Eccentric Training Changes The Muscle Tension Map Of The Upper Trapezius In Female Computer Users With Chronic Neck-Shoulder Pain

Background: Neck-shoulder pain (NSP) is a major cause of disability worldwide. Differences in the viscoelastic properties of the neck-shoulder muscles have been reported in individuals with NSP compared to healthy controls. An abnormal resting muscle tone (or muscle tension) has been proposed as a source of musculoskeletal pain within this population. Strength training may relieve NSP and influence the muscle state of tension. To date, topographical mapping technology has not been used to evaluate the spatial distribution of upper trapezius muscle tension in computer users with NSP. Assessing the neck-shoulder muscles tension may help to monitor NSP status and evaluate the efficacy of therapeutic interventions. Purpose: This study aimed to compare the muscle tension map of the upper trapezius in female computer users with and without chronic non-specific NSP (part A), and to investigate the effects of a 5-weeks unilateral eccentric training protocol on the upper trapezius muscle tension in females with chronic NSP (part B). Methods: In part A, a cross-sectional study was carried out including 20 female computer users with long-lasting NSP and 20 controls. In part B (longitudinal study), women with NSP followed a supervised unilateral upper trapezius eccentric training program for 5 consecutive weeks (twice a week). A topographical map of muscle state of tension, using a 15-point grid covering myotendinous (MT) and muscle belly (MB) sites, was assessed on the painful upper trapezius or the same side matched on dominance for controls, with a myotonometer device (Myoton AS, Tallinn, Estonia). Muscle tension was also measured at a control spot on the contralateral side. Outcomes were assessed before and immediately after training. For part A, a mixed-model analysis of variance (ANOVA) was used to compare the differences in upper trapezius muscle tension between groups (NSP and control) and sites (MT and MB). For part B, sites (MT, MB, and control spot), and sessions (before and after intervention) were introduced as within-subject factor in a repeated-measures ANOVA to detect differences in upper trapezius muscle tension. Results: One female with NSP dropped out after baseline. The ANOVA (part A) revealed significant differences in muscle tension between sites (F=39.277; p< 0.001), but not between groups (F=0.010; p=0.922). No Group*Site interaction was observed (F=0.470; p=0.495). In part B, there were significant differences between sessions (F=5.134; p=0.025), and sites (F=47.314; p< 0.001), although no Sessions*Site interaction was found (F=0.551; p=0.578). Upper trapezius muscle tension decreased significantly after intervention for MB sites (p=0.024), but not for MT sites (p=0.140) or the control spot (p=0.676). Conclusion(s): This study showed no differences in spatial distribution of the upper trapezius muscle tension in female computer users with or without chronic non-specific NSP. A supervised 5-weeks unilateral eccentric training protocol decreased upper trapezius muscle tension at MB sites in women with NSP. Implications: The lack of differences in upper trapezius muscle tension between women with and without chronic non-specific NSP support the contention that processes other than physiological changes may contribute to the pain experience in this population. Unilateral strength training involving repeated eccentric contractions revealed discrepant effects on muscle tension.