The effect of EMG biofeedback training on muscle activation in an impingement population.

Subacromial impingement syndrome (SAIS) is one of the most diagnosed causes of pain in the upper extremity. The purpose of this study was to investigate muscle activity between asymptomatic and SAIS shoulders on the same subject while understanding the effectiveness of EMG biofeedback training (EBFB) on bilateral overhead movements. Ten participants (7 male), that tested positive for 2/3 SAIS clinical tests, volunteered for the study. Bilateral muscle activity was measured via electrodes on the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and lumbar paraspinals (LP). Participants performed bilateral scapular plane overhead movements before and after EBFB. EBFB consisted of 10 bilateral repetitions of I, W, T, and Y exercises focused on reducing UT and increasing LT and SA activity. Prior to EBFB, no significant difference in muscle activity was present between sides. A significant main effect of time indicated that after EBFB both sides exhibited reduced UT activity at 60° (p = 0.003) and 90° (p = 0.036), LT activity was increased at all measured humeral angles (p < 0.0005), and SA muscle activity was increased at 110° (p = 0.001). EBFB in conjunction with scapular based exercise effectively alters muscle activity of asymptomatic and symptomatic scapular musculature.

Movement direction impacts knee joint kinematics during elliptical exercise at varying incline angles.

BACKGROUND: Elliptical trainers are a popular cardiovascular exercise for individuals with injuries or those post-operation. There is currently limited data on the impacts of direction while on elliptical trainers for knee joint kinematic risk factors. This study compared lower extremity kinematics between the forward and reverse direction at varying inclines on an elliptical trainer modified with converging footpath and reduced inter-pedal distance. METHODS: Twenty-four college age participants exercised on the modified elliptical in both directions at four ramp inclines: 6°, 12°, 25°, and 35°. Three-dimensional kinematics were collected for each direction and ramp incline. A 2 × 4 (direction × incline) repeated measures analysis of variance was run with an alpha of 0.05. Simple effects analysis was run with Bonferroni correction for significant interaction or main effect of ramp incline. RESULTS: The reverse direction had significantly greater peak knee valgus at 6° incline (mean difference [MD] = 1.35°, p < 0.014, d = 0.31) and 12° (MD = 2.41°, p < 0.001, d = 0.55), peak hip abduction at 6° (MD = 2.86°, p = 0.002, d = 0.49) and 12° (MD = 2.91°, p < 0.001, d = 0.51), but decreased peak knee flexion angles (p = 0.032) at all inclines. CONCLUSIONS: Individuals with knee pathologies such as knee osteoarthritis or anterior knee pain should exercise in the reverse direction at lower inclines. However, switching to the forward direction and/or increasing incline may increase quadriceps strength during a safe activity such as elliptical trainers.

The effects of a standard elliptical vs. a modified elliptical with a converging footpath on lower limb kinematics and muscle activity.

Elliptical trainers that increase the inter-pedal distance may have potential benefits for knee osteoarthritis by decreasing the amount of knee varus. Modifying elliptical trainers with a converging footpath and reduced inter-pedal distance may be beneficial for reducing anterior knee pathology risk by decreasing knee valgus angles. Twenty-one college students participated in a single testing session. Participants exercised on two different elliptical trainers, one modified with a converging footpath and reduced inter-pedal width, and a standard elliptical trainer. Participants exercised for 2 min at three ramps incline at 120 strides per minute and constant work rate. Three-dimensional kinematics and electromyography of the dominant lower limb were recorded. Multiple 2 × 3 (Elliptical x Incline) ANOVAs with Bonferroni corrections were used to compare the two elliptical trainers at each incline for kinematics and muscle activity. The modified elliptical trainer displayed significantly decreased peak knee valgus (p = 0.031, η p 2 = 0.234 ), peak knee flexion (p = 0.006, η p 2 = 0.246 ), and interactions for peak knee flexion (p = 0.001, η p 2 = 0.250 ) and vastus lateralis (p < 0.01, η p 2 = 0.380 ) muscle activity compared to the standard elliptical trainer. The decreased peak knee valgus and flexion angles could be beneficial for reducing long-term injury risk for anterior knee pathologies.

