DALLAS — In the futuristic world of winsome dreams, cheeseburgers have single-digit calories; workouts, single-digit minutes.
Well, hold tight to your jet pack. The magic wand has been waved — not for cheeseburgers, but it seems so for workouts.
Cases in point:
Research published in the American College of Sports Medicine's Health & Fitness Journal touts the effectiveness of a strength-training workout using only body weight and lasting merely seven — albeit very uncomfortable — minutes.
A Norwegian study found that four minutes of high-intensity activity — heart rate at 90 percent of maximum capacity — shares similar benefits to four such efforts separated by three minutes of downtime.
The benefits of high-intensity training have been known for a while, experts tell us. But in our busy lives, new research on shorter and shorter workouts continues to tantalize, especially when compared with the 150 weekly minutes of exercise recommended by the ACSM.
Three months after "The Scientific 7-Minute Workout" story appeared in The New York Times and its Well blog (Well.blog.nytimes.com), it's still among the top five viewed stories on the newspaper's health website. Don't let the numbers fool you, experts caution. Caveats abound.
"What's important to remember is that there's no magic in any of this," says Allen Jackson, chairman of the department of Kinesiology, Health Promotion and Recreation at the University of North Texas.
The point, he says, "is getting active, the muscle groups you're working, the specificity of training."
It's also the level of intensity, which, in order to make the exercises effective, has to be extreme. Four minutes at 90 percent of maximum heart rate is hardly casual.
"That's the highest range of intensity that the American College of Sports Medicine recommends," he says. "The highest! The highest! That's Michael Phelps!"
Benjamin Levine, medical director of the Institute of Exercise and Environmental Medicine at Texas Health Presbyterian Hospital Dallas, puts it this way:
"Here's the deal. We talk about exercise as medicine. Like any drug, exercise has a dose and a frequency. You can take a baby aspirin once a night or two to four times a day and get different effects.
"Exercise is the same way. Different types of exercise probably affect different systems in different ways."
Working out for the 150 recommended minutes spread over a week, for example, burns more calories than the shorter bursts. That's something to keep in mind if you're exercising to lose or maintain weight.
The trick of intervals, Levine says, is that they "allow you to do something harder for a short period of time and allow you to build up to that level of intensity. If it's just longer periods of lower intensity you do, you'll never be able to do more."
Plus, the shorter bursts offer positive physiological results.
"When you do high-intensity aerobic intervals, you have a nice change in the heart," Levine says. "The heart muscle gets stronger, your muscles get stronger and better able to utilize oxygen."
Without a doubt, Jackson says, "short bouts of intensive activity have performance benefits and health and fitness benefits. It's true."
There are problems inherent with these, he cautions: a "potential risk for injury," or a "cardiovascular event" because the heart is working extremely hard.
"More moderate, longer-term exercise will have lower risk for injury. Joggers get injured. Walkers don't very much. The drawback? It takes more time, and time is definitely a barrier."
Still, saying a workout will last four minutes, or seven, or even shorter periods of time isn't entirely accurate, Levine says.
"Of course you have to warm up. There's recovery between," he says. "Nobody should think you put on your shoes and in four minutes you'll be finished."
Additionally, these aren't workouts just anyone can plunge right into, Jackson says.
Still, he and Levine do agree that shorter stints can have a place in a workout regimen.
"Four minutes," he says, "would be better than no minutes. But make sure you're ready to do those four minutes."
pick up the pace
Here are some tips for incorporating single-digit workouts into your own regimen:
■ Go slowly. If you're just starting out, do each segment slower. As you build strength and confidence, pick up the speed.
■ Use it on a time-strapped day. "If you're normally a jogger but can't do your 30 minutes, and can get a hard run of four or five minutes in? Sure, do it," Jackson says. "Why not?"
■ Build in intensity. That's the principle of interval training, he says. "Swim two lengths easy, one hard." Or go at a normal pace on the elliptical trainer and then "for a few minutes now and then, go after it."
■ Try the four-minute-intervals-four-times workout. "We affectionately call it the 4-by-4," says Levine, who incorporates this at least weekly into his other training. For the four-minute segments, you go all-out. Between each, go slower — heart rate at 50 or 60 percent of maximum — for three minutes.
As each four-minute segment winds down, you should feel ready to stop, he says. At the end of the three-minute cool-downs, "you should be able to say, 'OK, I'm ready to go again.'"
"Patients with heart disease, with heart failure, with diabetes, with hypertension — everybody can do it. At the end of the day, it ends up being as hard as you can go for four minutes and keep going."