"My work is to show how every person can do sports," says 32-year-old Jean-Pierre Ernoult in his very understandable if not always flawless English, "and to train people to take care of themselves."

Ernoult is a professor of physical education in Grenoble, France, and sports consultant to the French government. At the invitation of Rockville Mayor William E. Hanna, Jr. he has spent two weeks in Rockville teaching his philosophy to the people whom he has made it his business to educate about exercise - senior citizens.

For the past two weeks, Ernoult has instructed Rockville recreation staff members during mornings and 23 senior citizens from various clubs in the afternoons at the Montgomery College physical education building. Each week in Grenoble, Ernoult teaches 2,000 senior citizens to enjoy such fairly strenuous sports as swimming, jogging, cycling and cross-country skiing.

"Cross-country is like walking, but in the snow," Ernoult explained. "When you know how to do it, it is fun."

No senior citizens in Rockville are donning their skis right now. During Ernoult's stay in Rockville, the senior citizens have trooped into his classes with their yellow folders, which they fill with diagrammed notes on the levels of sports activities.

"The sports are individual," explained the handsome, bearded Ernoult, who changed from a checked shirt and skin-tight pants into exercise pants and gym shoes for his lesson with the senior citizens. "I have to show people how to manage - how to do things at the right level."

That is why senior citizens, all of whom have some health problems past the age of 70 according to Ernoult, suffer no more than the occasional bruises and sprains that anyone physically active is susceptible to.

"We have to be careful to make sure that the pulse rate of the seniors does not exceed 150," said Ernoult. "We're careful to stay below that - at 120 or 130." Ernoult teaches his students to carefully monitor their pulses throughout the exercises and sports. As a result of continued training, the same exercise, done week after week, does not produce as much exertion or high pulse rate in the senior citizen, he said. Ernoult's French students range in age from 65 to 80.

"They must understand that exercise is not an obligation," Ernoult commented. "If someone feels a little pain, a little out of breath, they have to stop."

For those who are infirm and confined to nursing homes, Ernoult's staff goes into nursing homes simply to show people how to move around. For some of those who are healthy enough to live on their own, Ernoult can have them cycling 60 miles after three and a half months of training. "Some are in better shape than me," remarked Ernoult. "I sometimes go cycling with them and I have some problems."

At one of his Rockville sessions with senior citizens, Ernoult began simply by seating everyone in a semi-circle on folding chairs in the gymnasium. "The first thing we can do with our chairs is move them in," he said. "So move! Move! Move." Ernoult shouted enthusiastically as his students laughingly pulled their chairs into a small circle around the instructor.

With the next command they moved their chairs out across the floor, and proceeded to walk around them and then take wide steps, one leg going over the chair. "Up! Up! Up!" Ernoult cried.

"It's ideal," 84-year-old Fred B. Uhrich said in the gymnasium. "It puts you in a position where you exercise every muscle that you have or that you're supposed to have."

Under recreation department direction and with funds raised from a Baffle Bowl quiz show between two senior citizens and WMAL disc jockeys Bill Trumbull and Chris Core, Rockville will sponsor an exercise program based on Ernoult's French one.