Gentler. Kinder. These are the types of activities that are capturing the time and attention of more Americans. Elliptical-trainer workouts, yoga and tai chi are the fastest-growing fitness activities in the U.S., according to a six-year survey by the Sporting Goods Manufacturers Assn.

Conversely, high-impact aerobics has been declining from 1998 to 2004.

The SGMA presented these findings recently in Los Angeles.

Credit the aging baby-boomer generation for the growth of these activities, said Gregg Hartley, SGMA vice president, who counts himself in that group.

To hear boomers tell it, some are looking to preserve their joints – especially knees and ankles – that have been jarred or stressed during other activities. Other exercisers are seeking activities that promote the mind-body connection. Some simply want to add variety to or round out their regimen with activities that enhance flexibility or are low-impact.

The growth of fitness walking is outpacing fitness running, again because more people find walking accessible and gentler to the body.

Not surprisingly, more people are participating in Pilates, another mind-body exercise. The SGMA started monitoring Pilates in 2000, so statistics for a six-year period were not available.

People also are taking the time to work on strength. More are using dumbbells and resistance machines than other types of strength-training equipment. It’s probably because dumbbells and resistance machines are more user-friendly.

As for cardio equipment, elliptical-trainer use is skyrocketing, even if treadmills remain overall the most widely used machines across the nation. Elliptical-trainer use shot up nearly 305 percent over six years, compared with 28 percent for treadmill use.

Another indicator of the kinder, gentler phenomenon: More people are using the recumbent bike than the upright stationary bike, because sitting on a recumbent is more comfortable.

What equipment is becoming less popular?

The cross-country ski machine, the aerobic rider and stair-climber.

Although it provides a good workout without pounding the joints, the cross-country ski machine is probably spending more time gathering dust in the den than burning someone’s calories.