Shoulder Emg During Depression Raise In Men With Spinal Cord Injury: The Influence Of Lesion Level

Abstract

Background & Objective: The depression-style raise maneuver is commonly performed by persons with spinal cord injury (SCI) to relieve skin pressures and avoid skin ulceration. The demands of this critical activity, however, are not fully documented for individuals with higher spinal cord lesions. The purpose of this investigation was to determine the influence of SCI lesion level on shoulder muscle activity during a depression raise maneuver.

Experimental Design: Sample of convenience, group comparison.

Methods: Fine-wire intramuscular electrodes recorded electromyographic (EMG) activity from 1 2 shoulder muscles in 57 men with SCI while they performed depression raises (C6 tetraplegia, n = 1 0; C7 tetraplegia, n = 1 8; high paraplegia, n = 1 6; low paraplegia, n = 1 3). EMG intensity was normalized to a manual muscle test (MMT) effort.

Results: For persons with paraplegia and C7 tetraplegia, dominant EMG activity was recorded from latissimus dorsi, sternal pectoralis major, and triceps muscles (31 %-69% MMT) . Tetraplegic groups had significantly greater anterior deltoid activity (C6 = 53%, C7 = 22% MMT) than that recorded in paraplegic groups (high paraplegia = 1 0%, low paraplegia = 3% MMT). Participants with tetraplegia also had increased infraspinatus activity (C6 = 50%, C7 = 32% MMT) compared with participants with low paraplegia (7% MMT). All other muscles had low or very low EMG activity during the depression raise.

Conclusions: Persons with tetraplegia lack normal strength of the primary muscles used by participants with paraplegia for the depression raise (ie, latissimus dorsi, sternal pectoralis major, and triceps muscles) . Although increased anterior deltoid activation assisted with elbow extension, it potentially contributes to glenohumeral joint impingement. Alternate methods of pressure relief should be considered for persons with tetraplegia.

J Spinal Cord Med. 2003;26:59-64     

Shoulder EMG during depression raise in men with spinal cord injury: the influence of lesion level

BACKGROUND & OBJECTIVE: The depression-style raise maneuver is commonly performed by persons with spinal cord injury (SCI) to relieve skin pressures and avoid skin ulceration. The demands of this critical activity, however, are not fully documented for individuals with higher spinal cord lesions. The purpose of this investigation was to determine the influence of SCI lesion level on shoulder muscle activity during a depression raise maneuver. EXPERIMENTAL DESIGN: Sample of convenience, group comparison. METHODS: Fine-wire intramuscular electrodes recorded electromyographic (EMG) activity from 12 shoulder muscles in 57 men with SCI while they performed depression raises (C6 tetraplegia, n = 10; C7 tetraplegia, n = 18; high paraplegia, n = 16; low paraplegia, n = 13). EMG intensity was normalized to a manual muscle test (MMT) effort. RESULTS: For persons with paraplegia and C7 tetraplegia, dominant EMG activity was recorded from latissimus dorsi, sternal pectoralis major, and triceps muscles (31%-69% MMT). Tetraplegic groups had significantly greater anterior deltoid activity (C6 = 53%, C7 = 22% MMT) than that recorded in paraplegic groups (high paraplegia = 10%, low paraplegia = 3% MMT). Participants with tetraplegia also had increased infraspinatus activity (C6 = 50%, C7 = 32% MMT) compared with participants with low paraplegia (7% MMT). All other muscles had low or very low EMG activity during the depression raise. CONCLUSIONS: Persons with tetraplegia lack normal strength of the primary muscles used by participants with paraplegia for the depression raise (ie, latissimus dorsi, sternal pectoralis major, and triceps muscles). Although increased anterior deltoid activation assisted with elbow extension, it potentially contributes to glenohumeral joint impingement. Alternate methods of pressure relief should be considered for persons with tetraplegia.     

