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Anami K1, Urabe Y1, Sasadai J1, Kotoshiba S1, Maeda N1
1Hiroshima University, Graduate School of Biomedical and Health Sciences, Department of Sports Rehabilitation, Hiroshima, Japan
Background: In overhead sports, decreasing thoracic mobility causes throwing performance decline and occur troubles in other motor function (Velonica et al., 2012). Upper limbs movement and trunk motion act collaboratively, and previous studies shows that there is a correlation between range of thoracic spine extension and lower thorax expansibility (Theodoridis et al., 2002; Kawaguchi et al., 2004). So, it is considered that restriction of thorax expansion affects the spinal mobility and upper limbs elevation. There are many studies about muscle activities and movement of shoulder joint at the upper limbs elevation, however the function of shoulder joint when thorax expansion is restricted has not been clarified.
Purpose: This study aimed to compare the shoulder muscle activation during upper limbs elevation with and without thoracic expansion restriction.
Methods: Seven healthy men (22 ± 0.7 years, 171 ± 6.2 cm, 62.4 ± 5.1 kg) participated in this study. The subjects were assigned two conditions (restricted or not) and performed upper limbs flexion movement. Under each condition, circumference of the fifth and tenth rib was measured by using a cloth tape measure and wrapped non - elastic tape 50 mm (Ni - treat, Nitto Medical Ltd, Japan) around the xiphoid process in restricted condition. Anatomical markers of these measurement revels were determined at tip of the xiphoid process and tenth thoracic spinous process (Bockenhauser et al., 2007). The author calculated the thoracic expansion differences of maximum inspiratory and expiratory at these measurement revels. An electromyographic sensor was attached to the deltoid (anterior, middle, posterior), trapezius (upper, middle, lower), and infraspinatus. Root mean square (RMS) of these shoulder muscles activities were measured by using Personal - EMG plus (Oisaka Electronic Equipment Ltd, Japan). The differences in muscle activities between two conditions calculated using a paired t - test. The significance level was set at p 0.05.
Results: Under restricted condition, thoracic expansion differences decreased significantly at 5 and 10 rib revels compared to control (p 0.05). The muscle activities of middle deltoid, trapezius (upper, lower) increased significantly during upper limbs elevation (p 001). On the other hand, there was no significantly differences in infraspinatus muscles activities during upper limbs elevation between both conditions.
Conclusion(s): In this study, it was revealed that excessive muscle activities of deltoid and trapezius occurred when the expansion of the lower thorax was restricted. Previous studies indicated that increasing the activities of outer muscles such as deltoid and trapezius easy to cause impingement syndrome (Phadke, 2009). Furthermore, it is reported that excessive muscle activities not only inhibit sports performance but also lead to injury by accumulation fatigue (John et al., 1994). Therefore, this study suggests that focusing on lower thoracic expandability is important to prevent excessive muscle activities of shoulder joint and upper limbs disorders.
Implications: This research could be easy to understand the relationship between thoracic movement and upper limbs elevation and clarify the importance of thorax flexibility.
Keywords: Lower thorax expansibility, Shoulder muscle activity, Upper limbs elevation
Funding acknowledgements: We have no funding acknowledgement in this study.
Purpose: This study aimed to compare the shoulder muscle activation during upper limbs elevation with and without thoracic expansion restriction.
Methods: Seven healthy men (22 ± 0.7 years, 171 ± 6.2 cm, 62.4 ± 5.1 kg) participated in this study. The subjects were assigned two conditions (restricted or not) and performed upper limbs flexion movement. Under each condition, circumference of the fifth and tenth rib was measured by using a cloth tape measure and wrapped non - elastic tape 50 mm (Ni - treat, Nitto Medical Ltd, Japan) around the xiphoid process in restricted condition. Anatomical markers of these measurement revels were determined at tip of the xiphoid process and tenth thoracic spinous process (Bockenhauser et al., 2007). The author calculated the thoracic expansion differences of maximum inspiratory and expiratory at these measurement revels. An electromyographic sensor was attached to the deltoid (anterior, middle, posterior), trapezius (upper, middle, lower), and infraspinatus. Root mean square (RMS) of these shoulder muscles activities were measured by using Personal - EMG plus (Oisaka Electronic Equipment Ltd, Japan). The differences in muscle activities between two conditions calculated using a paired t - test. The significance level was set at p 0.05.
Results: Under restricted condition, thoracic expansion differences decreased significantly at 5 and 10 rib revels compared to control (p 0.05). The muscle activities of middle deltoid, trapezius (upper, lower) increased significantly during upper limbs elevation (p 001). On the other hand, there was no significantly differences in infraspinatus muscles activities during upper limbs elevation between both conditions.
Conclusion(s): In this study, it was revealed that excessive muscle activities of deltoid and trapezius occurred when the expansion of the lower thorax was restricted. Previous studies indicated that increasing the activities of outer muscles such as deltoid and trapezius easy to cause impingement syndrome (Phadke, 2009). Furthermore, it is reported that excessive muscle activities not only inhibit sports performance but also lead to injury by accumulation fatigue (John et al., 1994). Therefore, this study suggests that focusing on lower thoracic expandability is important to prevent excessive muscle activities of shoulder joint and upper limbs disorders.
Implications: This research could be easy to understand the relationship between thoracic movement and upper limbs elevation and clarify the importance of thorax flexibility.
Keywords: Lower thorax expansibility, Shoulder muscle activity, Upper limbs elevation
Funding acknowledgements: We have no funding acknowledgement in this study.
Topic: Sport & sports injuries
Ethics approval required: Yes
Institution: Hiroshima University
Ethics committee: Epidemiological Research
Ethics number: E-1077
All authors, affiliations and abstracts have been published as submitted.
