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High-Intensity Interval Training (HIIT) – Fit or Fad?

By Susan Hardin Rocchini, PT, DPT, OCS, MDT

High-intensity interval training (HIIT) is the premise behind many of “hot” Chicago exercise classes and studios today, such as Shred 415 and Orange Theory.  Just what is HIIT?

Interval training is nothing new and has been used by athletes for years to maximize performance.  Sessions include repeated bouts of high-intensity exercise (equal or superior to maximal lactic acid steady-state velocity) of variable length interspersed with recovery periods (light exercise or rest).1 The intense work periods may range from seconds up to 8 minutes long and are performed at 80 to 95% of a person’s maximum heart rate. The intense work period is followed by a recovery period in which a person works between 40 to 50% of his or her maximal heart rate. These work/recovery periods are alternated for 20 to 60 minutes.

Interval training has been shown to improve aerobic and anaerobic fitness, blood pressure, insulin resistance, cardiovascular health, cholesterol, and body weight.  The popularity of these workouts is due to similar benefits one can receive from a continuous workout without intervals in a shorter period of time. In addition, the calorie burn is often higher both during the workout and after the workout.  Your body continues to burn additional calories compared with your pre-exercise state because the body needs to restore itself and “cool down”. This type of post exercise recovery period helps burn about 6 to 15% more calories than those burned after a continuous work out.

Are HIIT classes for everyone? Those who have not regularly exercised or have adopted a sedentary lifestyle may be at increased coronary disease risk related to this type of high intensity exercise.  Therefore, the American College of Sports Medicine recommends that you seek clearance from a physician prior to beginning this type of exercise.  In addition, you should establish a fitness foundation by first exercising regularly for several weeks for 20 to 60 minutes, 3 to 5 times per week at a somewhat difficult level of intensity before beginning HIIT workouts.

At Lakeshore Sports Physical Therapy, we work with our clients to help them safely initiate exercising in these types of programs by helping them establish a fitness base or evaluate and treat any aches, pains or injuries that keep them from trying one of these popular exercise classes.  Because these classes include both strength and aerobic components, initiating a strengthening program prior to beginning these classes will minimize risk of injury.

Susan Hardin Rocchini, PT, DPT, OCS, MDT, is a physical therapist at Lakeshore Sports Physical Therapy, PC.  She can be reached at or (773) 665-9950.

1 Billat LV. Interval training for performance: a scientific and empirical practice—special recommendations for middle- and long- distance running. Part I: aerobic interval training. Sports Med. 2001;31:13–31.

Additional resources are available from the American College of Sports Medicine.