Electromyographic analysis of elbow function in tennis players

Medial Epicondylitis

Medial epicondylitis of the elbow involves pathologic alteration in the musculotendinous origins at the medial epicondyle. Although commonly referred to as "golfer's elbow", the condition may in fact be caused by a variety of sports and occupational activities. Accurate diagnosis requires a thorough understanding of the anatomic, epidemiologic, and pathophysiologic factors. Nonoperative treatment involves rest, ice, nonsteroidal anti-inflammatory agents, and possibly corticosteroid injection followed by guided rehabilitation and return to sport. Operative treatment is indicated for debilitating pain after exclusion of other pathologic causes that persists in spite of a well-managed nonoperative regimen spanning a minimum of 6 months. The surgical technique involves excision of the pathologic portion of the tendon, repair of the resulting defect, and reattachment of the origin of the flexor pronator muscle group to the medial epicondyle. Surgical treatment results in a high degree of subjective relief, although objective strength deficits may persist.

Experimental deep tissue pain in wrist extensors--a model of lateral epicondylalgia

The aim of this experimental study was to develop an in vivo model demonstrating sensory and motor interactions comparable to those seen in patients presenting with lateral epicondylalgia (i.e., deep tissue pain and hyperalgesia localised to specific sites in the wrist extensors, attenuation of wrist extension force). The effect of saline-induced deep pain combined with delayed onset muscle soreness (DOMS) on deep tissue sensitivity and motor function in wrist extensors was examined. Muscle pain intensity (visual analogue scale: VAS), distribution, and quality were assessed in 12 subjects. Pressure pain thresholds (PPTs) were recorded at five different sites around the elbow. Maximal wrist extension force was recorded. In the absence of DOMS, hypertonic saline administrated into different parts of the wrist extensors (extensor carpi radialis brevis, supinator, common extensor origin) induced significantly (P<0.05) higher VAS scores and larger pain areas compared with a control injection of isotonic saline. The typical quality of saline-induced pain was described as "drilling", "taut", "nagging" and "intense". In non-exercised wrist extensors, hyperalgesia to pressure was not detected during saline-induced pain but maximal wrist extensor force decreased significantly (P<0.05) compared with pre-pain recordings and recordings post isotonic saline. DOMS induced by eccentric wrist extension contractions generated moderate levels of soreness but no resting pain up to 24h post exercise. PPTs and maximal wrist extension force were significantly decreased (P<0.05) during DOMS compared with baseline and 7 days post exercise (P<0.05). VAS scores to injection of hypertonic saline into the DOMS arm were significantly increased (P<0.05) compared with injections into the unexercised arm. This is another manifestation of muscle hyperalgesia. Saline-induced pain combined with DOMS further decreased maximal wrist extension force (P<0.05). The simultaneous deep tissue pain and hyperalgesia linked with force attenuation support the use of the saline-induced deep tissue pain combined with DOMS as an experimental model simulating the clinical sensorimotor correlates of lateral epicondylalgia.

Isokinetic profile of elbow flexion and extension strength in elite junior tennis players

STUDY DESIGN

Descriptive study.

OBJECTIVES

To determine whether bilateral differences exist in concentric elbow flexion and extension strength in elite junior tennis players.

BACKGROUND

The repetitive nature of tennis frequently produces upper extremity overuse injuries. Prior research has identified tennis-specific strength adaptation in the dominant shoulder and distal upper extremity musculature of elite players. No previous study has addressed elbow flexion and extension strength.

METHODS AND MATERIALS

Thirty-eight elite junior tennis players were bilaterally tested for concentric elbow flexion and extension muscle performance on a Cybex 6000 isokinetic dynamometer at 90 degrees/s, 210 degrees/s, and 300 degrees/s. Repeated-measures ANOVAs were used to test for differences between extremities, muscle groups, and speed.

