Elsevier

Clinical Biomechanics

Volume 23, Issue 10, December 2008, Pages 1227-1236
Clinical Biomechanics

Upper limb motor strategies in persons with and without shoulder impingement syndrome across different speeds of movement

https://doi.org/10.1016/j.clinbiomech.2008.07.009Get rights and content

Abstract

Background

Activities requiring repetitive arm movements, including high velocity actions, have been identified as a risk factor for shoulder impingement. However, the effect of speed on upper limb motor strategies has yet to be evaluated for individuals with shoulder impingement. The aims of this study were to characterize upper limb motor strategies in individuals with and without shoulder impingement during reaching at natural speed and to evaluate their adaptation to higher speeds of movement.

Methods

Twenty healthy individuals and 33 individuals with shoulder impingement took part in one evaluation session. They performed reaching at natural and fast speeds, toward targets located at 90° of arm elevation in two different planes. Reaching speed, upper limb kinematics and shoulder muscular activity were used to characterize motor strategies.

Findings

Individuals with shoulder impingement present altered motor strategies during reaching tasks. However, changes with speed were comparable in both groups, showing similar adaptation to speed. Larger intergroup differences were found when individuals with shoulder impingement were separated into groups presenting higher or lower than normal clavicular elevation. In the frontal plane, increased clavicular elevation for individuals with impingement was associated with more trunk rotation, less elbow flexion and upper trapezius electromyographic activity during reaching, and a more anterior plane of shoulder elevation at the end of reaching as compared to the healthy individuals.

Interpretation

The present results demonstrate that not all individuals with shoulder impingement present the same abnormal motor strategy. Therefore, characterizing motor strategies before implementing rehabilitation intervention is essential.

Introduction

Shoulder impingement syndrome (SIS) has been described as a mechanical compression of the subacromial structures under the coracoacromial arch during arm elevation (Matsen and Arntz, 1990). Work, sport and daily living activities that require repetitive arm elevation movements have been identified as risk factors for the development of SIS (van der Heijden, 1999). Some of these activities involve repetitive arm movements performed with high velocity. Previous studies have shown that the biomechanical demand on upper limb joints during such activities varies with the velocity of movement (Thomas et al., 2003). However, the effect of movement speed has yet to be evaluated in individuals with shoulder impairments such as SIS.

To date, motor strategies of individuals with SIS during arm movement have only been characterized at natural speed. During such movement, impairments in the scapulohumeral and scapulathoracic muscular activation and the kinematics of the shoulder girdle were found (Michener et al., 2003). It has been shown that individuals with SIS present lower activity of the serratus anterior, higher activity of the upper and lower trapezius (Ludewig and Cook, 2000), lack of coordination between the different parts of the trapezius (Wadsworth and Bullock-Saxton, 1997), and lower activity of infraspinatus, subscapularis and middle deltoid during arm elevation (Reddy et al., 2000). As for kinematics, contrasting results have been observed between studies for scapular movement during arm elevation following SIS showing either an increase or decrease of scapular posterior tilting and lateral rotation (Borstad and Ludewig, 2002, Ludewig and Cook, 2000, Lukasiewicz et al., 1999, McClure et al., 2006). Increased clavicular elevation and retraction have also been observed (McClure et al., 2006). A better understanding of how individuals with SIS control high speed reaching will help define outcomes to follow motor recovery and develop rehabilitation interventions.

The evaluation of the kinematic and muscular activity impairments associated with SIS has been limited so far to the shoulder girdle during arm elevation. However, arm movements during functional activities usually involve goal directed reaching. During these actions, the goal of the shoulder joint is to carry the upper limb toward the target. Hence, most of arm movements require the coordination of numerous upper limb joints (Shumway-Cook and Woollacott, 2000). Therefore, it is necessary to evaluate the whole upper limb during multiarticular functional tasks in order to best represent the motor strategies during daily life activities. The aims of this study were first to characterize and compare the motor strategies of the upper limb used by healthy individuals and by individuals with SIS during reaching movements at a natural speed. Second, it was to evaluate their adaptation to higher speed movements and to determine whether any group differences were dependent on speed. We think that subjects with SIS will present motor deficits during natural speed reaching, mainly in the kinematic patterns of their proximal joints. Furthermore, higher speed of movement will amplify the deficits observed at natural speed and highlight additional deficits.

Section snippets

Participants

Twenty healthy subjects and 33 subjects with SIS voluntarily participated in the study. Subjects with SIS were diagnosed by an orthopaedic surgeon and included if they had at least one positive finding in each of these categories: painful arc of movement during flexion or abduction; positive Neer or Kennedy-Hawkins impingement signs; pain on resisted lateral rotation, abduction or Jobe test. Exclusion criteria were: calcification or fracture; shoulder instability (positive sulcus and

Results

The basic descriptive characteristics of the subjects are given in Table 1. No difference was observed between the SIS and control groups for age, weight, height, sex and dominance. The pain level in the SIS group was stable across the study. Twenty-seven out of the 33 subjects with SIS (82%) had pain during reaching. Their mean pain level was 1 (standard deviation (SD) = 0.7) out of 5, which represents a low level of pain.

Discussion

The individuals with SIS presented altered kinematics and muscular activation compared to a control group during multiarticular reaching tasks performed at a natural speed. These results concur with previous studies that have shown movement alterations during specific shoulder movements (Borstad and Ludewig, 2002, Ludewig and Cook, 2000, McClure et al., 2006). The alterations were mostly seen in the frontal plane, with decreased upper trapezius activity during pre-movement, a more anterior

Conclusion

Individuals with SIS presented altered motor strategies when performing reaching tasks. These alterations were mostly observed in the magnitude of the joints’ excursions and muscular activities; and not in the coordination or in the timing of these variables during reaching. The division of the SIS subjects into subgroups confirmed that not all subjects with SIS use the same motor strategy. This last result highlights the importance of evaluating motor strategies to guide rehabilitation

Conflict of interest statement

The authors declare that they have no competing interests.

Acknowledgements

The authors acknowledge the support of Guy St-Vincent and Dr. R. Lirette. This study was supported by a grant from the Ordre professionnel de la physiothérapie du Québec.

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