Creatine electrolyte supplement improves anaerobic power and strength: a randomized double-blind control study.

BACKGROUND: Creatine supplementation aids the Phosphagen system by increasing the amount of free creatine and phosphocreatine available to replenish adenosine triphosphate. The purpose of this study was to investigate the effects of a creatine and electrolyte formulated multi-ingredient performance supplement (MIPS) on strength and power performance compared to a placebo. Maximal strength along with total concentric work, mean rate of force development (mRFD), mean power, peak power, and peak force for both bench press and back squat were determined at pre-test and post-test separated by 6 weeks of supplementation. METHODS: Twenty-two subjects (6 females, 21 ± 2 yrs., 72.46 ± 11.18 kg, 1.72 ± 0.09 m) performed a one-repetition maximum (1RM) for back squat and bench press. Eighty percent of the subject's pre-test 1RM was used for a maximal repetition test to assess performance variables. Testing was separated by 6 weeks of supplementation of a MIPS dose per day in a double-blind fashion for comparison. A two-way mixed analysis of covariance (ANCOVA) was applied with an alpha level of 0.05. RESULTS: For their back squat 1RM, the MIPS group displayed significant increase of 13.4% (95% CI: 2.77, 23.8%) while placebo displayed a decrease of - 0.2% (95% CI: - 1.46, 2.87%) (p = 0.047, ηp2 = 0.201). The MIPS displayed a significant increase of 5.9% (95% CI: 2.5, 10.1%) and placebo displayed a non-significant increase of 0.7% (95% CI: - 3.49, 3.9%) in bench press maximal strength (p = 0.033,0.217). The MIPS group displayed a significant increase as well in total concentric work (26.5, 95% CI: 6.07, 46.87%, p = 0.008, ηp2 = 0.330) and mean power (17.9, 95% CI: 3.42, 32.46%, p = 0.003, ηp2 = 0.402) for the maximal repetition bench press test at 80% of their 1RM. CONCLUSIONS: The MIPS was found to be beneficial to recreationally trained individuals compared to a placebo. The greatest benefits are seen in bench press and back squat maximal strength as well as multiple repetition tests to fatigue during the bench press exercise.

Effects of finger taping on forearm muscle activation in rock climbers.

Flexor tendon pulley injury is associated with a change in relative activation of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) muscles. The purpose of this study was to determine the effect of taping of the fingers on relative muscle activation of the FDS and FDP muscles in uninjured rock climbers. Muscle activation in 10 healthy volunteers were recorded using intramuscular electromyography (EMG) during a static hang with subjects utilizing the crimp grip without tape, with a circumferential tape and with an H-tape in random order. EMG data were normalized to a static hang with a non-crimp grip (RVC). Average EMG activity of the FDS as a percentage of RVC was 102.4 ±â€¯59.1 without tape, 116.9 ±â€¯35.3 with H-tape and 99.3 ±â€¯35.3 with circumferential tape. Average EMG activity of the FDP as a percentage of RVC was 96.6 ±â€¯40.0 without tape, 98.9 ±â€¯30.3 with H-tape and 90.6 ±â€¯28.7 with circumferential tape. Taping did not have a significant effect on average relative muscle activation of the FDS or FDP muscles (p = 0.069). This study showed that finger taping may not significantly affect the activity of the FDS and FDP during static holds while rock climbing.

ACUTE EFFECTS OF TWO HIP FLEXOR STRETCHING TECHNIQUES ON KNEE JOINT POSITION SENSE AND BALANCE.