RESULTS

Significantly greater (P<0.002) dominant-arm elbow extension peak torque values were measured at 90 degrees/s, 210 degrees/s, and 300 degrees/s for males. Significantly greater (P<0.002) dominant-arm single-repetition work values were also measured at 90 degrees/s and 210 degrees/s for males. No significant difference was measured between extremities in elbow flexion muscular performance in males and for elbow flexion or extension peak torque and single-repetition work values in females. No significant difference between extremities was measured in elbow flexion/extension strength ratios in females and significant differences between extremities in this ratio were only present at 210 degrees/s in males (P<0.002).

CONCLUSION

These data indicate muscular adaptations around the dominant elbow in male elite junior tennis players but not females. These data have ramifications for clinicians rehabilitating upper extremity injuries in patients from this population.

Electromyographic analysis and phase definition of the overhead football throw

BACKGROUND

The phases of the football throw need definition so that muscle activation patterns during the overhead football throw can be fully described.

HYPOTHESIS

Electromyographic analysis of shoulder musculature can better define muscle activation patterns during the football throw.

STUDY DESIGN

Descriptive anatomic study.

METHODS

Videos of 20 elite-level quarterbacks were reviewed to define phases of the overhead football throw; 14 recreational male athletes underwent electromyography and motion analysis testing.

RESULTS

Four sequential phases of the football throw were consistently observed. Early cocking (49% +/- 11% of throw) was initiated at rear foot plant and continued to maximal shoulder abduction and internal rotation. Late cocking (20% +/- 6%) started at maximal shoulder abduction and internal rotation and ended with maximal shoulder external rotation. The acceleration phase (15% +/- 4%) began with maximal shoulder external rotation and ended with ball release. Follow-through (16% +/- 5%) was defined as the phase from ball release to maximal horizontal adduction (across the body).

CONCLUSION

The four phases demonstrated little variation in motion analysis and electromyographic activation between subjects and were associated with muscle activation patterns consistent with upper extremity movements.

CLINICAL RELEVANCE

A clearer understanding of muscle activation patterns may help to explain patterns of muscle injury and improve rehabilitation protocols in football-throwing athletes.

Overuse injuries of the upper extremity in tennis players

Several overuse injuries can affect the upper extremity of tennis players. A thorough understanding of anatomy and knowledge of these common conditions and their treatment facilitates the management of these athletes.

Epicondylitis in the athlete

Epicondylitis plagues a significant proportion of athletes and can result in prolonged symptoms and suboptimal athletic performance. The diagnosis can be confused with many other pathologic entities affecting the elbow, some of which can occur concurrently. Most patients will respond favorably to a well-guided nonsurgical treatment protocol. A minority of patients will have persistent problems and will require surgical intervention that can relieve pain effectively and return patients to their preinjury level of activity.

A new technique for the selective recording of extensor carpi radialis longus and brevis EMG

Tennis Elbow or Lateral Epicondylalgia is manifested by pain over the region of the lateral epicondyle of the humerus, related to use of the wrist extensor muscles. Extensor carpi radialis longus (ECRL) and brevis (ECRB) have been implicated in the dysfunction associated with Lateral Epicondylalgia. For muscles in the human forearm, particularly those in close proximity, selective recordings are nearly impossible without the use of fine wire, indwelling electrodes. These can be inserted in precise locations and have small recording areas. Standard electromyography texts indicate, however, that the activity of ECRL and ECRB cannot be distinguished, even with intramuscular electrodes. We present a new technique for determining the most appropriate sites at which to insert intramuscular electrodes for selective recordings of ECRB and ECRL. The location of ECRB and ECRL was measured on 10 cadaver specimens, 5 right arms and 5 left arms. The distance from the muscle origin to (1) insertion, (2) largest portion of the muscle belly, (3) most proximal fibres and (4) most distal fibres were measured and expressed relative to forearm length. The mean distance and 95% confidence interval was calculated for each of the four measures. These data indicated a significant separation of the belly of each muscle along the length of the forearm. These relative distances were used to mark electrode insertion points on three volunteers. Fine wire electrodes were used to record the electromyogram in three participants. Each participant was required to perform isometric contractions to produce (1) wrist extension torque, (2) radial deviation torque, (3) elbow flexion torque and (4) finger extension. The electromyographic recordings show clear differentiation of ECRB and ECRL with the relative activation patterns reflecting the underlying anatomical organisation of the two muscles. This technique provides an important objective method that can be used in conjunction with manual muscle testing to provide a means of ensuring accurate intramuscular electromyographic recording from these two muscles.

