The Physical Workload of Surgeons: A Comparison of SILS and Conventional Laparoscopy.

BACKGROUND: As extensively reported in the literature, laparoscopic surgery has many advantages for the patient. Surgeons, however, experience increased physical burden when laparoscopic surgery is compared with open surgery. Single-incision laparoscopic surgery (SILS) has been said to further enhance the patient's benefits of endoscopic surgery. Because in this surgical technique only 1 incision is made instead of the 3 to 5, as in conventional laparoscopic surgery (CLS), it is claimed to further reduce discomfort and pain in patients. Yet little is known about its impact on surgeons. This study aims to contribute by indicating the possible differences in physical workload between single-incision laparoscopy and CLS. METHODS: A laparoscopic box trainer was used to simulate a surgical setting. Participants performed 2 series of 3 different tasks in the box: one in the conventional way, the other through SILS. Surface electromyography was recorded from 8 muscles bilaterally. Furthermore, questionnaires on perceived workload were completed. RESULTS: Differences were found in the back, neck, and shoulder muscles, with significantly higher muscle activity in the musculus (M) longissimus, M trapezius pars descendens, and the M deltoideus pars clavicularis. Questionnaires did not indicate any significant differences in perceived workload. CONCLUSION: Performing SILS versus CLS increases the objectively measured physical workload of surgeons particularly in the back, neck, and shoulder muscles.

The impact of a total hip replacement on jaw position, upper body posture and body sway.

OBJECTIVES: The purpose of this study was to examine whether, and to what extent, a total hip replacement can influence the position and the movement of the jaw, the upper body posture and body sway. METHODS: Twenty test subjects (6 females, 14 males) participated in this study pre- and post-total hip replacement, in addition to a healthy control group of 20 subjects (5 females, 15 males). The measurements were conducted by means of an ultrasound system to measure jaw condyle position and movement of the lower jaw, a three-dimensional back scan to analyze upper back posture, and a static and dynamic force plate to measure body sway. For statistical analysis the Wilcoxon-Matched-Pairs-Test or Man-Whitney-U-Test, including a Bonferroni-Holm correction, respectively, was used. RESULTS: After surgery, the mean values of the left and right jaw condyles of the test group moved posterior, and the left condyle position was located more caudally. There were no significant differences concerning the jaw position between the two groups. There was little change in upper body posture in both groups. The test group had a more anteriorly inclined thoracic spine and a less pronounced lumbar lordosis. During static body sway measurements, increased fluctuations in the test group after surgery could be seen. CONCLUSION: Differences between both groups in the pre- and post-surgical condition could be detected. These differences were more prominent when the measured body segments were more distally located with respect to the hip region.

Lordosis facilitation by leptin in ovariectomized, estrogen-primed rats requires simultaneous or sequential activation of several protein kinase pathways.

The present study tested the hypothesis that the Janus kinase 2, Src tyrosine kinases, and mitogen-activated protein kinase interact to regulate lordosis behavior induced by leptin in ovariectomized, estrogen-primed rats. The role of protein kinase A and protein kinase C in lordosis facilitation by leptin was also assessed. In experiment 1, the intracerebroventricular administration of leptin to ovariectomized, estradiol-primed rats significantly stimulated lordosis behavior at 1, 2 and 4 h post-injection tests. In experiment 2, the Janus kinase 2 inhibitor AG490, the Src tyrosine kinase inhibitor PP2 and the mitogen-activated protein kinase inhibitor PD98059 were administered into the right lateral ventricle before leptin. The lordosis quotient and the lordosis score induced by leptin were significantly decreased by each of these kinase inhibitors. In experiment 3, we examined the effects of RpcAMPS and bisindolylmaleimide, protein kinase A and protein kinase C inhibitors on the lordosis elicited by leptin administration. Lordosis behavior induced by leptin was significantly decreased by both the protein kinase A and protein kinase C inhibitors at 1 h post-leptin injection. The results confirm that multiple intracellular pathways participate in the expression of lordosis behavior in estrogen-primed rats elicited by leptin.

The biochemical response to biomechanical tissue loading on the low back during physical work exposure.

