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C. Buz Swanik and Kathleen A. Swanik

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Kathleen A. Swanik, Kellie Huxel Bliven and Charles Buz Swanik

Context:

There are contradictory data on optimal muscle-activation strategies for restoring shoulder stability. Further investigation of neuromuscular-control strategies for glenohumeral-joint stability will guide clinicians in decisions regarding appropriate rehabilitation exercises.

Objectives:

To determine whether subscapularis, infraspinatus, and teres minor (anteroposterior force couple) muscle activation differ between 4 shoulder exercises and describe coactivation ratios and individual muscle-recruitment characteristics of rotator-cuff muscles throughout each shoulder exercise.

Design:

Crossover.

Setting:

Laboratory.

Participants:

healthy, physically active men, age 20.55 ± 2.0 y.

Interventions:

4 rehabilitation exercises: pitchback, PNF D2 pattern with tubing, push-up plus, and slide board.

Main Outcomes Measures:

Mean coactivation level, coactivation-ratio patterns, and level (area) of muscle-activation patterns of the subscapularis, infraspinatus, and teres minor throughout each exercise.

Results:

Coactivation levels varied throughout each exercise. Subscapularis activity was consistently higher than that of the infraspinatus and teres minor combined at the start of each exercise and in end ranges of motion. Individual muscle-recruitment levels in the subscapularis were also different between exercises.

Conclusion:

Results provide descriptive data for determining normative coactivation-ratio values for muscle recruitment for the functional exercises studied. Differences in subscapularis activation suggest a reliance to resist anteriorly directed forces.

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Stephen J. Thomas, Kathleen A. Swanik, Charles “Buz” Swanik, Kellie C. Huxel and John D. Kelly IV

Context:

Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal rotation (IR) and concurrent increases in external rotation (ER). In addition, alterations to scapular position have been identified in this population, but the chronology of these adaptations is uncertain.

Objectives:

To determine whether there is a change in range of motion and scapular position after a single baseball season.

Design:

Prospective cohort.

Setting:

High school.

Participants:

19 high school baseball players (age 16.6 ± 0.8 y, mass 78.6 ± 12.0 kg, height 180.3 ± 6.2 cm).

Interventions:

Subjects were measured for all dependent variables at preseason and postseason.

Main Outcome Measures:

Participants were measured for glenohumeral (GH) IR and ER with the scapula stabilized. Total GH range of motion was calculated as the sum of IR and ER. Scapular upward rotation was measured at 0°, 60°, 90°, and 120° of GH abduction in the scapular plane, and scapular protraction, at 0°, hands on hips, and 90° of GH abduction.

Results:

Overall, the dominant arm had significantly less GH IR (11.4°, P = .005) and significantly more ER (4.7°, P = .001) than the nondominant arm. Total motion in the dominant arm was significantly less than in the nondominant arm (6.7°, P = .001). Scapular upward rotation in the dominant arm significantly increased at 0° (2.4°, P = .002) and significantly decreased at 90° (3.2°, P = .001) and 120° (3.2°, P < .001) of abduction from preseason to postseason. Scapular protraction in the nondominant arm significantly decreased at 45° (0.32 cm, P = .017) and 90° (0.33 cm, P = .006) from preseason to postseason.

Conclusion:

These data suggest that scapular adaptations may be acquired over a relatively short period (12 wk) in a competitive baseball season. Competitive high school baseball players also presented with significant GH motion differences between their dominant and nondominant arms. Total motion was also significantly less in the dominant arm than in the nondominant arm.

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Hidetomo Suzuki, Kathleen A. Swanik, Kellie C. Huxel, John D. Kelly IV and C. Buz Swanik

Objective:

To determine the effect of scapular fatigue on shoulder and elbow kinematics and accuracy.

Design:

Pretest–posttest.

Setting:

Laboratory.

Participants:

30 healthy men.

Interventions:

Subjects performed seated overhead throws into a target before and after a standardized scapular-muscle-fatigue protocol.

Main Outcome Measurements:

Shoulder and elbow kinematic data were analyzed during throwing. Scapular upward rotation was measured (0°, 45°, and 90° humeral elevation in scaption) with an inclinometer. Throwing accuracy was measured as mean error distance from the target (cm).

Results:

After fatigue, there was a significant increase in total elbow motion (12 % more in cocking phase, P < .05) and elbow velocity in the follow-through phase (average and maximum into flexion, P < .05). Throwing accuracy decreased 26% after fatigue (P < .05).

Conclusions:

Scapular-muscle fatigue results in compensatory motions at the elbow that might affect performance and contribute to elbow pathologies.

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Kathleen A. Swanik, C. Buz Swanik, Scott M. Lephart and Kellie Huxel

Objective:

To determine whether functional training reduces the incidence of shoulder pain and increases strength in intercollegiate swimmers.

Design:

Pretest–posttest.

Setting:

Laboratory and weight room.

Participants:

26 intercollegiate swimmers (13 men, 13 women).

Intervention:

6-wk functional training program.

Main Outcome Measures:

Incidence of shoulder pain was recorded throughout the study. Isokinetic shoulder strength was assessed before and after training.

