RESUMEN
This study aimed to compare the force (F)-velocity (v)-power (P)-time (t) relationships of female and male world-class sprinters. A total of 100 distance-time curves (50 women and 50 men) were computed from international 100-m finals, to determine the acceleration and deceleration phases of each race: (a) mechanical variables describing the velocity, force, and power output; and (b) F-P-v relationships and associated maximal power output, theoretical force and velocity produced by each athlete (Pmax , F0 , and V0 ). The results showed that the maximal sprint velocity (Vmax ) and mean power output (W/kg) developed over the entire 100 m strongly influenced 100-m performance (r > -0.80; P ≤ 0.001). With the exception of mean force (N/kg) developed during the acceleration phase or during the entire 100 m, all of the mechanicals variables observed over the race were greater in men. Shorter acceleration and longer deceleration in women may explain both their lower Vmax and their greater decrease in velocity, and in turn their lower performance level, which can be explained by their higher V0 and its correlation with performance. This highlights the importance of the capability to keep applying horizontal force to the ground at high velocities.
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Rendimiento Atlético/fisiología , Carrera/fisiología , Aceleración , Fenómenos Biomecánicos , Desaceleración , Femenino , Humanos , MasculinoRESUMEN
This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.
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Ergometría/métodos , Modelos Biológicos , Esfuerzo Físico/fisiología , Carrera/fisiología , Adulto , Fenómenos Biomecánicos , Ergometría/instrumentación , Humanos , Adulto JovenRESUMEN
The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high-level athletes. Four elite (100-m best time 9.95-10.29 s) and five sub-elite (10.40-10.60 s) sprinters performed seven sprints in overground conditions. A single virtual 40-m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (FY), power (PY), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). FY-V, RF-V, and PY-V relationships were well described by significant linear (mean R(2) of 0.892 ± 0.049 and 0.950 ± 0.023) and quadratic (mean R(2) = 0.732 ± 0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world-class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion.
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Aceleración , Rendimiento Atlético/fisiología , Carrera/fisiología , Adulto , Fenómenos Biomecánicos , Prueba de Esfuerzo , Humanos , Cinética , Masculino , Carrera/clasificación , Grabación en Video , Adulto JovenRESUMEN
Research into the biomechanical manifestation of fatigue during exhaustive runs is increasingly popular but additional understanding of the adaptation of the spring-mass behaviour during the course of strenuous, self-paced exercises continues to be a challenge in order to develop optimized training and injury prevention programs. This study investigated continuous changes in running mechanics and spring-mass behaviour during a 5-km run. 12 competitive triathletes performed a 5-km running time trial (mean performance: Ì´17 min 30 s) on a 200 m indoor track. Vertical and anterior-posterior ground reaction forces were measured every 200 m by a 5-m long force platform system, and used to determine spring-mass model characteristics. After a fast start, running velocity progressively decreased (- 11.6%; P<0.001) in the middle part of the race before an end spurt in the final 400-600 m. Stride length (- 7.4%; P<0.001) and frequency (- 4.1%; P=0.001) decreased over the 25 laps, while contact time (+ 8.9%; P<0.001) and total stride duration (+ 4.1%; P<0.001) progressively lengthened. Peak vertical forces (- 2.0%; P<0.01) and leg compression (- 4.3%; P<0.05), but not centre of mass vertical displacement (+ 3.2%; P>0.05), decreased with time. As a result, vertical stiffness decreased (- 6.0%; P<0.001) during the run, whereas leg stiffness changes were not significant (+ 1.3%; P>0.05). Spring-mass behaviour progressively changes during a 5-km time trial towards deteriorated vertical stiffness, which alters impact and force production characteristics.
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Atletas , Rendimiento Atlético/fisiología , Fatiga Muscular/fisiología , Carrera/fisiología , Adolescente , Fenómenos Biomecánicos/fisiología , Humanos , Pierna/fisiología , Masculino , Factores de Tiempo , Adulto JovenRESUMEN
The aim of this study was to test the influence of 3 different horizontal distances between the blocks (bunched, medium and elongated) on the velocity of the centre of mass (VCM) and the kinetic energy (KE) of the body segments and of the whole body. 9 well-trained sprinters performed 4 maximal 10 m sprints. An opto-electronic Motion Analysis® system (12 digital cameras 250 Hz) was used to collect the 3D trajectories of 63 markers during the starting block phase. The results demonstrated that the elongated start, compared to the bunched or medium start, induced an increase of VCM at block clearing (2.89±0.13; 2.76±0.11; 2.84±0.14 m.s - 1) and a decrease of the performance at 5 and 10 m. Both results were explained by a greater pushing time on the blocks in the elongated condition. During the starting block phase, the KE of the whole body was greater in the elongated start (324.3±48.0 J vs. 317.4±57.2 J, bunched and 302.1±53.2 J, medium). This greater KE of the whole body was mainly explained by the KE of the head-trunk segments. Thus, to improve the efficiency of the starting block phase, the athlete must produce greater KE of the head and trunk segments in the shortest time.
