title: Acute effect of topical menthol on chronic pain in slaughterhouse workers with carpal tunnel syndrome: triple-blind, randomized placebo-controlled trial.
abstract: Topical menthol gels are classified "topical analgesics" and are claimed to relieve minor aches and pains of the musculoskeletal system. In this study we investigate the acute effect of topical menthol on carpal tunnel syndrome (CTS). We screened 645 slaughterhouse workers and recruited 10 participants with CTS and chronic pain of the arm/hand who were randomly distributed into two groups to receive topical menthol (Biofreeze) or placebo (gel with a menthol scent) during the working day and 48 hours later the other treatment (crossover design). Participants rated arm/hand pain intensity during the last hour of work (scale 0-10) immediately before 1, 2, and 3 hours after application. Furthermore, global rating of change (GROC) in arm/hand pain was assessed 3 hours after application. Compared with placebo, pain intensity and GROC improved more following application of topical menthol (P = 0.026 and P = 0.044, resp.). Pain intensity of the arm/hand decreased by -1.2 (CI 95%: -1.7 to -0.6) following topical menthol compared with placebo, corresponding to a moderate effect size of 0.63. In conclusion, topical menthol acutely reduces pain intensity during the working day in slaughterhouse workers with CTS and should be considered as an effective nonsystemic alternative to regular analgesics in the workplace management of chronic and neuropathic pain.
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen O, Denmark ; Institute for Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230 Odense M, Denmark.
authors.forename: Emil
authors.identifier: 0000-0001-7408-222X
authors.initials: E
authors.lastname: Sundstrup
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen O, Denmark ; Institute for Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230 Odense M, Denmark.
authors.forename: Markus D
authors.initials: MD
authors.lastname: Jakobsen
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen O, Denmark.
authors.forename: Mikkel
authors.identifier: 0000-0002-1415-3097
authors.initials: M
authors.lastname: Brandt
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen O, Denmark ; Institute for Sports Science and Clinical Biomechanics, University of Southern Denmark, 5230 Odense M, Denmark.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Jay
authors.affiliation: Laboratory of Physical Activity and Health, Research Group in Sport and Health, Department of Physical Education and Sports, University of Valencia, 46010 Valencia, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Colado
authors.affiliation: Department of Rehabilitation Medicine, The Sixth Affiliated Hospital of Sun Yat-sen University, No. 26 Yuancun 2nd Cross Road, Guangzhou 510655, China.
authors.forename: Yuling
authors.identifier: 0000-0002-2079-3568
authors.initials: Y
authors.lastname: Wang
authors.affiliation: National Research Centre for the Working Environment, Lersø Parkalle 105, 2100 Copenhagen O, Denmark.
authors.forename: Lars L
authors.identifier: 0000-0003-2777-8085
authors.initials: LL
authors.lastname: Andersen