What are the benefits of integrating HIIT into you training?


It is almost impossible to be training for endurance sports without ever having heard of interval training. Athletes from various sports have been doing such exercises for decades and it has been scientifically well established that hiit enhances endurance performance.


As its name suggests, hiit training is about alternating high intensity exercises for a given duration and low intensity recovery periods. The principle is that, when doing such workouts, one will be able to spend more time at the targeted intensity when compared to continuous training (CT). For instance, if you’re asked to run at VO2max pace (vVO2max), you might be able to hold this pace for around 5min. Total time spent at vVO2max = 5min. However, when performing a hiit session, you could go for 8-10 times 1min at vVO2max with 1min recovery between repetitions. Total time spent at vVO2max = 8-10min so around twice as long.

Another great advantage of such workout is that is it not much time consuming. If you’re short on time, warming up for around 10', doing the aforementioned session and doing a 10' cool down would only take around 40min and will lead to great results.


Several components must be taken into account when designing a hiit session. The first thing to address is the aim of the workout. Is the goal to develop maximal , supra-maximal or sub-maximal values? Depending on the answer then you need to decide:

  • What will the ratio between work and recovery be
  • How many reps
  • How many sets
  • What will the intensity be
  • What will the amplitude be



Depending on how you planned your season, you might want to focus on different aspects of performance. Here are a few exemples of hiit with various aims.

  • Repeated sprint training (RST). Used to increase anaerobic performance and maximal power output. It will include all-out sprints of up to 10s with a recovery time of less than 60s.
  • Short interval training (SIT < 60s). Great to enhance VO2max if the amplitude is low (around 20% to 30%). If the amplitude is high, then the focus will mostly be on specific neuromuscular adaptation but less on VO2max development.
  • Medium interval training (MIT = 1 to 5 min). Also great to enhance VO2max if the ratio is of 1/1 or 2/1. It also leads to great running economy adaptation, especially if the amplitude is low.
  • Long interval training (LIT= 5 to 20 min). Mostly used to develop running economy, lactate clearance and to target threshold pace.
  • In general, prioritize active breaks over passive ones! By staying active, you'll have better lactate clearance and can push yourself further towards the end of the workout!



When talking about HIIT, the ratio of a session is the difference between work and recovery time. In other words, the difference between time spent at high and low intensity.


The intensity of a repetition is usually compared to your vVO2max or PMA (Puissance Maximale Aérobie). vVO2max will be 100%. However, in ski-mountaineering, it is almost impossible to know exactly what your intensity is like at the moment of performing your workout. You can’t rely on power nor on speed, as the gradient of the slope you’re on will keep changing. What you can rely on, however, is your heart rate but the best tool is your own feeling. Heart rate is very useful when post-controlling your session and assess if you spent your time in the right zone.


The amplitude of your workout is the difference between work and recovery intensity divided by the mean of the session.

For instance, a work intensity of 90% and a recovery intensity of 30% will give an amplitude of:

(90-30)/60 = 100%




Remember the first article where we explained the principle of polarized training. If you haven't read it yet, please check on it for a full description. As a reminder, the principle is quite simple. 80% of the training is done below VT1, and 20% is done above VT2. We will introduce a slight modification to this rule. We will refer to it as the 80-5-15 principle, because in reality, 5% of the workouts are done between VT1 and VT2, either for races or for training at target paces. The reason for only 5% at the threshold? It's a zone that brings too much pain for not enough gain!

With all that, how often should I do interval training? If you're an amateur athlete training 3 to 6 times a week, one session of HIIT is perfectly sufficient! During certain training periods, two intensity sessions can be beneficial. However, overall, prioritize quality over quantity for optimal gains!


We still hear too often comments like: "No need for high-intensity training because the effort is too long", "For ultra, the only rule is to focus on endurance” or “Working on my VMA when I'm going to walk for 100km? It's absurd!”

In reality, it's not that absurd! While it's essential to build volume at low intensity to prepare for races lasting several hours, contrary to preconceived ideas, working at very high intensities will actually improve your endurance too. VT1 and VT2 will thus be shifted to the right (see figure X). Certainly, interval training helps enhance both maximum cardio-pulmonary capacity and endurance. By training smartly, you'll be able to complete your races at an equivalent heart rate but at faster speed.


To learn more about high intensity interval training:


  • Buchheit, M., & Laursen, P. B. (2013). High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis. Sports medicine, 43(5), 313-338.
  • Dupont, G., Millet, G. P., Guinhouya, C., & Berthoin, S. (2005). Relationship between oxygen uptake kinetics and performance in repeated running sprints. European journal of applied physiology, 95(1), 27-34.
  • Helgerud, J., Høydal, K., Wang, E., Karlsen, T., Berg, P., Bjerkaas, M., & Hoff, J. (2007). Aerobic high-intensity intervals improve V˙ O2max more than moderate training. Medicine & science in sports & exercise, 39(4), 665-671.
  • Seiler, S., & Tønnessen, E. (2009). Intervals, thresholds, and long slow distance: the role of intensity and duration in endurance training. Sportscience, 13.
  • Vaz, M. S., Picanco, L. M., & Del Vecchio, F. B. (2014). Effects of different training amplitudes on heart rate and heart rate variability in young rowers. The Journal of Strength & Conditioning Research, 28(10), 2967-2972.