Path Linearity of Elite Swimmers in a 400 m Front Crawl Competition

none6noIn the frontal crawl, the propulsive action of the limbs causes lateral fluctuations from the straight path, which can be theoretically seen as the best time saving path of the race. The purpose of the present work was to analyze the head trajectory of 10 elite athletes, during a competition of 400 m front crawl, in order to give information regarding the path linearity of elite swimmers. The kinematic analysis of the head trajectories was performed by means of stereo-photogrammetry. Results showed that the forward speed and lateral fluctuations speed are linearly related. Multiple regression analysis of discrete Fourier transformation allowed to distinguish 3 spectral windows identifying 3 specific features: strokes (0.7-5 Hz), breathings (0.4-0.7 Hz), and voluntary adjustments (0-0.4 Hz), which contributed to the energy wasting for 55%, 10%, and 35%, respectively. Both elite swimmers race speed and speed wastage increase while progressing from the 1st to the 8th length during a 400 m front crawl official competition. The main sources of the lateral fluctuations that lead to the increasing speed wastage could be significantly attributed to strokes and voluntary adjustments, while breathings contribution did not reach statistical significance. In conclusion, both strokes and voluntary adjustments are the main energy consuming events that affect path linearity.PubMed ID: 25729292 [PMID]openGatta, Giorgio; Cortesi, Matteo; Lucertini, Francesco; Benelli, Piero; Sisti, Davide; Fantozzi, SilviaGatta, Giorgio; Cortesi, Matteo; Lucertini, Francesco; Benelli, Piero; Sisti, Davide; Fantozzi, Silvi

The relationship between power generated by thrust and power to overcome drag in elite short distance swimmers

At constant average speed (v), a balance between thrust force (Ft) and drag force (Fd) should occur: Ft-Fd = 0; hence the power generated by thrust forces (Pt = Ft\ub7v) should be equal to the power needed to overcome drag forces at that speed (Pd = Fd\ub7v); the aim of this study was to measure Pt (tethered swims), to estimate Pd in active conditions (at sprint speed) and to compare these values. 10 front crawl male elite swimmers (expertise: 93.1 \ub1 2.4% of 50 m world record) participated to the study; their sprint speed was measured during a 30 m maximal trial. Ft was assessed during a 15 s tethered effort; passive towing measurement were performed to determine speed specific drag in passive conditions (kP = passive drag force/v2); drag force in active conditions (Fd = kA\ub7v2) was calculated assuming that kA = 1.5\ub7kP. Average sprint speed was 2.20 \ub1 0.07 m\ub7s-1; kA, at this speed, was 37.2 \ub1 2.7 N\ub7s2\ub7m-2. No significant differences (paired t-test: p > 0.8) were observed between Pt (399 \ub1 56 W) and Pd (400 \ub1 57 W) and a strong correlation (R = 0.95, p < 0.001) was observed between these two parameters. The Bland-Altman plot indicated a good agreement and a small, acceptable, error (bias: -0.89 W, limits of agreement: -25.5 and 23.7 W). Power thrust experiments can thus be suggested as a valid tool for estimating a swimmer's power propulsion

2D Video Analysis System to Analyze the Performance Model of Figure Roller Skating: A Pilot Study

Figure roller skating is a discipline composed of various movements which involve jumps, artistic figures and spins in a seamless program which has both technical and shapely difficult. A biomechanical analysis of a double salchow was performed using a 2D video analysis of one European and in two Italian roller skaters. On average, the high level (HL) roller skater showed a horizontal velocity of the center of mass higher than the average, especially in the prop stage, whereas the medium level (ML) and low level (LL) athletes reduced their velocity significantly. The spin angular velocity of the ML and LL skaters was always higher than of the HL. This phenomenon would seem to be a compensatory strategy for a lower jump height, with a reduced trunk-thigh angle and less thigh lever arm (coxo-femur/knee joints) during the take-off and landing phases of the double salchow jump

