Does HIIT Burn Fat or Muscle?


Everyone in the exercise-sphere is talking HIIT, or so it seems. You will hear from some advocates that HIIT will help you get rid of those excess pounds, but others claim you can use it to build muscle. So which one is it–does HIIT burn fat or build muscle?

HIIT (high-intensity interval training) burns calories more effectively than weightlifting or other resistance training. However, HIIT in conjunction with resistance training burns fat more effectively while increasing muscle mass.   

To know whether HIIT will let you accomplish your workout goals, you need to know what HIIT is, how it works, and what a high-intensity workout looks like. Then you will understand why these programs are geared toward weight loss and burning fat.  

What Is HIIT?

HIIT stands for high-intensity interval training. In a HIIT workout, you engage in one exercise intensely for several minutes and then take a break. For example, instead of a ten-minute run, you might do a five-minute sprint followed by five minutes of jogging or walking.  

HIIT is not an entirely new concept—runners have been using it since the 19th century, although the first written evidence was in 1902. Finnish runners were more systematic about their interval training, and Hannes Kolehmainen, the 1912 cross-country Olympic Gold medalist, used it to great success.

Although interval training continued to be refined by runners, HIIT really took off in the early part of the 20th century. Trainers and fitness professionals consider it the 2nd biggest exercise trend, right after wearable technology.

The list of HIIT programs has become overwhelming. There is the seven-minute workout, the one-minute workout, the 23-minute workout, and more. Your local YMCA probably has a HIIT program, chains like Orangetheory offer them, and if you cannot afford a gym membership, sites like Fitnessblender offer their HIIT exercises for free on YouTube.

Bottom line—if you want to try HIIT, you won’t have to look far.

Is Strength Training With Cardio HIIT?

Strength training with cardio is not HIIT, even if gyms advertise it as such. A routine that includes strength training with stretches of cardio is good exercise, but it is not built on the HIIT principle of high-intensity interval training.

Instead, they simply switch exercises from strength to cardio. For example, two minutes of deadlifts followed by one minute of running in place is excellent exercise, but it is not HIIT.  

Does HIIT Burn Fat or Muscle First?

HIIT burns fat first and more than it builds muscle. This is partly due to it being a cardiovascular exercise, and cardio exercises burn more calories than strength training. You can still build muscles with HIIT programs, but you won’t see the same gains as you would from resistance exercises.

For example, you will tone your body and develop muscles that are used repeatedly. If you choose a running routine, such as a treadmill, you will strengthen your leg muscles.  

You will often hear that HIIT works because you exercise less, but that is not true. Instead, high-intensity exercise works because of something known as EPOC. Sometimes called the after-burn effect, EPOC refers to the excess post-exercise oxygen consumption.

If HIIT worked because you exercise less, then how could it burn more calories? HIITs do not burn more calories during exercise but afterward. In the 2 hours after a session, the body returns to pre-exercise levels. The vigorous nature of the workouts increases the number of calories the body expends by somewhere around 10%.

The extra calorie expenditure from HIIT happens after the routine, not during it.  

Do Cardio Exercises Also Build Muscle?

Cardio exercises help you build muscles by conditioning your heart and lungs, thereby making it easier to do resistance training exercises, such as lifting weights. So most cardio exercises do not directly let you build muscle but make it easier to do so.

However, some weightlifting exercises combine cardio and muscle building. Kettlebell exercises are one example. They look like flattened balls with a handle or a tea kettle without a spout.

Kettlebell exercises fall into two categories:

  • Grinds. These exercises involve slower movements that look like traditional training exercises. For example, squats, deadlifts, overhead presses, and pushup variations can be used with a kettlebell.
  • Ballistic.  Once you have mastered grind movements, ballistic exercises add exercises that look more like cardio, except with weights.

Because Kettlebells can be pricey (check out this Lifeline Kettlebell on Amazon), consider trying them out at your local gym or YMCA. That way, you can try them and receive some personalized instruction. Otherwise, you run the risk of injury.

How Often Can You Do HIIT?

You should aim for two HIIT sessions a week, alternating them with resistance training. Also, build in rest days so that you can perform at your peak when you exercise. HIIT done every day comes with several risks. So don’t cancel your gym membership just yet. 

Excessive high-intensity exercise carries serious risks, including:

  • Increased chance of injury due to overtraining and not giving your muscle tissue time to repair itself.
  • Mental burnout from being tired of doing the same exercises and not having enough time to rest.  

Can Anyone Do a HIIT Program?

Most people can use a HIIT program, but people who do not exercise frequently should build up to it gradually. A person with hypertension, diabetes, high cholesterol levels, or a family history of coronary diseases should talk to their doctor first.

Whether that is your situation or not, you should still develop a foundational fitness level, often called a base fitness level. Aerobic training, done 3 to 5 times a week for a couple of weeks, will improve how well oxygen flows to the muscles. You risk injuring yourself if you start using HITT without ramping up how well your body copes to intensive exercise.

Finally, HIIT is not a contest to see who has the most intensity. So don’t judge yourself against others but celebrate when you see improvements in your skill level.

What a Typical HIIT Routine Looks Like

There are two types of HIIT routines. One is those often seen in gyms and combine strength training and cardio exercises. The proponents of this type of training are correct in that it combines the basic principle of intense exercise followed by recovery. But they are not actual HIIT routines.

The second type of routine is cardio-based. The 4-by-4 is a research-based HIIT routine that was developed by the Norwegian University of Science and Technology is as follows:

  • Warm-up
  • Four minutes of cardio exercise
  • Three-minute recovery period
  • Repeat three more times for a total of four intervals
  • Cool down

Running, cycling, even swimming are excellent cardiovascular exercises in a HIIT program. And the good news is that most of these routines do not require specialized equipment.  

You can find similar routines, such as a 1:1, with 3 minutes intense, 3 minutes recovery, or a spring interval routine, in which you exercise all out for 30 seconds and then 4 minutes of recovery. Experiment with different routines until you find one that is right for you.

Track Your Heart Rate While Doing HIIT

To be successful with high-intensity training, you need to track your heart rate. During the intense portions of the routine, your heart rate should be around 80% of what would be your maximal heart rate. And during the less intense part, the rate should drop down to 40-50%.

Age plays a significant role in determining one’s maximal heart rate. A good rule of thumb is to subtract your age from 220. For example, someone who is 30 should have a maximum heart rate of 190 beats per minute (bpm). At 50, the maximum rate should be 170 bpm.

So during the high-intensity portion of the routine, shoot for 80% of your tax rate. If you are 30, that would be 190 x .80=152 bpm. The good news is that you only must do the calculations once a year.

You can be less precise by following the talk test. During the high-intensity portion, you should feel like you are exercising extremely hard, and you could only carry on a conversation with great difficulty. During the recovery portion, you should feel extremely comfortable exercising.

A Balanced Exercise Program Needs a Balanced Diet

To lose weight, you need to burn more calories than you eat. You can accomplish this through diet alone, but combining diet and exercise is more efficient.

Combining diet and exercise means you don’t have to cut back on all your favorites. Instead of going from four brownies a week to zero, exercise will let you go from 4 to 2. 

Ashley Kelly, a personal trainer for Bach and an Olympian in track and field, says, “You can’t out-train a bad diet! So, make sure this workout schedule is paired with a healthy diet to maximize results.”

Bottom Line

Combine HIIT with a balanced diet to reach an ideal weight and burn some fat. Keeping track of your heart rate is key to achieving maximum results. Although some exercise is better than none, you will benefit more from doing true HIIT workouts twice a week and doing weightlifting or resistance training on different days.

Sources

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