BACKGROUND: Our understanding of low back disorder causality is limited in that how biomechanical loading acting on various spinal tissues initiates the pain pathway is not clear. Previous studies suggest that cytokines may be important in mediating the inflammatory responses in patients with back pain. This study quantified the acute biochemical responses to physical work stressing the low back and assessed the relationships between these systemic responses and specific lumbar spine tissue loads. METHODS: Twelve healthy males were tested under control and two weight-lifting conditions (light and heavy). Venous blood was sampled at various time points before and after the physical work and analyzed for cytokine, granulocyte, and creatine kinase levels. Biomechanical data were collected during the tasks and a biologically-assisted lumbar spine model was used to calculate spinal loads at various lumbar spine levels and trunk muscle forces. FINDINGS: Levels of interleukin-6, granulocytes, and creatine kinase all increased after both weight-lifting tasks, with the greatest changes observed with the heavier lifting task. Similarly, plasma levels of interleukin-1ß and tumor necrosis factor-α both increased following the heavier lifting task. These inflammatory responses were significantly correlated with specific spinal tissue loads. INTERPRETATION: This study suggests that it may be possible to use inflammatory cytokines as biomarkers to monitor the physiological responses of the human body to biomechanical loading. Identifying the possible sources of cytokine up-regulation using an advanced biomechanical model may help a more effective understanding of the causal pathways that lead to low back disorders.

Effects of the Twin Shoe (Darco) to compensate height differences in normal gait.

BACKGROUND: After foot surgery or in diseases such as diabetes, orthopaedic shoes with an elevated sole construction are used to off-load the affected foot. The height difference between the shoes results in a leg length discrepancy and an abnormal gait pattern arises which can cause long-term discomfort in the joints of the lower extremity and the lower back. To compensate for this discrepancy and to ensure a symmetrical gait pattern a Twin Shoe (Darco) has been designed. AIM: To investigate the effect of wearing orthopaedic shoes in combination with the Twin Shoe on normal gait biomechanics. STUDY DESIGN: Cross-sectional study in a laboratory setting. METHODS: Normal gait was recorded in 15 healthy subjects with a gait analysis system. Four different shoe conditions were measured. Selected biomechanical parameters were calculated and compared between the shoe conditions. RESULTS: Walking in orthopaedic shoes with an elevated sole without compensation on the contralateral side leads to significant asymmetrical joint movements and higher loads in feet, knees, hips and the lower back during gait. By using the Twin Shoe these abnormal patterns were improved but not entirely compensated. CONCLUSIONS: Using the Twin Shoe as a partner to orthopaedic shoes with an elevated sole construction improves gait asymmetry and increased loading of joints induced by functional leg length discrepancy.

The association of self-reported backpack use and backpack weight with low back pain among college students.

OBJECTIVE: Back pain has consistently ranked among the top general health complaints among college students, but few studies have examined risk factors for back pain in this age group. This cross-sectional survey evaluated the association between the self-reported annual low back pain with the estimated usual backpack weight among college students. METHODS: Data were collected from health education students during the spring semester of 2007 at the Colorado State University using an online survey. Adjusted odds ratios were calculated using logistic regression. RESULTS: Four hundred sixty-five (94.6%) health education students completed the online survey. The annual prevalence of low back pain was 29.2% (n = 136). A 25% increase in the odds of annual low back pain for each 4-kg increase in the estimated usual backpack weight was observed after adjusting for sex, smoking, reporting frequently feeling overwhelmed, and body mass index (adjusted odds ratio per 4-kg increase, 1.25; 95% confidence interval, 1.17-1.32). There was no evidence of an increased association of annual low back pain with carrying a backpack weight greater than 10% of the students body weight compared with those carrying less (adjusted odds ratio, 1.02; 95% confidence interval, 0.63-1.65). CONCLUSIONS: The results of this study suggest that increasing reported backpack weight is associated with increased prevalence of annual low back pain. However, these results do not provide evidence to support the recommendation that the backpack weight necessarily be less than 10% of body weight.

Differentiation between deep and superficial fibers of the lumbar multifidus by magnetic resonance imaging.