Background: Tightness of hip flexor muscles has been recognized as a risk factor for various musculoskeletal injuries in the lower extremities. Purpose: The purpose of this study was to examine the acute effects of two hip flexor stretching techniques (dynamic and hold-relax proprioceptive neuromuscular facilitation, HR-PNF) on hip extension (ROM), knee joint position sense (JPS) and balance in healthy college age students who exhibit tightness in hip flexor muscles. Study Design: Pretest-posttest randomized experimental groups. Methods: Thirty-six healthy college age students (mean = 22.37 years) with tight hip flexors participated in this study. Hip extension ROM, knee joint position sense and dynamic balance were tested pre- and post-stretching using a digital inclinometer, an iPod touch and the Y-Balance test, respectively. Subjects were randomly divided into dynamic and HR-PNF stretching groups. Three-way mixed analysis of variance was utilized to explore if an interaction existed between the groups in tested variables. Results: There was a significant effect of time on hip extension ROM in both groups (p < 0.001). There was also a significant effect of stretch type on hip extension ROM (p = 0.004) favoring hold-relax over dynamic stretching group. There was a non-significant effect of time on mean knee joint position replication error in both groups. There was a significant main effect of time on the Y-Balance test's mean distance of reach to posteromedial and posterolateral directions (p < 0.001). There was also a significant main effect of directions of reach on distances achieved (p < 0.001) favoring posterolateral over posteromedial, and the latter over anterior direction. Conclusions: The results of this study demonstrated the effectiveness of both HR-PNF and dynamic stretching techniques which resulted in a significant acute improvement in hip extension ROM and dynamic balance measures, with HR-PNF being more effective than dynamic stretch. However, there were no significant improvements in knee joint position replication over time in either stretching group. Level of Evidence: 2b.

Lower Extremity Strength and Range of Motion in High School Cross-Country Runners.

Cross-country running is becoming an increasingly popular sport, with a significant participation noted at the high school level. The aim of this study was to compare gender and bilateral hip extension range of motion and hip and knee extension strength of high school cross-country runners. 31 participants volunteered from a local high school cross-country team (16 males and 15 females). The modified Thomas test was utilized to measure hip extension range of motion bilaterally using a digital inclinometer. In order to measure hip and knee isometric strengths, an isokinetic dynamometer was employed. A mixed model approach revealed a statistically significant difference in peak hip extension strength between genders but not the side. Male athletes demonstrated a 29.2 Nm/kg (P < 0.05) greater force production than females during isometric hip extension strength testing. There were no significant differences in peak knee extension isometric strength, hip extension range of motion, and the ratio of peak hip and knee strength between genders and the dominant and nondominant leg. Female cross-country runners should focus on increasing hip extension strength to help maintain hip stability during running. This may be beneficial in decreasing the chances of experiencing patellofemoral pain in long-distance runners.

Creatine-electrolyte supplementation improves repeated sprint cycling performance: A double blind randomized control study.

BACKGROUND: Creatine supplementation is recommended as an ergogenic aid to improve repeated sprint cycling performance. Furthermore, creatine uptake is increased in the presence of electrolytes. Prior research examining the effect of a creatine-electrolyte (CE) supplement on repeated sprint cycling performance, however, did not show post-supplementation improvement. The purpose of this double blind randomized control study was to investigate the effect of a six-week CE supplementation intervention on overall and repeated peak and mean power output during repeated cycling sprints with recovery periods of 2 min between sprints. METHODS: Peak and mean power generated by 23 male recreational cyclists (CE group: n = 12; 24.0 ± 4.2 years; placebo (P) group: n = 11; 23.3 ± 3.1 years) were measured on a Velotron ergometer as they completed five 15-s cycling sprints, with 2 min of recovery between sprints, pre- and post-supplementation. Mixed-model ANOVAs were used for statistical analyses. RESULTS: A supplement-time interaction showed a 4% increase in overall peak power (pre: 734 ± 75 W; post: 765 ± 71 W; p = 0.040; ηp2 = 0.187) and a 5% increase in overall mean power (pre: 586 ± 72 W; post: 615 ± 74 W; p = 0.019; ηp2 = 0.234) from pre- to post-supplementation for the CE group. For the P group, no differences were observed in overall peak (pre: 768 ± 95 W; post: 772 ± 108 W; p = 0.735) and overall mean power (pre: 638 ± 77 W; post: 643 ± 92 W; p = 0.435) from pre- to post-testing. For repeated sprint analysis, peak (pre: 737 ± 88 W; post: 767 ± 92 W; p = 0.002; ηp2 = 0.380) and mean (pre: 650 ± 92 W; post: 694 ± 87 W; p < 0.001; ηp2 = 0.578) power output were significantly increased only in the first sprint effort in CE group from pre- to post-supplementation testing. For the P group, no differences were observed for repeated sprint performance. CONCLUSION: A CE supplement improves overall and repeated short duration sprint cycling performance when sprints are interspersed with adequate recovery periods.

