Getting Started with High-Intensity Interval Training (HIIT)

High-intensity interval training can be an effective addition to a workout routine for exercisers of all experience levels. Our Life Fitness Academy (LFA) certified trainers offer a few tips on how to incorporate HIIT into any exercise plan.

What is HIIT?

HIIT is a form of interval training in which work periods consist of high-intensity exercise and rest periods consist of low-intensity recovery. High intensity is defined as heart rate at or above 85% max HR or a perceived exertion of 8 or greater on a scale of 10.

Why does HIIT work?

Much of HIIT's effectiveness comes from the demands that high-intensity exercise places on the body. Instead of using predominantly slow-twitch muscle fibers like traditional cardio, the power requirements of HIIT call on fast-twitch muscle fibers as well. HIIT utilizes all three of the body's main energy systems to sustain exercise. All of this creates a great demand on the energy production systems, burning through calories to replace expended energy and training the energy systems to work more efficiently. It also creates demands to the muscle fibers themselves, stimulating adaptations. The interval design incorporates rest periods which allow the body to recover between intense work periods. This allows for higher levels of work than would be possible with steady-state exercise.

How can exercisers get started with HIIT?

While HIIT has many positive benefits, it is not without its risks. Injury from the type of activity used is always a risk, as are the normal risks associated with exercise. However, training too often at too high an intensity can place too much stress on the body. Therefore, people wanting to incorporate HIIT into their exercise routine should make it a small percentage of their total exercise time. LFA recommends, based on research, that only 4-9% of total training time per week should be spent above 90% HRmax.

Not all interval training has to be high intensity, though. Lower-intensity intervals can still be used to great effect in combination with HIIT. Many forms of exercise can be used in HIIT, including (but not limited to) running, cycling, rowing, stair climbers, and weight training.  Some methods, like cycling or rowing, maybe easier and safer for beginners to start with.

How many HIIT sessions should exercisers aim for each week?

This is dependent on the exerciser's experience and fitness levels. Beginners may only do 1 to 2 HIIT sessions per week, completing their exercise program with lower-intensity workouts on the other days. Advanced exercisers may use HIIT 3 to 5 times per week. However, sufficient rest is needed to recover from the high-intensity exercise, and 24 to 48 hours between HIIT sessions is recommended.

Exercisers, regardless of level, are encouraged to keep their time spend above 90% HRmax to less than 9% of their total training time per week. You can have too much of a good thing, so it is important to consider how HIIT fits into your overall training plan and be cognizant of overall training volume and intensity. 

Workout Example

Life Fitness On Demand (LFOD) virtual workouts are available across all compatible connected Life Fitness cardio machines. The wide range of instructor-led online exercises classes includes HIIT-style workouts. Here’s an example from one of the LFOD cardio classes that can ease beginners into high-intensity interval training:

15-Minute Beginner HIIT Treadmill Workout

• 2 x 30-second max intervals with 30 seconds of easy walking in between (alternate incline between 1% and 6%).
• 2 x 45-second max intervals with 45 seconds of easy walking in between.
• 2 x 1-minute max intervals with 1 minute of easy walking in between.
• 2 x 45-second max intervals with 45 seconds of easy walking in between.
• 1-minute max effort.