Context: The scapular retraction exercises are widely used among clinicians to balance the activity of the scapular muscles as well as the rotator cuff muscles in different shoulder abduction positions. Objectives: The aim of this study was to investigate the relationship between scapular (middle and upper trapezius) and shoulder muscles (middle deltoid and infraspinatus) activation level differences and acromiohumeral distance changes during shoulder abduction with scapular retraction. Design: Cross-sectional study. Setting: University research laboratory. Participants: Nineteen asymptomatic individuals were included (mean [SD]: age = 22.4 [1.8] y). Main Outcome Measure: The acromiohumeral distance was measured at 0° and 90° shoulder abduction when the scapula was in nonretracted and retracted position with ultrasound imaging. The relationship between muscle activation level changes and acromiohumeral distance difference was analyzed with the Pearson correlation test. Results: Middle trapezius muscle activity change correlated with acromiohumeral distance difference (r = .55, P = .02) from 0° to 90° shoulder abduction when scapula was retracted. For both nonretracted and retracted scapular positions, no correlations were found between middle deltoid, infraspinatus, and upper trapezius muscle activity changes with acromiohumeral distance differences during shoulder abduction (P > .05). Conclusions: Active scapular retraction exercise, especially focusing on the middle trapezius muscle activation, seems to be an effective treatment option to optimize the acromiohumeral distance during shoulder abduction.
Hande Guney-Deniz, Gulcan Harput, Ugur Toprak and Irem Duzgun
Hande Guney, Gulcan Harput, Filiz Colakoglu and Gul Baltaci
Glenohumeral (GH) internal-rotation deficit (GIRD) and lower eccentric external-rotator (ER) to concentric internal-rotator (IR) strength (ER:IR) ratio have been documented as risk factors for shoulder injuries, but there is no information on whether GIRD has an adverse effect on ER:IR ratio in adolescent overhead athletes.
The aim of this study was to investigate the effects of GIRD on functional ER:IR ratio of the adolescent overhead athletes.
University research laboratory.
52 adolescent overhead athletes.
Main Outcome Measures:
To determine GIRD, the range of GH IR and ER motion was measured with a digital inclinometer. An isokinetic dynamometer was used to assess eccentric and concentric IR and ER muscle strength of the dominant and nondominant shoulders. One-way ANCOVA where sport type was set as a covariate was used to analyze the difference between athletes with and without GIRD.
After standardized examinations of all shoulders, the athletes were divided into 2 groups, shoulders with (n = 27) and without GIRD (n = 25). There was a significant difference between groups in functional ER:IR ratio (P < .001). Athletes with GIRD had lower ER:IR ratio (0.56) than athletes without GIRD (0.83).
As GIRD has an adverse effect on functional ratio of the shoulder-rotator muscles, interventions for adolescent overhead athletes should include improving GH-rotation range of motion.
Gulcan Harput, A. Ruhi Soylu, Hayri Ertan, Nevin Ergun and Carl G. Mattacola
Coactivation ratio of quadriceps to hamstring muscles (Q:H) and medial to lateral knee muscles (M:L) contributes to the dynamic stability of the knee joint during movement patterns recommended during rehabilitation and important for daily function.
To compare the quadriceps-to-hamstring and medial-to-lateral knee muscles' coactivation ratios between men and women during the following closed kinetic chain exercises performed on a balance board: forward lunge, side lunge, single-leg stance, and single-leg squat.
20 healthy subjects (10 female and 10 male).
Main Outcome Measures:
Surface electromyography was used to measure the activation level of quadriceps (vastus lateralis and medialis) and hamstrings (biceps femoris and medial hamstrings) during forward- and side-lunge, single-leg-stance, and single-leg-squat exercises. Subjects were instructed during each exercise to move into the test position and to hold that position for 15 s. EMG was recorded during the 15-s isometric period where subjects tried to maintain a “set” position while the foot was on a balance board. Analysis of variance was used for statistical analysis.
There was a significant exercise-by-gender interaction for Q:H ratio (F 3,48 = 6.63, P = .001), but the exercise-by-gender interaction for M:L ratio was not significant (F 3,48 = 1.67, P = .18). Women showed larger Q:H ratio in side-lunge exercises than men (P = .002). Both genders showed larger M:L and lower Q:H ratio in a single-leg-stance exercise than in the other exercises.
The results indicate that the forward- and side-lunge and single-leg-squat exercises should not be recommended as exercise where a balanced coactivation between quadriceps and hamstring muscles is warranted. Single-leg-stance exercise could be used when seeking an exercise where the ratio is balanced for both women and men.
Gulcan Harput, H. Erkan Kilinc, Hamza Ozer, Gul Baltaci and Carl G. Mattacola
There is lack of information related to quadriceps and hamstring strength recovery during the early period of rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring-tendon graft (HTG).
To investigate quadriceps and hamstring isometric strength at 4-, 8-, and 12-wk time points after ACLR and to document the strength changes of these muscles over time.
24 patients (age 28.1 ± 8.1 y) who underwent unilateral single-bundle anatomic ACLR with 4-strand semitendinosus and gracilis tendon graft.
Main Outcome Measures:
The isometric strength of quadriceps and hamstring muscles was measured on an isokinetic dynamometer at a 60° knee-flexion angle 4, 8, and 12 wk after surgery.
Quadriceps and hamstring strength significantly increased over time for both the involved limb (quadriceps F 2,46 = 58.3, P < .001; hamstring F 2,46 = 35.7, P < .001) and uninvolved limb (quadriceps F 2,46 = 17.9, P < .001; hamstring F 2,46 = 56.9, P = .001). Quadriceps and hamstring indexes significantly changed from 4 wk (QI 57.9, HI 54.4) to 8 wk (QI 78.8, HI 69.9) and from 8 wk to 12 wk (QI 82, HI 75.7) (P < .001); however, there was no difference between indexes at the 12-wk time point (P = .17).
The results of this study serve as a reference for clinicians while directing a rehabilitation protocol for HTG ACLR patients to better appreciate expected strength changes of the muscles in the early phase of recovery.