The purpose of this study was to investigate the differentiation in muscle tissue characteristics and recruitment between the deep and superficial multifidus muscle by magnetic resonance imaging. The multifidus is a very complex muscle in which a superficial and deep component can be differentiated from an anatomical, biomechanical, histological and neuromotorial point of view. To date, the histological evidence is limited to low back pain patients undergoing surgery and cadavers. The multifidus muscles of 15 healthy subjects were investigated with muscle functional MRI. Images were taken under three different conditions: (1) rest, (2) activity without pain and (3) activity after experimentally induced low back muscle pain. The T2 relaxation time in rest and the shift in T2 relaxation time after activity were compared for the deep and superficial samples of the multifidus. At rest, the T2 relaxation time of the deep portion was significantly higher compared to the superficial portion. Following exercise, there was no significant difference in shift in T2 relaxation time between the deep and superficial portions, and in the pain or in the non-pain condition. In conclusion, this study demonstrates a higher T2 relaxation time in the deep portion, which supports the current assumption that the deep multifidus has a higher percentage of slow twitch fibers compared to the superficial multifidus. No differential recruitment has been found following trunk extension with and without pain induction. For further research, it would be interesting to investigate a clinical LBP population, using this non-invasive muscle functional MRI approach.

Physical characteristics of the back are not predictive of low back pain in healthy workers: a prospective study.

BACKGROUND: In the working population, back disorders are an important reason for sick leave and permanent work inability. In the context of fitting the job to the worker, one of the primary tasks of the occupational health physician is to evaluate the balance between work-related and individual variables. Since this evaluation of work capacity often consists of a physical examination of the back, the objective of this study was to investigate whether a physical examination of the low back, which is routinely performed in occupational medicine, predicts the development of low back pain (LBP). METHODS: This study is part of the Belgian Low Back Cohort (BelCoBack) Study, a prospective study to identify risk factors for the development of low back disorders in occupational settings. The study population for this paper were 692 young healthcare or distribution workers (mean age of 26 years) with no or limited back antecedents in the year before inclusion. At baseline, these workers underwent a standardised physical examination of the low back. One year later, they completed a questionnaire on the occurrence of LBP and some of its characteristics. To study the respective role of predictors at baseline on the occurrence of LBP, we opted for Cox regression with a constant risk period. Analyses were performed separately for workers without any back antecedents in the year before inclusion ('asymptomatic' workers) and for workers with limited back antecedents in the year before inclusion ('mildly symptomatic' workers). RESULTS: In the group of 'asymptomatic' workers, obese workers showed a more than twofold-increased risk on the development of LBP as compared to non-obese colleagues (RR 2.57, 95%CI: 1.09 - 6.09). In the group of 'mildly symptomatic' workers, the self-reports of pain before the examination turned out to be most predictive (RR 3.89, 95%CI: 1.20 - 12.64). CONCLUSION: This study showed that, in a population of young workers wh no or limited antecedents of LBP at baseline, physical examinations, as routinely assessed in occupational medicine, are not useful to predict workers at risk for the development of back disorders one year later.

Resistive simulated weightbearing exercise with whole body vibration reduces lumbar spine deconditioning in bed-rest.

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: Determine the effectiveness a resistive exercise countermeasure with whole-body vibration in relation to lumbo-pelvic muscle and spinal morphology changes during simulated spaceflight (bed-rest). SUMMARY OF BACKGROUND DATA: Spinal lengthening, flattening of the spinal curves, increases in disc size, and muscle atrophy are commonly seen in spaceflight simulation. This may represent a risk for low back injury. Consideration of exercise countermeasures against these changes is critical for success of long-term spaceflight missions. METHODS: Twenty healthy male subjects underwent 8-weeks of bed-rest with 6-months follow-up and were randomly allocated to an inactive control or countermeasure exercise group. Magnetic resonance imaging of the lumbo-pelvic region was conducted at regular time-points during and after bed-rest. Using uniplanar images at L4, cross-sectional areas of the multifidus, lumbar erector spinae, quadratus lumborum, psoas, anterolateral abdominal, and rectus abdominis muscles were measured. Sagittal scans were used to assess lumbar spine morphology (length, sagittal disc area and height, and intervertebral angles). RESULTS: The countermeasure group exhibited less multifidus muscle atrophy (P = 0.024) and its atrophy did not persist long-term as in the control group (up to 3-months; P < 0.006). Spinal lengthening (P = 0.03) and increases in disc area (P = 0.041) were also reduced. Significant partial correlations (P < 0.001) existed between spinal morphology and muscle cross-sectional area changes. CONCLUSION: The resistive vibration exercise countermeasure reduced, but did not entirely prevent, multifidus muscle atrophy and passive spinal tissue deconditioning during bed-rest. Atrophy of the multifidus muscles was persistent long-term in the inactive subjects. Future work could consider closer attention to spinal posture during exercise and optimizing exercise dose.

