Subjects were recruited from the Department of Physical Medicine and
Rehabilitation and the Outpatient
Physical Therapy Clinic at Stanford
University Medical Center. Only people who reported a recent onset of
low back pain (duration of 3
months) and the following signs and
symptoms were admitted: localized
low back pain at or above the waist
level, decreased lumbar extension
(assessed qualitatively while standing), and increased localized pain
with lumbar extension during standing. The primary exclusion criteria
were: spinal malignancy, cardiovascular disease, evidence of cord compression, aortic aneurysm, hiatal
hernia, uncontrolled hypertension,
spinal infection, severe respiratory
disease, pregnancy, abdominal hernia, prior low back surgery, gross
spinal deformity, spondylolisthesis,
known rheumatic joint disease, and
implanted devices that could interact with the magnetic field (eg, pacemakers, cochlear implants, or ferromagnetic cerebral aneurysm clips).In addition to these exclusion criteria, subjects were screened for any
clinical evidence of lumbar disk pathology. Therefore, subjects who
demonstrated any of the following
were excluded: radiating pain below
the level of the buttocks; sensation
changes in the lower extremities; diminished reflex; lower-extremity
weakness, neurological signs, or
both; urinary or fecal incontinence;
and increased peripheral pain with
repeated lumbar extension.