Adults with initial metabolic syndrome have altered muscle deoxygenation during incremental exercise.

OBJECTIVE: Reduced aerobic power is independently associated with metabolic syndrome (MetS) incidence and prevalence in adults. This study investigated whether muscle deoxygenation (proxy of microvascular O2 extraction) during incremental exercise is altered in MetS and associated with reduced oxygen consumption ( V˙O2peak ). METHODS: Twelve men with initial MetS (no overt diseases and medication-naive; mean ± SD, age 38 ± 7 years) and 12 healthy controls (HCs) (34 ± 7 years) completed an incremental cycling test to exhaustion, in which pulmonary ventilation and gas exchange (metabolic analyzer), as well as vastus lateralis deoxygenation (near infrared spectroscopy), were measured. RESULTS: Subjects with MetS, in contrast to HCs, showed lower V˙O2peak normalized to total lean mass, similar V˙O2 response to exercise, and earlier break point (BP) in muscle deoxygenation. Consequently, deoxygenation slope from BP to peak exercise was greater. Furthermore, absolute V˙O2peak was positively associated with BP in correlations adjusted for total lean mass. CONCLUSIONS: MetS, without overt diseases, altered kinetics of muscle deoxygenation during incremental exercise, particularly at high-intensity exercise. Therefore, the balance between utilization and delivery of O2 within skeletal muscle is impaired early in MetS natural history, which may contribute to the reduction in aerobic power.

Is the Frequency in Somatosensory Electrical Stimulation the Key Parameter in Modulating the Corticospinal Excitability of Healthy Volunteers and Stroke Patients with Spasticity?

Somatosensory electrical stimulation (SES) has been proposed as an approach to treat patients with sensory-motor impairment such as spasticity. However, there is still no consensus regarding which would be the adequate SES parameters to treat those deficits. Therefore, the aim of this study was to evaluate the effects of applying SES over the forearm muscles at four different frequencies of stimulation (3, 30, 150, and 300 Hz) and in two intervals of time (5' and 30') by means of transcranial magnetic stimulation and Hoffmann's reflex (H-reflex) in healthy volunteers (Experiments I and II). A group of stroke patients (Experiment III) was also preliminary evaluated to ascertain SES effects at a low frequency (3 Hz) applied for 30' over the forearm spastic flexors muscles by measuring the wrist joint passive torque. Motor evoked potentials and the H-reflex were collected from different forearm and hand muscles immediately before and after SES and up to 5' (Experiment I) and 10' (Experiments I and II) later. None of the investigated frequencies of SES was able to operate as a key in switching modulatory effects in the central nervous system of healthy volunteers and stroke patients with spasticity.

Waveform Similarity Analysis: A Simple Template Comparing Approach for Detecting and Quantifying Noisy Evoked Compound Action Potentials.

Experimental electrophysiological assessment of evoked responses from regenerating nerves is challenging due to the typical complex response of events dispersed over various latencies and poor signal-to-noise ratio. Our objective was to automate the detection of compound action potential events and derive their latencies and magnitudes using a simple cross-correlation template comparison approach. For this, we developed an algorithm called Waveform Similarity Analysis. To test the algorithm, challenging signals were generated in vivo by stimulating sural and sciatic nerves, whilst recording evoked potentials at the sciatic nerve and tibialis anterior muscle, respectively, in animals recovering from sciatic nerve transection. Our template for the algorithm was generated based on responses evoked from the intact side. We also simulated noisy signals and examined the output of the Waveform Similarity Analysis algorithm with imperfect templates. Signals were detected and quantified using Waveform Similarity Analysis, which was compared to event detection, latency and magnitude measurements of the same signals performed by a trained observer, a process we called Trained Eye Analysis. The Waveform Similarity Analysis algorithm could successfully detect and quantify simple or complex responses from nerve and muscle compound action potentials of intact or regenerated nerves. Incorrectly specifying the template outperformed Trained Eye Analysis for predicting signal amplitude, but produced consistent latency errors for the simulated signals examined. Compared to the trained eye, Waveform Similarity Analysis is automatic, objective, does not rely on the observer to identify and/or measure peaks, and can detect small clustered events even when signal-to-noise ratio is poor. Waveform Similarity Analysis provides a simple, reliable and convenient approach to quantify latencies and magnitudes of complex waveforms and therefore serves as a useful tool for studying evoked compound action potentials in neural regeneration studies.

