Objectives. To investigate associations between muscle strength and pain sensitivity among healthy volunteers and associations between different pain sensitivity measures. Methods. Twenty-eight healthy volunteers (21 females) participated. Pressure pain thresholds (PPTs) were obtained from 1) computer-controlled pressure algometry on the vastus lateralis and deltoid muscles and on the infrapatellar fat pad and 2) computerized cuff pressure algometry applied on the lower leg. Deep-tissue pain sensitivity (intensity and duration) was assessed by hypertonic saline injections into the vastus lateralis, deltoid, and infrapatellar fat pad. Quadriceps and hamstring muscle strength was assessed isometrically at 60-degree knee flexion using a dynamometer. Associations between pain sensitivity and muscle strength were investigated using multiple regressions including age, gender, and body mass index as covariates. Results. Knee extension strength was associated with computer-controlled PPT on the vastus lateralis muscle. Computer-controlled PPTs were significantly correlated between sites ( ) and with cuff PPT ( ). Saline induced pain intensity and duration were correlated between sites ( ) and with all PPTs ( ). Conclusions. Pressure pain thresholds at the vastus lateralis are positively associated with knee extensor muscle strength. Different pain sensitivity assessment methods are generally correlated. The cuff PPT and evoked infrapatellar pain seem to reflect the general pain sensitivity. This trial is registered with ClinicalTrials.gov: NCT01351558. 1. Introduction Musculoskeletal pain is very common. In Europe, as many as 1 out of 5 reports frequent and persistent musculoskeletal pain [1], and among those with musculoskeletal pain 50% have constant pain [2]. Thus, musculoskeletal pain is a significant challenge to society. While pain is the cardinal symptom in many musculoskeletal diseases, impaired muscle function is also a typical sign of musculoskeletal diseases, such as fibromyalgia and osteoarthritis [3, 4]. Adequate muscle function is crucial to maintain an independent life style, and reduced knee muscle strength is further associated with elevated risks of disability and mortality [5]. In recent years, many musculoskeletal diseases have been associated with increased pain sensitivity. Among patients with fibromyalgia, the increased pain sensitivity has been reported [6], and widespread increased pain sensitivity have also been demonstrated in subgroups of patients with osteoarthritis, lateral epicondylitis, and low back pain [7–9]. Jespersen et al.
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