You probably know that exercising at moderate intensity for 20 minutes elevates your mood for up to 12 hours. That exercise increases the production of a protein that supports the function, growth, and survival of brain cells. That exercise is one of the five daily habits a 30-year Harvard study shows can not only increase your lifespan by 12 to 14 years but also cut your risk of Alzheimer's in half.

And, of particular interest during times like these, that exercise helps you better manage stress.

But when you feel overworked, overwhelmed, and struggling to make sense of the new normal, it's tough to exercise regularly -- much less reap the benefits.

Science to the rescue.

According to a study published in Medicine & Science in Sports & Exercise, one 23-minute HIIT session per week can boost aerobic capacity, lower blood pressure, and lower body fat...and one session is nearly as effective as doing three 23-minute sessions per week. 

Researchers created three groups. One did an HIIT workout three times a week, another did one HIIT workout per week, the third did three moderate-intensity workouts per week, and the fourth group did nothing. (I've been a part of a few research studies and never got to be in the "do nothing" group.)

Both of the HIIT workout groups lost more body fat than the other two groups, but the one time per week group lost nearly as much -- and also reaped similar aerobic and blood pressure benefits.

Still, there's one major caveat: You can't just spin lightly on an exercise bike. You can't just breeze along on the elliptical. You can't just knock out 12 reps of dumbbell bicep curls with a five-pound weight while you check your email with your free hand.

Your HIIT workout has to be a true HIIT workout.

HIIT stands for High-Intensity Interval Training. The principle is simple. You go almost as hard as you can for a short period of time, then "rest" for enough time to let you recover enough to go hard again.

In running terms, that could mean sprinting for 30 seconds, jogging for 30 seconds, sprinting for another 30 seconds, etc. Here are plenty of different HIIT options, some aerobic, others strength-focused.

And here's a seemingly simple yet irritatingly difficult example:

Whatever HIIT workout you do, remember you have to go well beyond what feels comfortable. (Which means you should check with your physician to make sure you're up for it.) 

Your lungs need to burn. Your muscles need to burn. If it's not hard -- really hard -- then you're not doing a HIIT workout. 

Roughly speaking, your "on" effort should be at 80 to 90 percent of max heart rate, and your recovery period at 65 to 70 percent. (In general terms, you can calculate your max heart rate by subtracting your age from 220.) 

Or if you're doing longer "on" sessions, you may rest completely for shorter periods of time; it all depends on the workout. 

What won't vary is that a HIIT workout is no fun. 

But then again, you'll finish exercising in a third of the time it takes to grind your way through an hour-long spin class.

And science says you'll get significant benefits from doing it just one time a week.

Which leaves you more time to be as effective and efficient as possible with everything else on your plate. 

Can't beat that.