EER involved exercises using a MedX device and the
McKenzie extension exercise. The MedX exercise involved
20 repetitions of an isotonic exercise at a resistance of 50%
of the maximal extension muscle strength and the weight was
increased by 5% when the patient could execute more than
20 repetitions. In ER, it is more efficient if 1 set of a trunk
extension exercise makes the muscles more tired than when
multiple sets of exercise are performed. This is because the
nerve activity pattern decreases in the lumbar muscles over
multiple sets14). Therefore, only 1 set was performed at 70%
of the maximal isometric extension muscle strength.