Optimal normalization tests for shoulder muscle activation: An electromyographic study

To accurately compare electromyographic data from different muscles and different subjects, it is necessary to normalize the integrated data obtained from each muscle. The purpose of this study was to identify the manual muscle testing positions that elicit maximal neural activation (integrated electromyography) of three rotator cuff muscles (supraspinatus, infraspinatus, and subscapularis) and five shoulder synergists (pectoralis major, latissimus dorsi, and anterior, middle, and posterior deltoids). The electromyographic activity of these eight muscles was examined in the nondominant shoulders of nine subjects. Indwelling wire electrodes (supraspinatus, infraspinatus, and subscapularis) and surface adhesive electrodes (pectoralis major, latissimus dorsi, and anterior, middle, and posterior deltoids) were placed. Each subject performed a series of 27 isometric contractions, and optimal tests (maximal neural activation) were identified for each muscle. Four tests were identified that resulted in the maximal neural activation of all eight shoulder muscles: 90° of scapular elevation with ?45° of humeral rotation for the supraspinatus, anterior deltoid, and middle deltoid; external rotation at 90° of scapular elevation and ?45° of humeral rotation for the infraspinatus and posterior deltoid: internal rotation at 90° of scapular elevation and neutral humeral rotation for the subscapularis and latissimus dorsi: and internal rotation at 0° of elevation and neutral rotation for the pectoralis major. These results identify four standard testing positions that will provide reference values for normalization of maximal voluntary contraction for the eight muscles of the shoulder examined in this study. Standardization of these test positions offers normalization guidelines that can be used in future dynamic electromyography studies of the shoulder.     

Effect of reverse manual wheelchair propulsion on shoulder kinematics,kinetics and muscular activity in persons with paraplegia

Objective: Shoulder pain after spinal cord injury (SCI) is attributed to increased mobility demands on the arms and negatively impacts independence and quality of life. Repetitive superior and posterior shoulder joint forces produced during traditional wheelchair (WC) locomotion can result in subacromial impingement if unopposed, as with muscular fatigue or weakness. ROWHEELS^® (RW), geared rear wheels that produce forward WC movement with backward rim pulling, could alter these forces.

Design: Cross sectional.

Setting: Research laboratory at a rehabilitation hospital.

Participants: Ten manual WC users with paraplegia.

Outcome measures: Propulsion characteristics and right upper extremity/trunk kinematics and shoulder muscle activity were collected during ergometer propulsion: (1) self-selected free speed reverse propulsion with RW, (2) matched-speed reverse (rSW), and (3) forward propulsion (fSW) with instrumented Smartwheels (SW). Inverse dynamics using right-side SW rim kinetics and kinematics compared shoulder kinetics during rSW and fSW.

Results: Free propulsion velocity, cycle distance and cadence were similar during RW, rSW and fSW. Overall shoulder motion was similar except that peak shoulder extension was significantly reduced in both RW and rSW versus fSW. Anteriorly and inferiorly directed SW rim forces were decreased during rSW versus fSW propulsion, but posteriorly and superiorly directed rim forces were significantly greater. Superior and posterior shoulder joint forces and flexor, adductor, and external rotation moments were significantly less during rSW, without a significant difference in net shoulder forces and moments. Traditional propulsive-phase muscle activity was significantly reduced and recovery-phase muscle activity was increased during reverse propulsion.

Conclusion: These results suggest that reverse propulsion may redirect shoulder demands and prevent subacromial impingement, thereby preventing injury and preserving independent mobility for individuals with paraplegia.     

Electromyographic activity in the immobilized shoulder girdle musculature during contralateral upper limb movements

