Posture-movement changes following repetitive motion-induced shoulder muscle fatigue

Repetitive motion-induced fatigue not only alters local motion characteristics but also provokes global reorganization of movement. However, the three-dimensional (3D) characteristics of these reorganization patterns have never been documented in detail. The goal of this study was to assess the effects of repetitive reaching-induced arm fatigue on the whole-body, 3D biomechanical task characteristics. Healthy subjects (N = 14) stood and performed a continuous reaching task (RRT) between two targets placed at shoulder height to fatigue. Whole-body kinematic (Vicon^©), kinetic (AMTI^© force platforms) and electromyographic (EMG, Noraxon^©) characteristics were recorded. Maximal voluntary isometric efforts (MVIE) of the shoulder and elbow were measured pre- and post-RRT. Post-RRT shoulder elevation MVIE was reduced by 4.9 ± 8.3% and trapezius EMG amplitude recorded during the RRT increased by 46.9 ± 49.9% from the first to last minute of the RRT, indicating that arm fatigue was effectively induced. During fatigued reaching, subjects elevated their shoulder (11.7 ± 10.5 mm) and decreased their average shoulder abduction angle by 8.3 ± 4.4°. These changes were accompanied by a lateral shift of the body’s center of mass towards the non-reaching arm. These findings suggest a compensatory strategy to decrease the load on the fatigued shoulder musculature.     

Improved compensatory postural adjustments of the deep abdominals following exercise in people with chronic low back pain

The purpose of this study was to determine if 8 weeks of exercise affects motor control in people with chronic low back pain (CLBP), measured by anticipatory (APAs) and compensatory postural adjustments (CPAs). APAs and CPAs were measured prior to and following 8 weeks in two groups of people with CLBP: an exercise group (n = 12) who attended three exercise sessions per week for 8 weeks; and a non-exercise control group (n = 12) who were advised to continue their usual activities for the duration of the study. APAs and CPAs were recorded during unilateral arm flexion, bilaterally from rectus abdominis (RA), transverse abdominis/internal oblique (TA/IO), and erector spinae (ES) via surface electromyography. Analysis of muscle onsets and APA amplitudes suggests APAs did not change for either group. Ipsi-lateral TA/IO CPAs increased for the exercise group and ipsi-lateral TA/IO CPAs decreased for the control group. Only exercise promoted a pattern of TA/IO activity during CPAs similar to healthy individuals, suggesting improved control of rotational torques. These results show motor control improvement following exercise in people with CLBP, highlighted by improved side specific control of TA/IO.     

Effects of the pelvic compression belt on gluteus medius,quadratus lumborum,and lumbar multifidus activities during side-lying hip abduction

The aims of this study were to assess the effect of the pelvic compression belt on the electromyographic (EMG) activities of gluteus medius (GM), quadratus lumborum (QL), and lumbar multifidus (LM) during side-lying hip abduction. Thirty-one volunteers (15 men and 16 women) with no history of pathology volunteered for this study. Subjects were instructed to perform hip abduction in side-lying position with and without applying the pelvic compression belt. The pelvic compression belt was adjusted just below the anterior superior iliac spines with the stabilizing pressure using elastic compression bands. Surface EMG data were collected from the GM, QL, and LM of the dominant limb. Significantly decreased EMG activity in the QL (without the pelvic compression belt, 60.19 ± 23.66% maximal voluntary isometric contraction [MVIC]; with the pelvic compression belt, 51.44 ± 23.00% MVIC) and significantly increased EMG activity in the GM (without the pelvic compression belt, 26.71 ± 12.88% MVIC; with the pelvic compression belt, 35.02 ± 18.28% MVIC) and in the LM (without the pelvic compression belt, 30.28 ± 14.60% MVIC; with the pelvic compression belt, 37.47 ± 18.94% MVIC) were found when the pelvic compression belt was applied (p < 0.05). However, there were no significant differences of the EMG activity between male and female subjects. The findings suggest that the pelvic compression belt may be helpful to prevent unwanted substitution movement during side-lying hip abduction, through increasing the GM and LM and decreasing the QL.     