Results:

A t test showed significant differences (P < .05) for the incidence of shoulder pain between the experimental (mean episodes = 1.8 ± 2.1) and control (mean episodes = 4.6 ± 4.7) groups. ANOVA with repeated measures revealed no significant strength differences between groups but exhibited significant within-group increases.

Conclusions:

Incorporating functional exercises might reduce incidence of shoulder pain in swimmers. The results also validate the need to modify preventive programs as the demands of the sport change throughout the season.

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Martin Ramsi, Kathleen A. Swanik, Charles “Buz” Swanik, Steve Straub and Carl Mattacola

Context:

Changes in strength over the course of a swim season could predispose the shoulder to strength imbalances and lead to injury.

Objective:

To examine isometric shoulder internal- (IR) and external-rotator (ER) strength in high school swimmers over a 12-week competitive season.

Design:

Three 3 × 2 × 2 ANOVAs with repeated measures were used to determine significant main effects for IR, ER, and IR:ER strength ratio.

Participants:

27 (14 female, 13 male) high school varsity swimmers.

Main Outcome Measures:

IR and ER strength during preseason, midseason, and postseason.

Results:

Significant increases in IR strength in both groups were revealed for all test sessions. ER strength significantly improved in both males and females from preseason to midseason and from preseason to postseason. IR:ER ratio revealed a significant increase from preseason to postseason.

Conclusions:

Increases in IR strength without equal gains in ER strength were revealed and could contribute to future shoulder pathologies in competitive swimmers

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Stephen John Thomas, Charles Buz Swanik, Thomas W. Kaminski, Jill S. Higginson, Kathleen A. Swanik and Levon N. Nazarian

Context:

Subacromial impingement is a common injury in baseball players and has been linked to a reduction in the subacromial space. In addition, it has been suggested that decreases in scapular upward rotation will lead to decreases in the subacromial space and ultimately impingement syndrome.

Objective:

The objective of this study was to evaluate the relationship between acromiohumeral distance and scapular upward rotation in healthy college baseball players.

Design:

Posttest-only study design.

Setting:

Controlled laboratory setting.

Participants:

24 healthy college baseball players.

Intervention:

Participants were measured for all dependent variables at preseason.

Main Outcome Measures:

Acromiohumeral distance at rest and 90° of abduction was measured with a diagnostic ultrasound unit. Scapular upward rotation at rest and 90° of abduction was measured with a digital inclinometer.

Results:

Dominant-arm acromiohumeral distance at rest and 90° of abduction (P = .694, P = .840) was not significantly different than in the nondominant arm. In addition, there was not a significant correlation between acromiohumeral distance and scapular upward rotation at rest and 90° of abduction for either the dominant or the nondominant arm.

Conclusions:

These results indicate that the acromiohumeral distance is not adapting in the dominant arm in healthy throwing athletes. In addition, a relationship was not identified between acromiohumeral distance and scapular upward rotation, which was previously suggested. These results may suggest that changes that are typically seen in an injured population may be occurring due to the injury and are not preexisting. In addition, scapular upward rotation may not be the only contributing factor to acromiohumeral distance.

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Kathleen A. Swanik, Stephen J. Thomas, Aaron H. Struminger, Kellie C. Huxel Bliven, John D. Kelly and Charles B. Swanik

Context:

Plyometric training is credited with providing benefits in performance and dynamic restraint. However, limited prospective data exist quantifying kinematic adaptations such as amortization time, glenohumeral rotation, and scapulothoracic position, which may underlie the efficacy of plyometric training for upper-extremity rehabilitation or performance enhancement.

Objective:

To measure upper-extremity kinematics and plyometric phase times before and after an 8-wk upper-extremity strength- and plyometric-training program.

Design:

Randomized pretest–posttest design.

Setting:

Research laboratory.

Participants:

40 recreationally active men (plyometric group, age 20.43 ± 1.40 y, height 180.00 ± 8.80 cm, weight 73.07 ± 7.21 kg; strength group, age 21.95 ± 3.40 y, height 173.98 ± 11.91 cm, weight 74.79 ± 13.55 kg).

Intervention:

Participants were randomly assigned to either a strength-training group or a strength- and plyometric-training group. Each participant performed the assigned training for 8 wk.

Main Outcome Measures:

Dynamic and static glenohumeral and scapular-rotation measurements were taken before and after the training programs. Dynamic measurement of scapular rotation and time spent in each plyometric phase (concentric, eccentric, and amortization) during a ball-toss exercise were recorded while the subjects were fitted with an electromagnetic tracking system. Static measures included scapular upward rotation at 3 different glenohumeral-abduction angles, glenohumeral internal rotation, and glenohumeral external rotation.

Results:

Posttesting showed that both groups significantly decreased the time spent in the amortization, concentric, and eccentric phases of a ball-toss exercise (P < .01). Both groups also exhibited significantly decreased static external rotation and increased dynamic scapular upward rotation after the training period (P < .01). The only difference between the training protocols was that the plyometric-training group exhibited an increase in internal rotation that was not present in the strength-training group (P < .01).

Conclusion:

These findings support the use of both upper-extremity plyometrics and strength training for reducing commonly identified upper-extremity-injury risk factors and improving upper-extremity performance.