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Rendimiento Atlético/fisiología , Movimiento/fisiología , Carrera/fisiología , Adolescente , Atletas , Fenómenos Biomecánicos , Femenino , Humanos , Imagenología Tridimensional , Masculino , Adulto JovenRESUMEN
REASONS FOR PERFORMING STUDY: Arabian horses have morphological, muscular and metabolic features designed for endurance races. Their gas exchange and gait variables were therefore measured during a field exercise test. This study presents original respiratory and locomotor data recorded in endurance horses under field conditions. HYPOTHESIS AND OBJECTIVES: Respiratory gas exchange ratio (RER) of Arabian horses at the speed required to win endurance races (18 km/h for 120-160 km) are <1 and running economy (RE) is also low in order to maintain exercise intensity using aerobic metabolism for long intervals. The purpose of this study was to measure oxygen consumption and gait variables in Arabian endurance horses running in the field in order to estimate RER and RE. MATERIALS AND METHODS: Five Arabian horses trained for endurance racing were test ridden at increasing speeds on the field. Their speed was recorded and controlled by the rider using a GPS logger. Each horse was equipped with a portable respiratory gas analyser, which measured breath-by-breath respiratory variables and heart rate. The gait variables were recorded using tri-axial accelerometer data loggers and software for gait analysis. Descriptive statistics and linear regressions were used to analyse the speed related changes in each variable with P < 0.05 taken as significant. RESULTS: At a canter speed corresponding to endurance race winning speed (18 km/h), horses presented a VO(2) = 42 ± 9 ml/min/kg bwt, RER = 0.96 ± 0.10 and RE (= VO(2) /speed) = 134 ± 27 l/km/kg bwt. Linear relationships were observed between speed and VO(2,) HR and gait variables. Significant correlations were observed between VO(2) and gait variables. CONCLUSIONS AND POTENTIAL RELEVANCE: The RER of 0.96 at winning endurance speed indicates that Arabian horses mainly use aerobic metabolism based on lipid oxidation and that RER may also be related to a good coordination between running speed, respiratory and gait parameters.
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Marcha/fisiología , Caballos/fisiología , Consumo de Oxígeno/fisiología , Condicionamiento Físico Animal/fisiología , Resistencia Física/fisiología , Animales , Frecuencia Cardíaca , Oxígeno/metabolismo , Respiración , DeportesRESUMEN
The aim of this study was to test three different rotation sequences (YXY, ZXY, and XZY) on the shoulder kinematics (rotations of the humerus relative to the thorax) during an original movement such as the tennis flat serve (FS). Nine elite male and female players performed a minimum of five flat serves. An optoelectronic motion analysis system was used to record the movements. Segment kinematics during each FS was reconstructed from the spatial trajectories of the markers according to ISB recommendations. For each rotation sequence, three angles were reported for the shoulder joint, each corresponding to a rotation component around a defined axis. The occurrence of gimbal lock (GL) and angle amplitude coherences were examined. From these three rotation sequences tested, it appears that the XZY sequence was the only decomposition not to suffer from GL. Moreover, the rotation sequence XZY was found to be coherent for all rotation components. Thus, these results show that the best rotation sequence, from both GL and amplitude coherence points of view, is XZY to describe the shoulder kinematics during the tennis serve.
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Rango del Movimiento Articular/fisiología , Articulación del Hombro/fisiología , Tenis/fisiología , Adulto , Brazo/fisiología , Fenómenos Biomecánicos , Femenino , Humanos , Masculino , Hombro/fisiologíaRESUMEN
The aim of the present study was to measure during a sprint start the joint angular velocity and the kinetic energy of the different segments in elite sprinters. This was performed using a 3D kinematic analysis of the whole body. Eight elite sprinters (10.30+/-0.14s 100 m time), equipped with 63 passive reflective markers, realised four maximal 10 m sprints start on an indoor track. An opto-electronic Motion Analysis system consisting of 12 digital cameras (250 Hz) was used to collect the 3D marker trajectories. During the pushing phase on the blocks, the 3D angular velocity vector and its norm were calculated for each joint. The kinetic energy of 16 segments of the lower and upper limbs and of the total body was calculated. The 3D kinematic analysis of the whole body demonstrated that joints such as shoulders, thoracic or hips did not reach their maximal angular velocity with a movement of flexion-extension, but with a combination of flexion-extension, abduction-adduction and internal-external rotation. The maximal kinetic energy of the total body was reached before clearing block (respectively, 537+/-59.3 J vs. 514.9+/-66.0 J; p< or =0.01). These results suggested that a better synchronization between the upper and lower limbs could increase the efficiency of pushing phase on the blocks. Besides, to understand low interindividual variances in the sprint start performance in elite athletes, a 3D complete body kinematic analysis shall be used.
