Low back pain (LBP) ranks among the first diseases in term of years lived with disability. The latest Clinical Guideline from the American College of Physicians for acute LBP recommends to select "nonpharmacologic treatment with superficial heat, massage, acupuncture or spinal manipulation". The application of superficial heat ("thermal therapy") may provide enough pain relief in the acute phase to remain active, which is recommended to prevent the development of chronicity. However, no studies have tested if the combination of heat and exercises provide additional benefit on short, middle and long-term follow-up in people with acute LBP.

Hence, the main objective of this study is to determine the immediate, short-, middle- and long-term effect of continuous low-level thermal therapy in combination or not with exercises on pain, disability, and physical activity level in people with acute LBP.

Project hypothesis : The Thermal care + Exercises group will show greater improvement in pain, disability and physical activity level than both Thermal care and Control groups for immediate, short-, middle- and long-term follow-ups.

Sixty individuals with acute LBP will be recruited. This study will include six assessments over 6 months. At the baseline evaluation, participants will complete questionnaires on symptoms, disability, pain-related fear and self-efficacy. Afterwards, participants will be randomly assigned to one of three intervention programs: 1) Thermal care group, 2) Exercises + Thermal care group, and 3) Control group. They will immediately meet a physical therapist to review and perform their assigned program.

Participants will then take part in their assigned 7-day intervention program, during which they will wear a fitness wristband to track physical activity level. Finally, the same outcomes will be reassessed to determine the effect of intervention at 1 week, 1 month, 3 months and 6 months after baseline.

Low back pain (LBP) ranks among the first diseases in term of years lived with disability, which is mostly explained by the development of recurrent or chronic pain. A systematic review observed that 62% of patients still have pain 12 months after onset (recurrent and chronic) while another estimated that between 2% and 34% of acute cases will develop chronic LBP. These rates highlight the need to identify the best therapeutic approaches at the acute stage to prevent transition to chronicity and high recurrence. The latest Clinical Guideline from the American College of Physicians for acute LBP recommends to select "nonpharmacologic treatment with superficial heat, massage, acupuncture or spinal manipulation". The application of superficial heat ("thermal therapy") presented the strongest evidence (moderate) for short-term reduction in pain. Four randomized controlled trials (RCT) that tested the effect of a wearable heatwrap (the most studied form of thermal therapy in acute LBP) reported a reduction in pain and disability up to 2 days after cessation of the intervention: an effect superior to Ibuprofen, Acetaminophen or oral placebo. Heatwrap may provide enough pain relief in the acute phase to remain active, which is recommended to prevent the development of chronicity. One RCT showed that the addition of a heatwrap to exercise provided greater short-term improvement in pain/disability than exercise alone. Although some authors suggest that an increase in physical activity level may explain such an effect, this assumption has not been tested yet.

Hence, the main objective of this RCT is to determine the immediate, short-, middle- and long-term effect of continuous low-level thermal therapy in combination or not with exercises on pain, disability, and physical activity level in people with acute LBP.

Project hypothesis : The Thermal care + Exercises group will show greater improvement in pain, disability and physical activity level than both Thermal care and Control groups for immediate, short-, middle- and long-term follow-ups.

Participants: Individuals with acute LBP will be included according to the mentioned inclusion/exclusion criteria. They will be recruited from medical and through the electronic mailing list of Université Laval (> 52,000 individuals). The list of participants of the Quebec Low Back Pain Study (QLBPS Core Dataset, funded by the QPRN) will also be used - all participants in the Quebec City area recruited for the QLBPS Core Dataset will be referred for the present project.

Study Design: This study will include six assessments over 6 months : baseline pre, 1-hour post, 1 week, 1 month, 3 months, 6 months. At the baseline evaluation (baseline pre), participants will complete self-administered questionnaires on symptoms and disability (Numerical scale for pain, Oswestry Disability Index - ODI, Global Rating of Change - GRC), on pain-related fear (Tampa Scale of Kinesiophobia - TSK) and on pain-related self-efficacy (Chronic Disease Self-Efficacy Scale short version - CDSES-6). Finally, participants will be randomly assigned to one of three intervention programs: 1) Thermal care group, 2) Thermal care + Exercises group, and 3) Control group. Immediately after group assignment (same session), participants will meet a physical therapist (PT) to review their assigned program (60-minutes meeting), during which a ThermaCare® Heat wrap or a sham wrap will be applied by the PT. In Thermal Care + Exercises group, an exercise program will be taught by the PT then performed by participants. General advices on the management of acute LBP will be given to all participants. Thereafter, the immediate effect of thermal therapy on pain will be evaluated (1-hour post-intervention assesment).

After the baseline evaluation and PT session, participants will perform their assigned 7-day intervention program. Every day, they will complete a logbook related to their pain level during the previous day and to their adherence to their program. In addition, participants will wear a fitness wristband to track physical activity level for 7 days (number of steps per day). Then, pain, ODI, GRC, TSK and CDSES-6 will be assessed at 1 week, 1 month, 3 months and 6 months after baseline to determine short-, middle-, and long-term effect of interventions.

Randomisation: a list will be generated using a computer random number generator by an independent research assistant (allocation concealed in sealed and opaque envelopes).

Sample size & Statistical analyses: Based on sample size calculation, calculated for the primary outcome (ODI) and previous data from the project investigators group (n=50 with acute LBP), 20 participants are required per group (G*Power 3.1.7; effect size: 0.80, α = 0.05, β = 0.80, mean baseline ODI of 44.0 +/- 13.5, lost at follow-up = 10%). Thus, 60 participants with acute LBP will be recruited.

To determine the effect of interventions, two-way ANOVA (Group x Time) will be performed (after confirming normality and homogeneity of variance). Bonferroni adjustments for multiple comparisons will be used (posthoc), and effect sizes will be reported (η2).

Inclusion Criteria:

• to be suffering from low back pain (LBP) for a period of less than 6 weeks (with or without leg pain) that had limited one's activities or changed the daily routine for more than a day,
• to have been pain free for at least 3 months before the onset of the current LBP episode.

Exclusion Criteria:

• "red flag" signs that may suggest serious spinal pathology,
• history of spinal surgery,
• obvious lower limb radiculopathy
• fibromyalgia
• rheumatoid arthritis
• important skin lesion in the lumbar area
• alteration of cutaneous sensations or temperature perception
• being pregnant of trying to become

Outcomes assessor is blinded to participant's intervention allocation. Participants are blinded to the nature of interventions given in the other arms' groups.