HIIT can be highly effective training, but involves a risk of injury. HIIT has been shown to improve aerobic capacity in untrained and moderately active individuals more quickly than Continuous Moderate Exercise, as well as having potential benefits for highly trained athletes. HIIT has also been shown to reduce body fat in untrained people more effectively than Continuous Moderate Exercise. However, there is no evidence to suggest that HIIT can replace other forms of training for endurance races. High Intensity Interval Training (HIIT) uses repeated short periods of very intense cardiovascular exercise separated by lower intensity recoveries. (I’ve found the Stryd estimate of power output is the best approach to gauging effort during HIIT, though Moxy can provide some interesting insight from Muscle Oxygen Saturation.)
1 What is HIIT?
2 HIIT Recommendations
Below are my recommendations based on my interpretation of the available evidence. These recommendations for incorporating HIIT in your training depend on your current fitness goals.
3 Incorporating HIIT In Your Training Regime
Here are some suggestions for adding HIIT to your training. These are not hard and fast rules, as there is a lot of individual variability.
4 Types of HIIT
There are various different protocols for performing HIIT. While the Tabata is probably the most widely recognized name in HIIT, it is one of the least studied and the least used.
This style of HIIT is based around the Wingate test, which is used to measure peak anaerobic power and anaerobic capacity. The Wingate HIIT uses 30 seconds of ‘all out’ intensity, followed by ~4 minutes of recovery, repeated 4-6 times.
4.3 WinTab (Tabata style Wingate)
Because the WinTab workout involves such fast paces, it can easily lead to injury as the stride length requires a greater range of motion than more common paces. You can reduce the pace while maintaining the intensity by running up hill, something I call HillTab (Hill Tabata). While similar to the WinTab in some ways, this workout has a variable length recovery, as you have to run down the hill after each time, and it uses different muscle groups. To perform a HillTab, find a hill that is moderately steep; about 10-12% gradient works well. Find a marker to use as the start point, such as a suitable tree or rock, then find an initial finish marker that is about 45 seconds up the path. You’ll adjust the finish marker so that it takes about 30 seconds to cover the distance at your fastest speed. This will take a bit of trial and error, but don’t worry if the first few intervals are too long or too short. You could use an audible timer, but I prefer a visible marker to aim for. If you want to time each interval, have a watch in your hand, held so you can press the lap button without fumbling. For each interval:
For HIIT, I suspect that the hard acceleration is a key to the benefits of the workout. The acceleration achieves high levels of muscle activation, mimicking the effects of Plyometrics. (There advantages to Downhill Running, but the risk of injury while running at HIIT pace downhill are much higher.)
4.5 Traditional Anaerobic Intervals
High intensity Interval Training has been in use since before the Tabata study made the term popular. The Jack Daniel’s ‘R’ paced workouts are a classic example of this tradition of anaerobic interval training. The Jack Daniel’s ‘R’ intervals are performed at around mile/1500m pace, which is generally close to 100% V̇O2max. The ‘R’ workouts are 12-40 repeats of 30-60 seconds with 1-4 min rests. Jack Daniels mentions once having his athletes perform over 1,000 repetitions of one-minute HIIT (4-minute rest) in a 14-day period, with two male athletes averaging 5:00 min/mile pace and therefore covering 250 miles.
5 Fellrnr’s Tabata Audio
I created a short audio file for my Tabata (WinTab), adding a countdown and interval counts. I started with Darude’s Sandstorm, remixed it to 180 BPM and then extracted short snippets. I then recombined the snippets with voice countdowns so that I didn’t need to look at a watch or timer to execute the workout. You can download or play the MP3 file of Fellrnr’s Tabata. (I believe that I’m making fair use of Darude’s work, given I am only using a short section of the original and modifying it heavily. If you want to enjoy the overall song, this MP3 file is not it!)
6 HIIT Training Methods
There are various ways that HIIT could be performed, each with their own pros and cons. As this site is dedicated to running, my assumption is that you’re a runner primarily. If that’s not the case, then you’ll have to interpret the pros and cons slightly differently.
7 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 (V̇O2max). For each level, the 5K and marathon times are given, along with the pace that corresponds to 90%, 100% and 170% of V̇O2max.
8 HIIT and Stryd
9 The HIIT Science
10 Crossfit Endurance
Crossfit Endurance is a training approach that reduces the normal endurance training volumes while increasing the training intensity. The reduction in volume is quite dramatic compared with other training plans; for instance, the Crossfit Endurance marathon training plan has a 10 mile time trial as its longest run, which is combined with weight training and interval training. Crossfit Endurance claims that eight 100 meter intervals “accomplishes everything you would by jogging 20 miles but doesn’t put the same level of stress and damage on the body.” There is the caveat that “some kind of stamina work that lost more than the 70 seconds is required to “dial in technique, just rhythm, and formulate pace strategy.” While there are some testimonials to the Crossfit Endurance methodology, their approach is controversial. The science that is used to support Crossfit Endurance does not support replacing traditional Continuous Moderate Exercise with HIIT for endurance events, only using HIIT as a supplementary form of training. Most of the anecdotal reports suggest that people have set personal records at 5K and 10K distances and completed half marathons using the Crossfit Endurance approach, but there are few reports of longer races. The anecdotal reports are hard to interpret objectively without knowing the individuals prior training methodology. (I have some other concerns with CrossFit, such as their emphasis on forefoot landing, then approach to hydration that includes the overly simplistic “sweat rate test”, but that’s outside of the scope of this article that focuses on interval training.)