Common Questions About HIIT Answered … for the already-fit to the very out-of-shape, overweight or older.

Is HIIT safe?

Yes, even for a person with a BMI in the obese range. If you have (or think you may have) a medical or orthopedic condition, explain HIIT to your physician to make sure it’s not contraindicated.

It’s unlikely that your doctor will warn you not do to HIIT on a stationary bike. I once had a client with peripheral vascular disease who performed HIIT on a bike.

Besides torching off fat, what are other HIIT benefits?

HIIT makes time go faster, offers an inviting change from the same ‘ol steady-state, improves sports performance, bumps up release of growth hormone and testosterone, tones and tightens, encourages lean tissue growth, and saves an abundance of time.

What is the definition of “sprint,” as applied to HIIT?

This doesn’t mean take off like a bullet.

“Sprint” means your very best effort, your fastest movement, your giving-it-all-you’ve-got…even if it’s just 5 mph.

At the end of the interval, you should be drained.

Is it okay to do HIIT and weights on the same day?

No. If you do HIIT first, you’ll be too sapped to attack the weights.

If you do weights first, your HIIT won’t really be HIIT.

You’ll be functioning at sub-intense capacity. Do HIIT on separate days.

Will HIIT make me a faster runner?

Of course, if your HIIT sessions involve your fastest sprints.

Can HIIT improve my endurance?

Yes. Eight walking or jogging cycles on an inclined treadmill will carry over to an outdoor hike. Eight running cycles will improve your steady-state jogging.


How many cycles should I do?

Ideally do eight, and if you can do more, go for it.

If you can only get through four or six due to lack of conditioning or lack of time, that works too, but make at least eight a habit as much as possible.

Is it okay to do some steady-state after HIIT?

Yes. For example, steady-state walking on an incline or using the revolving staircase, following HIIT, will contribute to fitness needed for long challenging hikes.

It’s also okay to do steady-state sessions (under 20 minutes) before HIIT, as an extended warm-up.

What about work intervals under 15 seconds?

If you can run on a 15 percent treadmill incline at 10 mph for only 10 seconds before having to slow down to a 2 mph recovery walk, then this qualifies as an effective work interval. (Same with outdoor hills or steps)


A person’s absolute fastest run (relative to an incline) may not be what he or she can do for a 30-second work interval.

For instance, a particular individual needs to jog only 7 mph on a 15 percent incline, to reach complete exhaustion after 30 seconds.

However, what can he or she do, for only 10 seconds at the same incline, before total exhaustion? Perhaps this individual can handle a speed of 12 mph.

Another example is a person who can sustain a 12 mph run at zero incline for barely 30 seconds, yet is actually able to run 15 mph for 10 seconds on the zero incline (some treadmills go up to 15 mph).

Running your absolute fastest, given the medium, will produce superior results, even if you conk out after 10 seconds.

Can walking be done as HIIT?

Yes. If you’re fit, your work intervals will require steep hills to bring on exhaustion within 30 seconds.

You can increase intensity also with weighted vests.

If you’re out of shape, you may need only slight inclines or even no inclines, depending on your condition.

Can I be too out of shape to do HIIT?

No. You can be too out-of-shape to run, but not too-out-of shape to put out your best effort.

A 300-pound smoker can pedal hard for 30 seconds on a stationary bike or elliptical machine.

Shutterstock/Creativa Images

If you’re in really poor shape, don’t necessarily limit your intervals to the bike or elliptical.

Do moderate to sub-intense intervals on a track (walking or very slow jogging).

Build up from there, over time. You can also include steady-state sessions as part of your conditioning program to prepare your body for eventual HIIT.

Should I get into HIIT shape by first doing intensity intervals lasting several minutes?

This is a good start, but not a requirement if you’d rather start off with the shorter intervals.

Longer intervals are also an option for the very fit; throwing in a 5-minute intensity interval during a HIIT session is perfectly fine.

How many times a week should I do HIIT?

Two times, though three is doable.

The third session can actually be sub-intense, longer intervals.

Will HIIT bulk up my legs?

A competitive sprinter may have “big” legs, but competitive sprinters also train nearly every day, many hours a week, including with heavy barbell squats.

A couple 30-minute sessions per week on a treadmill or staircase will not duplicate the legs of a sprint competitor who can blitz 100 meters in 10.8 seconds.

Can HIIT be done punching a heavy bag?

Yes. If you have an injured leg/foot, then throw your meanest punches at a bag.

Shutterstock/Dmitry Kalinovsky

But first make sure you learn how to safely throw a skull-shattering blow (hooks, crosses, uppercuts), before going all-out on a heavy bag.

If your legs are fine, each punch can be quickly followed by a kicking technique for extra intensity.

Can HIIT be applied to weightlifting?

Most certainly. Weightlifting routines, done to absolute failure, with rests up to 1-3 minutes (some schools of thought say briefer rests), are a form of HIIT.

Each set is a work interval. Or, stationary scissor lunges, following completion of an 8-12-rep max of leg extensions, would be a HIIT superset.

Squat-jumps for 30 seconds can be a work interval. Be creative!

Hopefully all of your questions about high intensity interval training have been answered in this post!

Lorra Garrick is a former personal trainer certified through the American Council on Exercise. At Bally Total Fitness she trained women and men of all ages for fat loss, muscle building, fitness and improved health. 



Top image: ©Lorra Garrick