4. Maintenance and Warranty
The most common type of resistance machine is one that uses gravity as a resistance source. I use mainly this design in weight machines. Gravity in combination with a simple design of pulleys, wheels and inclines, uses a percentage of the weight of the user as I transfer the resistance. Other types of resistance machines can use other forces other than gravity to provide resistance. These include friction, spring-loaded, fan-loaded or fluid-loaded machines.