A simulation of muscle force and internal kinematics of extensor carpi radialis brevis during backhand tennis stroke: implications for injury

OBJECTIVE

The purpose of this work was use a computer simulation of the action of extensor carpi radialis brevis during a typical backhand tennis stroke of novice and advance players to examine a potential mechanism of injury.

DESIGN

This study uses established kinematic data in conjunction with a computer model to give a time varying description of muscle force and length changes.

BACKGROUND

Lateral epicondylitis or tennis elbow has been attributed to over-exertion of extensor carpi radialis brevis with novice tennis players being particularly susceptible.

METHODS

We used a simple Hill-type muscle model to predict muscle force and internal kinematics based on activation and joint angle changes as inputs. Magnetic resonance images were used to determine the morphometric dimensions of extensor carpi radialis brevis which were used to scale the mechanical properties determined from in vivo contractions of flexor pollicis longus.

RESULTS

The simulation indicated that the novice group generated considerably less force and the muscle was subjected to a substantial eccentric contraction as a result of racquet-ball impact. This eccentric contraction occurred with the muscle at a very long length with diminishing tension capabilities.

CONCLUSION

The observed pattern of activation and joint kinematics of novice tennis players results in substantial eccentric contractions which are likely the cause of repetitive microtrauma leading to tennis elbow injuries. Adopting the technique seen in advanced players would limit the eccentric contractions and reduce the likelihood of injury.

RELEVANCE

Lateral epicondylitis can be extremely problematic because of its chronic nature and relatively high incidence. This study offers one aetiology of the condition that results from improper kinematics during the tennis backhand stroke.

The manual muscle examination for rotator cuff strength. An electromyographic investigation

The electromyographic activity of eight muscles of the rotator cuff and shoulder girdle (supraspinatus, infraspinatus, subscapularis, pectoralis, latissimus dorsi, and the anterior, middle, and posterior deltoid) was measured from the nondominant shoulders of 11 subjects during a series of 29 isometric contractions. The contractions simulated different positions used for strength testing of the rotator cuff and involved elevation, external rotation, and internal rotation at three degrees of initial humeral rotation (-45 degrees of internal rotation, 0 degree, +45 degrees of external rotation) and scapular elevation (0 degree, 45 degrees, 90 degrees). Isolation of the supraspinatus muscle was best achieved with the test position of elevation at 90 degrees of scapular elevation and +45 degrees (external rotation) of humeral rotation. Isolation of the infraspinatus muscle was best achieved with external rotation at 0 degree of scapular elevation and -45 degrees (internal rotation) of humeral rotation. Isolation of the subscapularis muscle was best achieved with the Gerber push-off test. This study used four criteria for identifying the optimal manual muscle test for each rotator cuff muscle: 1) maximal activation of the cuff muscle, 2) minimal contribution from involved shoulder synergists, 3) minimal provocation of pain, and 4) good test-retest reliability. Based on the results of this study and known painful arcs of motion, an objective identification of the optimal tests for the manual muscle testing of the cuff was elucidated.

