A Cochrane review included 9 studies with a total of 1 117 subjects. Heat wrap therapy significantly reduced pain after five days (weighted mean difference [WMD] 1.06, 95% confidence interval [CI] 0.68 to 1.45, scale range 0 to 5; 2 trials, n=258) compared to oral placebo in a group with a mix of acute and sub-acute low-back pain. A heated blanket significantly decreased acute low-back pain immediately after application (WMD -32.20, 95%CI -38.69 to -25.71, scale range 0 to 100; 1 trial, n=90). One trial of 100 participants with a mix of acute and sub-acute low-back pain examined the additional effects of adding exercise to heat wrap, and found that it reduced pain after seven days. There is insufficient evidence to evaluate the effects of cold for low-back pain, and conflicting evidence for any differences between heat and cold for low-back pain.