Quantification of abdominal and pelvic floor muscle synergies in response to voluntary pelvic floor muscle contractions

The relative levels of pelvic floor muscle (PFM) activation and pressure generated by maximum voluntary PFM contractions were investigated in healthy continent women. The normal sequence of abdominal and PFM activation was determined.Fifteen women performed single and repeated maximum voluntary PFM contractions in supine, sitting and standing. PFM electromyographic (EMG) signals and associated intra-vaginal pressure data were recorded simultaneously. Surface EMG data were recorded from rectus abdominus (RA), external obliques (EO), internal obliques (IO) and transversus abdominus (TA).Abdominal and PFM EMG and intra-vaginal pressure amplitudes generated during voluntary PFM contractions were not different among the positions. Muscle activation sequence differed by position. In supine, EO activation preceded all other muscles by 27 ms (p = 0.043). In sitting, all of the muscles were activated simultaneously. In standing, RA and EO were activated 11 and 17 ms, respectively, prior to the PFMs and TA and IO were activated 10 and 12 ms, respectively, after the PFMs (p ≪ 0.001).The results suggest that women are able to perform equally strong PFM contractions in supine, sitting and standing, however the pattern of abdominal and PFM activation varies by position. These differences may be related to position-dependent urine leakage in women with stress incontinence.     

Copper,zinc and iron levels in premature infants following red blood cell transfusion

This study aimed to investigate effect of erythrocyte suspension (ES) transfusion on Cu, Zn, and Fe levels. It was conducted on 53 premature infants who were admitted to Hacettepe Hospital and received EST for first time. Blood samples were drawn before and 96 h after ES transfusion to determine Cu, Zn, and Fe levels in plasma and/or erythrocytes. The mean plasma Cu levels were 99 ± 3 μg/dl and 113 ± 3 μg/dl; Zn levels were 105 ± 2 μg/dl and 115 ± 23 μg/dl; mean plasma Fe level was 58.1 ± 19.4 and 75.2 ± 25.4 μg/dl and mean erythrocyte Fe level was 4182 ± 2314 μg/ml and 7009 ± 5228 μg/ml, before and after ES transfusion. The differences between before and after ES transfusion in Cu, Zn and Fe levels were significant. Correlation between plasma and erythrocyte Fe levels was significant both before and after ES transfusion. Though Fe overload is a major cause of morbidity/mortality after ES transfusion, alterations in trace elements should also be considered when transfusing blood to infants and children.     

Effect of instruction,surface stability,and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39–167%) during squats with instructions compared to the other squat conditions (P = 0.04–0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P = 0.04–0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.     

The effect of inspiratory and expiratory loads on abdominal muscle activity during breathing in subjects “at risk” for the development of chronic obstructive pulmonary disease and healthy

The abdominal muscle activity has been shown to be variable in subjects with chronic obstructive pulmonary disease (COPD) when respiratory demand increases and their recruitment pattern may change the mechanics, as well as the work and cost of breathing. The scientific evidence in subjects “at risk” for the development of COPD may be important to understand the natural history of this disease. This study aims to evaluate the effect of inspiratory and expiratory loads on the abdominal muscle activity during breathing in subjects “at risk” for the development of COPD and healthy. Thirty-one volunteers, divided in “At Risk” for COPD (n = 17; 47.71 ± 5.11 years) and Healthy (n = 14; 48.21 ± 6.87 years) groups, breathed at the same rhythm without load and with 10% of the maximal inspiratory or expiratory pressures, in standing. Surface electromyography was performed to assess the activation intensity of rectus abdominis (RA), external oblique and transversus abdominis/internal oblique (TrA/IO) muscles, during inspiration and expiration. During inspiration, in “At Risk” for COPD group, RA muscle activation was higher with loaded expiration (p = 0.016); however, in Healthy group it was observed a higher activation of external oblique and TrA/IO muscles (p < 0.050). During expiration, while in “At Risk” for COPD group, RA muscle activation was higher with loaded inspiration (p = 0.009), in Healthy group TrA/IO muscle showed a higher activation (p = 0.025). Subjects “at risk” for the development of COPD seemed to have a specific recruitment of the superficial layer of ventrolateral abdominal wall for the mechanics of breathing.     

