If your local fitness center has a set of Keiser exercise machines, don't waste time looking for the weight stack. There is none. Keiser machines use air pressure to provide resistance. The manufacturer designs pneumatic exercise machines for the upper body, lower body and core. Keiser also has an aerobic exercise-equipment line.
Kaiser Permanente is a health insurance organization that often supports national fitness programs, but despite the similarity of their names, it is not related to Keiser Equipment, spelled with an "e."
Mechanical engineer Dennis Keiser and his brother Randy introduced the first pneumatic exercise machines in 1978. In 1985, they began working with Olympic athlete Mike Powell, who broke the long-jump world record in 1991. The company has worked with NASA to create equipment for long-duration space flights, and with the Council on Aging and Adult Development to support research on aging and exercise.
Author Bill Pearl describes pneumatic exercise equipment function in his book titled "Getting Stronger: Weight Training for Men and Women." He explains that Keiser pneumatic technology uses an air compressor and a cylinder. The machines have thumb buttons that control the air pressure. Pressing the right thumb button increases air flow from the compressor to the cylinder. If the resistance is too heavy, pressing the left button reduces the air pressure. Unlike traditional weight machines, which usually have 10-lb. weight increase increments, users can increase or decrease the resistance on a Keiser machine in 8-oz. increments.
Traditional strength-training machines may cause injuries when performed at high speeds, but air-pressure resistance is smooth at any speed. This benefits everything from athletes (as it enhances athletic performance) to seniors (it makes everyday tasks like walking up stairs less taxing). Pneumatic machines safely support high-intensity workouts at higher speeds.
The Keiser Air 250 line features entry-level equipment with relatively light resistance. The Air 300 is a similar line, offering more resistance. The Air 350, Keiser's functional training line, enables movement in different planes of motion. The Infinity Series features pneumatic cable equipment. Keiser's Power Rack resembles a traditional Smith machine, but with some significant differences. The machine has pneumatic strength columns. Attach a bar with weight plates to the column, and combine the benefits of pneumatic and barbell training.
A study performed at the Department of Kinesiology at San Francisco State University detailed the effects of a 10-week, 30-minute strengths training program. Lead author Barbara Gale reported 21 to 30 percent increases in upper body strength and 22 to 44 percent increases in lower body strength amongst participants.