Biomedical subjects

M P Francescato

Publications and source records attributed to M P Francescato.

10 recordsLinked to original sources

PubMed1996

Primary motor and sensory cortex activation during motor performance and motor imagery: a functional magnetic resonance imaging study.

The intensity and spatial distribution of functional activation in the left precentral and postcentral gyri during actual motor performance (MP) and mental representation [motor imagery (MI)] of self-paced finger-to-thumb opposition movements of the dominant hand were investigated in fourteen right-handed volunteers by functional magnetic resonance imaging (fMRI) techniques. Significant increases in mean normalized fMRI signal intensities over values obtained during the control (visual imagery) tasks were found in a region including the anterior bank and crown of the central sulcus, the presumed site of the primary motor cortex, during both MP (mean percentage increase, 2.1%) and MI (0.8%). In the anterior portion of the precentral gyrus and the postcentral gyrus, mean functional activity levels were also increased during both conditions (MP, 1.7 and 1.2%; MI, 0.6 and 0.4%, respectively). To locate activated foci during MI, MP, or both conditions, the time course of the signal intensities of pixels lying in the precentral or postcentral gyrus was plotted against single-step or double-step waveforms, where the steps of the waveform corresponded to different tasks. Pixels significantly (r > 0.7) activated during both MP and MI were identified in each region in the majority of subjects; percentage increases in signal intensity during MI were on average 30% as great as increases during MP. The pixels activated during both MP and MI appear to represent a large fraction of the whole population activated during MP. These results support the hypothesis that MI and MP involve overlapping neural networks in perirolandic cortical areas.

Adult↗

PubMed1996

Effects of body size, body density, gender and growth on underwater torque.

Two forces act on a human body motionless in water: weight (W) and buoyancy (B). They are applied to the center of mass (CM) and to the center of volume (CV) of the subject, respectively. CM and CV do not coincide; this generates a torque that is a measure of the tendency of the upper part of the body to rise, rotating around its center of mass. To quantify this tendency, Pendergast & Craig defined 'underwater torque' (T') as the product of the net force with which the feet of a subject lying horizontally in water tend to sink, times the distance between the feet and the center of volume of the lungs. In this paper we have investigated: (a) the relationships between T' and body weight (BW), height (H), body surface area (BS), body density (BD) and leg density (LD) in a group of 30 subjects (group A, 14 females and 16 males, age range 16-50 years); and (b) the effect of gender and growth on T' in a group of 110 subjects (group B, 67 girls and 43 boys, age range 12-17 years). In group A, T' was found to be linearly related with BW (r=0.833, P<0.001), H (r=0.803, P<0.001), BS (r=0.866, P<0.001), BD (r=0.617, P<0.001) and LD (r=0.549, P<0.005). A multiple linear regression analysis showed that BS and BD explained about 85% of the variability of T' (r2=0.85). In group B, T' was found to increase linearly with age (r=0.47, P<0.01), the increasing rate being three times higher in boys compared with girls. As a consequence, the T' ratio between boys and girls increased with age, from 1.69 at 13 years to 2.04 at 16 years.

Adolescent↗

PubMed1996

Temporary threshold shift induced by physical exercise.

Several studies have demonstrated how physical exercise can increase noise-induced temporary threshold shifts (TTS), but until now no evidence of TTS exclusively attributable to physical activity has yet been reported. In this study the hearing pure-tone thresholds of 10 subjects were evaluated at rest and at three designated times following the end of a work load corresponding to 50% and 80% of the maximum oxygen uptake (VO2 max). The results obtained demonstrate a definite effect of physical exercise on the hearing threshold at 6000 and 8000 Hz and that the higher the frequency, the greater the chance of detecting a TTS. Evaluation of the variations in some physiologic parameters (VO2 max, blood lactate and blood pressure) could not statistically correlate the same with TTS. The physiopathologic mechanisms responsible for TTS are still unknown and require further studies which should make allowances for the deferred effects of metabolic variations on the cochlear function.

Adult↗

PubMed1996

[Functional mapping of the motor and primary sensorial cortex using magnetic resonance techniques. I. Preliminary data].