EMG synchrony to assess impaired corticomotor control of locomotion after stroke

Adapting one’s gait pattern requires a contribution from cortical motor commands. Evidence suggests that frequency-based analysis of electromyography (EMG) can be used to detect this cortical contribution. Specifically, increased EMG synchrony between synergistic muscles in the Piper frequency band has been linked to heightened corticomotor contribution to EMG. Stroke-related damage to cerebral motor pathways would be expected to diminish EMG Piper synchrony. The objective of this study is therefore to test the hypothesis that EMG Piper synchrony is diminished in the paretic leg relative to nonparetic and control legs, particularly during a long-step task of walking adaptability. Twenty adults with post-stroke hemiparesis and seventeen healthy controls participated in this study. EMG Piper synchrony increased more for the control legs compare to the paretic legs when taking a non-paretic long step (5.02 ± 3.22% versus 0.86 ± 2.62%), p < 0.01) and when taking a paretic long step (2.04 ± 1.98% versus 0.70 ± 2.34%, p < 0.05). A similar but non-significant trend was evident when comparing non-paretic and paretic legs. No statistically significant differences in EMG Piper synchrony were found between legs for typical walking. EMG Piper synchrony was positively associated with walking speed and step length within the stroke group. These findings support the assertion that EMG Piper synchrony indicates corticomotor contribution to walking.     

EMG normalization to study muscle activation in cycling

The value of electromyography (EMG) is sensitive to many physiological and non-physiological factors. The purpose of the present study was to determine if the torque–velocity test (T–V) can be used to normalize EMG signals into a framework of biological significance. Peak EMG amplitude of gluteus maximus (GMAX), vastus lateralis (VL), rectus femoris (RF), biceps femoris long head (BF), gastrocnemius medialis (GAS) and soleus (SOL) was calculated for nine subjects during isometric maximal voluntary contractions (IMVC) and torque–velocity bicycling tests (T–V). Then, the reference EMG signals obtained from IMVC and T–V bicycling tests were used to normalize the amplitude of the EMG signals collected for 15 different submaximal pedaling conditions. The results of this study showed that the repeatability of the measurements between IMVC (from 10% to 23%) and T–V (from 8% to 20%) was comparable. The amplitude of the peak EMG of VL was 99 ± 43% higher (p < 0.001) when measured during T–V. Moreover, the inter-individual variability of the EMG patterns calculated for submaximal cycling exercises differed significantly when using T–V bicycling normalization method (GMAX: 0.33 ± 0.16 vs. 1.09 ± 0.04, VL: 0.07 ± 0.02 vs. 0.64 ± 0.14, SOL: 0.07 ± 0.03 vs. 1.00 ± 0.07, RF: 1.21 ± 0.20 vs. 0.92 ± 0.13, BF: 1.47 ± 0.47 vs. 0.84 ± 0.11). It was concluded that T–V bicycling test offers the advantage to be less time and energy-consuming and to be as repeatable as IMVC tests to measure peak EMG amplitude. Furthermore, this normalization method avoids the impact of non-physiological factors on the amplitude of the EMG signals so that it allows quantifying better the activation level of lower limb muscles and the variability of the EMG patterns during submaximal bicycling exercises.     

On the usability of intramuscular EMG for prosthetic control: A Fitts’ Law approach

Previous studies on intramuscular EMG based control used offline data analysis. The current study investigates the usability of intramuscular EMG in two degree-of-freedom using a Fitts’ Law approach by combining classification and proportional control to perform a task, with real time feedback of user performance. Nine able-bodied subjects participated in the study. Intramuscular and surface EMG signals were recorded concurrently from the right forearm. Five performance metrics (Throughput, Path efficiency, Average Speed, Overshoot and Completion Rate) were used for quantification of usability. Intramuscular EMG based control performed significantly better than surface EMG for Path Efficiency (80.5 ± 2.4% vs. 71.5 ± 3.8%, P = 0.004) and Overshoot (22.0 ± 3.0% vs. 45.1 ± 6.6%, P = 0.01). No difference was found between Throughput and Completion Rate. However the Average Speed was significantly higher for surface (51.8 ± 5.5%) than for intramuscular EMG (35.7 ± 2.7%). The results obtained in this study imply that intramuscular EMG has great potential as control source for advanced myoelectric prosthetic devices.     

Slow expiration reduces sternocleidomastoid activity and increases transversus abdominis and internal oblique muscle activity during abdominal curl-up

The aim of this study was to investigate the effects of quiet inspiration versus slow expiration on sternocleidomastoid (SCM) and abdominal muscle activity during abdominal curl-up in healthy subjects. Twelve healthy subjects participated in this study. Surface electromyography (EMG) was used to collect activity of bilateral SCM, rectus abdominis (RA), external oblique (EO), and transversus abdominis/internal oblique (TrA/IO) muscles. A paired t-test was used to determine significant differences in the bilateral SCM, RF, EO, and TrA/IO muscles between abdominal curl-up with quiet inspiration and slow expiration. There were significantly lower EMG activity of both SCMs and greater EMG activity of both IOs during abdominal curl-up with slow expiration, compared with the EMG activity of both SCMs and IOs during abdominal curl-up with quiet inspiration (p < .05). The results of this study suggest that slow expiration would be recommended during abdominal curl-up for reduced SCM activation and selective activation of TrA/IO in healthy subjects compared with those in abdominal curl up with quiet inspiration.     