Back muscle response to sudden trunk loading can be modified by training among healthcare workers.

STUDY DESIGN: Experimental study of the effect of physical training on the reaction to sudden back loading. OBJECTIVE: To investigate the effect and sustainability of "on the job training" on the reaction to sudden back loading among employees at a geriatric ward. SUMMARY OF BACKGROUND DATA: Available data suggest that a delayed muscle reflex response to sudden trunk loading may increase the risk of low back injuries. We have previously shown that training may alter the response to sudden trunk loading in healthy subjects and decrease the time elapsed until stopping of the forward movement of the trunk (stopping time). Data on the possibilities of a training-induced improvement in the reflex response among workers exposed to sudden trunk loading on the job are, however, nonexistent, and there is no evidence of long-term benefits, i.e., the sustainability of a positive training effect. METHODS: The study included 23 participants and 14 controls. All were healthy without prior history of low back pain (LBP). The training group participated in a total of 18 training sessions during a 9-week period. The training focused on reactions to a variety of sudden trunk loadings. Before and after the training intervention and at a 1-year follow-up, all subjects were tested for their reaction to expected and unexpected sudden trunk loading by applying a horizontal force of 58 N to the upper back of the subjects and measuring the electromyographic (EMG) response from the erector spinae muscles. RESULTS: In the training group, the stopping time and the distance moved after unexpected sudden trunk loading decreased significantly (13%-19%, P = 0.02). The improved stopping time was associated with marked changes in the time-wise distribution of the EMG signal after training. In addition, the follow-up study showed a high sustainability of the training effect. CONCLUSIONS: The results demonstrated a training-induced improvement of the response to sudden trunk loading that may be beneficial in workers, such as nurses, who are exposed to sudden trunk perturbations during patient handling.

Investigations of back muscle fatigue by simultaneous 31P MRS and surface EMG measurements.

Investigations of back muscle fatigue are important for understanding the role of muscle strain in the development of low back pain. The aim of this contribution is to review the two main techniques used for in vivo investigations of metabolic and electrophysiological changes, namely magnetic resonance phosphorous spectroscopy ((31)P MRS) and surface electromyography (SEMG), and to report some of our recent results on simultaneous measurements using these techniques during isometric back-muscle contraction in volunteers. Since it appears that electrophysiological and metabolic factors are simultaneously involved in the processes of fatigue and muscle recovery during load application, simultaneous acquisition of complete information is quite promising for obtaining new insights into the metabolic origin of electrophysiological changes or vice versa. Performing these measurements simultaneously, however, is more intricate owing to the occurrence of signal artifacts caused by mutual signal interferences of both techniques. Besides these mutual disturbances, further experimental difficulties are related to spatial limitations within the bore of clinical whole-body high-field magnetic resonance (MR) systems (1.5 T) and the sensitivity of MR measurements to motion-induced artifacts. Our own experimental results are presented, and problems that occur using both techniques simultaneously, as well as possibilities to resolve them, are discussed. The results shed light on the interrelation of electrophysiological and metabolic changes during fatigue of the back muscle while performing an exercise.

Does reaching the back reflect the actual internal rotation of the shoulder?

To clarify the relationship between the vertebral level reached by the thumb and the internal rotation angle of the humerus, 7 shoulders in healthy volunteers were examined by use of an electromagnetic tracking device. Measurements were repeated in the hanging-arm position with the thumb pointing anteriorly and at the buttock, sacrum, and each vertebral level up to T6. From the hanging-arm position to the buttock, 54.3% of internal rotation occurred (mean, 39.8 degrees ), and from the buttock to the sacrum, 11.7% occurred (mean, 8.6 degrees ). In total, 66% of internal rotation occurred from the hanging-arm position to the sacrum. Above the sacrum, the contribution of elbow flexion to the level of the vertebral spine became much greater, and internal rotation of the shoulder did not change significantly above the T12 level. We recommend that the level of the thumb below the buttock be subdivided for more accurate assessment of internal rotation.

Effect of local analgesia on movement of the equine back.

