Swimmers' Effective Actions during the Backstroke Start Technique.

The analysis of the external forces of swimming starts has revealed how swimmers propel themselves out of the block, but data should be properly interpreted to fully understand force-generation mechanisms. This study aimed to assess horizontal and vertical forces in the backstroke start based on swimmers' structural and propulsive actions. Firstly, a simulated structural force was estimated by two transient backstroke-start inter-segmental realistic body positions: a maximally tucked position and an extended one (just before the hands-off and the take-off, respectively). Secondly, 10 competitive backstroke swimmers performed four 15 m maximal backstroke starts with the external forces estimated. Thirdly, the simulated structural force was subtracted from raw horizontal and vertical force data, measured between hands-off and take-off instants, resulting in the propulsive forces. The application of the algorithm has evidenced that backstrokers' horizontal and vertical simulated-structural-force components contributed to ~40% of total force during start propulsion (~0.2-0.12 s before the take-off), followed by the propulsive horizontal force increment and a progressive vertical component reduction (~0.05 s) with ~20° take-off angle. Based on these findings, researchers and coaches can better guide swimmers as to the proper mechanical strategies to achieve effectiveness in the backstroke start, and to improve direct transfer of resistance training programs.

Biomechanical Features of Backstroke to Breaststroke Transition Techniques in Age-Group Swimmers.

This study aimed to identify the biomechanical features of backstroke to breaststroke transition techniques (open, somersault, bucket, and crossover) in age-group swimmers. Eighteen preadolescent swimmers (12.2 ± 0.4 years old and 3-4 Tanner stages) underwent 4 weeks of systematic contextual interference training, comprising 16 sessions (40 min·session-1). Soon after, experimental testing was conducted where swimmers randomly performed 12 × 15 m maximal turns (composed of 7.5 m turn-in and 7.5 m turn-out of the wall segments), three in each transition technique. Kinematical, kinetic, and hydrodynamic variables were assessed with a dual-media motion capture system (12 land and 11 underwater cameras), triaxial underwater force plates, and inverse dynamics. Variables were grouped in turn-in (approach and rotation) and turn-out (wall contact, gliding, and pull-out) phases, with factor analysis used to select the variables entering on multiple regressions. For the turn-in phase, 86, 77, 89, and 87% of the variance for open, somersault, bucket, and crossover turning techniques, respectively, was accounted by the 7.5 and 2.5 m times, mean stroke length, and rotation time. For the turn-out phase, first gliding distance and time, second gliding depth, turn-out time, and dominating peak_Z push-off force accounted for 93% in open turn, while wall contact time, first gliding distance, breakout distance and time, turn-out time, dominating peak_Y push-off force, and second gliding drag coefficient accounted for 92% in a somersault turn. The foot plant index, push-off velocity, second gliding distance, and turn-out time accounted for 92% in bucket turn while breakout and turn-out time, non-dominating peak_Y and peak_Z push-off force, first and second gliding drag force and second gliding drag coefficient accounted for 90% in crossover turn, respectively. The findings in this study were novel and provided relevant biomechanical contribution, focusing on the key kinematic-temporal determinant during turn-in, rotation, and push-off efficacy, and the kinetic and hydrodynamic during turn-out, which would lead to improved backstroke to breaststroke transition techniques in 11-13 years-old age-group swimmers.

Eccentric flywheel post-activation potentiation influences swimming start performance kinetics.

This study aimed to assess the effects of post-activation potentiation in the strength related variables of a kick start. Thirteen competitive swimmers performed three kick starts after a standardized warm up (denoted USUAL) and another after inducing post-activation through five isotonic repetitions on an eccentric flywheel (denoted PAP). A T-test was used to quantify differences between USUAL and PAP warm up. The best trial of each subject achieved by natural conditions (denoted PEAK) was compared with data obtained after PAP. An instrumented starting block with independent triaxial force plates, collected the strength variables related with the impulse at take off. Improvements in the vertical components of force were observed after PAP compared with USUAL, meanwhile no differences were detected on the horizontal components of it. The velocity at take off was higher after PAP compared with USUAL (4.32 ± 0.88 vs 3.93 ± 0.60 m*s-1; p = 0.02). No differences in force or velocity were detected comparing PAP with PEAK (4.13 ± 0.62 m*s-1, p = 0.11). The PAP warm-up increased vertical force and it was transferred to a higher resultant velocity at take-off. This improvement would equal the best result possible obtained in natural conditions after some trials.

Explosive lower limb extension mechanics: An on-land vs. in-water exploratory comparison.