Unchanged H-reflex during a sustained isometric submaximal plantar flexion performed with an EMG biofeedback

The aim of this study was to assess H-reflex plasticity and activation pattern of the plantar flexors during a sustained contraction where voluntary EMG activity was controlled via an EMG biofeedback. Twelve healthy males (28.0 ± 4.8 yr) performed a sustained isometric plantar flexion while instructed to maintain summed EMG root mean square (RMS) of gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) muscles fixed at a target corresponding to 80% maximal voluntary contraction torque via an EMG biofeedback. Transcutaneous electrical stimulation of the posterior tibial nerve was evoked during the contraction to obtain the maximal H-reflex amplitude to maximal M-wave amplitude ratio (H_sup/M_sup ratio) from GL, GM and soleus (SOL) muscles. Neuromuscular function was also assessed before and immediately after exercise. Results showed a decrease in SOL activation during sustained flexion (from 65.5 ± 6.4% to 42.3 ± 3.8% maximal EMG, p < 0.001), whereas summed EMG RMS of GL and GM remained constant (59.7 ± 4.8% of maximal EMG on average). No significant change in the H_sup/M_sup ratio was found for SOL, GL and GM muscles. Furthermore, it appears that the decrease in maximal voluntary contraction torque (?20.4 ± 2.9%, p < 0.001) was related to both neural and contractile impairment. Overall, these findings indicate that the balance between excitation and inhibition affecting the motoneuron pool remains constant during a sustained contraction where myoelectrical activity is controlled via an EMG biofeedback or let free to vary.     

Upper limb and trunk muscle activation during an unexpected descent on the outstretched hands in young and older women

Falling on the outstretched hands (FOOSH), a protective mechanism to arrest the body and avoid injury, requires upper limb and trunk motor control for effective body descent. The purpose of this study was to investigate muscle activity during three phases of an unexpected FOOSH in healthy older and younger women. Twenty young (mean age 22.9 yrs, SD ± 3.7) and 20 older females (mean age 68.1 yrs, SD ± 5.0) performed five trials of unexpected FOOSHs. Surface electromyography (EMG) determined muscle activations for left shoulder girdle, elbow and abdominal muscles during an unexpected FOOSH. Root mean squared EMG data were calculated during three phases: (1) baseline (BL; 500 ms prior to release), (2) the preparatory phase (PRE; time between release and impact) (mean 257 ± 37 ms) and post-impact (POST; 200 ms after impact). A mixed MANOVA determined differences between phases and age groups. There was a significant multivariate interaction effect of age and time phase on muscle activity (p = 0.001). Younger women had significantly higher internal oblique/transversus abdominus activity during PRE (p = 0.006) as well as variations in muscle activity of shoulder girdle and elbow muscles. The age differences observed may lead to poorer preliminary trunk activation and greater arm bracing in older women, potentially increasing risk of fallrelated injury.     

Does local immersion in thermo-neutral bath influence surface EMG measurements? Results of an experimental trial

This study investigated the effect of water immersion on surface electromyography (EMG) signals recorded from the brachioradial muscle of 11 healthy subjects, both in a dry environment and a thermo-neutral forearm bath (36 °C). EMG measurements were registered in a sitting position, using waterproof electrodes under 3 conditions: relaxed muscle, maximum voluntary isometric contraction (MVC, 1 s, grip test) and 70% of the MVC (5 s). In relaxed muscle, mean EMG values were significantly higher under immersion compared to the dry conditions (dry: 5.4 ± 3.6 μV; water: 19.5 ± 14.9 μV; p = 0.014). In maximum voluntary isometric contraction, there was a significant difference, though not in the same direction (dry: 145.9 ± 58.9 μV; water: 73.2 ± 35.0 μV; p = 0.003). Under 70% MVC, there was no difference between wet and dry conditions (dry: 102.4 ± 75.0 μV; water: 100.4 ± 65.3 μV; p = 0.951). Results suggest that dry and underwater conditions influence EMG readings; however, the results are inconsistent. These findings indicate additional influences on resting muscle activity, as well as MVC. Further measurements with other muscle groups and different types of immersion are needed to clarify conflicting observations.     

