['We studied the impact of acute opioid administration on work-related exercise performance in patients with chronic back pain. A double-blinded, random-order, placebo-controlled, crossover trial was conducted. Subjects were predominantly men (63%), with a mean age of 49 years. Subjects performed a continuous lifting and lowering test to voluntary fatigue at a load equivalent to 33% of their predetermined maximal lifting load twice: Once after receiving a single intravenous dose of 1 mug/kg fentanyl (a narcotic analgesic) and once after saline placebo. Of the 30 subjects undergoing testing, 3 subjects were unable to complete testing due to medication-induced nausea. Subjects lifted on average 29.4 +/- 17.9 kg under the influence of fentanyl versus 25.6 +/- 3.1 kg with placebo (effect size = 0.23). Time to fatigue was higher in the fentanyl group (312 +/- 251.4 vs 231 +/- 199.9 seconds, effect size = 0.40), and these subjects also performed more total work (7004 +/- 5144 vs 4748 +/- 3147 J, effect size = 0.72). Opioid analgesia improves lifting performance in the short term in individuals with chronic back pain. Longer trials of the effectiveness of opioid analgesia as an adjunct to functional restoration programs are recommended.'] Does acute opioid administration improve work-related exercise performance in patients with chronic back pain?