The study subjects were 60 patients who underwent
PLIF in 2011, at least 3 months before the start of the
study. Patients with sudden or constant pain, neurologicalproblems, or mental problems, or who were pregnant, were
excluded from this study. All the subjects received an explanation
about the study and gave their voluntary informed
consent before participation. Pain was self-assessed on a
visual analog scale (VAS), and the low back disability index
was evaluated by conducting a survey about LBP symptoms
of the 60 PLIF patients. Lumbar extension strength was
measured using MedX, and the maximum strength of the
lumbar deep muscle was measured after 10 minutes of rest.
Using SPSS, we randomized the patients into 3 groups
according to the rehabilitation they underwent: ER, EER, or
SER (exercise rehabilitation group, ERG; extension exercise
rehabilitation group, EERG; and stability exercise rehabilitation
group, SERG; respectively). A pretest was conducted
after collecting physical and medical information. All the
groups were treated by 3 professional physical therapists
for 30 minutes, 3 times a week, with warm-up exercises
lasting for approximately 5–10 minutes before and after the
exercise training13). We varied each group’s treatment time
and instructed the subjects to not to talk about their treatment
to blind them as to which group they were in. After 8 weeks,
we measured the changes using the same methods used in
the pretest.