Differences in scapular kinematics and scapulohumeral rhythm during elevation and lowering of the arm between typical children and healthy adults

Scapular kinematics in healthy adults is well described in the literature but little is known on typical children. This study aimed to compare the three-dimensional (3-D) scapular kinematics and scapulohumeral rhythm during the elevation and lowering of the arm in the scapular plane in typical children and healthy adults. Twenty-six healthy adults (35.34 ± 11.65 years, 1.70 ± 0.10 m, 70.00 ± 12.30 kg) and 33 typical children (9.12 ± 1.51 years, 1.40 ± 0.10 m, 35.40 ± 10.45 kg) participated in this study. 3-D scapular kinematics were obtained using an electromagnetic tracking device. The subjects were asked to elevate and lower their arm in the scapular plane. Children showed less scapular protraction compared to adults at 120° during arm elevation, more anterior tilt than adults in the elevation and also at 60°, 90° and 120° during lowering of the arm. Children also showed higher scapulohumeral rhythm during lowering of the arm compared to adults from 90° to 60°. It was also found a low to little correlation between scapular position and age. The study showed small but significant differences in scapular kinematics and scapulohumeral rhythm between children and adults. These results can help clinicians to improve diagnosis and treatment protocols directed to children with dysfunction, as reference values on scapular kinematics in healthy children are also provided in this study.     

High-loading oil palm empty fruit bunch saccharification using cellulases from Trichoderma koningii MF6

Strain Trichoderma koningii D-64 was improved for enhanced cellulase production. A potential mutant MF6 was obtained and its enzymes contained filter paper cellulase (FPase), carboxymethylcellulase (CMCase), β-glucosidase and xylanase with respective activities of 2.0, 1.3, 2.0 and 3.0 folds of those for the parental strain. MF6 cellulases showed enhanced hydrolysis performance for the treated lignocellulosic biomass. Hydrolysis of treated oil palm empty fruit bunch (OPEFB), horticulture wastes (HW) and wood chips (WC) resulted in cellulose to glucose conversion of 96.3 ± 2.2%, 98.2 ± 3.0% and 81.9 ± 1.4%, respectively. The corresponding conversions of xylan to xylose were 96.9 ± 1.5%, 95.0 ± 2.2% and 76.1 ± 3.1%. Consistently, high sugar yield of 770–844 mg/g biomass was obtained for high-loading (10–16%, w/v) of OPEFB hydrolysis and sugar titer of 135.1 g/L was obtained for 16% (w/v) OPEFB loading at 96 h. In addition, MF6 enzymes alone performed equally well for high-loading OPEFB hydrolysis compared to the enzyme mixture of β-glucosidase from Aspergillus niger and cellulase from T. reesei Rut C30.     

Electromyographic responses of erector spinae and lower limb’s muscles to dynamic postural perturbations in patients with adolescent idiopathic scoliosis

The aim of this study was to evaluate electromyographic (EMG) responses of erector spinae (ES) and lower limbs’ muscles to dynamic forward postural perturbation (FPP) and backward postural perturbation (BPP) in patients with adolescent idiopathic scoliosis (AIS) and in a healthy control group. Ten right thoracic AIS patients (Cobb = 21.6 ± 4.4°) and 10 control adolescents were studied. Using bipolar surface electrodes, EMG activities of ES muscle at T10 (ES_T10) and L3 (ES_L3) levels, biceps femoris (BF), gastrocnemius lateralis (G) and rectus femoris (RF) muscles in the right and the left sides during FPP and BPP were evaluated. Muscle responses were measured over a 1s time window after the onset of perturbation. In FPP test, the EMG responses of right ES_T10, ES_L3 and BF muscles in the scoliosis group were respectively about 1.40 (p = 0.035), 1.43 (p = 0.07) and 1.45 (p = 0.01) times greater than those in control group. Also, in BPP test, at right ES_L3 muscle of the scoliosis group the EMG activity was 1.64 times higher than that in the control group (p = 0.01). The scoliosis group during FPP displayed asymmetrical muscle responses in ES_T10 and BF muscles. This asymmetrical muscle activity in response to FPP is hypothesized to be a possible compensatory strategy rather than an inherent characteristic of scoliosis.     

