Perturbed upper limb movements cause short-latency postural responses in trunk muscles

Addition of a load to a moving upper limb produces a perturbation of the trunk due to transmission of mechanical forces. This experiment investigated the postural response of the trunk muscles in relation to unexpected limb loading. Subjects performed rapid, bilateral shoulder flexion in response to a stimulus. In one third of trials, an unexpected load was added bilaterally to the upper limbs in the first third of the movement. Trunk muscle electromyography, intra-abdominal pressure and upper limb and trunk motion were measured. A short-latency response of the erector spinae and transversus abdominis muscles occurred similar to 50 ms after the onset of the limb perturbation that resulted from addition of the load early in the movement and was coincident with the onset of the observed perturbation at the trunk. The results provide evidence of initiation of a complex postural response of the trunk muscles that is consistent with mediation by afferent input from a site distant to the lumbar spine, which may include afferents of the upper limb.

Contraction of the pelvic floor muscles during abdominal maneuvers

Objective: To determine whether voluntary abdominal muscle contraction is associated with pelvic floor muscle activity. Design: Pelvic floor muscle activity was recorded during contractions of the abdominal muscles at 3 different intensities in supine and standing positions. Setting: Research laboratory. Participants: Six women and 1 man with no histories of lower back pain. Interventions: Not applicable. Main Outcome Measures: Electromyographic activity of the pelvic floor muscles was recorded with surface electrodes inserted into the anus and vagina. These recordings were corroborated by measurements of anal and vaginal pressures. Gastric pressure was recorded in 2 subjects. Results: Pelvic floor muscle electromyography increased with contraction of the abdominal muscles. With strong abdominal contraction, pelvic floor muscle activity did not differ from that recorded during a maximal pelvic floor muscle effort. The pressure recordings confirmed these data. The increase in pressure recorded in the anus and vagina preceded the pressure in the abdomen. Conclusions: In healthy subjects, voluntary activity in the abdominal muscles results in increased pelvic floor muscle activity. The increase in pelvic floor pressure before the increase in the abdomen pressure indicates that this response is preprogrammed. Dysfunction of the pelvic floor muscles can result in urinary and fecal incontinence. Abdominal muscle training to rehabilitate those muscles may be useful in treating these conditions.

Adenotonsillectomy improves the strength of respiratory muscles in children with upper airway obstruction

Objective: The aim of this paper is to study the respiratory muscle strength by evaluating the maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) and lung volume before and 3 and 6 months after adenotonsillectomy. This is an interventional, before and after trial. It was set at the Department of Otolaryngology. University of Sao Paulo, School of Medicine. We included 29 children (6-13 years old), both genders, consecutively recruited from the waiting list for adenotonsillectomy. Children were submitted to maximal inspiratory pressures (MIP), maximal expiratory pressure (MEP) evaluation using an analog manovacuometer, lung volume, using incentive expirotometer and thoracic and abdominal perimeter using a centimeter tape. Children were evaluated in 3 different moments: 1 week before and 3 and 6 months after surgery. Results: MIP improved significantly 3 months (p < 0.001) after adenotonsillectomy and MEP did not change (p = 1). There were increases in lung volume (p = 000), chest (p = 0.017) and abdominal perimeter (p = 0.05). Six months after surgery, all parameters improved. MIP (p = 0), MEP (p = 0), lung volume (p = 0.02), chest (p = 0.034) and abdominal perimeter (p = 0.23). Conclusion: This study suggests that there was an improvement in respiratory muscular strength, once there was a significant improvement in maximal inspiratory pressure, lung volume and other parameters after adenotonsillectomy. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Contraction of the abdominal muscles associated with movement of the lower limb

Background and Purpose. Activity of the trunk muscles is essential for maintaining stability of the lumbar spine because of the unstable structure of that portion of the spine. A model involving evaluation of the response of the lumbar multifidus and abdominal muscles to leg movement was developed to evaluate this function. Subjects. To examine this function in healthy persons, 9 male and 6 female subjects (mean age = 20.6 years, SD = 2.3) with no history of low back pain were studied. Methods. Fine-wire and surface electromyography electrodes were used to record the activity of selected trunk muscles and the prime movers for hip flexion, abduction, and extension during hip movements in each of these directions. Results. Trunk muscle activity occurring prior to activity of the prime mover of the limb was associated with hip movement in each direction. The transversus abdominis (TrA) muscle was invariably the first muscle that was active. Although reaction time for the TrA and oblique abdominal muscles was consistent across movement directions, reaction time for the rectus abdominis and multifidus muscles varied with the direction of limb movement. Conclusion and Discussion. Results suggest that the central nervous st stem deals with stabilization of the spine by contraction of the abdominal and multifidus muscles in anticipation of reactive forces produced by limb movement. The TrA and oblique abdominal muscles appear to contribute to a function not related to the direction of these forces.

