How to 'HIIT' your exercise targets

Have you "HIIT" your cardio workouts with what may be an especially effective way to promote heart health? Doctors and fitness experts will tell you there are many ways to achieve a great workout with aerobic exercise.

"Many people find some activity that is sustainable and perform it continuously for a set amount of time," said Wesley Tyree, MD, a cardiologist and independent member of the HonorHealth Medical Staff. "As exercisers, we try to maintain some sustained effort for the duration of the activity. 'Find what you like and break a sweat' is what I tell my patients over and over. The current recommendation for healthy adults is to perform at least 30 minutes of moderate-intensity continuous training five days a week."

As an alternative to moderate-intensity training, the concept of High Intensity Interval Training (HIIT) is increasing in popularity, Dr. Tyree said. This involves exercise at high exertional levels, from 80 to 95% of maximal heart rate for short periods, followed by a recovery period that is usually 40 to 50% of maximal heart rate.

What's maximal heart rate?

  • The fastest a human heart can beat is 220 beats per minute but an adult heart rate that fast isn't healthy. Doctors use your age to determine what they call your maximal heart rate, or MHR--the fastest your heart should beat during exertion.
  • High Intensity Interval Training is dependent on knowing your MHR. Here's how to find it: 220 - your age = your maximal heart rate (MHR). That means if you're 35 years old, you subtract 35 from 220 to arrive at the fastest your heart should beat: 185 beats per minute.
Interval training from health and fitness experts at HonorHealth

Doing your HIIT workout

  • Begin by aiming to achieve 60 to 70% of your MHR in the first five minutes or so of your workout.
  • Then, boost the intensity so that you achieve between 80 and 95% of your MHR for as long as you can sustain it (anywhere from 30 seconds to a few minutes, depending on your fitness level).
  • Next, slow down until you achieve a heart rate of between 40 and 50% of your MHR. For example, a 35-year-old should aim to bring the heart rate down to between 74 and 92 beats per minute. This is known as the recovery phase and should be sustained for about three minutes (or longer, if necessary) once the lower heart rate is achieved.
  • After the recovery phase, the high-intensity phase resumes and the cycle is repeated.

When you're first trying out HIIT, include one high-intensity session per week, incorporated in your normal exercise routine. Dr. Tyree noted, "As you progress, you can add more HIIT days during the week, and increase the duration of the high exertional periods as fitness levels improve."

HIIT can be easily applied to your favorite current aerobic activities. "Whether biking, running or using any of the widely available fitness machines," Dr. Tyree said, "heart rates can easily be tracked with technology available today."

Benefits of High-Intensity Interval Training

Workouts of this type, Dr. Tyree said, accomplish several things:

  • They create a state in the body "where oxygen use is increased for up to two hours after the workout is completed. This results in up to 15% more calories burned than traditional moderate-intensity exercises and can go a long way in helping achieve caloric goals as well. Try to burn 2,000 calories per week to see a noticeable drop in cholesterol levels to lower risk for heart disease.
  • They show that HIIT is more than just optimizing calories burned during your workout. "Significantly improved aerobic fitness levels have been documented, with increase in peak VO2 capacity (maximum amount of oxygen that an individual can utilize during intense exercise) when compared to medium-intensity workouts," Dr. Tyree said, adding that peak VO2 is "one of the best predictors of cardiorespiratory fitness."
  • They have been shown to improve insulin sensitivity, allowing more efficient use of glucose by the muscles. There are also notable improvements in cholesterol levels and blood pressure with HIIT in line with what is seen with moderate-intensity exercise.

Overall, he said, HIIT appears to be "a promising way to maximize the gains of most any exercise program."

Starting a workout plan?

If you're starting a workout plan, consult with your physician. Find a primary care doctor or a cardiologist in the Phoenix area.

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