Keiser Air Resistance Advantages over Weight Stack Provided Resistance

- No shock loading to connective tissues and joints.
- The ability to change resistance at any time w/ fingertip controls.
- A consistent variable resistance curve at any speed.
- Offers privacy of workload.
- Resistance changeable at 1/10 pound increments on Infinity Series
- Large Digital display/Counts repetitions.
- Equipment of choice in over 70 peer-reviewed research studies on training.

The U.S. Consumer Product Safety Commission reports that sports injuries are on the rise among those aged 25 to 65. They claim the increase in weight training injuries is due to not only age and technique, but also the shock loading to aging joints from weight stack machines. A recent study clearly illustrates the difference between the old method of weight stacks vs. the revolutionary pneumatic resistance provided by Keiser equipment.

Keiser Pneumatic - Weight Stack Machine

Graph 1. It can be seen that the acceleration forces of inertia increase dramatically with a weight stack machine depending upon the speed of movement. Also the weight stack shows a loss of resistance because of gravity and momentum. Keiser pneumatic resistance strength curve remains consistent at all three training speeds. Weight stack cam machines were designed to take into consideration the forces due to acceleration and deceleration (starting and stopping the weight stack) so it can counteract the effects of inertia and momentum. The problem with weight stack machines is that they were designed to work at one restricted speed of movement to counteract the effects of inertia and momentum.


Graph 2. 4 Second training speed, inertia force load is 20 lbs. greater 2 Second training speed, inertia force load is 60 lbs. greater.


Graph 3. 1 Second training speed, inertia force load is 80 lbs. greater.

Keiser was invented to provide high resistance with very little inertia (moving mass), and without the dependence upon gravity. The elimination of a weight stack reduces the mass; therefore the force due to acceleration is virtually eliminated, which leaves only pure variable resistant force. The reduction of the acceleration forces and the elimination of dependence on gravity allow the variable resistance strength curve to remain consistent over a wide range of training speeds. Read the the full research study and judge for yourself.

Full Article
"The Science of Resistance"

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"A comparison of the Kinematics, Kinetics, and Muscle Activity Between Pneumatic and Free Weight Resistance" Frost, Cronin, & Newton