So is the butterfly the best single exercise that there is? Well, no. The butterfly "would probably get my vote for the worst" exercise, said Greg Whyte, a professor of sport and exercise science at Liverpool John Moores University in England and a past Olympian in the modern pentathlon, known for his swimming. The butterfly, he said, is "miserable, isolating, painful." It requires a coach, a pool and ideally supplemental weight and flexibility training to reduce the high risk of injury.
Ask a dozen physiologists which exercise is best, and you'll get a dozen wildly divergent replies. "Trying to choose" a single best exercise is "like trying to condense the entire field" of exercise science, said Martin Gibala, the chairman of the department of kinesiology at McMaster University in Hamilton, Ontario.
But when pressed, he suggested one of the foundations of old-fashioned calisthenics: the burpee, in which you drop to the ground, kick your feet out behind you, pull your feet back in and leap up as high as you can. "It builds muscles. It builds endurance." He paused. "But it's hard to imagine most people enjoying" an all-burpees program, "or sticking with it for long."
And sticking with an exercise is key, even if you don't spend a lot of time working out. The health benefits of activity follow a breathtakingly steep curve. "The majority of the mortality-related benefits" from exercising are due to the first 30 minutes of exercise, said Timothy Church, M.D., who holds the John S. McIlhenny endowed chair in health wisdom at the Pennington Biomedical Research Center in Baton Rouge, La. A recent meta-analysis of studies about exercise and mortality showed that, in general, a sedentary person's risk of dying prematurely from any cause plummeted by nearly 20 percent if he or she began brisk walking (or the equivalent) for 30 minutes five times a week. If he or she tripled that amount, for instance, to 90 minutes of exercise four or five times a week, his or her risk of premature death dropped by only another 4 percent. So the one indisputable aspect of the single best exercise is that it be sustainable. From there, though, the debate grows heated.
"I personally think that brisk walking is far and away the single best exercise," said Michael Joyner, M.D., a professor of anesthesiology at the Mayo Clinic in Rochester, Minn., and a leading researcher in the field of endurance exercise.
As proof, he points to the work of Hiroshi Nose, M.D., Ph.D., a professor of sports medical sciences at Shinshu University Graduate School of Medicine in Japan, who has enrolled thousands of older Japanese citizens in an innovative, five-month-long program of brisk, interval-style walking (three minutes of fast walking, followed by three minutes of slower walking, repeated 10 times). The results have been striking. "Physical fitness — maximal aerobic power and thigh muscle strength — increased by about 20 percent," Dr. Nose wrote in an e-mail, "which is sure to make you feel about 10 years younger than before training." The walkers' "symptoms of lifestyle-related diseases (hypertension, hyperglycemia and obesity) decreased by about 20 percent," he added, while their depression scores dropped by half.
Walking has also been shown by other researchers to aid materially in weight control. A 15-year study found that middle-aged women who walked for at least an hour a day maintained their weight over the decades. Those who didn't gained weight. In addition, a recent seminal study found that when older people started a regular program of brisk walking, the volume of their hippocampus, a portion of the brain involved in memory, increased significantly.
But let's face it, walking holds little appeal — or physiological benefit — for anyone who already exercises. "I nominate the squat," said Stuart Phillips, Ph.D., a professor of kinesiology at McMaster University and an expert on the effects of resistance training on the human body. The squat "activates the body's biggest muscles, those in the buttocks, back and legs." It's simple. "Just fold your arms across your chest," he said, "bend your knees and lower your trunk until your thighs are about parallel with the floor. Do that 25 times. It's a very potent exercise." Use a barbell once the body-weight squats grow easy.
The squat, and weight training in general, are particularly good at combating sarcopenia, he said, or the inevitable and debilitating loss of muscle mass that accompanies advancing age. "Each of us is experiencing sarcopenia right this minute," he said. "We just don't realize it." Endurance exercise, he added, unlike resistance training, does little to slow the condition.
Resistance training is good for weight control, as well. In studies conducted by other researchers, a regimen of simple weight training by sedentary men and women led to a significant decrease in waist circumference and abdominal fat. It also has been found to lower the risk of developing diabetes and cardiovascular disease. Counterintuitively, weight training may even improve cardiovascular fitness, Phillips said, as measured by changes in a person's VO2max, or the maximum amount of oxygen that the heart and lungs can deliver to the muscles. Most physiologists believe that only endurance-exercise training can raise someone's VO2max. But in small experiments, he said, weight training, by itself, effectively increased cardiovascular fitness.
"I used to run marathons," he said. Now he mostly weight-trains, "and I'm in better shape."
But there's something undignified and boring about a squats-only routine. And the science supporting weight training as an all-purpose exercise approach, while provocative, remains inconclusive. Is there a single activity that has proved to be, at once, more strenuous than walking while building power like the squat?
"I think, actually, that you can make a strong case for H.I.T.," Gibala said. High-intensity interval training, or H.I.T. as it's familiarly known among physiologists, is essentially all-interval exercise. As studied in Gibala's lab, it involves grunting through a series of short, strenuous intervals on specialized stationary bicycles, known as Wingate ergometers. In his first experiments, riders completed 30 seconds of cycling at the highest intensity the riders could stand. After resting for four minutes, the volunteers repeated the interval several times, for a total of two to three minutes of extremely intense exercise. After two weeks, the H.I.T. riders, with less than 20 minutes of hard effort behind them, had increased their aerobic capacity as much as riders who had pedaled leisurely for more than 10 hours. Other researchers also have found that H.I.T. reduces blood-sugar levels and diabetes risk, and Gibala anticipates that it will aid in weight control, although he hasn't studied that topic fully yet.
The approach seems promising, since most of us have minimal time to exercise each week. Gibala last month published a new study of H.I.T., requiring only a stationary bicycle and some degree of grit. In this modified version, you sprint for 60 seconds at a pace that feels unpleasant but sustainable, followed by 60 seconds of pedaling easily, then another 60-second sprint and recovery, 10 times in all. "There's no particular reason why" H.I.T. shouldn't be adaptable to almost any sport, Gibala said, as long as you adequately push yourself.
Of course, to be effective, H.I.T. must hurt. But a study published last month found that when a group of recreational runners practiced H.I.T. on the track, they enjoyed the workout more than a second group of runners who jogged continuously for 50 minutes. The H.I.T. runners, the study's authors suspect, were less bored.
The only glaring inadequacy of H.I.T. is that it builds muscular strength less effectively than, say, the squat. But even that can be partially remedied, Gibala said: "Sprinting up stairs is a power workout and interval session simultaneously."Meaning that running up steps just might be the single best exercise of all. Great news for those of us who could never master the butterfly.