Changes

[[File:Sprinter.jpg|right|thumb|400px|To run HIIT intervals requires a longer stride length, so other modes, such as a stationary bike may be more appropriate.]]

{{DISPLAYTITLE:High Intensity Interval Training (HIIT) Tabata and Wingate}}

=What is HIIT?=

High Intensity Interval Training is a form of [[Introduction to Interval Training| Interval Training]] using short intervals of 10 seconds to 5 minutes at an intensity at or above 90% [[VO2max|V̇O₂max]]<ref name="Boutcher2011"/>. High Intensity Interval Training, abbreviated to HIIT or HIT, is sometimes called High-Intensity Intermittent Exercise<ref name="Trapp-2008"/> or Sprint Training<ref name="Gibala-2006"/>.

=HIIT Training Methods=

There are various ways that HIIT could be performed, each with their own pros and cons.

! Mode

! Pros

=HIIT Running Paces=

I don't generally recommend running HIIT workouts because of the high speeds required. Below is a sampling of the HIIT paces for different fitness levels ([[VO2max|V̇O₂max]]). For each level, the 5K and marathon times are given, along with the pace that corresponds to 90%, 100% and 170% of [[VO2max|V̇O₂max]].

! [[VO2max|V̇O₂max]]

! 35

| 2:41/Mile

|}

=The HIIT Science=

This section looks at the scientific evidence, divided into three sections. Studies that compare HIIT with other modes of training are the most interesting, though they don't cover highly trained athletes. I've included a few other studies that are not comparative because they have some particularly dramatic results. The third section looks at the studies that have looked at HIIT for highly trained athletes.

==HIIT Comparisons on Untrained or Moderately Active Subjects==

The table below looks at studies that have compared HIIT with other types of training, often Continuous Moderate Exercise (CME). These studies on untrained or moderately trained subjects generally show a greater improvement in fitness measure compared with other forms of training, or similar improvements for far less training time.

! Study

! Subjects

5 pound/2.5 Kg reduction in body fat

Significant 31% reduction in fasting insulin

| rowspan="2" rowspan="2"|

HIIT

1 pound/0.5 Kg gain in body fat

Non-significant 9% reduction in fasting insulin

|-

| rowspan="2" rowspan="2"|

* HIIT improved peak power output and 40 Km time trial in elite cyclists<ref name="Lindsay-1996"/><ref name="Westgarth-Taylor-1997"/>

* A study of elite cyclists used various HIIT workouts as shown in the table below, with the best results seen group 4 or group 1<ref name="Stepto-1999"/>. Group 4 trained at 85% peak power, which corresponds to the intensity normally seen in the 40K time trial, which takes ~60 minutes for an elite cyclist. Not surprisingly, this intensity is commonly used for cyclists training for 40K time trials. However, the higher intensity of group 1 is more intriguing; the time trial performance improved without an improvement in peak power, suggesting that a different mechanism may be responsible. This raises the possibility that the benefits of the different intensities might be combined. Note that there were only four athletes in each group, and responses tended to vary, so caution should be used in interpreting the results.

! Group

! Number of intervals

* Well trained, competitive runners trained twice a week for four weeks with intervals at 100% [[VO2max|V̇O₂max]] for either 6x 60% [[vVO2max|T_lim]] (133 sec) or 5x 70% (154 sec) [[vVO2max|T_lim]], resting for twice the interval time. Their 3K time improved by 17.6 sec (60% [[vVO2max|T_lim]]) or 6.3 sec (70% [[vVO2max|T_lim]]), but there was no change in their 5K time<ref name="Smith-2003"/>.

* 41 elite ([[VO2max|V̇O₂peak]] ~65) cyclists and triathletes were split into four groups, with three groups using the HIIT described below and the fourth acting as a control that followed only low to moderate intensity training<ref name="Laursen-3-2002"/>. Note that groups 1 and 2 vary only in their rest time, which is based on [[Heart Rate]] dropping to 65% of [[Maximum Heart Rate|HR_max]] in group 2 (averaging around 180 seconds). This was a demanding regime, as the subjects reached exhaustion on nearly every HIIT training session, with '''only 64% of the dictated intervals actually completed'''. Note that like comparison of different workouts above, the shorter HIIT produced a similar improvement in 40K performance without the accompanying rise in [[VO2max|V̇O₂max]] which was not statistically different between group 3 and the controls.

! Group

! Intended number of intervals