Proponents of
free weights and
weight machines are very much like sheepmen and cattlemen in the old west: both feel strongly about their point of view and have inflexible attitudes toward the other side.
Machines are convenient, high tech, comfortable and attractive. However, they move joints through fixed ranges of motion that can create excessive torque and
unnatural stresses. Also, the exercises are artificial and do not transfer well to functional movement.
Angelo Cacchio and coworkers from the University of Rome in Italy and Illinois State University found that
exercising on a machine that provided free motion similar to
dumbbell and barbell exercises created greater activation of shoulder girdle muscles than a machine that forced movement in a fixed path. They concluded that unconstrained weight training is superior to fixed path
weight machines because it builds intramuscular coordination that might transfer better to functional activities.