Vibration parameters affecting vibration-induced reflex muscle activity.

PURPOSE: To determine vibration parameters affecting the amplitude of the reflex activity of soleus muscle during low-amplitude whole-body vibration (WBV). MATERIALS AND METHODS: This study was conducted on 19 participants. Vibration frequencies of 25, 30, 35, 40, 45, and 50 Hz were used. Surface electromyography, collision force between vibration platform and participant's heel measured using a force sensor, and acceleration measured using an accelerometer fixed to the vibration platform were simultaneously recorded. RESULTS: The collision force was the main independent predictor of electromyographic amplitude. CONCLUSION: The essential parameter of vibration affecting the amplitude of the reflex muscle activity is the collision force.

Validation of Duruöz Hand Index in patients with tetraplegia.

STUDY DESIGN: Cross-sectional, clinical measurement. PURPOSE: To investigate the validity of the Duruöz Hand Index (DHI) in the assessment of hand function in patients with tetraplegia. METHODS: A total of 40 patients with tetraplegia participated. Patients' upper extremities were assessed on the level of 'body function and structure' [The American Spinal Cord Injury Association (ASIA) Impairment Scale (AIS) 2000 revised criteria, upper extremity motor score (UEMS), neurologic level of injury and visual analogue scale of hand function (VAS-HF)], 'activity' [DHI and Quadriplegia index of function-short form (QIF-SF)] and 'body function and structure, activity and participation' [Health Survey Short Form-36 (SF-36)] according to International Classification of Function. RESULTS: The DHI showed significant correlations with UEMS, AIS, QIF-SF, VAS-HF, physical functioning and physical compound summary scores of SF-36. CONCLUSIONS: The DHI was found a valid method in the assessment of hand functions in patients with tetraplegia. LEVEL OF EVIDENCE: Diagnostic III.

Whole-body vibration-induced muscular reflex: Is it a stretch-induced reflex?

[Purpose] Whole-body vibration (WBV) can induce reflex responses in muscles. A number of studies have reported that the physiological mechanisms underlying this type of reflex activity can be explained by reference to a stretch-induced reflex. Thus, the primary objective of this study was to test whether the WBV-induced muscular reflex (WBV-IMR) can be explained as a stretch-induced reflex. [Subjects and Methods] The present study assessed 20 healthy males using surface electrodes placed on their right soleus muscle. The latency of the tendon reflex (T-reflex) as a stretch-induced reflex was compared with the reflex latency of the WBV-IMR. In addition, simulations were performed at 25, 30, 35, 40, 45, and 50 Hz to determine the stretch frequency of the muscle during WBV. [Results] WBV-IMR latency (40.5 ± 0.8 ms; 95% confidence interval [CI]: 39.0-41.9 ms) was significantly longer than T-reflex latency (34.6 ± 0.5 ms; 95% CI: 33.6-35.5 ms) and the mean difference was 6.2 ms (95% CI of the difference: 4.7-7.7 ms). The simulations performed in the present study demonstrated that the frequency of the stretch signal would be twice the frequency of the vibration. [Conclusion] These findings do not support the notion that WBV-IMR can be explained by reference to a stretch-induced reflex.

A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity.

BACKGROUND: Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. AIMS: The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. STUDY DESIGN: A prospective, randomised, controlled, double-blind, parallel-group clinical trial. METHODS: Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. RESULTS: In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15.2% (p=0.031) in the exercise group and increased by 20.8% (p=0.028) in the control group. A change in the sclerostin index was an important predictor of a change in the vibration-induced normalised Root Mean Square of the semitendinosus muscle (R2=0.7, p=0.0001). Femoral neck bone mineral density was an important predictor of muscle strength gain (R2=0.26, p=0.035). CONCLUSION: This study indicates that bone tissue may have an effect on vibration-induced muscle strength gain and vibration-induced reflex muscle activity. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01310348.

Trigemino-cervical reflex in spinal cord injury.

Abnormal enhancement of polysynaptic brainstem reflexes has been previously reported in patients with spinal cord injury (SCI). We aimed to investigate trigemino-cervical reflex (TCR) in SCI since it may reflect alterations in the connections of trigeminal proprioceptive system and cervical motoneurons. Consecutive 14 patients with SCI and 16 healthy subjects were included in this study. All patients were in the chronic phase. TCR was recorded over sternocleidomastoid (SCM) and splenius capitis (SC) muscles by stimulation of infraorbital nerve. We measured onset latency, amplitudes and durations of responses and compared between groups. We obtained stable responses over both muscles after one sided stimulation in healthy volunteers whereas probability of TCR was decreased in patients over both SCM (78.6% vs. 100%, p=0.050) and SC (71.4% vs. 100%, p=0.022). The absence of TCR was related to use of oral baclofen (≥50mg/day). However, when present, responses of SCI group had higher amplitudes and were more persistent. We demonstrated that TCR probability was similar to healthy subjects in SCI patients who used no or low dose oral baclofen. But it had higher amplitudes and longer durations. It was not obtained in only two patients who used oral baclofen more than 50mg/day.

Effects of osteocytes on vibration-induced reflex muscle activity in postmenopausal women.