Dynamic electromyographic analysis of trunk musculature in professional golfers

Using dynamic surface electrode electromyography, we evaluated muscle activity in 13 male professional golfers during the golf swing. Surface electrodes were used to record the level of muscle activity in the right abdominal oblique, left abdominal oblique, right gluteus maximus, left gluteus maximus, right erector spinae, left erector spinae, upper rectus abdominis, and lower rectus abdominis muscles during the golfer's swing. These signals were synchronized electronically with photographic images of the various phases of the golf swing; the images were recorded in slow motion through motion picture photography. The golf swing was divided into five phases: take away, forward swing, acceleration, early follow-through, and late follow-through. Despite individual differences among the subjects' swings, we observed reproducible patterns of trunk muscle activity throughout all phases of the golf swing. Our findings demonstrate the importance of the trunk muscles in stabilizing and controlling the loading response for maximal power and accuracy in the golfer's swing. This study provides a basis for developing a rehabilitation program for golfers that stresses strengthening of the trunk muscles and coordination exercises.

Spectral analysis during fatigue. Surface and fine wire electrode comparison

Fine wire (FW) intramuscular electrodes and spectral analysis have not previously been used to quantify metabolic muscle fatigue in deep muscles not accessible with surface electrodes. This study compares initial median frequency (IMF) and decline in median frequency with fatigue (SLOPE) using surface and FW electrodes. Eighteen men performed isometric biceps contractions for 100 s. Electromyographic signals were collected using FW and surface electrodes. The recordings of SLOPE was greater with FW (-0.44 v -0.23 %IMF/s) and IMF was higher (195 v 69 Hz). Intrasession reliability for slope was better with FW electrode (intraclass correlation coefficient (ICC) = 0.74; P<0.0001) than with the surface electrode (ICC = 0.43; P = 0.006), but intersession reliability was best with the surface electrode (ICC = 0.50; P = 0.03). Spectral analysis using FW electrodes provides earlier detection of muscle fatigue and can be used in deep muscles, but the reliability must be improved before clinical application.

Medial epicondylitis. An electromyographic analysis and an investigation of intervention strategies

Flexor and extensor muscle-tendon unit activity at the elbow during the golf swing was recorded from subjects with and without medial epicondylitis. There was no significant difference in total swing time between symptomatic (1.23 +/- 0.15 sec) and asymptomatic (1.15 +/- 0.13 sec) subjects nor between golfers with low (1 to 6 handicap, N = 8) and high (11 to 19 handicap, N = 8) scoring abilities. Symptomatic and asymptomatic subjects displayed similar electromyographic profiles for flexor and extensor muscles of the forearm. Electromyographic activity of the common extensor muscles was persistent throughout the four swing phases, ranging from 33.59% of maximum voluntary contraction at address to 58.77% at contact. Common flexor muscles produced a consistent burst of electromyographic activity during contact phase (flexor burst, 90.77% of maximum voluntary contraction). Symptomatic subjects' mean flexor muscle electromyographic activity was significantly greater than that of asymptomatic subjects in both address and swing phases. When forearm brace and oversized grips were imposed on symptomatic subjects, there was no significant difference in mean electromyographic magnitude or muscle activation pattern during the golf swing. Thus, the method of symptomatic relief of the intervention strategies tested is still in question.

Isokinetic concentric versus eccentric training of shoulder rotators with functional evaluation of performance enhancement in elite tennis players

Thirty elite tennis players were randomly assigned to three groups to evaluate shoulder isokinetic internal and external rotation training: an isokinetic concentric group, an isokinetic eccentric group, and a control group with no training. Subjects were tested before and after training both concentrically and eccentrically using an isokinetic dynamometer. Functional output before and after training was assessed by the average and peak velocity of six maximal serves. The effect of training on serve velocity endurance was also assessed. Statistically significant concentric and eccentric strength gains (11%) were obtained in both training groups when compared with controls (decreased total average strain of 2%) (P < 0.0004). Serve velocity increased by greater than 11% in both training groups, which was a significant increase from the average of 1% in the control group (P < 0.0001). In the endurance study, training group subjects displayed a tendency to maintain their serve velocity (loss of approximately 2%) greater than controls (loss of 6.4%) (P < 0.05). Isokinetic training led to increases in objective and functional output in elite tennis players. This training regimen may have significance in the final stages of the rehabilitation of injured shoulders as well as in improved performance and reduced injury risk.

