Table 1 Inclusion criteria for the current systematic review, including cut-offs for clinical relevance

Study design

Systematic review of RCTs. A review was considered systematic if the review authors had identified it as such.

Population

Adult (18–65 years) patients with non-specific acute LBP (onset to 6 weeks). If the systematic review contained primary studies on other populations, e.g., adolescents, at least 70% of the included studies had to be on adult populations. Findings for populations with acute LBP had to be separable from other populations.

Interventions

Interventions classified as exercise therapy (earlier defined in the background) used by physiotherapists.

Comparisons

Placebo, sham, waiting list, no treatment, usual care, minimal intervention, non-steroid anti-inflammatory drugs (NSAIDs), analgesics, or other physiotherapeutic interventions.

Outcomes

Pain intensity (hereafter referred to as pain), disability, recurrence, adverse effects.

Length of follow-up

Post-treatment, short-term (closest to three months), intermediate-term (closest to 6 months), and long-term (closest to 12 months) follow-up.

Minimal important difference (MID)^a

15 mm on the Visual Analogue Scale (VAS) (0–100), 5 on the Roland Morris Disability Questionnaire (RMDQ) (0–24), and 10 for the Oswestry Disability Index (ODI) (0–100) [37].

Clinical relevance for pooled effect sizes

Small mean difference (MD) < 10%; medium MD 10–20%; large MD > 20% of the scale (e.g., < 10 mm on a 100 mm VAS). For relative risk: small standardized mean difference (SMD) < 0.4; medium SMD 0.41 to 0.7; large SMD > 0.7 [38].

Settings

Primary care physiotherapy or other settings in which the intervention could be practiced, such as home or gym.