Biomedical subjects

A Belli

Publications and source records attributed to A Belli.

At least 19 recordsLinked to original sources

PubMed2006

Development and evaluation of a new bicycle instrument for measurements of pedal forces and power output in cycling.

Determination of pedal forces is a prerequisite to analyse cycling performance capability from a biomechanical point of view. Comparing existing pedal force measurement systems, there are methodological or practical limitations regarding the requirements of scientific sports performance research and enhancement. Therefore, the aim of this study was to develop and to validate a new bicycle instrument that enables pedal forces as well as power output measurements with a free choice of pedal system. The instrument (Powertec-System) is based on force transducer devices, using the Hall-Effect and being mounted between the crank and the pedal. Validation of the method was evaluated by determining the accuracy, the cross talk effect, the influence of lateral forces, the reproducibility and, finally, a possible drift under static conditions. Dynamic tests were conducted to validate the power output measurement in reference to the SRM-System. The mean error of the present system was -0.87 +/- 4.09 % and -1.86 +/- 6.61 % for, respectively, the tangential and radial direction. Cross talk, lateral force influence, reproducibility and drift mean values were < +/- 7 %, < or = 2.4 %, < 0.8 % and 0.02 N x min (-1), respectively. In dynamic conditions, the power output measurement error could be kept below 2.35 %. In conclusion, this method offers the possibility for both valid pedal forces and power output measurements. Moreover, the instrument allows measurements with every pedal system. This method has an interesting potential for biomechanical analyses in cycling research and performance enhancement.

Bicycling↗

PubMed2006

Influence of the contact time on coupling time and a simple method to measure coupling time.

The enhancement of performance in stretch shortening cycle (SSC) exercises has been attributed to the recoil of elastic energy stored during the stretching phase and depends on the duration of the coupling time (T(coupling)) i.e., the duration of the isometric phase occurring between the stretch and the shortening of the muscle. However, instead of T(coupling), the contact time (T(contact))--i.e., the sum of T(coupling) plus the duration of the stretching and shortening phases that precede and follow T(coupling)--is more easily and often measured. The aim of this study was to investigate the T(coupling) changes within a large range of T(contact), in order to propose a possible relationship between T(coupling) and T(contact), thus allowing the accurate measurement of T(coupling )only from a tachometer and force data obtained classically in vertical jumps, jumps on sledge apparatus and running on force treadmills. Eleven subjects performed SSC exercises on a sledge apparatus with a large range of T(contact) (400, 700, 1,000, 1,500, 2,000 and 2,500 ms). The T(coupling) and T(contact) values were measured individually, from force platform recordings and the velocity of the carriage seat obtained by a tachometer. For the longest T(contact) (i.e., from 850 to 2,500 ms), we observed a significant linear relationship between T(contact) and T(coupling). This transition between T(contact) shorter or longer than about 850 ms seems to be important and to correspond to T(coupling) close to 300 ms. This limit observed in the present study could be explained physiologically due to a possible modification of the cross-bridges formation.

Adult↗

PubMed2006

Role of the C2 articular branches in occipital headache: an anatomical study.

One of the most important structures involved in the pathogenesis of occipital headache is the lateral atlanto-axial joint. Previous studies demonstrated that injection of this joint with local anesthetic can alleviate occipital headache, while injection of contrast medium exacerbates it. The aim of our study is to improve the understanding of the nerve supply to the lateral atlanto-axial joint by the C2 nerve elements, in order to determine the optimal target for an anesthetic block of this area. Ten C2 spinal nerves and roots were dissected in five embalmed cadavers with the aid of a 40X microscope and the lateral atlanto-axial joint was shown to be extensively supplied by articular branches of C2 nerve elements (dorsal ganglion, spinal nerve, and ventral ramus). Following our observations on their distribution, we propose a target for local anesthetic injection of the C2 articular branches that is based on reliable landmarks and is easily identifiable at fluoroscopy. We suggest that local anesthetic injection at this target point could be of benefit in the relief of occipital pain due to cervical trauma or degenerative disease involving the lateral atlanto-axial joint.

Anesthetics, Local↗

PubMed2006

Spring-mass model characteristics during sprint running: correlation with performance and fatigue-induced changes.