Characterization of the mechanomyographic signal of three different muscles and at different levels of isometric contractions.

PURPOSE: Lateral (X) and longitudinal (Y) mechanical oscillations of muscle fibers that take place during muscular contraction seem to contain information additionally to the myoelectric activity, which can contribute to the interpretation of some muscle gradation force mechanisms. However, no previous study was found that had investigated the relationship between the muscle force and features associated to the mechanomyographic (MMG) signal obtained by means of a biaxial accelerometer in three different muscles. Therefore, the aim of this study was to evaluate the relationship between the force output at different load levels (20% to 100%) of the maximum voluntary isometric contraction (%MVIC) and the two signals supplied by a biaxial accelerometer and, in addition, the so-called resultant (R) acceleration signal derived from the two signals mentioned previously. Twenty seven male volunteers participated in this study. METHODS: The force output related to the right biceps brachii, soleus and gastrocnemius medialis muscles was studied by means of linear regression models fit to log-transformed of the root mean square (RMS) values of the MMG signals in X, Y, and R axes versus each %MVIC. The phase angle of R acceleration (PhaseR) and anthropometric data were also considered. RESULTS: The angular coefficient a and the antilog of y-intercept b from the log-transformed of MMG data values versus force output were able to distinguish partially motor unit strategies during isometric contractions in the three muscles studied. CONCLUSION: The findings suggest that biaxial accelerometer seems to be an interesting approach in the assessment of muscle contraction properties.

Knee bioelectric impedance assessment in healthy/with osteoarthritis subjects.

The present study analyzes parameters estimated by bioelectric impedance spectroscopy (BIS) in subjects with healthy and with osteoarthritis (OA) knees. Thirty-two male volunteers, members of the Parachute Military Infantry Brigade of Rio de Janeiro, Brazil, participated in the study (62 knee joints). Clinical specialists used the Dejour scale for OA classification and divided the subjects into a control (without OA) and a pathological group (with different degrees of OA). BIS data were obtained in a standing position using a BIS technique based on the current response to a step voltage excitation. Differences between groups were measured by means of a Wilcoxon-Mann-Whitney test. Results indicate that raw bioimpedance parameters seem to be sensitive to the physiological changes associated with OA. Thus, data indicate that extra-cellular resistance (Re) and reactance of the equivalent capacitance (Xcx) increase according to the disease intensity (p < 0.001). In conclusion, the BIS technique seems to be able to provide the objective and non-invasive basis for helping the diagnosis of knee OA.

Intra- and inter-tester reproducibility of venous occlusion plethysmography: comparison between a manual and a semi-automatic method of blood flow analysis.

Venous occlusion plethysmography (VOP) is a valid non-invasive method to assess peripheral blood flow (BF) in humans. Our aim was to determine intra- and inter-tester reproducibility of BF analysis using a traditional manual method and a novel system, based on a semi-automatic approach. Ten healthy subjects and ten subjects with chronic heart failure (CHF) were evaluated. Blood flow was measured on the forearm at baseline and after 5 min of circulatory occlusion (reactive hyperemia (RH)). Two testers independently and blindly analyzed each VOP recording. Both methods were highly reproducible intra- and inter-testers. In addition, there was a high association between the methods, since the intraclass correlation coefficients (ICCs) for healthy subjects were 0.99, 0.99 and 0.99, and the coefficients of variation (CVs) were 1.8, 2.4 and 1.6% for baseline, RH peak and RH area under the curve, respectively. For CHF subjects, the ICCs were 0.99, 0.98 and 0.99, and the CVs were 2.9, 3.6 and 2.0%. In addition, the time spent on the semi-automatic analyses was shorter (p < 0.05). In conclusion, both methods demonstrated high intra- and inter-tester reproducibility for baseline and RH BF analysis. However, since the semi-automatic method was faster to generate the results, the present study supports its usage for the analysis of BF measured by VOP.

