The study intervention is a 12-week personalized physical back training program. It consists of six to eight exercises selected from a predefined set by a physical therapist or medical doctor. These exercises are selected through a clinical reasoning process, i.e., they are tailored and problem-oriented, based on the results of a clinical assessment.
An initial one-on-one training session will take place to familiarize participants with the back training program, corresponding to the first week's session of the 12-week intervention period. During the 12-week intervention period, the training comprises one supervised group session per week, lasting 30 minutes, along with three individual unsupervised sessions, each lasting 10-15 minutes. Our procedures ensures that both participants and instructors are blinded to the group allocation, allowing both groups to train together (e.g., mixed training groups).