Within each noncompetitive Curves facility, female fitness seekers are invited to move through a 30-minute circuit of hydraulic-resistance machines that are designed to promote weight loss, protect against osteoporosis, and deal with arthritis. Shunning cumbersome weight stacks, the hydraulic gadgets adapt to each exerciser's body weight and fitness level to complement her individual abilities, subsequently decreasing the risk of soreness or injury. And because traditional lift-and-lower motions tend to create bulky muscles, Curves' machines promote push-and-pull movements to sculpt toned, lean muscles, perfect for crushing unsuspecting grapefruit. Experienced trainers are always nearby to help clients manage their machine maneuvering, and a soundtrack of fun, upbeat music includes cues to let women know when it's time to move on to the next station or break for an air viola solo. Customers who wish to continue their membership after the trial will need to pay an enrollment fee of $49 in addition to the monthly rate.