Functional Magnetic Resonance Imaging (fMRI) techniques sensitive to the local changes in blood flow, volume and oxygenation accompanying neuronal activation are powerful tools to investigate the human brain function. Experiments were performed on 10 right-handed healthy volunteers (age range: 20-39 years), using a 1.5 T whole-body MRI system. Two oblique contiguous planes were investigated along the central sulcus of the left hemisphere. Functional images were acquired using a Gradient Echo sequence while the subjects repetitively performed sequential finger to thumb opposition movements of the right hand or mental imagery of a visual scene. Twelve images for each task were obtained over a 6-min experimental period; they were then analyzed with the software provided by the manufacturer. In all the subjects small areas were activated in both the precentral and postcentral gyrus, mean percentage signal increases during finger movement being 10.7% and 3.8%, respectively. These values are fairly higher than literature ones. However several factors, such as voxel volume, are involved in determining the measured signal increase during activation. Moreover, in most cases the software procedures provided with the MR equipment to analyze the functional images imply subjective choices. It is thus necessary to implement new software packages for the analysis of fMRI images to apply more appropriate statistical procedures and to obtain more homogeneous and objective final information.

Adult↗

PubMed1996

[Functional mapping of the motor and primary sensorial cortex using magnetic resonance techniques. II. Image analysis techniques].

Functional Magnetic Resonance Imaging (fMRI) techniques to investigate brain function are now available on clinical MR systems. However, the software packages provided with the MR equipment to analyze the functional images are often inadequate. In the present study, two registration algorithms for correcting motion artifacts and three procedures of statistical analysis (t-test, correlation analysis, Kolmogorov-Smirnov test) were compared using programs implemented on a graphic workstation. For both registration algorithms, transformation parameters for in plane translations and rotation of images were significantly affected by the task, being higher during sequential finger movements than during the control (visual imagery) condition. Regions of interest were identified on the anatomical images and their boundaries automatically projected on functional images. The number of significantly activated pixels in the pre- and postcentral areas was not significantly different after the registration with the two procedures. The percentage of pixels of the pre- and postcentral areas whose signal intensity was significantly different between the two tasks decreased with respect to the adopted threshold of significance as a power function. For an area identified outside the brain, the same relation was linear: no activated pixel was found for p < 0.001. The application of the t-test or of the correlation analysis yielded similar results. The analysis of the profile of mean normalized signal intensity showed higher increases in signal intensities during the motor task in the precentral gyrus than in the postcentral gyrus. This appears to be due to a greater number of activated pixels during motor performance. The application of registration procedures, the identification of the regions of interest on the basis of the anatomical images and appropriate statistical analyses allow a more detailed characterization of task-related activation.

Adult↗

PubMed1995

Energy cost and energy sources in karate.

Energy costs and energy sources in karate (wado style) were studied in eight male practitioners (age 23.8 years, mass 72.3 kg, maximal oxygen consumption (VO2max) 36.8 ml.min-1.kg-1) performing six katas (formal, organized movement sequences) of increasing duration (from approximately 10 s to approximately 80 s). Oxygen consumption (VO2) was determined during pre-exercise rest, the exercise period and the first 270 s of recovery in five consecutive expired gas collections. A blood sample for lactate (la-) analysis was taken 5 min after the end of exercise. The overall amount of O2 consumed during the exercise and in the following recovery increased linearly with the duration of exercise (t) from approximately 1.51 (for t equal to 10.5 s (SD 1.6)) to approximately 5.8 l, for t equal to 81.5 s (SD 1.0). The energy release from la- production (VO2la-) calculated assuming that an increase of 1 mmol.l-1 la- corresponded to a VO2 of 3 mlO2.kg-1 was negligible for t equal to or less than 20 s and increased to 17.3 ml.kg-1 (la- = 5.8 mmol.l-1 above resting values) for t equal approximately to 80 s. The overall energy requirement (VO2eq) as given by the sum of VO2 and VO2la- was described by VO2eq = 0.87 + 0.071.t (n = 64; r2 = 0.91), where VO2eq is in litres and t in seconds. This equation shows that the metabolic power (VO2eq.t-1) for this karate style is very high: from approximately 9.5 l.min-1 for t equal to 10 s to approximately 4.9 l.min-1 for t equal to 80 s, i.e. from 3.5 to 1.8 times the subjects' VO2max. The fraction of VO2eq derived from the amount of O2 consumed during the exercise increased from 11% for t equal to 10 s to 41% for t equal to 80 s whereas VO2la- was negligible for t equal to or less than 20 s and increased to 13% for t equal to 80 s. The remaining fraction (from 90% for t equal to 10 s to 46% for t equal to 80 s), corresponding to the amount of O2 consumed in the recovery after exercise, is derived from anaerobic alactic sources, i.e. from net splitting of high energy phosphates during the exercise.

Adult↗

PubMed1995

Oxygen cost of internal work during cycling.

