Why are interval training sessions important for progress?

In running, interval training sessions are the sessions we dread a little, because they are demanding, because they sting. They are nevertheless essential for progress, whatever your starting level. Along with basic endurance sessions and threshold sessions, they are part of the range of key training sessions in addition to muscle strengthening sessions. These interval training sessions allow you to gain speed and power. After a basic endurance warm-up period, they consist of alternating intervals or blocks of intense effort with recovery periods before finishing with a cool-down, again in basic endurance. Here is a brief overview of the reasons why these interval training sessions are essential for progressing in running.

Increased speed and power

Short, intense efforts during high-intensity intervals use fast muscle fibers, which generate speed and explosive strength. Fast muscle fibers contract faster than slow muscle fibers. They generate more tension per fiber, which creates explosive force, the kind that allows you to jump or sprint. On the other hand, they consume a lot of energy quickly (glycogen). In longer races like a half marathon or a marathon, slow fibers are used the most, but fast fibers, even if they are not used as much as in a sprint, contribute to greater pushing power with each stride. This increase in the power of each stride allows you to maintain a higher speed for longer. They are also activated to maintain pace when slow fibers begin to fatigue, as in a marathon (often after the ^30th kilometer).

Improvement of _VO2 max

Intervals or blocks push the cardiovascular system to 'work' at high intensity during short bursts. This improves blood circulation, cardiac efficiency, and VO ₂ max. VO ₂ max is the maximum volume of oxygen our body can consume per minute during intense exercise, per kilogram of body weight. It is measured in ml/kg/min. The higher the VO₂ max, the more energy the body is able to produce from the supply of oxygen and the greater its endurance and performance. A higher VO₂ max allows you to run faster for longer before starting to fatigue.

Acceleration of metabolism

After an intense session like an interval training session, the body continues to consume more oxygen to return to its normal (resting) state. This phenomenon is called EPOC ( Excess Post-Exercise Oxygen Consumption ). We therefore continue to burn calories even after the end of the interval training session. This helps increase our metabolism, which is the set of reactions that occur in our body to produce energy. Basal metabolism is the one linked to the body's activity at rest and active metabolism is the one linked to physical effort. It is the latter, of course, that the interval training session allows us to increase during and even after the session.

Short or long split

Short interval or long interval? Ideally, both. But first, what are the differences between a short interval session and a long interval session? The intervals during a short interval session last less time (less than a minute) but they are run at a very high intensity (90% to 100% of VO ₂ max) while those run during a long interval session last longer (several minutes) but are run at an intensity that is still high but more sustainable (80% to 90% of VO ₂ max). Short interval training develops maximum speed and explosiveness. It strengthens fast muscle fibers and improves anaerobic capacity (short effort, without oxygen supply to produce energy) . Long interval training increases endurance and cardiovascular capacity and improves the threshold between aerobic and anaerobic to run faster for longer. It is recommended to alternate interval training sessions between short interval training to work on explosiveness and power and long interval training to improve threshold endurance. Whatever your starting level, alternating these two types of short and long interval training sessions allows you to both gain 'pure' speed and be able to maintain a higher speed for longer.

Hill sessions

Another alternative to interval training on flat ground or on a track can be to perform a hill interval session. This involves repeating fast intervals uphill on a hill, for example, about ten repetitions of fast climbs for 30 seconds, then slowly descending in short strides to recover before the next climb. These sessions specifically target power and strength (more than 'pure speed'). They also put more strain on the quadriceps and calves and require a good upper body workout during the climbs. Be sure to warm up well for about fifteen or twenty minutes at basic endurance before tackling the hills, because these sessions are demanding for the leg muscles.

In summary, interval training sessions (short or long) or hill sessions to vary the 'pleasures', it is difficult to escape them to be able to progress in running. It is important to plan them either after a rest day, or the day after a recovery session. If you plan to do two in the same week, space them out with at least one day between the two sessions: either a rest day, or a day with an easy session. These interval training sessions are demanding, especially the last repetitions but in the long run, the work and effort pay off and you will be able to run more easily, faster and longer thanks to these famous interval training sessions.