Normothermic frozen elephant trunk: our experience and literature review

none6Background and Objective: The frozen elephant trunk (FET) technique has undoubtable advantages in treating complex and extensive disease of the aortic arch and the thoracic descending aorta. Despite several improvements in cardiopulmonary bypass conduction and surgical strategy, operative times and the institution of systemic circulatory arrest remain the main determinants of early mortality, cerebral/spinal cord injury and visceral organs dysfunction. We have conducted this review to highlight the recent technical advances in arch and FET surgery aiming at the reduction/avoidance of systemic circulatory arrest, and their impact on early outcomes. Methods: A literature search (from origin to January 2022), limited to publications in English, was performed on online platforms and database (PubMed, Google, ResearchGate). After a further review of associated or similar papers, we found 4 experiences, described by 11 peer-reviewed published papers, which focused on minimising or avoiding systemic circulatory arrest during total arch replacement plus stenting of the descending thoracic aorta. Key Content and Findings: Recent experiences reported the use of an antegrade endoaortic balloon, advanced and inflated into the stent graft, to provide an early systemic reperfusion soon after the deployment of the stented portion of the FET prosthesis and minimize the circulatory arrest time (down to a mean of 5 minutes), thus avoiding the need of moderate or deep hypothermia (mean systemic temperature 28-30 ???) while allowing a complete arch and FET repair. Our approach, based on off-pump retrograde vascular stent graft deployment in distal arch/descending thoracic aorta, and the use of a retrograde endoballoon, allows the repair of extensive aortic pathologies during uninterrupted normothermic cerebral and lower body perfusion. Conclusions: The use of endoballoon occlusion has emerged in recent years as a safe and effective strategy to allow distal perfusion during FET repair. This technique minimizes or avoids the detrimental effects of hypothermia and systemic circulatory arrest and significantly reduces the operative times.Malvindi, PG; Alfonsi, J; Berretta, P; Cefarelli, M; Gatta, E; Di Eusanio, MMalvindi, Pg; Alfonsi, J; Berretta, P; Cefarelli, M; Gatta, E; Di Eusanio,

Mechanical power, thrust power

The purpose of this study was to explore the relationships between mechanical power, thrust power, propelling efficiency and sprint performance in elite swimmers. Mechanical power was measured in 12 elite sprint male swimmers: i) in the laboratory, by using a whole body swimming ergometer (W’TOT); and ii) in the pool, by measuring full tethered swimming force (FT) and maximal swimming velocity (Vmax): W’T = FT .Vmax. Propelling efficiency ( P) was estimated based on the “paddle wheel model“ at Vmax. Vmax was 2.17 ± 0.06 m . s-1, P was 0.39 ± 0.02, W’T was 374 ± 62 W and W’TOT was 941 ± 92 W. Vmax was better related to W’T (useful power output: R=0.943, P<0.001) than to W’TOT (total power output: R=0.744, P<0.01) and this confirms the use of the full tethered test as a valid test to assess power propulsion in sprinters and to estimate swimming performance. The ratio W’T/ W’TOT (0.40 ± 0.04) represents the fraction of total mechanical power that can be utilized in water (e.g. P) and was indeed the same as that estimated based on the “paddle wheel model”; this supports the use of this model to estimate P in swimming

Markerless analysis of front crawl swimming

a b s t r a c t Research on motion analysis of swimmers is commonly based on video recordings of the subject&apos;s motion, which are analyzed by manual digitization of feature points by an operator. This procedure has two main drawbacks: it is time-consuming, and it is affected by low repeatability. Therefore, the application of video-based, automatic approaches to motion analysis was investigated. A video-based, markerless system for the analysis of arm movements during front crawl swimming was developed. The method proposed by was modified in order to be used into water environment. Three dimensional coordinates of shoulder, elbow and wrist joints centers of 5 sprint swimmers performing front crawl swimming were determined. Wrist joint velocity was also calculated. Accuracy and reliability of the proposed technique were evaluated by means of comparison with traditional manual digitization (SIMI Reality Motion Systems GmbH). Root mean square distance (RMSD) values between trajectories estimated with the two techniques were determined. Results show good accuracy for wrist joint (RMSD o 56 mm), and reliability, evaluated on one subject, comparable to the inter-operator variability associated with the manual digitization procedure. The proposed technique is therefore very promising for quantitative, wide-scale studies on swimmers&apos; motion

