HIIT – High Intensity Interval Training

Endurance and Intensity Training

Have you heard the term HIIT (high intensity interval training)?  What is HIIT?  Are you currently dabbling in off season workouts?  Well, research is now proving why adding HIIT is beneficial for not just burning fat, but also for long distance athletes, like you.  Doctor Izumi Tabata has been studying training techniques, which boost endurance athletes and teams.  Tabata found that approximately 4 minutes of extreme intensive exercise, 4 days a week, improved the body’s ability to deliver oxygen to the muscle (VO2max), that was compared to 60 minutes of medium exercise intensity 5 days a week (Tabata et al. 1996).

HIIT not only increases VO2max, but has shown improvements in how the muscle is able to use oxygen to burn stored fuel for work.  The process of using carbohydrates & fats during exercising is key to athletic performance0.  HIIT, also increases the number of mitochondria in the body, which is what turns nutrients and oxygen into energy.  Mitochondria is knows as the cells powerhouse.

The benefits listed above are reasons alone for someone to add HIIT into their weekly workout regimen, but for entrance athletes how could this actually help their performance?  Most endurance athletes use what is called low intensity training (LIT), to enhance the oxygen and fuel in muscle fibers with the mindset of more distance must equal a great return.  Research is now indicating that HIIT improves many of the physiological and production systems in greater ways than LIT.

There are two systems in our body called aerobic (low-medium heart rate) and anaerobic (higher heart rate), which both help fuel our bodies with energy.  The aerobic system uses oxygen to break down fats and carbohydrates for longer duration of exercise.  The anaerobic system is broken into two divisions:  speed and strength.   The ATP and creatine phosphate (ATP-PCr) last for 3-15 seconds before recovery is needed to replenish the muscle cells.   The anaerobic glycolytic system that uses glucose (carbs) for fuel.  The anaerobic glycolytic can withstand higher workloads for brief periods of time 3-120 seconds, but can also work with the aerobic system to promote work at higher levels of intensities.

How does this effect the endurance athlete?

Studies conducted by Gibala and McGee (2008) show that HIIT places high demands on both the aerobic and anaerobic systems, triggering and increase in muscle fiber recruitment.  Type 2 fibers (fast-twitch and glycolytic) and type 1 (slow twitch) are recruited and trained during HIIT.  The boosts of intensity enhances the mitochondria and increases the oxidative enzymes that are normally associated with LIT.

Remember, mitochondria breaks down fuel for energy in the cells, therefore the more recruitment of motor units the more energy the body can provide,  recruit, challenge, and train more motor units.  The body then can refresh during lower intensities in alternating rest/work cycles.  An athlete with the more active motor units can cycle through the motor units delaying fatigue.

This does not mean you can compete in an full Ironman distance by doing HIIT alone.  LIT has many benefits, such as improving store volume, recovery, and improvement in circulatory response. There is a need for both types of training to create a balanced and effective program that will help athletes achieve their goals.  To learn more on how to implement HIIT, contact me at amanda@fitstudiotn.com.

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