Context: Alterations in scapular muscle activation, which are common with glenohumeral (GH) injuries, affect stability and function. Rehabilitation aims to reestablish activation between muscles for stability by progressing to whole-body movements.Objective Design: Cross-sectional study. Setting: Laboratory.Patients or Other Participants: Thirty-nine participants who had GH injuries (n ¼ 20; age ¼ 23.6 6 3.2 years, height ¼ 170.7 6 11.5 cm, mass ¼ 74.7 6 13.1 kg) or were healthy (n ¼ 19; age ¼ 24.4 6 3.3 years, height ¼ 173.6 6 8.6 cm, mass ¼ 74.7 6 14.8 kg) were tested.Intervention(s): Clinical examination confirmed each participant's classification as GH injury or healthy control. Participants performed 4 exercises (bow and arrow, external rotation with scapular squeeze, lawnmower, robbery) over 3 seconds with no load while muscle activity was recorded.Main Outcome Measure(s): We used surface electromyography to measure UT, MT, LT, and SA muscle activity. Scapular muscle-activation ratios (UT:MT, UT:LT, and UT:SA) were calculated (normalized mean electromyography of the UT divided by normalized mean electromyography of the MT, LT, and SA). Exercise 3 group analyses of variance with repeated measures were conducted.Results: No group differences for activation ratios or individual muscle activation amplitude were found (P . .05). Similar UT:MT and UT:LT activation ratios during bow-andarrow and robbery exercises were seen (P . .05); both had greater activation than external-rotation-with-scapular-squeeze and lawnmower exercises (P , .05). The bow-and-arrow exercise elicited the highest activation from the UT, MT, and LT muscles; SA activation was greatest during the externalrotation-with-scapular-squeeze exercise.Conclusions: Scapular muscle activation was similar between participants with GH injuries and healthy control participants when performing the unloaded multiplanar, multijoint exercises tested. High activation ratios during the bow-andarrow exercise indicate UT hyperactivity or decreased MT, LT, and SA activity. Our GH injury group may be comparable to high-functioning injured athletes. Study results may assist clinicians in selecting appropriate exercises for scapular muscle activation when caring for injured athletes.Key Words: force couple, glenohumeral joint, rehabilitation, serratus anterior muscle, trapezius muscle Key PointsMuscle balance to promote scapular upward rotation, as indicated by muscle-activation ratios, was present and similar between participants with glenohumeral injuries and healthy control participants when performing 4 unloaded multiplanar, multijoint functional exercises. Clinicians should use caution when prescribing the bow-and-arrow exercise because it produced high scapular muscle-activation ratios, indicating upper trapezius hyperactivity and decreased middle trapezius, lower trapezius, and serratus anterior activity. Exercises that promote activation of the middle trapezius, lower trapezius, and serratus anterior muscles while minimizing upper trapezius hyperactivity are ...