Experimental validation of specificity of the squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) assay in patients with cirrhosis

Background: Squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) is a useful biomarker for the risk of development of hepatocellular carcinoma (HCC) in patients with cirrhosis due to its progressive increase associated to HCC evolution. In patients with cirrhosis, other assays have been affected by interfering reactivities of IgM. In this study, the analytical specificity of the SCCA-IgM assay was assessed by evaluating SCCA-IgM measurement dependence on different capture phases, and by measuring the recovery of SCCA-IgM reactivity following serum fractionation. Methods: Serum samples from 82 patients with cirrhosis were analyzed. SCCA-IgM was measured using the reference test (Hepa-IC, Xeptagen, Italy) that is based on rabbit oligoclonal anti-squamous cell carcinoma antigen (SCCA) and a dedicated ELISA with a mouse monoclonal anti-SCCA as the capture antibody. Results: SCCA-IgM concentrations measured with the reference assay (median value=87 AU/mL) were higher than those measured with the mouse monoclonal test (median value=78 AU/mL). However, the differences in the SCCA-IgM distribution were not statistically significant (p&#62;0.05). When SCCA-IgM concentrations measured with both tests were compared, a linear correlation was found (r=0.77, p&#60;0.05). Fractionation of the most reactive sera by gel-filtration chromatography showed that total recovery of SCCA-IgM reactivity was seen only in the fractions corresponding to components with a molecular weight higher than IgM and SCCA (&#62;2000 kDa) with both tests. Conclusions: The equivalence of both SCCA-IgM assays and the absence of reactivity not related to immune complexes support the analytical specificity of SCCA-IgM measurements. The results validate the assessment of SCCA-IgM for prognostic purposes in patients with cirrhosis. Clin Chem Lab Med 2010;48:217–23.Peer Reviewe

Transcatheter Aortic Valve Implantation (TAVI) Planning with Dual-Layer Spectral CT Using Virtual Monoenergetic Image (VMI) Reconstructions and 20 mL of Contrast Media

Transcatheter aortic valve implantation (TAVI) is a less invasive alternative to surgical implantation and its implementation is progressively increasing worldwide. We routinely perform pre-procedural aortic angiography CT to assess aortic dimensions and vascular anatomy. This study aims to evaluate the image quality of CTA for TAVI planning using dual-layer spectral CT, with virtual monoenergetic image reconstructions at 40 keV. Thirty-one patients underwent a CTA protocol with the injection of 20 mL of contrast media. Image quality was assessed by measuring the mean density in Hounsfield Units (HU), the signal-to-noise ratio, and the contrast-to-noise ratio in VMI reconstructions. Additionally, a blinded subjective analysis was conducted by two observers. The results showed significant enhancement at all sampled vascular levels with a gradual decrease in HU from proximal to distal regions. Favourable subjective ratings were given for all parameters, with greater variability in the evaluation of iliac axes. A significant negative correlation (p &lt; 0.05) was observed between BMI and CA at all vascular levels, indicating reduced contrast enhancement with increasing BMI. Spectral CT, along with reducing iodine load, allows for obtaining high-quality images without a significant increase in noise. The reduction in iodine load can have positive implications in clinical practice, improving patient safety and resource efficiency

RNA polymerase III drives alternative splicing of the potassium channel–interacting protein contributing to brain complexity and neurodegeneration

An RNA polymerase III–transcribed noncoding RNA promotes alternative splicing of KCNIP4, altering amyloid precursor protein processing and contributing to neurodegeneration