Context: Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern.Objective: To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes.Setting: Human performance research laboratory. Design: Descriptive laboratory study. Patients or Other Participants: Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side. Intervention(s):We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction.Main Outcome Measure(s): Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences. Results:We found a decrease in ascending-phase and descending-phase lower trapezius activity (F 1,25 = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F 1,25 = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F 1,24 = 3.7, P = .04) postfatigue.Conclusions: The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular and glenohumeral force couples. Fatigue-induced alterations in the lower trapezius might predispose the infraspinatus to injury through chronically increased activation.Key Words: muscle function, rotator cuff, upper extremity Key Points • Shoulder external rotation muscle fatigue contributed to altered scapular muscle activation and kinematics.• From prefatigue to postfatigue, lower trapezius activation decreased by 4%, infraspinatus activity increased in the descending phase by 4%, and scapular upward rotation motion increased in the ascending phase by 3°.• Upper trapezius and serratus activation did not change from prefatigue to postfatigue.• The force couple between the lower trapezius and infraspinatus was interdependent, and alterations in the lower trapezius due to shoulder external rotation muscle fatigue might predispose the shoulder to injury.

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BackgroundDisplaced olecranon fractures after a simple fall are common in elderly patients. This patient group often has multiple medical co-morbidities and low functional demands. Standard treatment for these fractures has been operative fixation, using either wires or a plate. Recent case series suggest that such injuries can be managed without surgery with good functional outcomes. There has been no published trial comparing operative to non-operative treatment for displaced olecranon fractures.This project aims to test for superiority of operative treatment versus non-operative treatment for displaced olecranon fractures in the elderly, by comparing pain and function in the affected limb up to one year after the injury.Methods/DesignSOFIE is an international study with a multicentre pragmatic randomised controlled trial design. The primary objective of the study is to compare a patient related outcome, the Disability of the Arm Shoulder and Hand (DASH) Score, between patients treated operatively and non-operatively at twelve months.Patients will be considered for the study if they are 75 years of age or older, medically fit for surgery, have an isolated displaced olecranon fracture, and present within 14 days of injury. Eligible patients willing to participate will be randomised either to operative fixation, with surgery using the preferred technique of the treating orthopaedic surgeon (tension band wiring or plate fixation), or to non-operative treatment involving early range of motion as tolerated.Secondary outcome measures will include pain, active range of motion, elbow extension strength, and any adverse events (infection, secondary interventions) at 3 and 12 months.DiscussionThe study will answer an important clinical question about the effectiveness of a commonly performed orthopaedic procedure, and will guide future treatment for displaced olecranon fractures in the elderly.Trial registration numberWorld Health Organisation Universal Trial Number (WHO UTN) - U111111574090.Australian and New Zealand Clinical Trials Registry (ANZCTR) - ACTRN12614000588695.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-015-0789-6) contains supplementary material, which is available to authorized users.

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