block of 30-30 intervals. As slow as your oxygen uptake increases as slow it decreases as well. During a 3×8 minute block of 30-30s, you get 24 minutes of training effect for just 12 minutes of suffering. Tell me a better deal.
Are Short Intervals the Best Intervals for Cyclists?
However, the elevated oxygen uptake also led to confusion because of a study done by Ronnestad et al. In that study, 30/15 intervals were compared with 4×5 minute HIT intervals, where the 30/15 intervals came out as the winners.
But, there are two problems with the study.
The first is that the study compared just the high-intensity part, you have 19.5 minutes total time for the 30/15 intervals and 20 minutes for the 4×5 minute intervals. No surprise that 30/15 came out as the clear winner as subjects were able to produce much higher power for the 30/15 intervals compared to the 5-minute intervals.
The second problem is that as already addressed during the rest period of short intervals oxygen uptake is still elevated which means the whole block of intermittent exercises needs to be counted. So for 3x13x30/15 intervals, you get 29min15sec of effective training stimulus for VO2max.
If you compare the total time of 30/15 intervals to a total time of 4×8 minutes HIT intervals, the difference between these two might be minor.
Apart from that, I prefer 30-30 intervals over 30-15 intervals because even though I send some of my athletes to the lab to determine their VO2max power they were unable to complete the 30/15 protocol at the prescribed power. Accordingly, I find the 30-30 intervals to be a more sustainable workout for most cyclists.
The Frequency of High-Intensity Intervals
As 30-30 intervals are very demanding I recommend only doing two interval sessions weekly. Perform these intervals when you’re the freshest which is after rest days.
How can you schedule these HIT sessions in your seasonal training plan? Looking at the training distribution of gold medal endurance performers we see that the intensity increases when race season approaches. That’s no surprise as we don’t need a lot of high-intensity sessions to see improvements.
Studies looking at the effects of high-intensity training on well-trained athletes have shown that just six HIT sessions were enough to cause a substantial performance response in anaerobic capacity and VO2max.
As fast as these gains come, you get to the point of diminishing returns. Doing HIT intervals all year is an excellent way to get burned out. A good approach is to place 30-30 intervals before race season or your goal event and use it sparingly during the offseason.
Wrapping it up
If done right 30-30 intervals are a great way to see huge improvements in your cycling performance. While the response to intervals differs across individuals it’s important to do things and see how you perform with them.
Just remember to keep a certain degree of intensity control and try to keep an 8 out of a 10 on an RPE scale on the first set and finish it off with a 9 on your last set. Complete at least 8 minutes of 30-30 intervals to achieve a solid training response and progress to more time at intensity as you get better and more used to the workout format.
When you apply these basic principles correctly you might find a fun and challenging workout you can add to your staples.
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References
- Tabata training: one of the most energetically effective high-intensity intermittent training methods
- Billat intervals: the magic bullet for your next PB?
- Superior performance improvements in elite cyclists following short-interval vs effort-matched long-interval training
- Is there an optimal training intensity for enhancing the maximal oxygen uptake of distance runners
- The Road to Gold: Training and Peaking Characteristics in the Year Prior to a Gold Medal Endurance Performance
- Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists
- Specific Intensity for Peaking: Is Race Pace the Best Option?
- Time at or near VO2max during continuous and intermittent running. A review with special reference to considerations for the optimisation of training protocols to elicit the longest time at or near VO2max