Spring-mass model properties of eight non-specialized male runners were measured during four straight 100-m sprints on an athletics track. A recently developed simple measurement method allowed to calculate leg and vertical stiffness, vertical displacement of the center of mass, and stride temporal characteristics. Changes in these mechanical parameters were studied and correlated with those of sprint performance. During the first 100 m, forward velocity showed significant variations (mean value of 8.10 +/- 0.31 m x s(-1) over the entire 100-m), while leg and vertical stiffnesses (19.5 +/- 4.3 kN x m(-1) and 93.9 +/- 12.4 kN x m(-1), respectively) remained constant. No significant link was found between mechanical and performance parameters over this first sprint. During the following three sprints, vertical stiffness, step frequency, and contact time significantly decreased (20.6 +/- 7.9%, 8.03 +/- 3.34%, and 14.7 +/- 7.2% of the first 100-m value, respectively) with decreasing maximal and mean velocities (10.9 +/- 2.0% and 7.30 +/- 5.23%, respectively), whereas leg stiffness and maximal force remained constant. Furthermore, changes between these mechanical and performance parameters were significantly related, showing the clear relationship between impairment in spring-mass model properties of the runners' lower limbs and the decrease in performance in fatigue conditions induced by the repetition of these all-out efforts.

Adaptation, Physiological↗

PubMed2006

Free phenytoin concentration measurement in brain extracellular fluid: a pilot study.

This article investigates the relationship between brain extracellular fluid free phenytoin concentration and plasma free phenytoin concentration in adults with acute brain injury. Daily cerebral microdialysate free phenytoin concentration was measured in eight adults with acute brain injury and compared with simultaneous measurement of plasma free phenytoin concentration. The group data revealed no significant correlation between microdialysate and plasma free phenytoin concentration (r = 0.34, p = 0.41). However, in two patients, with a sufficient number of samples for intra-individual analysis, there was a significant correlation between microdialysate and plasma free phenytoin concentration (r = 0.92, p < 0.001 and r = 0.88, p < 0.01). In vitro microdialysis relative recovery for phenytoin was 2.1%. In the context of acute brain injury, measurement of free plasma phenytoin concentration may not provide an accurate reflection of regional brain extracellular fluid free phenytoin concentration and may have limitations with respect to achieving reproducible brain extracellular fluid free phenytoin concentrations. This has implications for dosing regimens relying on plasma phenytoin levels.

Adolescent↗

PubMed2006

Operative and hardware complications of deep brain stimulation for movement disorders.

The objective of this investigation was to present the operative and hardware complications encountered during follow-up of patients with in situ deep brain stimulators. The study took the form of a retrospective chart review on a series of consecutive patients who were treated successfully with insertion of deep brain stimulators at a single centre by a single surgeon between 1999 and 2005. During the study period, a total of 60 patients underwent 96 procedures for implantation of unilateral or bilateral DBS electrodes. The mean follow-up period was 43.7 months (range 6-78 months) from the time of the first procedure. No patients were lost to follow-up or died. Eighteen patients (30%) developed 28 adverse events, requiring 28 electrodes to be replaced. Seven patients developed two adverse events and two patients developed three adverse events. The rate of adverse events per electrode-year was 8%. We observed a higher proportion of early complications (<6 months postoperatively) in patients with Parkinson's disease, while dystonic patients had more late complications (>6 months postoperatively) and no early complications. Thirty per cent of our patients developed an adverse event that could potentially lead to revision of the implanted hardware. In patients with Parkinson's disease most of the complications tend to occur during the first 6 months postoperatively, while in dystonic patients most occur between 12 and 24 months postoperatively.

Adult↗

PubMed2005

Extracellular fluid S100B in the injured brain: a future surrogate marker of acute brain injury?

The authors describe the measurement of S100B protein in brain extracellular fluid (ECF) of patients with acute brain injury (traumatic brain injury and subarachnoid haemorrhage) using the technique of microdialysis. To our knowledge, this is the first report of S100B measurement in the human brain. Acute Brain Injury (ABI) is a leading cause of death and disability and the need for a practical and sensitive biochemical marker for monitoring these patients is urgent. The calcium binding astrocyte protein, S100B, may be a candidate for this role. Previous serum studies have shown S100B to be a sensitive predictor of mortality and rise in intracranial pressure in ABI, but it has never before been measured directly within the brain. The ECF reflects the local biochemistry of the brain parenchyma, and the use of intracerebral microdialysis opens up the possibility of studying many novel surrogate markers of injury in the laboratory, in addition to the conventional markers it measures at the bedside (lactate, pyruvate, glucose, and glycerol). In this preliminary report of two cases, the authors demonstrate the quantification of S100B in ECF microdialysate, and investigate whether changes in hourly S100B profile can be related to secondary brain injury. It is shown that extracellular concentrations of S100B change markedly in response to secondary brain injury. Further investigation is required to determine whether extracellular S100B measurement in ABI could assist in patient management.