Individuals With Knee Osteoarthritis Demonstrate Interlimb Asymmetry in Pedaling Power During Stationary Cycling.

Cycling is commonly prescribed for physical rehabilitation of individuals with knee osteoarthritis (OA). Despite the known therapeutic benefits, no research has examined interlimb symmetry of power output during cycling in these individuals. We investigated the effects of external workload and cadence on interlimb symmetry of crank power output in individuals with knee OA versus healthy controls. A total of 12 older participants with knee OA and 12 healthy sex- and age-matched controls were recruited. Participants performed 2-minute bouts of stationary cycling at 4 workload-cadence conditions (75 W at 60 rpm, 75 W at 90 rpm, 100 W at 60 rpm, and 100 W at 90 rpm). Power output contribution of each limb toward total crank power output was computed over 60 crank cycles from the effective component of pedal force, which was perpendicular to the crank arm. Across the workload-cadence conditions, the knee OA group generated significantly higher power output with the severely affected leg compared with the less affected leg (10% difference; P = .02). Healthy controls did not show interlimb asymmetry in power output (0.1% difference; P > .99). For both groups, interlimb asymmetry was unaffected by external workload and cadence. Our results indicate that individuals with knee OA demonstrate interlimb asymmetry in crank power output during stationary cycling.

Scapular kinematic is altered after electromyography biofeedback training.

Electromyography (EMG) biofeedback training affords patients a better sense of the different muscle activation patterns involved in the movement of the shoulder girdle. It is important to address scapular kinematics with labourers who have daily routines involving large amounts of lifting at shoulder level or higher. This population is at a heightened risk of developing subacromial impingement syndrome (SAIS). The purpose of this study was to investigate the acute effects of scapular stabilization exercises with EMG biofeedback training on scapular kinematics. Twenty-three healthy subjects volunteered for the study. Electrodes were placed on the upper and lower trapezius, serratus anterior, and lumbar paraspinals to measure EMG activity. Subjects underwent scapular kinematic testing, which consisted of humeral elevation in the scapular plane, before and after biofeedback training. The latter consisted of 10 repetitions of the I, W, T, and Y scapular stabilization exercises. Subjects were told to actively reduce the muscle activation shown on the screen for the upper trapezius during the exercises. The scapular external rotation had a statistically significant difference at all humeral elevation angles (p<0.004) after biofeedback was administered. After the exercises, the scapula was in a more externally rotated orientation with a mean difference of 6.5°. There were no significant differences found with scapular upward rotation, or posterior tilt at all humeral elevation angles following biofeedback. Scapular kinematics are altered by EMG biofeedback training utilizing scapular stabilization exercises. However, only scapular external rotation was affected by the exercises.

The effects of exercise type and elbow angle on vertical ground reaction force and muscle activity during a push-up plus exercise.

BACKGROUND: Proper alignment of the scapula during upper extremity motion is important in maintaining shoulder joint function and health. Push-up plus exercise is considered as one of the best exercise to strengthen the muscles that stabilize the scapula. The purpose of the study is to examine the effects of push-up plus variants and elbow position on vertical ground reaction force and electromyographical activity of four shoulder muscles during concentric contraction. METHODS: A total of 22 healthy subjects volunteered for the study. Each of the subjects performed both modified and traditional push-up plus. Modified push-up plus was performed with both knees and hands touching the ground while the traditional push-up plus was executed with hands and feet contacting the ground. Electromyography (EMG) of the upper trapezius (UT), lower trapezius (LT), infraspinatus (INFRA), and serratus anterior (SA), and vertical ground reaction forces (vGRF) were collected. RESULTS: The traditional push-up plus exhibited higher EMG activity in all muscles tested (P < .05) and vertical ground reaction force (P < .001) compared to modified push-up plus. The highest difference in EMG activity between the two exercises was observed with the Serratus Anterior muscle (22%). Additionally, the traditional push-up plus presented a higher vGRF compared to the modified push-up plus (P < .001) by 17%. The SA had the greatest EMG activity compared to the other muscles tested during the concentric phase of the traditional push-up plus, and this did not occur during the plus phase of the exercise. CONCLUSION: The highest activity of the serratus anterior occurred at 55° of elbow extension during the concentric phase of the traditional PUP and not at the plus phase of the exercise. This suggests that when prescribing an exercise to target the serratus anterior, a traditional push-up is adequate and the plus-phase is not necessary. However, for patients that cannot perform a traditional push-up, the modified push-up plus would be a great alternative to strengthen their serratus anterior.