Contractions of specific abdominal muscles in postural tasks are affected by respiratory maneuvers

The influence of respiratory activity of the abdominal muscles on their reaction time in a postural task was evaluated. The electromyographic (EMG) onsets of the abdominal muscles and deltoid were evaluated in response to shoulder flexion initiated by a visual stimulus occurring at random throughout the respiratory cycle. Increased activity of the abdominal muscles was produced by inspiratory loading, forced expiration below functional residual capacity, and a static glottis-closed expulsive maneuver. During quiet breathing, the latency between activation of the abdominal muscles and deltoid was not influenced by the respiratory cycle. When respiratory activity of the abdominal muscles increased, the EMG onset of transversus abdominis and internal oblique, relative to deltoid, was significantly earlier for movements beginning in expiration, compared with inspiration [by 97-107 ms (P < 0.01) and 64-90 ms (P < 0.01), respectively]. However, the onset of transversus abdominis EMG was delayed by 31-54 ms (P < 0.01) when movement was performed during a static expulsive effort, compared with quiet respiration. Thus changes occur in early anticipatory contraction of transversus abdominis during respiratory tasks but they cannot be explained simply by existing activation of the motoneuron pool.

Effects of phonophoresis with Arnica montana onto acute inflammatory process in rat skeletal muscles: An experimental study

This study aimed at verifying the effects of phonophoresis associated with Arnica montana on the acute phase of an inflammatory muscle lesion. Forty Wistar male rats (300 +/- 50 g), of which the Tibialis Anterior muscle was surgically lesioned, were divided into four groups (n = 10 each): control group received no treatment; the ultrasound group (US) was treated in pulsed mode with 1-MHz frequency, 0.5 W/cm(2) intensity (spatial and temporal average - SATA), duty cycle of 1: 2 (2 ms on, 4 ms off, 50%), time of application 3 min per session, one session per day, for 3 days; the phonophoresis or ultrasound plus arnica (US+A) group was treated with arnica with the same US parameters plus arnica gel; and the arnica group (A) was submitted to massage with arnica gel, also for 3 min, once a day, for 3 days. Treatment started 24 h after the surgical lesion. On the 4th day after lesion creation, animals were sacrificed and sections of the lesioned, inflamed muscle were removed for quantitative (mononuclear and polymorphonuclear cell count) and qualitative histological analysis. Collected data from the 4 groups were statistically analyzed and the significance level set at p < 0.05. Results show higher mononuclear cell density in all three treated groups with no significant difference between them, but values were significantly different (p < 0.0001) when compared to control group`s. As to polymorphonuclear cell density, significant differences were found between control group (p = 0.0134) and US, US+A and A groups; the arnica group presented lesser density of polymorphonuclear cells when compared (p = 0.0134) to the other groups. No significant difference was found between US and US+A groups. While the massage with arnica gel proved to be an effective anti-inflammatory on acute muscle lesion in topic use, these results point to ineffectiveness of Arnica montana phonophoresis, US having seemingly checked or minimized its anti-inflammatory effect. (C) 2008 Elsevier B. V. All rights reserved.

Relationship between limb movement speed and associated contraction of the trunk muscles

Rapid shoulder movement is preceded by contraction of the abdominal muscles to prepare the body for the expected disturbance to postural equilibrium and spinal stability provoked by the reactive forces resulting from the movement. The magnitude of the reactive forces is proportional to the inertia of the limb. The aim of the study was to investigate if changes in the reaction time latency of the abdominal muscles was associated with variation in the magnitude of the reactive forces resulting from variation in limb speed. Fifteen participants performed shoulder flexion at three different speeds (fast, natural and slow). The onset of EMG of the abdominal muscles, erector spinae and anterior deltoid (AD) was recorded using a combination of fine-wire and surface electrodes. Mean and peak velocity was recorded for each limb movement speed for five participants. The onset of transversus abdominis (TrA) EMG preceded the onset of AD in only the fast movement condition. No significant difference in reaction time latency was recorded between the fast and natural speed conditions for all muscles. The reaction time of each of the abdominal muscles relative to AD was significantly delayed with the slow movement compared to the other two speeds. The results indicate that the reaction time latency of the trunk muscles is influenced by limb inertia only with limb movement below a threshold velocity.

Analysis of patellar stabilizers muscles and patellar kinematics in anterior knee pain subjects

Patella stabilizer muscle response and patellar kinematics were evaluated in 19 women with anterior knee pain (AKP) and 20 healthy women during maximum voluntary isometric contraction (MVIC) with the knee positioned at 15 degrees, 30 degrees and 45 degrees flexion during open (OKC) and closed (CKC) kinetic chain exercises. Patellar kinematics was evaluated through patellar tilt and displacement, and the electrical activity of patellar stabilizers through the root mean square normalized during MVIC and OKC with the knee at 90 degrees flexion. Data revealed that the vastus medialis oblique muscle (VMO) was more active in the control group compared to the AKP group during OKC exercises with the knee at 45 degrees flexion. However, no difference in the patellar kinematics was observed between these groups; nevertheless, the correlation between these parameters also showed, with the knee at 45 degrees flexion, that lateral patellar tilt increase was associated with a reduction in the activity of lateral patellar stabilizers in the control group and with an increase in the VMO activity in the AKP group. In conclusion, electrical activity is an important factor in evaluating AKP and in AKP treatment evolution. (C) 2010 Elsevier Ltd. All rights reserved.

