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Patterson A1, Ribeiro DC1
1University of Otago, School of Physiotherapy, Dunedin, New Zealand
Background: Inferior shoulder mobilisation is used for improving range of motion and reducing pain in patients with shoulder disorders. The mechanisms underlying improvements in pain and range of motion are unclear.
Purpose: The primary aim was to investigate the effect of inferior shoulder mobilisation on shoulder and scapular muscle activity, during resisted shoulder abduction in asymptomatic individuals. The secondary aims were to assess the within-session reliability of muscle activity measurements and the presence of carry-over effects.
Methods: This is a repeated-measures, cross-over, randomised controlled study. Twenty-two participants were recruited. The order of intervention was randomised. Each participant performed five repetitions of resisted shoulder abduction before and after the control and mobilisation conditions. The dosage of inferior glide mobilization was set at: grade +IV, three sets, duration of sixty seconds. Surface electromyography recorded activity levels of: anterior, middle and posterior deltoids; supraspinatus; infraspinatus; upper and lower trapezius; serratus anterior; and latissimus dorsi muscles. The primary outcome measure was the mean muscle activity level for each monitored muscle, expressed as a percentage of MVIC. We used mixed-effect models for repeated measures analysis of variance for assessing differences within- and between-conditions (i.e. control and mobilization) and carry-over effects. Changes in activity levels from baseline to follow-up of each monitored muscle were considered as dependent variable. To assess the presence of carry-over effect, we included in the model an interaction between 'Condition x Period x Time Point'. The intraclass correlation coefficient (two-way mixed model, consistency definition, ICC) was used to assess within-session reliability, assuming a single rater. Standard error of measurement (SEM) were calculated to assess variability between the baseline and follow-up measurements using data from control condition.
Results: There were significant reductions in muscle activity levels at follow-up, during the eccentric phase of shoulder abduction, for the mobilisation condition compared to control. Reductions in activity levels were observed for the following muscles: anterior deltoid [-33.3% MVIC, 95%CI: -50.3 to -16.3], middle deltoid [-25.6% MVIC, 95%CI: -30.3 to -20.9]; and serratus anterior [-41.4 %MVIC, 95% CI: -53.9 to -28.9]. No carry-over effects were observed. The within-session reliability was excellent. ICC scores ranged from 0.94 to 0.99, and SEM ranged from 0.7 % MVIC to 22.0 % MVIC.
Conclusion(s): Inferior shoulder mobilisation resulted in significant reductions in muscle activity levels only during the eccentric phase, compared to the control condition. That may be caused by differences in neural control between concentric and eccentric contractions. These findings contribute to a deeper understanding of the mechanisms underlying shoulder joint mobilisation.
Implications: The effects of passive joint mobilisation on shoulder and scapular muscle activity levels may be driven by biomechanical and/or neurophysiological mechanisms. It is possible that: (1) extensibility of the inferior glenohumeral ligament and capsule might have increased following inferior shoulder mobilisation; (2) inferior shoulder mobilisation amplified inhibitory pathways that act at the spinal cord during eccentric contractions. This provides a neurophysiological basis for the inhibitory response observed in shoulder and scapular muscles following inferior shoulder mobilisation.
Keywords: Shoulder, manual therapy, EMG
Funding acknowledgements: Daniel Cury Ribeiro is supported by The Sir Charles Hercus Health Research Fellowship - Health Research Council of New Zealand
Purpose: The primary aim was to investigate the effect of inferior shoulder mobilisation on shoulder and scapular muscle activity, during resisted shoulder abduction in asymptomatic individuals. The secondary aims were to assess the within-session reliability of muscle activity measurements and the presence of carry-over effects.
Methods: This is a repeated-measures, cross-over, randomised controlled study. Twenty-two participants were recruited. The order of intervention was randomised. Each participant performed five repetitions of resisted shoulder abduction before and after the control and mobilisation conditions. The dosage of inferior glide mobilization was set at: grade +IV, three sets, duration of sixty seconds. Surface electromyography recorded activity levels of: anterior, middle and posterior deltoids; supraspinatus; infraspinatus; upper and lower trapezius; serratus anterior; and latissimus dorsi muscles. The primary outcome measure was the mean muscle activity level for each monitored muscle, expressed as a percentage of MVIC. We used mixed-effect models for repeated measures analysis of variance for assessing differences within- and between-conditions (i.e. control and mobilization) and carry-over effects. Changes in activity levels from baseline to follow-up of each monitored muscle were considered as dependent variable. To assess the presence of carry-over effect, we included in the model an interaction between 'Condition x Period x Time Point'. The intraclass correlation coefficient (two-way mixed model, consistency definition, ICC) was used to assess within-session reliability, assuming a single rater. Standard error of measurement (SEM) were calculated to assess variability between the baseline and follow-up measurements using data from control condition.
Results: There were significant reductions in muscle activity levels at follow-up, during the eccentric phase of shoulder abduction, for the mobilisation condition compared to control. Reductions in activity levels were observed for the following muscles: anterior deltoid [-33.3% MVIC, 95%CI: -50.3 to -16.3], middle deltoid [-25.6% MVIC, 95%CI: -30.3 to -20.9]; and serratus anterior [-41.4 %MVIC, 95% CI: -53.9 to -28.9]. No carry-over effects were observed. The within-session reliability was excellent. ICC scores ranged from 0.94 to 0.99, and SEM ranged from 0.7 % MVIC to 22.0 % MVIC.
Conclusion(s): Inferior shoulder mobilisation resulted in significant reductions in muscle activity levels only during the eccentric phase, compared to the control condition. That may be caused by differences in neural control between concentric and eccentric contractions. These findings contribute to a deeper understanding of the mechanisms underlying shoulder joint mobilisation.
Implications: The effects of passive joint mobilisation on shoulder and scapular muscle activity levels may be driven by biomechanical and/or neurophysiological mechanisms. It is possible that: (1) extensibility of the inferior glenohumeral ligament and capsule might have increased following inferior shoulder mobilisation; (2) inferior shoulder mobilisation amplified inhibitory pathways that act at the spinal cord during eccentric contractions. This provides a neurophysiological basis for the inhibitory response observed in shoulder and scapular muscles following inferior shoulder mobilisation.
Keywords: Shoulder, manual therapy, EMG
Funding acknowledgements: Daniel Cury Ribeiro is supported by The Sir Charles Hercus Health Research Fellowship - Health Research Council of New Zealand
Topic: Musculoskeletal: upper limb; Musculoskeletal; Sport & sports injuries
Ethics approval required: Yes
Institution: University of Otago
Ethics committee: University of Otago Ethics Committee
Ethics number: H18/048
All authors, affiliations and abstracts have been published as submitted.
