Scapula-Focused Exercises With or Without Biofeedback and Corticospinal Excitability in Recreational Overhead Athletes With Shoulder Impingement

Abstract

Context: Individuals with shoulder impingement syndrome (SIS) exhibit changes in corticospinal excitability, scapular kinematics, and scapular muscle-activation patterns. To restore the scapular kinematics and muscle-activation patterns in individuals with SIS, treatment protocols usually include scapula-focused exercises, such as scapular-orientation and strength training.

Objective: To investigate whether scapular-orientation and strength training can reverse the altered corticospinal excitability of recreational overhead athletes with SIS.

Design: Randomized controlled clinical trial.

Setting: University laboratory.

Patients or other participants: Forty-one recreational overhead athletes with SIS: 20 in the scapular-orientation group (age = 26.45 ± 4.13 years, height = 171.85 ± 7.88 cm, mass = 66.70 ± 10.68 kg) and 21 in the strengthening group (age = 26.43 ± 5.55 years, height = 171.62 ± 5.87 cm, mass = 68.67 ± 10.18 kg).

Intervention(s): Both groups performed a 30-minute training protocol consisting of 3 exercises to strengthen the lower trapezius (LT) and serratus anterior muscles without overactivating the upper trapezius muscles. Participants in the scapular-orientation group were instructed to consciously activate their scapular muscles with electromyographic biofeedback and cues, whereas the strengthening group did not receive biofeedback or cues for scapular motion.

Main outcome measure(s): Corticospinal excitability was assessed using transcranial magnetic stimulation. Scapular kinematics and muscle activation during arm elevation were also measured.

Results: After training, both groups demonstrated an increase in motor-evoked potentials in the LT (P = .004) and increases in scapular upward rotation (P = .03), LT activation (P < .001), and serratus anterior activation (P < .001) during arm elevation. Moreover, the scapular-orientation group showed higher LT activation levels during arm elevation after training than the strengthening group (P = .03).

Conclusions: With or without biofeedback and cues, scapula-focused exercises improved scapular control and increased corticospinal excitability. Adding biofeedback and cues for scapular control during exercise helped facilitate greater LT activation, so feedback and cues are recommended during scapula-focused training.

Keywords: scapular dyskinesis; scapular-orientation exercise; strength training; transcranial magnetic stimulation.

Figure 1

Exercise program for both scapular-orientation and strengthening groups consisted of, A, arm elevation in the scapular plane to 90° in the sitting position, B, shoulder flexion to 90° in the side-lying position, and C, shoulder external rotation in the side-lying position.

Figure 2

Flowchart of the study. ^a All participants (n = 41) received the measurement of transcranial magnetic stimulation (TMS) in the pretest. Three participants did not demonstrate the defined responses (>0.1 mV in 5 of 10 trials) even at 100% of maximum stimulator output (MSO). Therefore, their active motor threshold (AMT) and motor-evoked potential (MEP) were not available. ^b Among those providing AMT and MEP (n = 38), 10 had high AMT, so their testing intensity (150% AMT) of cortical silent period (CSP) was >100% MSO. Therefore, their CSP was not available. ^c We changed TMS setup after we recruited 8 participants, so we excluded the first 8 participants from analysis.

Figure 3

Individual data and bar graphs with means and SEs of transcranial magnetic stimulation (TMS) variables at pretest and posttest in the scapular-orientation and strengthening groups. A, Motor-evoked potential at 120% of active motor threshold of the lower trapezius (LT). B, Motor-evoked potential of the serratus anterior. C, Active motor threshold of the LT. D, Cortical silent period of the LT. Motor-evoked potential was normalized by maximal voluntary isometric contraction (MVIC). Abbreviation: MSO, maximum stimulator output. ^a Time effect (P < .05).

Figure 4

Scapular kinematics (means and SEs) during arm elevation at pretest and posttest in the scapular-orientation and strengthening groups. A and B, Upward/downward rotation. C and D, Posterior/anterior tilt. E and F, Internal/external rotation. A time effect was found in upward rotation (P = .03).

Figure 5

Muscle activation (means and SEs) during pretest and posttest arm elevation of the upper trapezius in, A, scapular-orientation and, B, strengthening groups; lower trapezius in, C, scapular-orientation and, D, strengthening groups; and serratus anterior in the, E, scapular-orientation and, F, strengthening groups. ^a Difference between groups at posttest (P = .03). ^b Difference between pretest and posttest (P < .05).