Passive hip range of motion is reduced in active subjects with chronic low back pain compared to controls.

BACKGROUND: Non-specific low back pain is a common condition often without a clear mechanism for its presentation. Recently more attention has been placed on the hip and its potential contributions to non-specific chronic low back pain (NSCLBP). Emphasis in research has mainly been placed on motor control, strength and endurance factors in relation to NSCLBP. Limited focus has been placed on hip mobility and its potential contribution in subjects with NSCLBP. PURPOSE/AIM: The aim of this study was to compare passive ROM in hip extension, hip internal rotation, hip external rotation and total hip rotation in active subjects with NSCLBP to healthy control subjects. The hypothesis was that active subjects with NSCLBP would present with decreased total hip ROM and greater asymmetry when compared to controls. DESIGN: Two group case controlled. SETTING: Clinical research laboratory. PARTICIPANTS: 30 healthy subjects without NSCLBP and 30 active subjects with NSCLBP. Subjects categorized as NSCLBP were experiencing pain in the low back area with or without radicular symptoms of greater than three months duration. MAIN OUTCOME MEASURE: Passive hip extension (EXT), hip internal rotation (IR), hip external rotation (ER) and total hip rotation ROM. A digital inclinometer was used for measurements. RESULTS: There was a statistically significant difference (p<0.001) in hip passive extension ROM between the control group and the NSCLBP group bilaterally. Mean hip extension for the control group was 6.88 bilaterally. For the NSCLBP group, the mean hip extension was -4.28 bilaterally. This corresponds to a difference of means between groups of 10.88. There was no statistically significant differences (p>0.05) in hip IR, ER, or total rotation ROM between groups. CONCLUSIONS: The results of this study indicate that a significant difference in hip extension exists in active subjects with NSCLBP compared to controls. It may be important to consider hip mobility restrictions and their potential impact on assessment of strength in NSLBP subjects. Future studies may be needed to investigate the relationship between measurements and intervention strategies. LEVEL OF EVIDENCE: 2b.

Patellofemoral pain subjects exhibit decreased passive hip range of motion compared to controls.

BACKGROUND: Patellofemoral pain is a common condition without a clear mechanism for its presentation. Recently significant focus has been placed on the hip and its potential role in patellofemoral pain (PFP). The majority of the research has examined hip strength and neuromuscular control. Less attention has been given to hip mobility and its potential role in subjects with PFP. PURPOSE/AIM: The purpose of this study was to compare passive hip range of motion (ROM) of hip extension and hip internal and external rotation in subjects with PFP and healthy control subjects. The hypothesis was that subjects with PFP would present with less total hip ROM and greater asymmetry than controls. DESIGN: Two groups, case controlled. SETTING: Clinical research laboratory. PARTICIPANTS: 30 healthy subjects without pain, radicular symptoms or history of surgery in the low back or lower extremity joints and 30 subjects with a diagnosis of PFP. MAIN OUTCOME MEASURES: Passive hip extension, hip internal rotation (IR) and hip external rotation (ER). A digital inclinometer was used for measurements. RESULTS: There was a statistically significant difference (p<0.001) in hip passive extension between the control group and the PFP group bilaterally. Mean hip extension for the control group was 6.8° bilaterally. For the PFP group, the mean hip extension was -4.0° on the left and -4.3° on the right. This corresponds to a difference of means between groups of 10.8° on the left and 11.1° on the right with a standard error of 2.1°. There was no statistically significant difference (p>0.05) in either hip IR or ER ROM or total rotation between or within groups. CONCLUSIONS: The results of this study indicate that a significant difference in hip extension exists in subjects with PFP compared to controls. These findings suggest that passive hip extension is a variable that should be included within the clinical examination of people with PFP. It may be valuable to consider hip mobility restrictions and their potential impact on assessment of strength and planned intervention in subjects with PFP. LEVEL OF EVIDENCE: 2b.