The energy cost of internal work and its relationships with lower limb mass and pedalling frequency were studied in four male subjects [age 22.2 (SD 1.5) years, body mass 81.0 (SD 5.1) kg, maximal O2 uptake (VO2max) above resting 3.06 (SD 0.4) l.min-1]. The subjects cycled at 40, 60, 80 and 100 rpm and at five different exercise intensities for every pedalling frequency (unloaded condition, UL); the same exercises were repeated after having increased the lower limbs' masses by 40% (loaded condition, L). The exercise intensities were chosen so that the oxygen consumption (VO2) did not exceed 75% of VO2max. For all the subjects and all the conditions, the rate of VO2 above resting increased linearly with the mechanical power (W). The y-intercepts of the linear regressions of VO2 on W, normalised per kilogram of overall lower limbs mass were the same in both UL and L and increased with the 4.165 power of pedalling frequency (fp). These intercepts were taken to represent the metabolic counterpart of the internal power dissipation in cycling; they amounted to 0.78, 0.34, 3.29 and 10.30 W.kg-1 for pedalling frequencies of 40, 60, 80 and 100 rpm respectively. The slope of the regression lines (delta W/delta VO2) represents the delta efficiency of cycle ergometer exercise; this was also affected by fp, ranging, on average, from 22.9% to 32.0%. These data allowed us to obtain a comprehensive description of the effects of fp (per minute), exercise intensity (W, watts) and lower limbs' mass with or without added loads (mL, kg), on VO2 (ml.min-1) during cycling: VO2 = [mL.(4.3.10(-8).fp4.165/0.35)] + (1/[(3.594.10(-5).fp2 - 0.003.fp + 0.326).0.35]).W. The mean percentage error between the VO2 predicted from this equation and the actual value was 12.6%. This equation showed that the fraction of the overall VO2 due to internal work, for a normal 70-kg subject pedalling at 60 rpm and 100 W was of the order of 0.2.

Adult↗

PubMed1995

The energy cost of level walking in patients with hemiplegia.

The energy cost of level walking (Cw) was measured from the ratio of O2 consumption to speed (from 0.1 to 1.2 m.s-1) in hemiplegic patients (n = 20) and in a control group of healthy subjects (n = 17). Average age and body mass were 58, 54 years and 73, 78 kg, respectively. In hemiplegic patients Cw was higher than in control subjects (average value at 1.0 m.s-1 = 3.6 and 3.3 J.m-1.kg-1, respectively) and this difference increased at lower speeds (from 5.1% at 1.2 m.s-1 to 28.7% at 0.1 m.s-1).

Energy Metabolism↗

PubMed1995

Bioenergetics and biomechanics of front crawl swimming.

"Underwater torque" (T') is one of the main factors determining the energy cost of front crawl swimming per unit distance (Cs). In turn, T' is defined as the product of the force with which the swimmer's feet tend to sink times the distance between the feet and the center of volume of the lungs. The dependency of Cs on T' was further investigated by determining Cs in a group of 10 recreational swimmers (G1: 4 women and 6 men) and in a group of 8 male elite swimmers (G2) after T' was experimentally modified. This was achieved by securing around the swimmers' waist a plastic tube filled, on different occasions, with air, water, or 1 or 2 kg of lead. Thus, T' was either decreased, unchanged, or increased compared with the natural condition (tube filled with water). Cs was determined, for each T' configuration, at 0.7 m/s for G1 and at 1.0 and 1.2 m/s for G2. For T' equal to the natural value, Cs (in kJ.m-1.m body surface area-2) was 0.36 +/- 0.09 and 0.53 +/- 0.13 for G1 in women and men, respectively, and 0.45 +/- 0.05 and 0.53 +/- 0.06 for G2 at 1.0 and 1.2 m/s, respectively. In a given subject at a given speed, Cs and T' were linearly correlated. To compare different subjects and different speeds, the single values of Cs and T' were normalized by dividing them by the corresponding individual averages. These were calculated from all single values (of Cs or T') obtained from that subject at that speed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

A new EDP assisted dietary survey employing a simple and concise data collection method.

The aim of the work was a diet analysis practice both accurate and simple to be used in daily applications. The subject records in real time his intake by employing the portion of food as unit of measure. Through the recipes, which may be obtained in deferred time, data are then reorganized by EDP to match food composition data of literature. A food composition table management system was developed which avoids vacancies of data: nine different sources from literature were used. The fact that the subjects records in a simple and concise way his intakes permits prolonged investigation: slight alterations of the diet are possible without changing his food preferences and with minimum reduction of compliance.

Computers↗