Adult↗

PubMed2005

Mechanical comparison of barefoot and shod running.

In order to further compare shod versus barefoot running, 35 subjects ran two bouts of 4 minutes at 3.33 m x s(-1) on a treadmill dynamometer. Parameters were measured on about 60 consecutive steps. Barefoot showed mainly lower contact and flight time (p < 0.05), lower passive peak (1.48 versus 1.70 body weight, p < 0.05), higher braking and pushing impulses (p < 0.05), and higher pre-activation of triceps surae muscles (p < 0.05) than shod. It was concluded that when performed on a sufficient number of steps, barefoot running leads to a reduction of impact peak in order to reduce the high mechanical stress occurring during repetitive steps. This neural-mechanical adaptation could also enhance the storage and restitution of elastic energy at ankle extensors level.

Adult↗

PubMed2005

Influence of speed variation and age on ground reaction forces and stride parameters of children's normal gait.

The aim of this study was to assess the influence of both age and speed on ground reaction forces and temporal parameters during normal gait in children. Fifteen children aged 4-6 years (group 1), 16 aged 6-8 years (group 2), and 16 aged 8-10 years (group 3) walked at 2.7 km/h, 3.6 km/h, and 4.5 km/h on a treadmill. For each child thirty successive steps were recorded. The influence of speed and age on normalized gait parameters was examined with two-way analysis of variance. The first vertical peak force (Fz1) and all the antero-posterior forces of group 1 were higher than those of the other groups for the three speeds. The minimum vertical force (Fz2), the second vertical peak force (Fz3), and the duration of stride and stance were significantly higher in groups 2 and 3. For all the groups, Fz1 and all the antero-posterior forces increased with the speed while Fz2, stride, stance, and double-stance duration decreased. Fz3 was not influenced by speed variation. The results of this study show that age and walking speed influence ground reaction forces and stride time parameters in 4- to 10-year-old children.

Acceleration↗

PubMed2005

Axonal pathology in subarachnoid and intracerebral hemorrhage.

Electrically active axons degenerate in the presence of nitric oxide (NO) in vitro. High CSF NO concentrations have been observed in patients with hemorrhagic brain injury such as subarachnoid hemorrhage (SAH) and intracerebral hemorrhage (ICH). This study investigated the evidence for axonal injury in SAH and ICH and related this to CSF NO levels. In this study, neurofilament phosphoforms (NfH(SMI34), NfH(SMI35), NfH(SMI38), NfH(SMI310)), surrogate markers for axonal injury, and NO metabolites (nitrate, nitrite = NOx) were measured by ELISA in cerebrospinal fluid (CSF) from patients with SAH and ICH and from a group of controls. Injury severity was classified using the Glasgow Coma Scale, and survival was used as the outcome measure. Compared to the control group, a higher proportion of patients with SAH and ICH had elevated NfH(SMI34) levels from day 0 to day 6 (p < 0.001), elevated NfH(SMI35) levels from day 1 to 6 (p < 0.001), and elevated NfH(SMI310) levels at day 0, 1, 4, and 6 (p < 0.001). The NOx levels were higher in the SAH and ICH patients than in the controls (p < 0.05) and distinguished the non-survivors from the survivors (p < 0.05). No direct correlation was found for NOx with any of the NfH phosphoforms. This study provides evidence for primary and secondary axonal injury in patients with SAH and ICH, with non-survivors also having higher NOx levels. CSF NfH phosphoforms might emerge as a putative surrogate marker for monitoring the development for secondary axonal degeneration in neurocritical care and guiding targeted neuroprotective strategies.

Adult↗

PubMed2005

Epithelioid haemangioma in association with a deep arteriovenous malformation.

Epithelioid haemangiomas are benign, vascular tumours characterized by the proliferation of epithelioid endothelial cells with abundant eosinophilic hyaline cytoplasm. We report a case of epithelioid haemangioma in association with a deep arteriovenous malformation of the subclavian artery. The association of reactive vascular proliferations with arteriovenous malformations is uncommonly reported.

Adult↗

PubMed2005

Sprint running: a new energetic approach.

