Effect of physical training on function of chronically painful muscles: A randomized controlled trial
Pain and tenderness of the upper trapezius muscle is frequent in several occupational groups. The objective of this study is to investigate the effect of three contrasting interventions on muscle function and pain in women with trapezius myalgia. A group of employed women (n=42) with a clinical diagnosis of trapezius myalgia participated in a 10 week randomized controlled intervention; specific strength training of the neck and shoulder muscles (SST), general fitness training performed as leg-bicycling (GFT), or a reference intervention without physical activity (REF). Torque and electromyography (EMG) were recorded during maximal shoulder abductions in an isokinetic dynamometer at -60, 60, 0 and 180 degrees. Further, a submaximal reference contraction with only the load of the arms was performed. Results: Significant changes were observed only in specific strength training. Pain decreased 42-49%. While EMG activity of the unaffected deltoid remained unchanged during the maximal contractions, an increase in EMG amplitude (42-86%) and median power frequency (19%) were observed for the painful trapezius muscle. Correspondingly, torque increased 18-53%. EMG during the reference contraction decreased significantly for both the trapezius and deltoid muscles.
In conclusion, specific strength training relieves pain and increases maximal activity specifically of the painful trapezius muscle, leading to increased shoulder abduction strength in women with trapezius myalgia. Further, decreased relative workload may indirectly augment pain reduction.