The purpose of this study was to quantify electromyographic (EMG) activity in the immobilized shoulder girdle musculature at rest and during a battery of contralateral upper limb activities. Six asymptomatic men, aged 22 to 33 years, volunteered to participate. Fine-wire (supraspinatus, infraspinatus) and surface (deltoids, trapezii, biceps, serratus anterior) electrodes recorded the mean peak normalized (percent maximal voluntary contraction [%MVC]) EMG activity from each immobilized muscle at rest and during slow, fast, and incrementally resisted contralateral upper limb motions (5, 15, and 25 lb). EMG activity in all muscles was low during quiet immobilized standing (<1.5% maximal voluntary contraction [MVC]). During slow contralateral upper limb motions, activity ranged from 0.7% to 51.6% MVC (highest in trapezii) and was less than 15% MVC in the supraspinatus, infraspinatus, and anterior deltoid. Bimanual jar opening increased biceps activity from 7.8% to 16.1% MVC. During fast contralateral upper limb motions, peak infraspinatus activity increased to 56.7% during a fast straightforward reach. Supraspinatus activity was relatively high during all resisted backward-pulling motions (25.2%-32.1% MVC), whereas resisted forward reaching produced relatively little activity in the anterior deltoid, supraspinatus, infraspinatus, or biceps. Several slow and fast motions produced high trapezius activity (>45% MVC) with low supraspinatus, biceps, and anterior deltoid activities (<10% MVC). Our findings suggest that (1) immobilized shoulder girdle muscle EMG activity during quiet standing is negligible in asymptomatic individuals; (2) contralateral upper limb motions at self-selected speeds are not likely to be harmful to healing tissues; (3) during early healing periods, patients with biceps-labral injury should minimize bimanual activities, those with supraspinatus injury should avoid backward-pulling motions, and those with infraspinatus injury should avoid fast straightforward reaches; and (4) cross-body, straightforward, or downward reaches at either a slow or fast speed may be appropriately prescribed as rehabilitative exercises that can be initiated while the shoulder remains immobilized.     

Dynamic electromyographic analysis of the throwing shoulder with glenohumeral instability

Fifteen male athletes who were skilled in throwing and who had chronic anterior instability of the shoulder (Group 1) were evaluated by dynamic intramuscular electromyography while pitching a baseball. Indwelling wire electrodes recorded the levels of activity in the biceps, middle deltoid, supraspinatus, infraspinatus, pectoralis major, subscapularis, latissimus dorsi, and serratus anterior throughout the entire pitching sequence. These signals were synchronized electronically with records of the pitch that were made using high-speed photography. The pitch was divided into five phases: wind-up, early cocking, late cocking, acceleration, and follow-through. The results were compared with previous identical studies of twelve healthy, uninjured male athletes who were skilled in throwing (Group 2). Activity increased mildly in the biceps and supraspinatus in Group 1 as compared with Group 2. Similar patterns of activity were demonstrated in the deltoid. In Group 1 the infraspinatus had increased activity during early cocking and follow-through but had decreased activity during late cocking. The pectoralis major, subscapularis, latissimus dorsi, and serratus anterior in Group 1 all were shown to have markedly decreased activity. The study revealed a difference between Groups 1 and 2 in all of the muscles of the shoulder that were tested with the exception of the deltoid. The mildly increased activity levels of the biceps and supraspinatus that were found in Group 1 may compensate for anterior laxity. The marked reduction in activity in the pectoralis major, subscapularis, and latissimus dorsi added to the anterior instability by decreasing the normal internal-rotation force that is needed during the phases of late cocking and acceleration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Using a mobility assistance dog reduces upper limb effort during manual wheelchair ramp ascent in an individual with spinal cord injury

Abstract

Objective

To compare the mechanical and muscular efforts generated in the non-dominant upper limb (U/L) when ascending a ramp with and without the use of a mobility assistance dog (AD_Mob) in a manual wheelchair user with a spinal cord injury.

Method

The participant ascended a ramp at natural speed using his personal wheelchair with (three trials) and without (three trials) his AD_Mob. Movement parameters of the wheelchair, head, trunk, and non-dominant U/L (i.e. hand, forearm, and arm segments) were recorded with a motion analysis system. The orthogonal force components applied on the hand rims by the U/Ls were computed with instrumented wheels. Muscular activity data of the clavicular fibers of the pectoralis major, the anterior fibers of the deltoid, the long head of the biceps brachii, and the long head of the triceps brachii were collected at the non-dominant U/L.

Results

During uphill propulsion with the AD_Mob, the total and tangential forces applied at the non-dominant handrim, along with the rate of rise of force, were reduced while mechanical efficiency was improved compared to uphill propulsion without the AD_Mob. Similarly, the resultant net joint movements (wrist, elbow, and shoulder) and the relative muscular demands (biceps, triceps, anterior deltoid, pectoralis major) decreased during uphill propulsion with an AD_Mob versus without an AD_Mob.