Military parachuting injuries in Brazil.

The purpose of the present study was to identify the main injuries caused by military parachuting jumping techniques in Brazil. With this aim, their distribution by anatomical site and their association with aircraft type and drop zone characteristics were analysed. Data for the study were obtained by the analysis of accident reports, completed after each jumping training mission in which an injury occurred, during the period January 2005-August 2006. The overall lesion rate during the period was 1.2%, with 189 injured subjects, and the highest injury rate was detected for the foot/ankle anatomical site (32.8%). The relative injury rates according to drop zone were 1.00% (main drop zone-Afonsos) and 2.94% for the remaining zones. Regarding aircraft type, these rates were 0.91% for the C130, 2.03% for the C115 and 2.68% for the C95 airplanes. The relative risk for the drop zone categories (reference category Afonsos) was 2.94 (95% CI: [2.10; 4.04]); while for aircraft types (reference category C130) these values were 2.95 (95% CI: [2.18; 3.98]; C95 aircraft) and 2.23 (95% CI: [1.34; 3.70]; C115). The study suggests that ankle stabilisers should be put into use by military parachuters, and that a better-planned schedule should be implemented for the used drop zones.

Evaluation of arm dominance by using the mechanomyographic signal.

The authors collected and compared mechanomyo-graphic (MMG) signal behavior from the biceps brachii of left and right arms of right-handed men (n = 19) and women (n = 20) who performed isometric contractions at 5 contraction levels. Mean frequency (MF) and RMS values were calculated from the MMG signals that arose from lateral oscillations of muscle fibers. Across genders and arms, RMS values increased with contraction level and MF values decreased with increase in muscle contraction. The authors found no significant difference in those parameters between dominant and nondominant arms. Therefore, summation of muscle twitches obtained from the MMG signal collected in biceps brachii muscle does not reveal any difference between dominant and nondominant arms.

Assessment of characteristic of the vasomotor control dynamics based on plethysmographic blood flow measurement.

Enhancing the knowledge about the characteristic of the vasomotor control can help physicians to improve the treatment of cardiovascular diseases and their consequences in people's daily activities. Vessels are generally evaluated from a static point of view, where some vascular features are obtained in a given space of time, or expressed as an average of some evaluation. The present study presents a method to assess some characteristics of the vasomotor control dynamics. Such a method is based on a mathematical description of the temporal profile of the blood flow observed during a reactive hyperemia condition induced by a protocol of 5 min of ischemia. The parameters for such a mathematical descriptive function were evaluated by searching for sensitivity to identify normal and vasomotor alterations induced by oral administration of ibuprofen (1200 mg) in ten healthy volunteers. The results indicated by the proposed mathematical description fitted appropriately experimental blood flow data (fitting-error of 0.18 ml/100 ml of tissue/min). Additionally, one parameter of the mentioned function was statistically different (P < 0.05) when one considers the normal and altered conditions of the vessel, even when the traditional peak and the basal flow values did not hint at the distinction.

Longitudinal study of the fundamental frequency of hunger cries along the first 6 months of healthy babies.

SUMMARY: Potentially rich in information, the baby's cry has motivated several researches along the years. Although most of these studies have generated important knowledge about the baby's cry, they were focused on the neonatal period. The few longitudinal studies on changes in the acoustical features of the cry over the baby's growth have been done with a small sample and a large recording interval. Aiming to overcome such methodological limitations, this work investigated hunger cries using a more representative sample size (30 babies) and time resolution (biweekly intervals) from birth to 6 months of baby's age. The findings indicate that the fundamental frequency (f0) of the cry signals did vary more than previously reported in the literature. The results showed a widespread oscillatory behavior in f0 evolution along all the 6 months with an especially significant decrease from birth to the 15th day of life. The present results are not clinically applicable yet, but they pointed some novel aspects of the f0 mean values along the baby's growth. These findings and further longitudinal studies can help standardize age-related cry parameters, which are essential for medical and language development researches.