REASONS FOR PERFORMING STUDY: Diagnostic infiltration of local anaesthetic solution is commonly used in cases of equine back pain. Evaluation is subjective and it is not known how local analgesia of the back affects horses without clinical signs of back pain. OBJECTIVES: To evaluate the effect of infiltration of local anaesthetics on the movement of the back in horses without clinical signs of back pain, and to evaluate the usefulness of kinematic studies as an objective and quantitative tool in evaluating local analgesia in clinical practice. METHODS: The kinematics of the back in 10 clinically sound horses were measured on 2 occasions at walk and trot before and after injections with mepivacaine and sodium chloride around the interspinous spaces between T16 and L2. The kinematics were compared between the 2 occasions before injections and before and after each injection. RESULTS: The range of motion (ROM) for dorsoventral flexion-extension (FE) of the back was increased significantly in all measured segments other than T10 at walk, as was lateral bending (LB) at T10, L3 and L5 after injection of mepivacaine. For lateral excursion (LE), total movement increased at all measured segments. At trot the only affected segment was L3, where the injection with mepivacaine decreased the ROM for FE. After injection of sodium chloride the ROM for FE increased at T13 and T17 at walk. Lateral bending and LE were not affected at walk. At trot, LB increased at L3 and L5. CONCLUSIONS AND POTENTIAL RELEVANCE: Diagnostic infiltration of local anaesthetic solution affects the function of the back in clinically sound horses, which must be considered when interpreting the use of this clinical aid in assessing clinical cases of back dysfunction. Kinematics can qualitatively and quantitatively evaluate the effect of local analgesia of the back.

Relationship of energy settings and impedance in different anatomic areas using a radiofrequency device.

BACKGROUND: Radiofrequency (RF) used for volumetric heating into the deep dermis has been used effectively for rejuvenation of the face. The delivery of the RF energy depends on several variables, including the electrical impedance of the underlying tissue. OBJECTIVE: To describe the effects of impedance on energy delivery into the treated site. MATERIALS AND METHODS: We report four patients who underwent treatment using the ThermaCool TC system (Thermage, Inc, Hayward, CA, USA). Five sites on each patient were selected for impedance evaluation at two treatment levels. RESULTS: Impedance levels varied only slightly between treatment levels. The impedance levels varied greatly between patients and from site to site in each patient. The impedance levels for each of the patients were greatest on the arm, followed by the forehead, cheeks, and back. CONCLUSION: Energy delivery to a treated area is directly related to the impedance of the tissue. The impedance is shown to vary by site and can be changed by manipulation of the tissue, such as by injection of local anesthesia. Alteration of the impedance may have an effect on the uniform delivery of the selected energy.

The effect of sampling frequency on EMG measures of occupational mechanical exposure.

The purpose of the present study was to determine how much it is possible to downsample EMG without loosing the accuracy of some EMG measures of occupational mechanical exposure frequently used in the literature. The EMG signals of four muscles (two trapezius, right deltoid and right extensor digitorum) were collected (sampling frequency: 1024 Hz) from 20 subjects while performing a 20 min computer work task. The EMG RMS amplitude was computed from 0.125 s successive time-windows for the original (1024 Hz) and four additional digitally resampled (at 512, 256, 128 and 64 Hz) EMG signals. Three of the most frequently used data reduction methods (1. gaps analysis, 2. amplitude probability distribution function and 3. exposure variation analysis) were used to summarise the 20 min EMG activation profiles. The results from the exposure variation analysis were summarized into three variables using a new method detailed here. In general, the ANOVA for repeated measures demonstrated that a decrease of the sampling frequency significantly changed the EMG measures (relative to the 1024 Hz sampling condition) most of the time at 64 and 128 Hz, occasionally at 256 Hz, but practically never at 512 Hz. An analysis of the maximal errors (relative to the 1024 Hz condition) across all subjects supported these findings. Consequently, it was concluded that 512 Hz is quite conservative and should practically never lead to invalid EMG parameters estimations. Conversely, 256 Hz represents the lowest limit tolerable for some EMG parameters (gaps analysis, amplitude probability distribution function) while it is unacceptable for others (modified exposure variation analysis).