BACKGROUND/AIM: To assess whether osteocytes have an effect on reflex myoelectrical activity during whole-body vibration (WBV) in postmenopausal women. MATERIALS AND METHODS: Participants were classified into 2 groups: the low bone mineral density (BMD) group (n = 37) and normal BMD group (n = 43). Hip BMD was measured using dual-energy X-ray absorptiometry. Surface electromyography data recorded from the adductor longus muscle were processed to obtain vibration-induced reflex myoelectrical activity. Changes in plasma sclerostin (SOST) levels with WBV were expressed as a standardized vibration-induced SOST index. RESULTS: The standardized vibration-induced SOST index was 1.03 ± 0.24 in the low BMD group and 0.99 ± 0.33 in the normal BMD group. For plasma SOST levels, no group-by-time interaction was found. The resting myoelectrical activities of adductor muscles increased significantly during WBV in both groups. However, there was no significant difference in the main effects of WBV on resting myoelectrical activity between the groups. The standardized vibration-induced plasma SOST index was found to be a significant independent predictor of the standardized vibration-induced reflex myoelectrical activity of the adductor muscle in both groups. CONCLUSION: This study suggests that osteocytes serve as mechanoreceptors of reflex electromyography during WBV.

Effects of whole-body vibration on plasma sclerostin level in healthy women.

BACKGROUND/AIM: To determine whether plasma sclerostin levels are affected by applying whole-body vibration treatments. MATERIALS AND METHODS: Following a pilot study, the pretsent prospective, randomized, controlled single-blind study was performed on 16 healthy volunteer women (ages 20 to 40 years). Subjects were randomly divided into 2 groups, and whole-body vibration was applied to the treatment group but not to the controls. The plasma sclerostin levels were measured before the treatment and at the 10th minute after whole-body vibration on the 1st, 2nd, and 5th days of application. RESULTS: The plasma sclerostin level measured at 10 min after the whole-body vibration treatment increased 91% (P = 0.024) on the 1st day and decreased 31.5% (P = 0.03) on the 5th day in the whole-body vibration group. In the control group, there was no change in the plasma sclerostin level at any time. A progressive increase in baseline plasma sclerostin levels during the 5 days of vibration sessions was also found. CONCLUSION: Our study demonstrated that whole-body vibration can change plasma sclerostin levels, and that this change is detectable 10 min after whole-body vibration treatments.

Comparison of the data classification approaches to diagnose spinal cord injury.

In our previous study, we have demonstrated that analyzing the skin impedances measured along the key points of the dermatomes might be a useful supplementary technique to enhance the diagnosis of spinal cord injury (SCI), especially for unconscious and noncooperative patients. Initially, in order to distinguish between the skin impedances of control group and patients, artificial neural networks (ANNs) were used as the main data classification approach. However, in the present study, we have proposed two more data classification approaches, that is, support vector machine (SVM) and hierarchical cluster tree analysis (HCTA), which improved the classification rate and also the overall performance. A comparison of the performance of these three methods in classifying traumatic SCI patients and controls was presented. The classification results indicated that dendrogram analysis based on HCTA algorithm and SVM achieved higher recognition accuracies compared to ANN. HCTA and SVM algorithms improved the classification rate and also the overall performance of SCI diagnosis.

Risk factors for complex regional pain syndrome in patients with traumatic extremity injury.

BACKGROUND: It is not clear why complex regional pain syndrome (CRPS) develops in some patients but not in others, despite similar initiating events. The aim of this study was to investigate risk factors for CRPS in cases who had suffered traumatic upper extremity injury. METHODS: One hundred sixty-five patients who had suffered a mechanical traumatic injury isolated to their hand or forearm were included in this study. Age, gender, body mass index, tissue types injured, and side of affected forearm/hand were investigated as possible risk factors for CRPS. RESULTS: CRPS was diagnosed in 84 patients. Female/male ratio was higher in patients with CRPS versus those without. The mean age was higher in patients with CRPS. The affected forearm/hand was the dominant side in 62.9% of patients without CRPS and in 64.2% of patients with CRPS. CRPS incidence was higher in patients with motor nerve injury and in patients with sensory nerve injury. A logistic regression showed that risk for CRPS was higher in patients with motor nerve injury and in females. CONCLUSION: This study indicates that motor nerve injury and female gender are risk factors for CRPS. The prevention measures should be focused mainly on females and patients with motor nerve injury in order to reduce the risk of CRPS.

A quantitative skin impedance test to diagnose spinal cord injury.

The purpose of this study was to develop a quantitative skin impedance test that could be used to diagnose spinal cord injury (SCI) if any, especially in unconscious and/or non-cooperative SCI patients. To achieve this goal, initially skin impedance of the sensory key points of the dermatomes (between C3 and S1 bilaterally) was measured in 15 traumatic SCI patients (13 paraplegics and 2 tetraplegics) and 15 control subjects. In order to classify impedance values and to observe whether there would be a significant difference between patient and subject impedances, an artificial neural network (ANN) with back-propagation algorithm was employed. Validation results of the ANN showed promising performance. It could classify traumatic SCI patients with a success rate of 73%. By assessing the experimental protocols and the validation results, the proposed method seemed to be a simple, objective, quantitative, non-invasive and non-expensive way of assessing SCI in such patients.