You say you're running eight miles a day, but you need a shot of B-12 so you can pick up the cat? After a year of aerobic dance, your shoulders still look like pork mousse? You've got only half an hour to exercise, and you want to hit the cardiac red line with the shortest possible warm- up? Dr. Leonard Schwartz says you need Heavyhands-- those red-padded dumbbells that seem to be sold everywhere but the 7-Eleven and look like leftovers from a Bruce Lee movie.

A powerful odor of snake oil hangs over Schwartz's promotional claims, which promise the combined equivalent of The Golden zoor, Richard Simmons and two weeks at Lourdes: "a higher level of fitness than that produced by any known aerobic exercise" and the fastest per-minute calorie consumption in the pop- workout biz with the least discomfort. All this by merely weighting the hands while jogging, walking in place, dancing or shadow-boxing, indoors or out.

But you may remain a padded dumbbell yourself if you don't give it a try. The regimen devised by the Pittsburgh psychiatrist and sports-doc (explained in his book at a hefty $14.95) is based on an appallingly simple but incontrovertible observation: Most aerobic schemes, and running in particular, "used too little muscle mass at any given moment, were overconcerned with prolonged endurance and speed, and almost studiously neglected the driving power of the arms." Yet of all sports, the top oxygen-burner is cross-country skiing, with its maniacal flailing of poles.

Schwartz's solution: Load up the hands for simultaneous "panaerobic" involvement of leg, arm and trunk muscles. After all, your legs are in fair shape already, thanks to bipedal evolution, the national trotting fetish and the cost of Saudi crude. Even the fleet elite, Schwartz says, "cannot improve their legs' workload intensity by more than 25 percent." But the arms can increase by 100 percent: Despite their smaller volume, "ounce for ounce, the upper-torso muscles can do more work than the leg muscles."

Thus by adding arm effort to running, walking or stretching, one should be able to achieve target pulse (start with 220; subtract your age; take 80 percent of the result) both faster and with less exertion of each muscle set while burning a whopping amount of chow. A 156- pound person consumes about 1.25 calories a minute while asleep, two to three times that while awake and waddling around, 12 times as much while running at 7 mph. Add upper-torso torque, and 20 calories per minute is not unthinkable for the average specimen. And you'll be sucking up air like a four-barrel Holley on a hot day at Daytona, says Dr. Richard Reff, an orthopedic surgeon on the D.C. Medical Society's sports medicine committee and an enthusiastic user: "It really does increase the aerobic component of whatever kind of exercise you do." But "a jogger shouldn't run with more than two or three pounds in each hand. I'm about 180 pounds and I'm pretty strong. And at three pounds, my arms were killing me."

Schwartz's index for load levels is the 1-10-100 "pump 'n' walk" test--10 minutes of walking in place at 100 steps per minute, rhythmically alternating swings with the one-pound weights. Compare the resulting heartbeat with your target pulse, and add weight or repetitions accordingly. Our moderately fit 160- pound tester hit a triple-digit spike at trying to calculate 11/4 steps per second, but soon leveled out to a 20-beat increase. Now deeply skeptical, he took to the turf with three pounds in each mitt.

Normally capable of four or five road miles in about 40 minutes, he had gone barely a mile at customary velocity when he started making a sound like a tuba stuffed with Brillo pads and felt like Mr. T was doing the Funky Chicken on his chest. Yet nothing hurt, and the sensation of balanced strain was decidedly pleasant. ("It feels easier," Schwartz says, because "lots of units, each doing less, can add to more.")

A prudent speed adjustment revealed that Heavyhands are an excellent way to regulate heart rate: Swinging the weights head-high while loafing downhill, but only to mid-chest when lugging on an upgrade. Afterward, he was astonished to find a mild muscle-burn in the upper arms and shoulders, despite a daily diet of racquet sports.

Hardly surprising, says Dr. Robert Nirschl, whose Arlington sports medicine practice uses weight therapy to treat occupational muscle imbalance in professional athletes. Baseball pitchers, he says, have flabby adductors and tennis pros tend to weak biceps and triceps; both have strong internal rotators (muscles that turn the palm down), but poor external rotators. With proper weight loads ("even pitchers don't start beyond two pounds in certain body positions"), he generally approves Schwartz's system, except for neophyte fatties, for whom shaking any added booty could compound the dangers of running: a "pounding effect" producing bone spurs, shin splints and stress on lower spine, foot and ankle. Reff warns that one should consider sore spots before beginning, since dumbbells "can aggravate a tendinitis which is either pre-existing or predestined."

And you're almost certain to sprain your wallet. Though most jockos will want two or three pounds to start, the one-pound handles are sold separately at $19.95 in various sizes (get the largest you can manage, Reff says, since "the harder you squeeze your hands into a fist, the higher your blood pressure"), with add-on weight sets apparently price-keyed to the London gold fix (three pounds for $11.99). Still, they beat sweat-slick metal barbells, and the retaining strap minimizes fist-clinch. In all, Heavyhands may be one of the best ways to get a leg up on health.