Marilyn Pink

EMG analysis of the scapular muscles during a shoulder rehabilitation program

The purpose of this study was to determine which exercises most effectively use the scapular muscles. Eight muscles in 9 healthy subjects were studied with indwelling electromyographic electrodes and cinema tography while performing 16 exercises. The 8 muscles studied were the upper, middle, and lower trapezius; levator scapula; rhomboids; pectoralis minor; and the middle and lower serratus anterior. Each exercise was divided into arcs of motion and the electromyographic activity was quantified as a percentage of the maximal manual muscle test. The optimal exercises for each muscle were identified based on intensity (greater than 50% maximal manual muscle test) and duration (over at least 3 consecutive arcs of motion) of the muscle activity. Twelve of the exercises qualified as top exer cises for all of the muscles. On further analysis, a group of 4 exercises was shown to make up the core of a scapular muscle strengthening program. Those 4 ex ercises include scaption (scapular plane elevation), row ing, push-up with a plus, and press-up.

An electromyographic analysis of the upper extremity in pitching

The upper extremity is vulnerable to injury during the baseball pitch because of the repetitious nature of the action, the extremes in range of motion, and the high angular velocities and torques generated at the shoulder and elbow. Hence this study was designed to describe the muscle-firing patterns through fine-wire electromyography in 29 muscle bellies in the upper extremities of skilled pitchers during the fastball pitch. The results demonstrated that the muscles functioned with precise timing for joint stabilization to prevent injury, joint activation to transfer forces to the ball, and joint deceleration to dissipate forces after ball release. The synchrony of reciprocal and sequential muscle contraction necessary to accomplish these functions was clearly evident. This study provides a better understanding of the coordinated sequence of muscle activity during the throwing motion; this understanding is crucial to the development of exercise protocols and surgical procedures used for treatment and prevention of shoulder and elbow injuries in the throwing athlete.

The normal shoulder during freestyle swimming : an electromyographic and cinematographic analysis of twelve muscles

The purpose of this paper is to describe the patterns of activity of 12 shoulder muscles in painful shoulders, and compare those patterns of activity with normal shoulders. The results show significant differences in 7 of the 12 muscles. Those muscles included the anterior deltoid, middle deltoid, infraspinatus, subscapularis, up per trapezius, rhomboids, and the serratus anterior. There were no significant differences between muscle activity patterns of normal versus painful shoulders in the latissimus dorsi, pectoralis major, teres minor, su praspinatus, or the posterior deltoid. This information will contribute to the development of muscle condition ing programs to optimize performance and prevent injury, as well as develop programs for scientific reha bilitation strengthening.

Arthroscopic Findings in the Overhand Throwing Athlete: Evidence for Posterior Internal Impingement of the Rotator Cuff

SUMMARY The purpose of this article is to describe the outcome of an arthroscopic examination and the pathology in symptomatic shoulders of 41 professional overhand throwing athletes. With the arm in the position of the relocation test, 100% of the subjects had either contact between the rotator cuff undersurface and the posterosuperior glenoid rim or osteochondral lesions. Other key findings included undersurface cuff fraying in 93%, posterosuperior labral fraying in 88%, and anterior labral fraying in 36% of the subjects. This study supports the concept of impingement of the posterior cuff undersurface with the posterosuperior glenoid rim in the overhand throwing athlete with shoulder pain.

An Electromyographic Analysis of the Knee During Functional Activities II. The Anterior Cruciate Ligament-deficient and -reconstructed Profiles

This study compared the electromyographic activity of normal (N = 22), rehabilitated anterior cruciate ligament-deficient (N = 8), and -reconstructed knees (N = 10) while subjects performed activities. Each sub ject had evaluation of 8 muscles during 7 functional ac tivities. Sixty-seven percent of the differences in the quadriceps muscle reflected increased activity in the vastus lateralis muscle of the rehabilitated group; 75% of the differences in the hamstrings muscles noted in creased biceps femoris muscle activity in the rehabili tated group; 56% of the differences in the lower leg mus culature showed increased tibialis anterior muscle activity in the rehabilitated group. Eighty-six percent of the statistically different intervals involved rehabilitated subjects demonstrating increased activity over recon structed or normal subjects or both. The presence of a quadriceps-hamstrings muscles coordinated response was identified consistently in all 3 groups in each ac tivity. This study supports surgical reconstruction for the anterior cruciate ligament-deficient knee. It also dem onstrates the importance of the vastus lateralis, biceps femoris, and tibialis anterior musculature in the reha bilitation of the anterior cruciate ligament-deficient patient. The presence of a quadriceps-hamstrings muscles coordinated response indicates that mechano receptors mediating this reflex arc exist in structures other than the cruciate ligament.