The speed of the initial 30 m of an all-out run from a stationary start on a flat track was determined for 12 medium level male sprinters by means of a radar device. The peak speed of 9.46+/-0.19 m s(-1) (mean +/- s.d.) was attained after about 5 s, the highest forward acceleration (a(f)), attained immediately after the start, amounting to 6.42+/-0.61 m s(-2). During acceleration, the runner's body (assumed to coincide with the segment joining the centre of mass and the point of contact foot terrain) must lean forward, as compared to constant speed running, by an angle alpha = arctang/a(f) (g = acceleration of gravity). The complement (90-alpha) is the angle, with respect to the horizontal, by which the terrain should be tilted upwards to bring the runner's body to a position identical to that of constant speed running. Therefore, accelerated running is similar to running at constant speed up an ;equivalent slope' ES = tan(90-alpha). Maximum ES was 0.643+/-0.059. Knowledge of ES allowed us to estimate the energy cost of sprint running (C(sr), J kg(-1) m(-1)) from literature data on the energy cost measured during uphill running at constant speed. Peak Csr was 43.8+/-10.4 J kg(-1) m(-1); its average over the acceleration phase (30 m) was 10.7+/-0.59 J kg(-1) m(-1), as compared with 3.8 for running at constant speed on flat terrain. The corresponding metabolic powers (in W kg(-1)) amounted to 91.9+/-20.5 (peak) and 61.0+/-4.7 (mean).

Acceleration↗

PubMed2005

Endovascular stent graft repair of mycotic aneurysms of the thoracic aorta.

Traditional open surgical repair for mycotic aneurysms of the thoracic aorta is associated with significant morbidity and mortality. Endovascular repair has been reported as an alternative treatment in patients with mycotic thoracic aneurysms. This article reports our experience of endovascular stent graft placement in three patients with mycotic aneurysms of the thoracic aorta and compares the results with similar reports on the literature.

Aged↗

PubMed2004

[Influence of speed variation and age on the intrasubject variability of ground reaction forces and spatiotemporal parameters of children's normal gait].

OBJECTIVE: To assess the effect of age and speed on the variability of ground reaction forces (GRF) and stride parameters of gait in normal children. MATERIAL AND METHOD: Forty-seven children aged 4-10 years were split into three age groups. Each child walked at three constant speeds on a treadmill. Thirty consecutive steps of each leg were recorded. For each child, the mean parameters of the 30 steps were calculated. The mean parameter of each child was taken to calculate the mean parameters of the group. The variability was evaluated by the coefficient of variation (CV). The influence of both age and speed on the variability was examined with a to-way analysis of variance. RESULTS: The cross effect of age and speed on the variability was not significant. The variability of the parameters decreased significantly with age between 4 and 8 years. The variability of vertical forces increased significantly with speed (between 2.7 and 4.5 km/h), while the variability of antero-posterior forces, the stride and the stance decreased between 2.7 and 3.6 km/h. However, the variability of double stance was not influenced by walking speed between 2.7 and 4.5 km/h. Except the time of production of the vertical force of propulsion (Tz3), the variability of temporal vertical parameters decreased significantly with speed between 2.7 and 4.5 km/h and the variability of temporal antero-posterior parameters decreased significantly between 2.7 and 3.6 km/h. DISCUSSION-CONCLUSION: The variability of the GRF and spatio-temporal parameters in children was influenced by age between 4 and 8 years old and by speed between 2.7 and 3.6 km/h. Moreover, the effect of age on the GRF persists up to 8 years. The variabilities of the time of production of the antero-posterior force of propulsion (Ty2) and stance duration were lower than the variabilities of the others parameters. These two variables could be the most reliable parameters when assessing gait in children aged 4-10 years, walking at speeds between 2.7 and 4.5 km/h.

Age Factors↗

PubMed2004

A simple method for field measurements of leg stiffness in hopping.

A new method to measure the leg stiffness in hopping and bouncing, with simple technical equipment and under field conditions, is introduced and validated. The leg stiffness (K (N)) was calculated from only contact and flight times measured by a contact mat. It was compared to the reference stiffness (K (R)) obtained from force platform measurements. Eight subjects performed, first, submaximal hopping movements at different frequencies (1.8 to 4 Hz, by step 0.2 Hz) and, second, maximal hopping. In sub maximal hopping K (N) was significantly correlated with K (R) (r = 0.94; p < 0.001) and the difference between K (N) and K (R) ranged from -7.2 % to 6.9 % (at 1.8 and 3.6 Hz respectively) with a limit of agreement of -1.5 kN x m (-1). In maximal hopping K (N) was also related to K (R) (r = 0.98, p < 0.001) and the inter individual rank order was respected (R = 0.87). It was concluded that the new method could be applied to study extensively intra individual and inter individual variations of leg stiffness in respectively sub maximal and maximal hopping and thus to simplify further investigations in field conditions of the role of stiffness regulation in the optimization of human locomotion.