Electromyographic and cinematographic analysis of elbow function in tennis players with lateral epicondylitis

Lateral epicondylitis occurs frequently in tennis players and appears to be caused by tears in the extensor aponeurosis. The purpose of this study was to compare the electromyographic activities of 5 muscles in players with lateral epicondylitis with those of injury-free players during the single-handed backhand tennis stroke. Finewire electrodes were placed into the extensor digitorum communis, extensor carpi radialis longus and brevis, pronator teres, and flexor carpi radialis muscles in competitive tennis players; 8 players had lateral epicondylitis and 14 had normal upper extremities. The backhand stroke then was recorded on high-speed film and synchronized with the electromyographic signal. The injured players had significantly greater activity for the wrist extensors and pronator teres muscles during ball impact and early follow-through. This activity increase may have been caused by the abnormal mechanics evident on film, including a "leading elbow," wrist extension and an open racquet face near the time of ball impact, and ball contact in the lower half of the strings. These mechanics not only result in a lower level of play but also leave the wrist extensors and the pronator teres muscles vulnerable to injury. This is the first study that documents increased activity in muscles that have been previously injured.

Lateral and Medial Epicondylitis of the Elbow

Epicondylitis of the elbow involves pathologic alteration in the musculotendinous origins at the lateral or medial epicondyle. Although commonly referred to as "tennis elbow" when it occurs laterally and "golfer's elbow" when it occurs medially, the condition may in fact be caused by a variety of sports and occupational activities. The accurate diagnosis of these entities requires a thorough understanding of the anatomic, epidemiologic, and pathophysiologic factors. Nonoperative treatment should be tried first in all patients, beginning with an initial phase of rest, ice, nonsteroidal anti-inflammatory agents, and possibly corticosteroid injection. A second phase includes coordinated rehabilitation, consisting of range-of-motion and strengthening exercises and counterforce bracing, as well as technique enhancement and equipment modification if a sport or occupation is causative. Nonoperative treatment has been deemed highly successful, yet the few prospective reports available suggest that symptoms frequently persist or recur. Operative treatment is indicated for debilitating pain that is diagnosed after the exclusion of other pathologic causes for pain and that persists in spite of a well-managed nonoperative regimen spanning a minimum of 6 months. The surgical technique involves excision of the pathologic portion of the tendon, repair of the resulting defect, and reattachment of the origin to the lateral or medial epicondyle. Surgical treatment results in a high degree of subjective relief, although objective strength deficits may persist.

Electromyographic and cinematographic analysis of elbow function in tennis players using single- and double-handed backhand strokes

It is generally believed that tennis players using a double-handed backhand rarely develop lateral epicondylitis since the helping arm appears to absorb more energy and changes the mechanics of the swing. The purpose of this paper was to compare muscle activity about the elbow in single- and double-handed backhand strokes in competitive tennis players. Muscle activity in 3 elbow extensors, a wrist flexor, and a forearm pronator of the dominant arm was compared during the single-handed (N = 14) and double-handed (N = 13) backhand ground strokes using indwelling electromyography and high-speed cinematography. Significantly higher activity was seen in the double-handed technique in the flexor carpi radialis muscle in the preparation phase and in the pronator teres muscle in the acceleration phase. Higher flexor carpi radialis muscle activity in preparation of the double-handed stroke appeared to be a function of the double-handed grip used on the racquet, and the increased pronator teres muscle activity in acceleration indicated maintenance of greater pronation provided by the grip of the non-dominant hand. The decreased occurrence of lateral epicondylitis in players using a double-handed backhand may not be caused by decreased extensor activity, but rather by factors associated with flawed stroke mechanics more often seen in the single-handed technique.