Conclusion

Propelling uphill with the assistance of an AD_Mob reduces U/L efforts and improves efficiency compared to propelling uphill without its assistance in a manual wheelchair user with a spinal cord injury.     

The influence of testing positions and resistance locations on muscle activities during shoulder internal rotation strength measurements in young healthy adults

BackgroundAlthough some tests of shoulder internal rotator strength including subscapularis are commonly used in clinical practice, the differences in shoulder muscle activities other than subscapularis muscle among those tests are not well understood. The purpose of this study was to examine the activities of the superficial shoulder muscles in addition to internal rotation strength during two belly-press and three lift-off test positions.MethodsThirteen healthy young adult men (age 29.5 ± 5.4 years) were recruited for the present study. They performed isometric shoulder internal rotation against manual resistance during the belly-press test positions with two different resistance locations and the lift-off test with three different arm positions. The surface electromyographic activities of the superficial shoulder muscles, including the deltoid (anterior, middle, posterior), pectoralis major, long head of triceps and latissimus dorsi muscle, were collected and compared between the two belly-press tests, and among the three lift-off test positions (P < 0.05).ResultsThe belly-press test position with resistance to elbow showed significantly greater activities of the anterior and middle deltoid muscle than the original belly-press test; but showed significantly smaller activities of pectoralis major, triceps and latissimus dorsi muscle than the original belly-press test. Among the three lift-off tests, all muscle activities, except for the pectoralis major, were greater in the lift-off at L4/5 than in the lift-off at buttock and thigh. Lift-off at thigh showed significantly smaller activity of pectoralis major than the lift-off at L4/5 and buttock.ConclusionsThe findings of the present study suggest that clinician should give attention to compensatory motions by excessive shoulder extensor and adductor muscle activities for the original belly press test, by excessive deltoid muscle activities for the modified belly-press, and by excessive shoulder extensor muscle activities for the lift off test in the inferior arm positions.     

Effect of fore-aft seat position on shoulder demands during wheelchair propulsion: part 2. An electromyographic analysis

BACKGROUND/OBJECTIVES: Shoulder pain is common in persons with complete spinal cord injury. Adjustment of the wheelchair-user interface has been thought to reduce shoulder demands. The purpose of this study was to quantify the effect of seat fore-aft position on shoulder muscle activity during wheelchair propulsion. METHODS: Shoulder electromyography (EMG) was recorded while 13 men with paraplegia propelled a wheelchair in the following 2 seat positions: (a) shoulder joint center aligned with the wheel axle (anterior) and (b) shoulder joint center 8 cm posterior to the wheel axle (posterior) in 3 test conditions (free, fast, and graded). Duration of EMG activity and median and peak intensities were compared. RESULTS: During free propulsion, the median EMG intensity of all muscles was similar between anterior and posterior seat positions. The major propulsive muscles (pectoralis major and anterior deltoid) demonstrated significant reductions in their median and peak intensities in the posterior seat position. Pectoralis major median intensity was significantly reduced in the posterior position during fast (52% vs 66% maximal muscle test [MMT]) and graded (41 % vs 49% MMT) conditions, and peak intensity was significantly reduced in the free condition (29% vs 52% MMT) and the fast condition (103% vs 150% MMT). Anterior deltoid intensity was significantly reduced in the posterior position during fast propulsion only (26% vs 31% MMT). For all muscles, EMG duration was similar between positions in all test conditions. CONCLUSIONS: Reduction in the intensity of the primary push phase muscles (pectoralis major and anterior deltoid) during high-demand activities of fast and graded propulsion may reduce the potential for shoulder muscle fatigue and injuries.     