Concurrent validity of digital inclinometer and universal goniometer in assessing passive hip mobility in healthy subjects.

BACKGROUND: Hip range of motion is an important component in assessing clinical orthopedic conditions of the hip, low back and lower extremities. However it remains unclear as to what constitutes the best tool for clinical measurement. The purpose of this study was to investigate the concurrent validity of passive range of motion (ROM) measurements of hip extension and hip internal and external rotation using a digital inclinometer and goniometer. DESIGN: Criterion Standard. SETTING: Clinical research laboratory. PARTICIPANTS: 30 healthy subjects without pain, radicular symptoms or history of surgery in the low back or hip regions. MAIN OUTCOME MEASURES: Passive hip range of motion for extension, hip internal rotation and hip external rotation. A digital inclinometer and universal goniometer were utilized as the tools for comparisons between measurements. RESULTS: There was a statistically significant difference (p < 0.05) between the goniometer and digital inclinometer in measured hip ROM except for measurements of right hip external rotation (p > 0.05). The mean difference between the goniometer and digital inclinometer in left hip extension, internal rotation and external rotation were 3.5°, 4.5° and 5.0° respectively. The mean difference between the two devices in right hip extension, internal rotation and external rotation were 2.8°, 4.2° and 2.6° respectively. On average, the difference between the goniometer and digital inclinometer in extension was 3.2°, internal rotation was 4.5° and external rotation was 3.8°. The digital inclinometer had greater measurement during EXT and ER. Furthermore, there was no statistically significant difference (p > 0.05) in hip ROM between the left and right side for either goniometric or digital inclinometer measurements. CONCLUSIONS: This results of this study indicate that a significant difference exists between the two devices in all measurements with exception of right hip extension. The differences were noted to be between 3-5 degrees for all planes measured. These findings suggest that caution should be used if these two devices are to be used interchangeably to quantify passive hip range of motion in either clinical practice or when comparing studies that utilize different instruments. LEVEL OF EVIDENCE: 2b.

Scapular kinematics and shoulder elevation in a traditional push-up.

CONTEXT: Proper scapulothoracic motion is critical for the health and function of the shoulder and represents a principal focus in the rehabilitation setting. Variants of the traditional push-up are used frequently to help restore proper scapular kinematics. To date, substantial research has focused on muscle activation levels of rotator cuff and scapular-stabilizing musculature, whereas a dearth of literature exists regarding scapular kinematics during push-up variants. OBJECTIVE: To examine the effect of shoulder position on scapular kinematics across the range of motion (ROM) of a traditional push-up. DESIGN: Cross-sectional study. SETTING: University laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixteen healthy participants without a history of upper extremity or spine injury requiring rehabilitation or surgery. INTERVENTION(S): Participants performed a traditional push-up while kinematic measurements were acquired from multiple upper extremity segments. The 3 shoulder position conditions were (1) self-selected position, (2) shoulder adducted upon ascent (at side), and (3) shoulder elevated to approximately 90°. MAIN OUTCOME MEASURE(S): Scapular posterior tilt, upward rotation, and external rotation were examined across elbow-extension ROM and compared across conditions. RESULTS: Posterior tilt was greater in the self-selected and at-side conditions than in the elevated condition and increased linearly with elbow extension. External rotation was greater in the self-selected and at-side conditions compared with that in the elevated condition. In the at-side condition, upward rotation began lower than in the other conditions at the start of the concentric phase but increased above the others soon after the elbow started to extend. CONCLUSIONS: Performing a traditional push-up with the shoulders elevated may place the scapula in a position of impingement. Clinicians should be cognizant of shoulder elevation when prescribing and monitoring exercise progression. The results of this study will provide further direction for clinicians in prescribing rehabilitation exercises for the upper extremity, especially closed chain exercises for shoulder conditions.

