Pitching biomechanics as a pitcher approaches muscular fatigue during a simulated baseball game.

BACKGROUND: The effects of approaching muscular fatigue on pitching biomechanics are currently unknown. As a pitcher fatigues, pitching mechanics may change, leading to a decrease in performance and an increased risk of injury. HYPOTHESIS: As a pitcher approaches muscular fatigue, select pitching biomechanical variables will be significantly different than they were before muscular fatigue. STUDY DESIGN: Controlled laboratory study. METHODS: Ten collegiate baseball pitchers threw 15 pitches per inning for 7 to 9 innings off an indoor throwing mound during a simulated baseball game. A pitching session ended when each pitcher felt he could no longer continue owing to a subjective perception of muscular fatigue. A 6-camera 3D automatic digitizing system collected 200-Hz video data. Twenty kinematic and 11 kinetic variables were calculated throughout 4 phases of the pitch. A repeated-measure analysis of variance (P < .01) was used to compare biomechanical variables between innings. RESULTS: Compared with the initial 2 innings, as a pitcher approached muscular fatigue during the final 2 innings he was able to pitch, there was a significant decrease in ball velocity, and the trunk was significantly closer to a vertical position. There were no other significant differences in kinematics or kinetics variables. CONCLUSION: The relatively few differences observed imply that pitching biomechanics remained remarkably similar between collegiate starting pitchers who threw between 105 and 135 pitches for 7 to 9 innings and approached muscular fatigue. CLINICAL RELEVANCE: This study did not support the idea that there is an increase in shoulder and elbow forces and torques as muscular fatigue is approached. It is possible that if a pitcher remained in a fatigued state for a longer period of time, additional changes in pitching mechanics may occur and the risk of injury may increase.

Electromyographic analysis of the supraspinatus and deltoid muscles during 3 common rehabilitation exercises.

CONTEXT: Investigators have observed electromyographic (EMG) activity of the supraspinatus muscle and reported conflicting results. OBJECTIVE: To quantify EMG activity of the supraspinatus, middle deltoid, and posterior deltoid muscles during exercises commonly used in rehabilitation. DESIGN: One-factor, repeated-measures design. SETTING: Controlled laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-two asymptomatic subjects (15 men, 7 women) with no history of shoulder injury participated. MAIN OUTCOMES MEASURE(S): The dominant shoulder was tested. Fine-wire EMG electrodes were inserted into the supraspinatus, middle deltoid, and posterior deltoid muscles. The EMG data were collected at 960 Hz for analysis during maximal voluntary isometric contraction (MVIC) and 5 repetitions of 3 exercises: standing elevation in the scapular plane ("full can"), standing elevation in the scapular plane with glenohumeral internal rotation ("empty can"), and prone horizontal abduction at 100 degrees with glenohumeral external rotation ("prone full can"). We calculated 1-way repeated-measures analysis of variance (P < .05) and post hoc 2-tailed, paired t tests to detect significant differences in muscle activity among exercises. RESULTS: No statistical difference existed among the exercises for the supraspinatus. The middle deltoid showed significantly greater activity during the empty-can exercise (77 +/- 44% MVIC) and prone full-can exercise (63 +/- 31% MVIC) than during the full-can exercise (52 +/- 27% MVIC) (P = .001 and .017, respectively). The posterior deltoid showed significantly greater activity during the prone full-can exercise (87 +/- 53% MVIC) than during the full-can (P = .001) and the empty-can (P = .005) exercises and significantly greater activity during the empty-can exercise (54 +/- 24% MVIC) than during the full-can exercise (38 +/- 32% MVIC) (P = .012). CONCLUSIONS: While all 3 exercises produced similar amounts of supraspinatus activity, the full-can exercise produced significantly less activity of the deltoid muscles and may be the optimal position to recruit the supraspinatus muscle for rehabilitation and testing. The empty-can exercise may be a good exercise to recruit the middle deltoid muscle, and the prone full-can exercise may be a good exercise to recruit the posterior deltoid muscle.

Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises.

STUDY DESIGN: Prospective single-group repeated-measures design. OBJECTIVES: To quantify electromyographic (EMG) muscle activity of the infraspinatus, teres minor, supraspinatus, posterior deltoid, and middle deltoid during exercises commonly used to strengthen the shoulder external rotators. BACKGROUND: Exercises to strengthen the external rotators are commonly prescribed in rehabilitation, but the amount of EMG activity of the infraspinatus, teres minor, supraspinatus, and deltoid during these exercises has not been thoroughly studied to determine which exercises would be most effective to achieve strength gains. METHODS AND MEASURES: EMG measured using intramuscular electrodes were analyzed in 10 healthy subjects during 7 shoulder exercises: prone horizontal abduction at 100 degrees of abduction and full external rotation (ER), prone ER at 90 degrees of abduction, standing ER at 90 degrees of abduction, standing ER in the scapular plane (45 degrees abduction, 30 degrees horizontal adduction), standing ER at 0 degrees of abduction, standing ER at 0 degrees of abduction with a towel roll, and sidelying ER at 0 degrees of abduction. The peak percentage of maximal voluntary isometric contraction (MVIC) for each muscle was compared among exercises using a 1-way repeated-measures analysis of variance (P<.05). RESULTS: EMG activity varied significantly among the 7 exercises. Sidelying ER produced the greatest amount of EMG activity for the infraspinatus (62% MVIC) and teres minor (67% MVIC). The greatest amount of activity of the supraspinatus (82% MVIC), middle deltoid (87% MVIC), and posterior deltoid (88% MVIC) was observed during prone horizontal abduction at 100 degrees with full ER. CONCLUSIONS: Results from this study provide initial information to develop rehabilitation programs. It also provides information helpful for the design and conduct of future studies.