Randomization and blinding
After surgery, the participants will be randomized into
either the combined back-specific (combination of
strength training and training of control of the neutral
lumbar spine position) and aerobic training arm or to
the control arm. The allocation will be based on computer
randomization in blocks of four patients. The
randomization will be performed and the randomization
lists maintained by the research nurses, who will not be
involved in the assessment or treatment of the participants.
The first list will be used to randomize the participants
with isthmic spondylolisthesis and the second list
to randomize those with degenerative spondylolisthesis.
Both centres will have their own randomization lists.
Assessors will be blind to the treatment group in both
study centres. Physiotherapists will not be blind to group
membership; instead, but both study arms will have their
own physiotherapist who will carry out postoperative
guidance. Blinding the patients to the allocation is not
possible due to the nature of the intervention.