During a horizontal underwater push-off, performance is strongly limited by the presence of water, inducing resistances due to its dense and viscous nature. At the same time, aquatic environments offer a support to the swimmer with the hydrostatic buoyancy counteracting the effects of gravity. Squat jump is a vertical terrestrial push-off with a maximal lower limb extension limited by the gravity force, which attracts the body to the ground. Following this observation, we characterized the effects of environment (water vs. air) on the mechanical characteristics of the leg push-off. Underwater horizontal wall push-off and vertical on-land squat jumps of two local swimmers were evaluated with force plates, synchronized with a lateral camera. To better understand the resistances of the aquatic movement, a quasi-steady Computational Fluid Dynamics (CFD) analysis was performed. The force-, velocity- and power-time curves presented similarities in both environments corresponding to a proximo-distal joints organization. In water, swimmers developed a three-step explosive rise of force, which the first one mainly related to the initiation of body movement. Drag increase, which was observed from the beginning to the end of the push-off, related to the continuous increase of body velocity with high values of drag coefficient (CD) and frontal areas before take-off. Specifically, with velocity, frontal area was the main drag component to explain inter-individual differences, suggesting that the streamlined position of the lower limbs is decisive to perform an efficient push-off. This study motivates future CFD simulations under more ecological, unsteady conditions.

The effect of different foot and hand set-up positions on backstroke start performance.

Foot and hand set-up position effects were analysed on backstroke start performance. Ten swimmers randomly completed 27 starts grouped in trials (n = 3) of each variation, changing foot (totally immersed, partially and totally emerged) and hand (lowest, highest horizontal and vertical) positioning. Fifteen cameras recorded kinematics, and four force plates collected hands and feet kinetics. Standardised mean difference and 95% confidence intervals were used. Variations with feet immersed have shown lower vertical centre of mass (CM) set-up position (0.16 m), vertical impulse exerted at the hands, horizontal and vertical impulse exerted at the feet (0.28, 0.41, 0.16 N/BW.s, respectively) than feet emerged with hands horizontal and vertically positioned. Most variations with feet partially emerged exhibited higher and lesser vertical impulse exerted at hands than feet immersed and emerged (e.g. vertical handgrip, 0.13, 0.15 N/BW.s, respectively). Variation with feet emerged and hands on the lowest horizontal handgrip depicted shorter horizontal (0.23, 0.26 m) and vertical CM positioning at flight (0.16, 0.15 m) than the highest horizontal and vertical handgrip, respectively. Start variations have not affected 15-m time. Variations with feet partially or totally emerged depicted advantages, but focusing on the entry and underwater biomechanics is relevant for a shorter start time.

Effective Swimmer's Action during the Grab Start Technique.

The external forces applied in swimming starts have been often studied, but using direct analysis and simple interpretation data processes. This study aimed to develop a tool for vertical and horizontal force assessment based on the swimmers' propulsive and structural forces (passive forces due to dead weight) applied during the block phase. Four methodological pathways were followed: the experimented fall of a rigid body, the swimmers' inertia effect, the development of a mathematical model to describe the outcome of the rigid body fall and its generalization to include the effects of the inertia, and the experimental swimmers' starting protocol analysed with the inclusion of the developed mathematical tool. The first three methodological steps resulted in the description and computation of the passive force components. At the fourth step, six well-trained swimmers performed three 15 m maximal grab start trials and three-dimensional (3D) kinetic data were obtained using a six degrees of freedom force plate. The passive force contribution to the start performance obtained from the model was subtracted from the experimental force due to the swimmers resulting in the swimmers' active forces. As expected, the swimmers' vertical and horizontal active forces accounted for the maximum variability contribution of the experimental forces. It was found that the active force profile for the vertical and horizontal components resembled one another. These findings should be considered in clarifying the active swimmers' force variability and the respective geometrical profile as indicators to redefine steering strategies.

Domino versus deceased donor liver transplantation: association with early graft function and perioperative bleeding.