The effect of limb support on muscle activation during shoulder exercises

The purpose of this study was to determine the difference in demands on glenohumeral musculature during unsupported and supported active range-of-motion (AROM) shoulder exercises. Twenty healthy subjects volunteered for this study. Surface or fine-wire bipolar electrodes were applied to the infraspinatus, posterior deltoid, anterior deltoid, pectoralis major, and supraspinatus muscles. Subjects performed vertical wall slides and diagonal wall slides (45 degrees angle) with their hand in contact with the wall (supported) and not in contact with the wall (unsupported). Significantly greater supraspinatus activity was found in the unsupported exercises versus the supported exercises (F(4,76) = 4.38, P = .003). Exercises performed in the 45 degrees diagonal position were more demanding on shoulder musculature than vertical exercises (F(1,19) = 19.3, P < .001). Although our results were obtained in healthy subjects and the implications in a pathological population are not clear, we suggest that when designing a progression of exercises for increasing shoulder muscular activity, supported short lever arm AROM exercises should precede unsupported long lever arm AROM exercises.     

Restoration of anterior–posterior rotator cuff force balance improves shoulder function in a rat model of chronic massive tears

The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff “force couple,” is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior–posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two‐tendon rotator cuff tears in a rat model. Forty‐eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two‐tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two‐tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two‐tendon tear may be sufficient to restore adequate function. An in vivo model system for two‐tendon repair of massive rotator cuff tears is presented. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1028–1033, 2011     

Nutrient Intake and Body Habitus After Spinal Cord Injury: An Analysis by Sex and Level of Injury

Background/Objectives: To examine nutrient intake and body mass index (BMI) in the spinal cord injury (SCI) population according to level of injury and sex.

Design: Cross-sectional study conducted at 2 SCI treatment centers.

Participants/Methods: Seventy-three community-dwelling individuals with C5-T12 ASIA Impairment Scale (AIS) A or B SCI. Subjects were divided into 4 groups: male tetraplegia (N = 24), male paraplegia (N = 37), female tetraplegia (N = 1), and female paraplegia (N = 11). Mean age was 38 years; 84% were male; 34% were white, 41 % were African American, and 25% were Hispanic. Participants completed a 4-day food log examining habitual diet. Dietary composition was analyzed using Food Processor II v 7.6 software.

Results: Excluding the 1 woman with tetraplegia, total calorie intake for the other 3 groups was below observed values for the general population. The female paraplegia group tended to have a lower total calorie intake than the other groups, although macronutrient intake was within the recommended range. The male tetraplegia group, male paraplegia group, and the 1 woman with tetraplegia all had higher than recommended fat intake. Intake of several vitamins, minerals, and macronutrients did not meet recommended levels or were excessively low, whereas sodium and alcohol intake were elevated. Using adjusted BMI tables, 74.0% of individuals with SCI were overweight or obese.

Conclusions: Women with paraplegia tended to maintain healthier diets, reflected by lower caloric and fat intakes, fewer key nutrients falling outside recommended guidelines, and less overweight or obesity. Individuals with tetraplegia tended to take in more calories and had higher BMIs, and using adjusted BMI, the majority of the population was overweight or obese. The majority of people with SCI would benefit from nutritional counseling to prevent emerging secondary conditions as the population with SCI ages.     

Shoulder musculature activation during upper extremity weight-bearing exercise

STUDY DESIGN: Repeated-measures design comparing 7 static weight-bearing shoulder exercises. OBJECTIVE: The purpose of this study was to determine the demand on shoulder musculature during weight-bearing exercises and the relationship between increasing weight-bearing posture and shoulder muscle activation. BACKGROUND: Weight-bearing shoulder exercises are commonly prescribed in the rehabilitation of shoulder injuries. Limited information is available as to the demands placed on shoulder musculature while these exercises are performed. METHODS: Eighteen healthy college students volunteered for this study. Surface bipolar electrodes were applied over the infraspinatus, posterior deltoid, anterior deltoid, and pectoralis major muscles. Fine-wire bipolar intramuscular electrodes were inserted into the supraspinatus muscle. Electromyographic (EMG) root mean square signal intensity was normalized to 1 second of EMG obtained with a maximal voluntary isometric contraction (MVIC). Subjects were tested under 7 isometric exercise positions that progressively increased upper extremity weight-bearing posture. RESULTS: There was a high correlation between increasing weight-bearing posture and muscular activity (r = 0.97, P < 0.01). There was relatively little demand on the shoulder musculature for the prayer and quadruped positions (2%-10% MVIC). Muscular activation was greater for the infraspinatus than for other shoulder muscles throughout most of the exercise positions tested. CONCLUSION: These results indicate that alterations of weight-bearing exercises, by varying the amount of arm support and force, resulted in very different demands on the shoulder musculature. Specifically, the infraspinatus was particularly active during the weight-bearing exercises used in this study.     

