If you've been beating your feet in the Valley's health clubs--and hurting--the word is out: "Low-impact" aerobics will knock you for a new kind of loop. This trend on the fitness scene sends your heart rate into the heavens while your feet stay firmly on planet Earth.
The big deal is injury prevention. If you had X-ray vision and watched your body react to the jumping and jostling of traditional aerobics, you'd see how jarring force can cause fractures in leg and hip bones and damage to ligaments, cartilages and tendons. In a low-impact exercise class, however, you're less likely to be hurt, quite simply, because pressure on the body is reduced.
A low-impact class uses only walking and stepping actions--bending the knees and straightening the legs. Even if an instructor of a low-impact class leads with a step-hop sequence, the hop is always followed by a step, never by another hop. Without the bouncing choreography, you don't get the momentum to be truly airborne, so there is no physical stress in the landing.
You can still get the beneficial cardiovascular workout without the shock to the system. Low-impact aerobics just takes five minutes longer than the regular variety, said Jaci Gross, an instructor who used to manage Jane Fonda's Workout in Encino.