This study sought to evaluate the potential impact of domino liver transplantation (DLT) on initial graft function and early postoperative outcome in patients with cirrhosis in a Portuguese liver transplantation center. A retrospective comparative analysis was performed between 77 domino recipients (from familial amyloidotic polyneuropathy donors) and 91 deceased donor recipients, all submitted to primary elective whole liver transplantation, using the piggyback technique, in a 42-month period. Outcome parameters included graft dysfunction (defined as either primary nonfunction or initial poor function, according to the Ploeg-Maring criteria) and Clavien II-IV complications in the first postoperative week. Domino and deceased donor recipients had similar preoperative severity indices (Child-Pugh classification and Model for End-Stage Liver Disease score) and immediate postoperative severity scores (APACHE II [Acute Physiology and Chronic Health Evaluation II] and SAPS II [Simplified Acute Physiology Score II]). In DLT, donors were younger, cold ischemia time was shorter, and intraoperative transfusion requirements of packed red blood cells and fresh-frozen plasma were significantly lower. Graft dysfunction incidence was 3.4-fold lower in DLT: 5.2% (only 4 cases of initial poor function) versus 18.0% (1 primary nonfunction and 15 cases of initial poor function), P = 0.010. Postoperative bleeding was the most frequent early Clavien II-IV complication (n = 29, 17.3%), with an incidence 2.2-fold lower in domino recipients. A statistically significant difference was not found in the other analyzed Clavien II-IV complications, intensive care unit stay, mechanical ventilation time, intensive care unit mortality, and 1-year survival rate. In conclusion, in this study the younger donors and shorter ischemic time associated with DLT may provide a protective role in regards to graft dysfunction and perioperative bleeding, which are 2 important determinants of early morbidity after liver transplantation.

Acute myocardial infarction associated with anomalous origin of coronary arteries (a rare case of origin of the left coronary artery from the ostium of the right coronary artery).

Origin of the left coronary artery from the ostium or proximal segment of the right coronary artery (single coronary artery) is a rare congenital anomaly (0.03 to 0.4%) and an unusual angiographic finding (0.6 to 1.3%). The most common congenital anomaly is separate origin of the left anterior descending artery and circumflex artery from the left coronary sinus. The second most common anomaly is the origin of the circumflex artery from the right coronary sinus. We present a patient with acute inferior myocardial infarction and cardiogenic shock, in whom it was not possible to perform catheterization of the left coronary artery because of the absence of the ostium of the left coronary sinus. Multislice computed tomography of the coronary arteries was the tool that enabled us to visualize the origin and course of the left coronary artery.

Impact of RIFLE classification in liver transplantation.

Acute renal failure (ARF) is common after orthotopic liver transplantation (OLT). The aim of this study was to evaluate the prognostic value of RIFLE classification in the development of CKD, hemodialysis requirement, and mortality. Patients were categorized as risk (R), injury (I) or failure (F) according to renal function at day 1, 7 and 21. Final renal function was classified according to K/DIGO guidelines. We studied 708 OLT recipients, transplanted between September 1992 and March 2007; mean age 44 +/- 12.6 yr, mean follow-up 3.6 yr (28.8% > or = 5 yr). Renal dysfunction before OLT was known in 21.6%. According to the RIFLE classification, ARF occurred in 33.2%: 16.8% were R class, 8.5% I class and 7.9% F class. CKD developed in 45.6%, with stages 4 or 5d in 11.3%. Mortality for R, I and F classes were, respectively, 10.9%, 13.3% and 39.3%. Severity of ARF correlated with development of CKD: stage 3 was associated with all classes of ARF, stages 4 and 5d only with severe ARF. Hemodialysis requirement (23%) and mortality were only correlated with the most severe form of ARF (F class). In conclusion, RIFLE classification is a useful tool to stratify the severity of early ARF providing a prognostic indicator for the risk of CKD occurrence and death.

High incidence of thrombotic complications early after liver transplantation for familial amyloidotic polyneuropathy.

Early thrombotic complications are critical causes of in-hospital morbidity after orthotopic liver transplantation (OLT), potentially culminating in graft loss. The aim of this study was to retrospectively analyse these complications, trying to identify associated independent risk factors. This retrospective analysis included 223 OLTs performed on 213 patients, in a 30-month period. Eighty-six OLTs were performed on familial amyloidotic polyneuropathy (FAP) patients. Preoperative details (primary diagnosis and Child-Turcotte-Pugh classification, when applicable), surgical features (including type of arterial reconstruction), postoperative variables and outcome were analysed. The observation period ended 30 days post-OLT, until discharge or in-hospital death. Early thrombotic complications were diagnosed in 16 cases (7.2%), affecting mainly FAP patients (n = 12). Hepatic artery thrombosis (HAT) was the most frequent early thrombotic event (n = 12): incidence in FAP patients 11.6% (n = 10) versus incidence in non FAP patients 1.5% (n = 2), P = 0.001. By logistic regression analysis, FAP turned out to be an independent risk factor for early thrombotic complications, and specifically for HAT. The type of arterial reconstruction and other analysed surgical and medical factors did not influence early HAT occurrence. In conclusion, FAP was identified in this study as an independent risk factor for early HAT, a new datum not yet described in the literature.