Electromyographic analysis of deltoid and rotator cuff function under varying loads and speeds

The purpose of this study was to compare the effect of increasing loads and doubling speed on the deltoid and rotator cuff muscles during isotonic scapular plane abduction (scaption) with neutral humeral rotation. These muscles were studied in 16 volunteers with asymptomatic shoulders with the use of fine wire electromyography. The addition of load to the arm during scaption caused an increase in electromyographic activity during the first 90 degrees of motion. Furthermore electromyographic activity decreased during the final 30 degrees of motion with each increase in load. Doubling the speed caused an increase in electromyographic activity during the first 60 degrees of motion while causing a decrease in activity in the final 60 degrees. This study demonstrates the response of the rotator cuff and deltoid muscles to varying loads and speeds during the most basic shoulder motion. With the data obtained in this study, rehabilitation exercises and experimental shoulder models can be refined to reflect this more physiologic situation.

Functional Anatomy of the Flexor Pronator Muscle Group in Relation to the Medial Collateral Ligament of the Elbow

To describe the relationship of the pronator teres, flexor carpi radialis, flexor digitorum superficialis, and flexor carpi ulnaris muscles to the medial collateral ligament at 30°, 90°, and 120° of elbow flexion, we dissected 11 cadaveric specimens. The flexor carpi ulnaris muscle is the predominant musculotendinous unit overlying the medial collateral ligament in the majority of cases and is the only one at 120° of elbow flexion. The flexor digi torum superficialis muscle is the only other significant contributor. The medial collateral ligament is the pri mary stabilizer of the medial elbow with elbow flexion greater than 30°, as in throwing. The flexor carpi ulnaris muscle, because of its position directly over the medial collateral ligament, and the flexor digitorum superficialis muscle, with its near proximity and relatively large bulk, are the specific muscles best suited to provide medial elbow support. This is especially relevant to overhand throwing athletes who encounter extreme valgus force across the elbow during the cocking and acceleration phases of the throwing motion. Exercise and condition ing of the medial elbow musculature, specifically the flexor digitorum superficialis muscle and the flexor carpi ulnaris muscle, may prevent injury or assist in rehabili tation of medial elbow instability, especially in overhand throwing athletes.

THE PAINFUL SHOULDER IN THE SWIMMING ATHLETE

Given the popularity of swimming and the high risk of injury associated with the sport, many clinicians come into contact with the swimmers shoulder. This article describes the mechanism of injury, diagnostic tools, and subtle signs of injury for swimmers shoulder. It focuses on conservative treatment for the injury, including methods for stretching and strengthening and eliminating acute inflammation.

An electromyographic analysis of the elbow in normal and injured pitchers with medial collateral ligament insufficiency

Electromyography and high-speed film were used to examine the muscle activity in the elbows of pitchers with medial collateral ligament insufficiency compared to the activity in uninjured elbows. Ten competitive baseball pitchers with medial collateral insufficiency and 30 uninjured competitive pitchers were tested while throwing the fastball and the curveball. The extensor carpi radialis brevis and longus in the injured pitchers showed greater activity than in the uninjured pitchers for both pitches. The triceps, flexor carpi radialis, and pronator teres all showed less activity in the injured pitchers during the fastball, but only the triceps had less activity during the curveball. The differences were seen during the late cocking and acceleration phases, which place the greatest stress on the medial collateral ligament. If the flexor carpi radialis and pronator teres were substituting for the deficient medial collateral lig ament and functioning as dynamic stabilizers, one would expect enhanced muscle activity. However, the opposite was found. This pattern of asynchronous mus cle action with medial collateral ligament injury may predispose the joint to further injury. The muscular differences seen are critical to the understanding of the pathomechanics of patients with medial collateral liga ment deficiency, and provide a basis for rehabilitation.

Electromyographic analysis of the trunk in golfers

Golf is a popular sport for both men and women. The trunk is the most common area of injury during the golf swing. The purpose of this study was to describe and compare the muscle firing patterns in the trunk during the golf swing. Twenty-three golfers with handicaps of five or below volunteered for this study. Surface elec tromyographic electrodes were placed on the abdomi nal oblique and erector spinae muscles bilaterally. High- speed cinematography was used in conjunction with the electromyographic electrodes. The results demon strated relatively low activity in all muscles during tak eaway (below 30% of maximal muscle test), and rela tively high and constant activity throughout the rest of the swing (above 30% maximal muscle test, with the exception of the contralateral erector spinae during late follow-through, which was 28% maximal muscle test). This high and constant activity demonstrated the im portance of the trunk muscles during a golf swing. These results indicate the need for an effective preven tive and rehabilitative exercise program for the golfer.