Stretch Injuries of Skeletal Muscles: Experimental Study in Rats` Soleus Muscle

The study aimed to verify the physiological injury behavior by stretching the soleus muscle of rats, using a noninvasive experimental model. Twenty-four rats were used and divided into three groups of eight animals: control group (A), group that performed tetanus followed by electrical stimulation and a sudden dorsiflexion of the left paw performed by a device equipped with a mechanism of muscle soleus rapid stretching (B); and a group that only received the tetanus (C). Three days later, the animals were killed, and the soleus muscle was resected and divided into three segments. Morphological changes indicative of muscle damage appeared in all three segments of group B. In a lesser degree, similar changes were also detected in muscles subjected to only tetanus. This model was effective; reproducing an injury similar to what occurs in human sports injuries.

Reliability of electromyographic amplitude values of the upper limb muscles during closed kinetic chain exercises with stable and unstable surfaces

The purpose of the present study was to evaluate the intra and interday reliability of surface electromyographic amplitude values of the scapular girdle muscles and upper limbs during 3 isometric closed kinetic chain exercises, involving upper limbs with the fixed distal segment extremity on stable base of support and on a Swiss ball (relatively unstable). Twenty healthy adults performed the exercises push-up, bench-press and wall-press with different effort levels (80% and 100% maximal load). Subjects performed three maximal voluntary contractions (MVC) in muscular testing position of each muscle to obtain a reference value for root mean square (RMS) normalization. Individuals were instructed to randomly perform three isometric contraction series, in which each exercise lasted 6 s with a 2-min resting-period between series and exercises. Intra and interday reliabilities were calculated through the intraclass correlation coefficient (ICC 2.1), standard error of the measurement (SEM). Results indicated an excellent intraday reliability of electromyographic amplitude values (ICC >= 0.75). The interday reliability of normalized RMS values ranged between good and excellent (ICC 0.52-0.98). Finally, it is suggested that the reliability of normalized electromyographic amplitude values of the analyzed muscles present better values during exercises on a stable surface. However, load levels used during the exercises do not seem to have any influence on variability levels, possibly because the loads were quite similar. (C) 2007 Elsevier Ltd. All rights reserved.

ONSET OF ELECTRICAL ACTIVITY OF PATELLAR STABILIZER MUSCLES IN SUBJECTS WITH PATELLOFEMORAL PAIN

Objective: To asses the onset (%) of patella stabilizer muscles during maximal isometric contraction exercises (MIC) in individuals with and without signs of patellofemoral pain syndrome (PFPS) in open (OKC) and closed (CKC) kinetic chain exercises, Method: Assessments were carried out on 22 women; ten with no complains of anterior knee pain, and 12 with PFPS signs during MIC in OKC and CKC with the knee flexed at 90 degrees. The onset of the electromyographic activity of the vastus mediallis obliquus (VMO), vastus lateralis obliquus (VLO) and vastus lateralis longus (VLL) was identified by means of an algorithm in the Myosystem Br 1 software. The statistical analysis used was Chi-Square test and student`s t test, which are both tests with a level of significance at 5%. Results: The VMO and VLO muscles presented a greater onset compared to the VLL during OKC exercises for both groups and for the PFPS group without CCF No differences were observed between the groups. Conclusion: CKC and OKC exercises seem to benefit the synchronism of the musculature that supposedly benefits the patella stabilizer musculature, and can be recommended in physiotherapeutic treatment programs.

Activation of the shoulder and arm muscles during axial load exercises on a stable base of support and on a medicine ball

The purpose of this study was to compare SEMG activities during axial load exercises on a stable base of support and on a medicine ball (relatively unstable). Twelve healthy male volunteers were tested (x = 23 +/- 7y). Surface EMG was recorded from the biceps brachii, anterior deltoid, clavicular portion of pectoralis major, upper trapezius and serratus anterior using surface differential electrodes. All SEMG data are reported as percentage of RMS mean values obtained in maximal voluntary contractions for each muscle studied. A 3-way within factor repeated measures analysis of variance was performed to compare RMS normalized values. The RMS normalized values of the deltoid were always greater during the exercises performed on a medicine ball in relation to those performed on a stable base of support. The trapezius showed greater mean electric activation amplitude values on the wall-press exercise on a medicine ball, and the pectoralis major on the push-up. The serratus and biceps did not show significant differences of electric activation amplitude in relation to both tested bases of support. Independent of the base of support, none of the studied muscles showed significant differences of electric activation amplitude during the bench-press exercise. The results contribute to the identification of the levels of muscular activation amplitude during exercises that are common in clinical practice of rehabilitation of the shoulder and the differences in terms of type of base of support used. (C) 2006 Elsevier Ltd. All rights reserved.