Adult↗

PubMed2003

The use of stent grafts for the treatment of aneurysms and dissections of the thoracic aorta: a single centre experience.

OBJECTIVE: To review the results of stent graft treatment for diseases of the thoracic aorta. DESIGN: A retrospective study of the results of thoracic stent graft procedures in a single centre. METHODS: The results of 30 procedures performed in 24 patients were analysed. Eleven patients had aneurysmal dilatation of the descending thoracic aorta (>5.5 cm), nine patients had complicated type B dissection, three had penetrating ulcers and one had a traumatic pseudoaneurysm. Imaging follow-up consisted of CT scans performed at one, three, six and 12 months following the procedure and annually thereafter. RESULTS: One technical failure occurred due to a ruptured external iliac artery. There were no other immediate failures. The primary technical success rate was 83%. The 30-day procedural and patient mortality rates were 7 and 8%, respectively. No neurological complications occurred. Seven patients had the subclavian artery covered without complications. Secondary intervention was required in 21%. During the follow-up period (mean 11 months, range 1-48 months.) there were five deaths, two of which were related to stent graft infection. CONCLUSION: Thoracic stent grafts offer a realistic alternative to surgery.

Aged↗

PubMed2003

Influence of the base-line determination on work efficiency during submaximal cycling.

AIM: The purpose of this study was to compare work efficiency values (WE = work accomplished/energy expenditure above exercising with 0 load) among different unloaded base-line correction techniques for different power outputs. METHODS: Twelve healthy men performed 6 5-min steady-state exercises of 0 (unloaded), 40, 80, 120, 160 and 200 W at a pedalling rate of 90 rpm on a cycle ergometer. Three different unloaded base-line corrections were used for WE calculation: an actual measurement of VO(2) corresponding to the unloaded pedalling exercise, the y-intercept value of the linear regression between VO(2) and power output and the y-intercept value of the curvilinear VO(2)-power regression. RESULTS: The present study demonstrated that WE was significantly higher when determined using the actual measurement of the unloaded VO(2) than y-intercept values of the linear (p<0.001) and curvilinear (p<0.05) VO(2)-power regressions. WE based on theoretical determinations (linear vs curvilinear regressions) were not significantly different. The power output significantly affected all WE index, with higher WE being measured when the power output was low and lower WE when power output was high. CONCLUSION: The high WE values determined using the actual VO(2) measurement could be explained by (i) the additional energy expended to stabilise the body in addition to the energy expenditure of moving the lower limbs without power production and by (ii) the difficulty to experimentally reproduce the unloaded condition. The large range of WE values measured in the present study is due to differences in the procedures used to determine the unloaded VO(2) (and thus differences in unloaded VO(2) values) as well as differences in the cycling intensities.

Adult↗

PubMed2002

Moment and power of lower limb joints in running.

The aim of this study was to test the suitability of inverse dynamics method for instantaneous expression of joint kinetics and muscle function with various parts of the ground contact when running at different speeds. Nine male runners ran at speeds of 4.0 m x s(-1), 6.0 m x s(-1) and at their maximal speed. 2-D video analysis (200-frame x s(-1)) was synchronized with 3-D ground reaction force measurements (10 m-long force platform). Mechanical joint power was computed from 2-D segment dynamics associated with joint forces and net moments in multi-body movements. From these computations two successive functional phases during contact were found in the ankle and knee joints: 1) extensor negative and 2) extensor positive work. The hip joint showed three phases: 1) extensor positive, 2) flexor negative and 3) flexor positive work. Peak joint power increased in every investigated joint with increasing running speed. The highest changes were observed in the hip joint: from 327 +/- 203 W at a speed of 4.0 m x s(-1) to 1642 +/- 729 W (p < 0.01) at the maximal speed. The results may suggest that the role of the ankle and knee extensors is to create high joint stiffness before and during the contact phase, while the hip extensors are the prime forward movers of the body with increasing running speed. In conclusion, the inverse dynamics method may be of importance for use in specifying the joint kinetics and muscle function. However, the interpretation may become clearer when this method is used simultaneously with EMG measurements.

Adult↗