Extensor digitorum brevis manus: a raremuscle on the dorsum of the hand

The extensor digitorum brevis manus is one of the rare anatomic variations which occur on the dorsum of the hand. Only some 295 articles were found worldwide in an extensive bibliographic review carried out in 2003. This muscle was dissected bilaterally on a male corpse at the Human Anatomy Laboratory of the Morphophysiological Department of the “Faculty of Medical Sciences of Minas Gerais”. It is an elongated, small muscle, originating at the carpal bones and at the extensor retinaculum and inserting into one of the tendons of the finger’s extensor muscle. Even though it does not present an essential function in the movement of the fingers nor the hand, it can lead to pain when hypertrophied, creating the need for clinical or even surgical treatment.

Kinematic evaluation of the back in fully functioning riding horses.

REASONS FOR PERFORMING STUDY: Clinical history and examination are important features in diagnosis of equine back dysfunction. However, interpretation is subjective and therefore may vary substantially. OBJECTIVES: To establish a clinical tool to objectively evaluate the function of the equine back, in the form of a database on the kinematics of the back at the walk and trot in fully functioning riding horses. METHODS: Thirty-three fully functioning riding horses walked and trotted on a treadmill. Morphometrics and kinematics were tested for correlations to age, height, weight and stride length, and differences between gender (geldings and mares) and use (dressage and showjumping). RESULTS: A database for range of movement and symmetry of movement for extension and flexion, lateral bending, lateral excursion and axial rotation was presented. Symmetry values were very high for all variables. Significant differences were observed in use and gender. Age was negatively correlated to extension and flexion of the thoracolumbar junction. CONCLUSIONS: Interrelationships between use, gender and age to conformation and movement were established. POTENTIAL RELEVANCE: The database provides a basis for objective reference for diagnosis, therapy and rehabilitation of clinical cases of back dysfunction.

The effect of feedback training on lumbosacral compression during simulated occupational lifting.

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p=0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p<0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.

Dermolipectomias dorsais altas: técnicas e resultados / Upper dorsal dermolipectomies: techniques and results

Grandes emagrecimentos ou lipoaspirações de grandes volumes ocasionam o aparecimento de dobras cutâneas bastante desgraciosas na região dorsal. Em virtude de o tratamento desse problema exigir ressecções cutâneas com cicatrizes extensas, sem dobras cutâneas para dissimulá-las, pouco tem sido abordado sobre esse tipo de tratamento a não ser para casos severos de grandes perdas ponderais. Os autores apresentam técnica de excisão transversal, discutem considerações técnicas e apresentam resultados e a aplicabilidade para casos moderados.

Large weight loss or large volume liposuction may cause skin folds in the upper dorsal region. To correct that problem is necessary to excise skin, resulting large scars difficult to hide. For this reason the treatment is performed rarely and few papers are published about the theme and only in severe cases. The authors present the surgical treatment for mild and severe cases discussing indications, technique considerations and present results.

Electromyographic responses of back and limb muscles associated with spinal manipulative therapy.

STUDY DESIGN: Ten young, asymptomatic male subjects underwent 11 clinically relevant spinal manipulative treatments along the length of the spine to test the magnitude and extent of reflex responses associated with the treatments. OBJECTIVES: To determine the magnitude and extent of reflex responses elicited by spinal manipulative treatments. SUMMARY OF BACKGROUND DATA: Spinal manipulative treatments have been associated with a reflexogenic relief of pain and a loss of hypertonicity in muscles within the treatment area. However, there is no study in which results show the probability of occurrence or the extent of reflex responses during spinal manipulative treatments. METHODS: Asymptomatic subjects received spinal manipulative treatments on the cervical, thoracic, and lumbar levels and on the sacroiliac joint. Reflex activities were measured using 16 pairs of bipolar surface electrodes placed on the back and proximal limb musculature. The percentage of occurrence and the extent of reflex responses in the back and proximal limb musculature were determined. RESULTS: Each treatment produced consistent reflex responses in a target-specific area. The reflex responses occurred within 50-200 msec after the onset of the treatment thrust and lasted for approximately 100-400 msec. The responses were probably of multireceptor origin and were elicited asynchronously. CONCLUSIONS: This is the first study in which results show a consistent reflex response associated with spinal manipulative treatments. Because reflex pathways are evoked systematically during spinal manipulative treatment, there is a distinct possibility that these responses may cause some of the clinically observed beneficial effects, such as a reduction in pain and a decrease in hypertonicity of muscles.