Should I do long or short intervals? What am I aiming to improve with each type of interval? Performing intervals is more than just running fast; it’s crucial to know what you want to improve in order to choose the right type of interval. In this blog, I’ll try to explain how you can choose which type of interval to use to achieve your goals.

As we’ve seen in previous blogs, the acronym HIT stands for “High-Intensity Training.” If you haven’t read the blog “HIT: What Is It? And Types of HIT,” I invite you to read it before starting this post.

Also, as we’ve seen, in the colloquial language of endurance sports, HIT workouts are often referred to as “intervals.” The main goal of this type of training is to improve VO2max (see the blog on VO2max), although we can also improve other aspects such as the anaerobic threshold.

As we discussed in the blog “HIT: What Is It? And Types of HIT,” there are different types of intervals depending on the duration and intensity:

• HIT with long intervals (90-100% of vVO2max and lasting 2 to 8 minutes).
• HIT with short intervals (100-120% of vVO2max and lasting 10 to 60 seconds).
• RST, repeated sprints (120-160% of vVO2max and lasting 10 seconds or less).
• SIT (all-out sprints lasting 10 to 30 seconds).

What Do We Improve with Each Type of Interval?

1. HIT with Long Intervals:

   • Very long intervals (4 to 8 minutes): Intensities are lower than in other intervals (90-95% of vVO2max), producing a greater oxidative stimulus. With this type of HIT, while improving VO2max, we also significantly raise the “anaerobic threshold.”
   • Long intervals (2 to 4 minutes): Intensities are slightly higher (95-100% of vVO2max), and unlike the longer durations, this type has a greater influence on VO2max and less on the “anaerobic threshold.”

   In both types, the focus is on increasing VO2max in terms of capacity rather than power—meaning more on developing the time we can sustain VO2max rather than increasing it.

2. HIT with Short Intervals:

   • In this type of interval, the work intensities are higher (100-120% of vVO2max). This makes the effort more muscular than cardiopulmonary, so the adaptations will be cardiovascular, muscular, and neural.
   • In terms of VO2max, this type of interval focuses more on power, meaning increasing the VO2max value rather than the capacity to maintain that speed for a longer time.

3. RST (Repeated Sprints Training):

   • This type of HIT training is mainly used in team sports (football, basketball, etc.) or racquet sports (tennis, padel, etc.) due to the similar demands of these sports: very high efforts of short duration and many of them during a match.

   Since it’s not used in endurance sports, we won’t discuss it further.

4. SIT (Sprint Interval Training):

   • Although this type of training may seem less specific to endurance sports, studies show significant improvements in performance for cyclists (Burgomaster et al., 2008) and runners (Koral et al., 2018).
   • With just 4 to 5 minutes of active training (5 to 7 intervals of 30 seconds), you can achieve significant improvements in endurance events due to the increase in VO2max.
   • This improvement is due to neural and muscular stress rather than cardiopulmonary. As with short intervals, the focus is on power, increasing the VO2max value while also significantly improving neuromuscular aspects. In runners, careful consideration should be given before introducing it due to its risk/benefit ratio concerning injuries; the athlete should be well-trained and have optimal strength levels. In trail running, it could be done more safely on steep inclines, and as in cycling, the neuromuscular work involved could be very beneficial.

How to Choose Which Type of Interval to Use?

This is where the importance of having a qualified coach comes in, someone who can plan which type of HIT is most beneficial for you as an athlete.

The choice will depend on both the athlete’s physiology and the competition demands.

Here are some examples, though it’s important not to generalize:

1. The Athlete’s Physiology:

   • Does the athlete’s VO2max closely match their “anaerobic threshold”? If the anaerobic threshold (see the blog on the anaerobic threshold) is at 85% or higher of VO2max, we should focus on increasing the VO2max value. Here, shorter or not very long intervals would be used.
   • Is the athlete’s “anaerobic threshold” below 85% of VO2max? In this case, longer intervals may be more beneficial to raise both components simultaneously.

2. Competition Demands:

   • Does the competition require maximum effort sprints? In cycling, it’s more common to have to sprint briefly to catch a group that’s breaking away, launch an attack, or exit a corner in a triathlon. Here, SIT can be very beneficial.
   • Does the competition demand repeated efforts at these intensities or more capacity to endure these efforts over time? A road race is not the same as a trail race; in trail running, efforts are more intermittent due to the ascents and descents. Similarly, in mountain biking, we need to be more capable of repeating high VO2max values than maintaining them over time.

I hope this blog has been interesting, and as always, if you have any questions, feel free to comment below, and we’ll be happy to respond.

Additionally, if you’d like help improving your times and understanding why you do each workout, tell me your story, and I’d be happy to assist you.

Best regards, and happy running!

Bibliography:

• Buchheit & Laursen (2013). High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis. Sports Med, 43(5):313-38.
• Burgomaster, Howarth, Philips, et al. (2008). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol, 586(1):151-60
• Koral, Oranchuk, Herrera & Millet (2018). Six sessions of sprint interval training improve running performance in trained athletes. J Strength Cond Res, 32(3):617-623