Effect of pain location on spatial reorganisation of muscle activity

IntroductionWe aimed to determine whether the changes in muscle activity (in terms of both gross electromyography (EMG) and motor unit (MU) discharge characteristics) observed during pain are spatially organized with respect to pain location within a muscle which is the main contributor of the task.MethodsSurface and fine-wire EMG was recorded during matched low-force isometric plantarflexion from soleus (from four quadrants with fine-wire EMG and from the medial/lateral sides with surface EMG), both gastrocnemii heads, peroneus longus, and tibialis anterior. Four conditions were tested: two control conditions that each preceded contractions with pain induced in either the lateral (Pain_L) or medial (Pain_M) side of soleus.ResultsNeither the presence (p = 0.28) nor location (p = 0.19) of pain significantly altered gross muscle activity of any location (lateral/medial side of soleus, gastrocnemii, peroneus longus and tibialis anterior). Group data from 196 MUs show redistribution of MU activity throughout the four quadrants of soleus, irrespective of pain location. The significant decrease of MU discharge rate during pain (p < 0.0001; Pain_L: 7.3 ± 0.9–6.9 ± 1.1 Hz, Pain_M: 7.0 ± 1.1 to 6.6 ± 1.1 Hz) was similar for all quadrants of the soleus (p = 0.43), regardless of the pain location (p = 0.98). There was large inter-participant variation in respect to the characteristics of the altered MU discharge with pain.ConclusionResults from both surface and fine-wire EMG recordings do not support the hypothesis that muscle activity is reorganized in a simple systematic manner with respect to pain location.     

Adaptations of upper trapezius muscle activity during sustained contractions in women with fibromyalgia

The study compared the distribution of electromyographic (EMG) signal amplitude in the upper trapezius muscle in 10 women with fibromyalgia and in 10 healthy women before and after experimentally-induced muscle pain. Surface EMG signals were recorded over the right upper trapezius muscle with a 10 × 5 grid of electrodes during 90° shoulder abduction sustained for 60 s. The control subjects repeated the abduction task following injections of isotonic and hypertonic (painful) saline into the upper trapezius muscle. The EMG amplitude was computed for each electrode pair and provided a topographical map of the distribution of muscle activity. The pain level rated by the patients at the beginning of the sustained contraction was 5.9 ± 1.5. The peak pain intensity for the control group following the injection of hypertonic saline was 6.0 ± 1.6. During the sustained contractions, the EMG amplitude increased relatively more in the cranial than caudal region of the upper trapezius muscle for the control subjects (shift in the distribution of EMG amplitude: 2.3 ± 1.3 mm; P < 0.01). The patient group showed lower average EMG amplitude than the controls during the contraction (P < 0.05) and did not show different changes in EMG amplitude between different regions of the upper trapezius. A similar behavior was observed for the control group following injection of hypertonic saline. The results indicate that muscle pain prevents the adaptation of upper trapezius activity during sustained contractions as observed in non-painful conditions, which may induce overuse of similar muscle compartments with fatigue.     

Does the presence of a vaginal probe alter pelvic floor muscle activation in young,continent women?

Vaginal probes may induce changes in pelvic floor muscle (PFM) recruitment by the very presence of the probes. Fine-wire electrodes allow us to detect muscle activation parameters without altering the natural position and shape of the PFMs. The purpose of this study was to determine whether PFM activation is altered by changes in sensory feedback, muscle length or tissue position caused by two different vaginal probes used to record surface electromyography (EMG). Twelve continent women (30.1 ± 5.4 years), performed PFM maximal voluntary contractions (MVCs) in supine while fine-wire EMG was recorded bilaterally from the PFMs under three conditions: (a) without any probe inserted into the vagina, (b) while a Femiscan? probe was in situ, and (c) while a Periform? vaginal probe was in situ. The reliability of the fine wire EMG data was assessed using intra-class correlation coefficients (ICCs) and coefficients of variation (CV). A repeated measures analysis of variance (ANOVA) model was used to determine if there were differences in EMG amplitude recorded when the different vaginal probes were in situ. For each condition the between-trial reliability was excellent, ICC_(3,1) = 0.93–0.96, (p < 0.001) and CV = 11.2–21.8%. There were no differences in peak EMG amplitude recorded during the MVCs across the three conditions (no probe 63.4 ± 48.4 μV, Femiscan? 55.3 ± 42.4 μV, Periform? 59.4 ± 42.2 μV, p = 0.178). These results suggest that women produce consistent MVCs over multiple contractions, and that PFM muscle activation is not affected by different probes inserted into the vagina.