Abstract
BackgroundContractile tissue plays an important role in mobility deficits in frozen shoulder (FS). However, no study has assessed the effect of the muscle release technique on the muscle activation and kinematics in individuals with FS. The purposes of this study were to assess the differences in shoulder muscle activity and kinematics between the FS and asymptomatic groups; and to determine the immediate effects of muscle release intervention in the FS group.MethodsTwenty patients with FS and 20 asymptomatic controls were recruited. The outcome measures included muscle activity of the upper and lower trapezius (UT and LT), infraspinatus (ISp), pectoralis major (PM), and teres major (TM), shoulder kinematics (humeral elevation, scapular posterior tilt (PT) and upward rotation (UR), shoulder mobility, and pain. Participants in the FS group received one-session of heat and manual muscle release. Measurements were obtained at baseline, and immediately after intervention. Multivariate analysis of variance was used for data analysis. The level of significance was set at α=0.05.ResultsCompared to the controls, the FS group revealed significantly decreased LT (difference =55.89%, P=0.001) and ISp muscle activity (difference =26.32%, P =0.043) during the scaption task, and increased PM activity (difference =6.31%, P =0.014) during the thumb to waist task. The FS group showed decreased humeral elevation, scapular PT, and UR (difference = 35.36°, 10.18°, 6.73° respectively, P <0.05). Muscle release intervention immediately decreased pain (VAS drop 1.7, P <0.001); improved muscle activity during scaption (UT: 12.68% increase, LT: 35.46% increase, P <0.05) and hand to neck (UT: 12.14% increase, LT: 34.04% increase, P <0.05) task; and increased peak humeral elevation and scapular PT during scaption (95.18°±15.83° to 98.24°±15.57°, P=0.034; 11.06°±3.94° to 14.36°±4.65°, P=0.002), and increased scapular PT during the hand to neck (9.47°±3.86° to 12.80°±8.33°, P=0.025) task. No statistical significance was found for other group comparisons or intervention effect.ConclusionPatients with FS presented with altered shoulder muscle activity and kinematics, and one-session of heat and manual muscle release showed beneficial effects on shoulder muscle performance, kinematics, mobility, and pain.Trial registrationRetrospectively registered on Jan 18, 2016 (ACTRN 12616000031460).
Highlights
Contractile tissue plays an important role in mobility deficits in frozen shoulder (FS)
Our results demonstrated that the FS group had decreased infraspinatus activation during scaption, but we failed to find any group difference in teres major muscle activation
Our study showed muscle release combined with local heat intervention resulted in increased upper and lower trapezius muscle activation during the scaption and hand to neck task, approaching the level found in the asymptomatic group (Table 3)
Summary
Contractile tissue plays an important role in mobility deficits in frozen shoulder (FS). Known as frozen shoulder (FS) is a common shoulder disorder with a prevalence of up to 26% of the adult population [1, 2]. It is characterized by chronic shoulder pain, mobility deficits, and functional limitations [1, 2]. Recent publications suggested that the role of contractile tissue in shoulder mobility deficits and functional limitations might have been overlooked [9, 10]. Hung et al (2010) found patients with FS had higher muscle stiffness, which was related to the shoulder ROM limitation [10]
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