Humeral head translation after a suprascapular nerve block.

Subacromial impingement syndrome is the most common shoulder disorder. Abnormal superior translation of the humeral head is believed to be a major cause of this pathology. The first purpose of the study was to examine the effects of suprascapular nerve block on superior translation of the humeral head and scapular upward rotation during dynamic shoulder elevation. The secondary purpose was to assess muscle activation patterns during these motions. Twenty healthy subjects participated in the study. Using fluoroscopy and electromyography, humeral head translation and muscle activation were measured before and after a suprascapular nerve block. The humeral head was superiorly located at 60 degrees of humeral elevation, and the scapula was more upwardly rotated from 30 to 90 degrees of humeral elevation after the block. The differences were observed during midrange of motion. In addition, the deltoid muscle group demonstrated increased muscle activation after the nerve block. The study's results showed a compensatory increase in humeral head translation, scapular upward rotation, and deltoid muscle activation due to the nerve block. These outcomes suggest that increasing muscular strength and endurance of the supraspinatus and infraspinatus muscles could prevent any increased superior humeral head translation. This may be beneficial in reducing shoulder impingement or rotator cuff tears over time.

Prevalence of myofascial trigger points in the hip in patellofemoral pain.

OBJECTIVES: To determine the prevalence of myofascial trigger points (MTrPs) in the gluteus medius (GMe) and quadratus lumborum (QL) for subjects with patellofemoral pain (PFP), and to examine the relationship between MTrPs and force production of the GMe after treatment. DESIGN: Randomized controlled trial. SETTING: A physical therapy clinic. PARTICIPANTS: Subjects (N=52; mean age ± SD, 30±12y; mean height ± SD, 172±10cm; mean mass ± SD, 69±14kg) volunteered and were divided into 2 groups: a PFP group (n=26) consisting of subjects with PFP, and a control group (n=26) with no history of PFP. INTERVENTIONS: Patients with PFP received trigger point pressure release therapy (TPPRT). MAIN OUTCOME MEASURES: Hip abduction isometric strength and the presence of MTrPs. RESULTS: Prevalence of bilateral GMe and QL MTrPs for the PFP group was significantly higher compared with controls (P=.001). Subjects in the PFP group displayed significantly less hip abduction strength compared with the control group (P=.007). However, TPPRT did not result in increased force production. CONCLUSIONS: Subjects with PFP have a higher prevalence of MTrPs in bilateral GMe and QL muscles. They demonstrate less hip abduction strength compared with controls, but the TPPRT did not result in an increase in hip abduction strength.

Measuring humeral head translation using fluoroscopy: a validation study.

Numerous techniques have been employed to monitor humeral head translation due to its involvement with several shoulder pathologies. However, most of the techniques were not validated. The objective of this study is to compare the accuracy of manual digitization and contour registration in measuring superior translation of the humeral head. Eight pairs of cadaver scapulae and humerii bones were harvested for this study. Each scapula and humerus was secured in a customized jig that allowed for control of humeral head translations and a vise that permitted rotations of the scapula about three axes. Fluoroscopy was used to take images of the shoulder bones. Scapular orientation was manipulated in different positions while the humerus was at 90 degrees of humeral elevation in the scapular plane. Humeral head translation was measured using the two methods and was compared to the known translation. Additionally, accuracy of the contour registration method to measure 2-D scapular rotations was assessed. The range for the root mean square (RMS) error for manual digitization method was 0.27 mm-0.43 mm and the contour registration method had a RMS error ranging from 0.18 mm-0.40 mm. In addition, the RMS error for the scapular angle rotation using the contour registration method was 2.4 degrees . Both methods showed acceptable errors. However, on average, the contour registration method showed lesser measurement error compared to the manual digitization method. In addition, the contour registration method was able to show good accuracy in measuring rotation that is useful in 2-D image analysis.

Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.