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.     

Differences in shoulder muscle activity between patients with generalized joint laxity and normal controls

The aim of the present study was to analyze shoulder muscle activity in patients with generalized joint laxity and shoulder instability and to compare it with muscle activity recorded in healthy subjects from an earlier study. Electromyographic (EMG) activity was recorded from eight shoulder muscles in six patients using surface and intramuscular fine-wire electrodes. Recordings were made from the subscapularis, supraspinatus, infraspinatus, pectoralis major (sternoclavicular part), the anterior, middle, and posterior parts of the deltoid, and the latissimus dorsi. The EMG signal was low-pass filtered, full-wave rectified, and time-average. Normalization of the EMG allowed interindividual and intraindividual comparisons. During abduction and flexion, muscle activity in the anterior and middle parts of the deltoid was significantly decreased in the patients, and during internal rotation activity in the subscapularis was increased. As in healthy subjects, patients showed simultaneous activity in both those muscles producing the movement and in the antagonistic muscles. The altered muscle activity observed in patients with generalized joint laxity provides (1) a basis for understanding the mechanism of their shoulder instability and (2) the rationale for a physical training program for these patients.     

An electromyographic study on elevation of the shoulder joint

To quantitatively analyze the electromyographic activity of the shoulder girdle muscles during elevation of the arm, the action potentials of nine muscles were integrated over 10-degree intervals of corresponding elevation angle. The trapezius, supraspinatus and deltoideus (anterior and middle fibers) muscles showed high activity and their activity increased in accordance with the magnitude of the elevation angle. The integrated EMG activity in the trapezius, supraspinatus and deltoideus (middle and posterior fibers) muscles increased as the plane of elevation was changed from the sagittal plane to the frontal plane. The correlation between the calculated work and the integrated EMG activity during scapular abduction from 0 to 90 degrees was analyzed. The regression coefficients of the trapezius, supraspinatus and deltoideus (anterior and middle fibers) muscles were higher than those of other muscles. The correlation coefficient of the supraspinatus was significantly lower than those of the trapezius, deltoideus and pectoralis major muscles.     

Lipid Profiles of Persons With Paraplegia and Tetraplegia: Sex Differences

Abstract

Background/Objective: To examine the lipoprotein profiles of men and women with paraplegia and tetraplegia. Impairment of the sympathetic nervous system (dependent on the level of injury) and the extent of physical capacity and activity were correlated with the lipid profile in men with spinal cord injury (SCI). Sex-related differences of the lipoprotein profiles could be found in nondisabled and premenopausal women with SCI mainly because of the different effects of sexual hormones.

Methods: Lipoprotein profiles of 112 participants with SCI (32 premenopausal women, 80 men) were analyzed and correlated to sex, lesion level, and physical performance capacity.

Results: Women with tetraplegia or paraplegia showed significantly higher levels of high-density lipoprotein and lower ratios of total cholesterol to high-density lipoprotein-cholesterol compared with men with corresponding lesion levels, without a difference in peak oxygen consumption. Concentrations of very-low-density lipoproteins were lower in women with paraplegia than in men with paraplegia, no differences were found in total cholesterol, low-density lipoprotein-cholesterol, and triglycerides. Sexindependent elevations in total cholesterol and low-density lipoprotein-cholesterol were associated with paraplegia, and sex-independent elevations in triglyceride levels were associated with tetraplegia.

Conclusions: Persons with SCI showed sex-related differences in their lipoprotein profiles. Independent of physical fitness, the lipoprotein profile of premenopausal women with SCI did not exhibit the adverse lipoprotein characteristics observed in men with SCI, probably because of the influence of sexual hormones independent of lesion level.     

