Why high intensity interval training is the best type of exercise for unfit / moderately fit people

  • High-intensity interval training (HIIT) has become popular because it is a time-efficient way to increase endurance.
  • An intriguing and so-far-unanswered question is how a few minutes of HIIT can be that effective.
  • New research has now shown that interval training (as little as 10 sets of 30" full-intensity cycling alternated by 4' of rest between sets!) causes free radical damage on a muscle cell protein called ryanodine receptor 1 (RyR1).
  • This ultimately causes "mitochondrial biogenesis", i.e. the creation of new mitochondria (mitochondria are the powerhouses of the cell, the place where most of cell energy production occurs).
  • In summary: high intensity interval training > more mitochondria > more energy production > more fitness!
  • As these changes depend on free radical damage, taking antioxidants (such as Vitamin C, Vitamin E, CoQ10, Alpha Lipoic Acid, polyphenols etc.) stops this process, and this has been proven experimentally.
  • So practically you should not take antioxidants one day before, on the same day and one day after doing HIIT training.
  • Furthermore these adaptations to HIIT did not occur on elite athletes, because they are fully adapted to high intensity training due to their daily gruelling training regime.  
  • This practically means that interval training is ideal for unfit or moderately fit people. The only limitation is that you need to have generally good cardiovascular health.
  • Interval training is not a good idea for people with cardiovascular problems, as high intensity training puts a lot of pressure on the heart and may lead to too high or too low blood pressure.
  • Source: Ryanodine receptor fragmentation and sarcoplasmic reticulum Ca2+ leak after one session of high-intensity interval exercise, http://m.pnas.org/content/early/2015/10/28/1507176112