Interval training: is it effective?

What is interval training?

Training involves three basic variables: intensity, duration and frequency. Interval training usually involves varied increases in intensity and can last anywhere between 10 seconds and 30 minutes with varied recovery times in between each interval. Longer intervals (LI) (3-30 min) are usually trained with fewer repetitions than short intervals (SI) (<30 sec – 3 min). 

Interval training does not always require giving full power, it can also include lower intensities. To get you familiar, let’s start by explaining the different training intensities. Each intensity range has its own key duration of how long an interval should last and the duration of recovery between each interval. Interval training mainly involves intensities above or at your functional threshold power (FTP). 

Here is an overview of the different training intensities and what they are most commonly used for:

Active regeneration (<55% FTP): Easy warm up/ cool down, active recovery

Endurance (56-75% FTP): Basic endurance, endurance adaptations

Tempo (76-90% FTP): Basic endurance, steady long rides

Threshold (91-105% FTP): Interval training (8-30 min)

VO2max (106-120% FTP): Interval training (3-8 min)

Anaerobic capacity (121-150% FTP): Interval training (30 sec – 3 min)

Neuromuscular power (maximal): Interval training (<30 sec)

How will intervals help me to improve my performance?

Interval training can help keep your training fresh and new. If you only train at one pace, after a while you will hit a plateau in your training and your performance will most likely stop improving. It challenges the body and mind to step out of your comfort zone. It creates physiological adaptations not only in the muscles such as increases in power output but also cardiac responses such as increases in VO2 max (the maximal amount of oxygen your body can take in and utilize), all important for improving performance. Interval training is also extremely time efficient. For those who do not have hours a day to train, interval training can be a much more effective method to improve performance on limited time schedules.

Are short intervals more effective than longer intervals?

Interval training has been used for centuries, however, structured short interval (SI) training first came to life in the 1990s when Dr. Izumi Tabata first introduced short duration efforts (20 seconds versus moderate-intensity endurance training). The study showed that by integrating short high intensity efforts, greater improvements are seen in both aerobic and anaerobic capacity compared to longer steady efforts at 70% of VO2max (1). This made way to introduce short high intensity efforts into training to optimize performance alongside longer efforts.

Recently, an interesting article by Rønnestad et al. came to similar conclusions. They compared SI (3 series with 13 × 30 seconds max RPE efforts with 15 seconds recovery between efforts and 3 minutes between each series) versus effort-matched long intervals (LI) (4 series of 5 minutes at max RPE with 2.5 minutes of recovery between efforts) on performance improvements (2). 

The study showed a larger relative increase in power output at 4 mmol/ L and peak aerobic power output after the SI training than LI. Greater improvements of mean power output of a 20-minute cycling test were also seen in the SI group compared to the LI group. However, the topic of SI versus LI will always be debated between sports scientists and coaches and cannot be decided by two studies. The type of training also depends on what you are trying to achieve and should not focus on one aspect of performance. Different components of training are all needed to create an all-rounded athlete.

LI serves just as important a purpose than SI (3)(4). They both have their own time and place as to when they can be most valuable. For example, LI are mainly used to build up aerobic performance and SI to improve sharp end power outputs, anaerobic capacity as well as aerobic aspects (4)(5).

How many interval sessions should I train per week?

Not all phases of training include interval training. Intervals are usually included more into training building up to and around competitions. Due to the need to recover following interval sessions, research shows around 2-3 training sessions per week can include interval training (4). This should, however, vary weekly to ensure sufficient recovery. 

Whether the sessions include LI or SI will also depend on the phase of your training and what your specific goals are. To get the most out of your training, it is best to work with an expert trainer that can help guide and structure your training in the correct way. Our app can provide the guidance you need to optimize your training.


  1. Tabata, I., Nishimura, K., Kouzaki, M., Hirai, Y., Ogita, F., Miyachi, M., & Yamamoto, K. (1996). Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Medicine and science in sports and exercise, 28 10, 1327-30.
  2. Rønnestad, B. R., Hansen, J., Nygaard, H., & Lundby, C. (2020). Superior performance improvements in elite cyclists following short-interval vs effort-matched long-interval training. Scandinavian journal of medicine & science in sports, 30(5), 849–857. 
  3. Seiler, S., & Tønnessen, E. (2009). Intervals, Thresholds, and Long Slow Distance : The Role of Intensity and Duration in Endurance Training. Training, 13(13), 32–53. 
  4. Etxebarria, N., Anson, J. M., Pyne, D. B., & Ferguson, R. A. (2014). High-intensity cycle interval training improves cycling and running performance in triathletes. European Journal of Sport Science, 14(6), 521–529. 
  5. Milanović, Z., Sporiš, G., & Weston, M. (2015). Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Medicine, 45(10), 1469–1481.