Shoulder electromyography in multidirectional instability

We studied shoulder muscle activity in multidirectional instability (MDI) and multidirectional laxity (MDL) of the shoulder, our hypothesis being that altered muscle activity plays a role in their pathogenesis. Six muscles (supraspinatus, infraspinatus, subscapularis, anterior deltoid, middle deltoid, and posterior deltoid) were investigated by use of intramuscular dual fine-wire electrodes in 7 normal shoulders, 5 MDL shoulders, and 6 MDI shoulders. Each subject performed 5 types of exercise (rotation in neutral, 45 degrees of abduction, 90 degrees of abduction, flexion/extension, and abduction/adduction) on an isokinetic muscle dynamometer at two rates, 90 degrees /s and 180 degrees /s. After filtering, rectification, and smoothing, the electromyography signal was normalized by using the peak voltage of the movement cycle. In subjects with MDI, compared with normal subjects, activity patterns of the anterior deltoid were different during rotation in neutral and 90 degrees of abduction, whereas those of the middle and posterior deltoid were different during rotation in 90 degrees of abduction. In subjects with MDL, the posterior deltoid showed increased activity compared with normal subjects during adduction. Activity patterns of the supraspinatus, infraspinatus, and subscapularis appeared similar in both groups. Dual fine-wire electromyography offers insight into the complex role of shoulder girdle muscle function in normal movement and in instability. Altered patterns of shoulder girdle muscle activity and imbalances in muscle forces support the theory that impaired coordination of shoulder girdle muscle activity and inefficiency of the dynamic stabilizers of the glenohumeral joint are involved in the etiology of MDI. Interestingly, the abnormalities are in the deltoid rather than the muscles of the rotator cuff.     

The impact of level of injury on patterns of cognitive dysfunction in individuals with spinal cord injury

Context: While it is well recognized that physical and physiological changes are more prominent in individuals with higher neurologic levels of spinal cord injury (SCI), the impact of level of lesion on cognition is less clear.

Design: Cross-sectional, 3-group.

Setting: Non-profit rehabilitation research foundation.

Participants: 59 individuals with SCI (30 with tetraplegia, 29 with paraplegia) and 30 age-matched healthy controls (HC).

Interventions: None.

Outcome Measures: Neuropsychological tests in the domains of attention, working memory, processing speed, executive control, and learning and memory.

Results: Results indicated significantly lower test performance in individuals with paraplegia on new learning and memory testing compared to HC. In contrast, compared to HC the group with tetraplegia, showed a significantly impaired performance on a processing speed task, and both the tetraplegia and the paraplegia groups were similarly impaired on a verbal fluency measure. SCI groups did not differ on any cognitive measure.

Conclusion: Individuals with SCI may display different patterns of cognitive performance based on their level of injury.     

Relative contributions of infraspinatus and deltoid during external rotation in healthy shoulders

Balanced forces around the shoulder are important for normal function; however, rehabilitation guidelines are not well defined because the muscle contributions and optimal exercise technique to recruit them are poorly understood. This study aimed to determine (1) the conditions of resisted isometric external rotation that optimized the contribution of infraspinatus and (2) the load of external rotation at which the adduction strategy was most effective at reducing deltoid contributions. Eighteen subjects with healthy shoulders (n = 36) performed resisted isometric external rotation at 3 increasing loads--10%, 40%, and 70% of their maximal resisted external rotation voluntary isometric contraction--with and without adduction. Surface electromyographic activity of the infraspinatus, posterior and middle deltoid, and pectoralis major was recorded and normalized against the average activity of all 4 muscles, representing each muscle's relative contribution to the task. To optimize the relative contribution of the infraspinatus with the least deltoid involvement during isometric external rotation, a load between 10% and 40% maximal voluntary isometric contraction is appropriate. At low loads, use of the adduction strategy during external rotation reduces middle deltoid involvement. In contrast, the posterior deltoid is activated in parallel with the infraspinatus at low loads and may even act as an adductor with the arm by the side. This study provides a useful guide to optimize rehabilitative exercises for rotator cuff dysfunction; in particular, highlighting that activation of the deltoid could be counterproductive to infraspinatus retraining.