Cardiac tamponade secondary to methicillin-resistant Staphylococcus aureus pericarditis.

Since the advent of antibiotics, bacterial pericarditis has become relatively rare. Cardiac tamponade is a potentially lethal complication, especially when caused by methicillin-resistant Staphylococcus aureus (MRSA). In the intensive care setting other predisposing factors for purulent pericarditis, besides immunosuppression, are the high incidence of nasal and skin colonization and invasive techniques such as indwelling catheters. We present two case reports of cardiac tamponade in young patients, with underlying immunosuppression of different etiologies (HIV infection and liver transplantation). In both, clinical evolution was complicated by severe sepsis, with MRSA being isolated in various biological products, followed by bacterial pericarditis and tamponade. The authors highlight the need for a high degree of suspicion for the diagnosis of bacterial pericarditis in immunosuppressed patients, an ever-growing population, as well as the importance of echocardiographic monitoring during clinical evolution.

[Pneumocystis and cytomegalovirus pneumonia in HIV patients - two clinical cases]. / Pneumonia por Pneumocystis e citomegalovírus no doente VIH - A propósito de dois casos clínicos.

Cytomegalovirus is capable of causing disease in immunocompromised patients. In people infected by the Human Immunodeficiency Virus (HIV) it becomes an important agent when there is advanced immunosupression. Its role as a pulmonary pathogen in these patients has been questioned. In the case of pneumocystosis the presence of Cytomegalovirus doesn't seem to worsen prognosis, except in cases where corticosteroids are used. Authors present two cases of patients with HIV infection and advanced immunosupression who were admitted in the intensive care unit for respiratory failure. In both Pneumocystis jirovecii was isolated from.

Small coronary arteries treated with sirolimus-eluting stents: one-year results of the PORTO multicentre registry.

AIMS: To assess the effectiveness and safety of sirolimus-eluting stents (SES) in de novo native coronary lesions in small vessels (/= 23 mm).The mean (SD) reference vessel diameter of the treated segment was 2.08 (0.33) mm and lesion length 11.04 (6.0) mm. After six months, LL was 0.07 (0.37) mm. BR was 5.1% in-stent and 9.1% in-segment. At one year, TLR was 5.6% and TVR was 9.0%. MACE rate was 2.6% at six months and 8.6% at one year with 2.3% cardiac death and 1.5% non-fatal myocardial infarction. Stent thrombosis rate at one year was 0.8% per protocol. There were more MACE in diabetic patients (12.8%) than in non-diabetic (5.4%, p=0.046), but no other significant differences in clinical and angiographic parameters were noted between the subgroups analysed. CONCLUSIONS: The use of SES for lesions in very small coronary arteries proved to be safe and efficacious, irrespective of the size and length of the stents, with low restenosis and repeat revascularisation rates at one year.

Avaliaçäo do desempenho ventricular no infarto agudo do miocárdio: I. Consideraçöes gerais / Evaluation of ventricular performance in acute myocardial infarction: I. General considerations

A disfunçäo do ventrículo esquerdo (VE) constitui a principal causa de morte dos doentes com infarto agudo do miocárdio (IAM) que säo internados em Unidades de Tratamento Intensivo de Coronários. Deste modo, compreende-se que a avaliaçäo do desempenho do VE tenha uma importância relevante na escolha da terapêutica a instituir, na apreciaçäo de sua eficácia e no prognóstico dos doentes com IAM. Na primeira seçäo deste Simpósio, analisa-se a fisiopatologia da disfunçäo do VE no IAM; na segunda, referem-se diversos indicadores clínicos do desempenho ventricular no IAM, nomeadamente as classes de Killip e o índice de Norris; na terceira, baseado num estudo efetuado em 250 doentes, valoriza-se a contribuiçäo do exame hemodinâmico com o cateter de Swan-Ganz para a avaliaçäo da funçäo cardíaca e para o prognóstico dos doentes com IAM; na quarta, decrevem-se os critérios hemodinâmicos que permitem o diagnóstico de infarto do ventrículo direito; na quinta, fundamentado num estudo que abrangeu 107 doentes, referem-se diversos índices fonomecanocardiográficos do desempenho do VE no IAM, designadamente: amplitude da onda a e morfologia do apexocardiograma; intervalos de tempo sistólico e diastólicos