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Transferencia de Energía/fisiología , Articulaciones/fisiología , Modelos Biológicos , Movimiento/fisiología , Esfuerzo Físico/fisiología , Carrera/fisiología , Simulación por Computador , Humanos , Masculino , Rotación , Adulto JovenRESUMEN
Three series of novel 2-benzylthio-4-chloro-5-R1-benzenesulfonamides bearing the N-(benzoxazol-2-yl) (10-19), N-(benzothiazol-2-yl) (20-21) or N-(1,3-dihydro-2H-benzimidazol-2-ylidene) (22-25) moiety were synthesized by reacting N-(2-benzylthio-4-chloro-5-R1-benzenesulfonyl)cyanamide potassium salts (5-9) with 2-aminophenols, 2-aminothiophenol and o-phenylenediamines, respectively. Compounds with carbamoyl substituent at position 5 (14-16, 21 and 25, R1=CONH2) were further dehydrated to the corresponding nitriles (26-30, R1=CN). The in vitro antitumor activity of the compounds obtained was determined at the National Cancer Institute (NCI), and the structure-activity relationships were discussed. N-(2-benzoxazolyl)-2-benzylthio-4-chloro-5-(4-fluorophenylcarbamoyl)benzenesulfonamide (18) is the prominent of the compounds due to its remarkable activity and selectivity toward non-small cell lung cancer (NCI-H522) and melanoma (SK-MEL-2) cell lines (GI50=0.1 microM, TGI=0.5-0.6 microM).
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Antineoplásicos/síntesis química , Antineoplásicos/farmacología , Compuestos de Bencilo/síntesis química , Compuestos de Bencilo/farmacología , Sulfonamidas/síntesis química , Sulfonamidas/farmacología , Antineoplásicos/química , Compuestos de Bencilo/química , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Estructura Molecular , Estereoisomerismo , Relación Estructura-Actividad , Sulfonamidas/químicaRESUMEN
The first purpose of this study was to assess the eventual training adaptations in the time to exhaustion at the same severe velocity occurring after severe interval-training programs in few- and well-trained subjects. In the event of such training adaptations, the second purpose was to identify the discriminant factors of performance improvement according to the initial training status. Seven few- and six well-trained subjects performed: firstly, an incremental test to determine the maximal oxygen consumption (VO2max), the energy cost of running (ECR), the velocity associated with the achievement of VO2max (vVO2max) and the lactate threshold (LT expressed in VO2, km x h(-1), % vVO2max); secondly, an all-out test at the velocity corresponding to the midway between vLT and vVO2max (vdelta50) to determine the time to exhaustion (tmax); such tests were carried out before and after 4- and 8-week severe interval-training programs. In the few-trained subjects, all factors of performance (i.e., VO2max, ECR, vVO2max, LT expressed in VO2, km x h(-1), % vVO2max) and tmax at the pre-training vdelta50 were improved after training (+8, -8, +7, +9, +14, +6% and +79%, respectively); only the increase in vLT was related to the one in tmax (r = 0.714, p < or = 0.05, n = 7). In the well-trained subjects, only vVO2max was improved (+3%) due to the decrease in ECR (-3%), tmax at the pre-training vdelta50 did not vary after training; only the three subjects (over six) who improved their vLT (+0.5, +0.5, +0.8 km x h(-1), respectively) improved their tmax (+10, +24, +101%, respectively) (r = 0.895, p < or = 0.01, n = 6). So, whichever the initial training status, any training-induced adaptation in vLT appeared as a major factor of performance improvement especially at supra-LT velocities.
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Adaptación Fisiológica/fisiología , Ejercicio Físico/fisiología , Ácido Láctico/metabolismo , Educación y Entrenamiento Físico/métodos , Resistencia Física/fisiología , Aptitud Física/fisiología , Carrera/fisiología , Adulto , Humanos , Consumo de Oxígeno/fisiología , Análisis y Desempeño de TareasRESUMEN
PURPOSE: This study tested the hypothesis that free versus constant pace enhanced the performance (i.e., distance run) in suprathreshold runs between 90 and 105% of the velocity associated with the maximal oxygen consumption determined in an incremental test (v.VO(2max)). Moreover, we hypothesized that variable pace could decrease the slow phase of oxygen kinetics by small spontaneous recoveries during the same distance run at an average velocity. METHOD: Eleven long-distance runners performed nine track runs performed until exhaustion. Following an incremental test to determine v.VO(2max), the runners performed, in a random order, four constant-velocity runs at 90, 95, 100, and 105% of v.VO(2max) to determine the time to exhaustion (tlim90, tlim95, tlim100, and tlim105) and the distance limit at 90, 95, 100 and 105% of v.VO(2max) (dlim90, dlim95, dlim100, and dlim105). Finally, they performed the distance limit determined in the constant velocity runs but at variable velocity according to their spontaneous choice. RESULTS: The coefficient of variation of velocity (in percent of the average velocity) was small and not significantly different between the four free pace dlim (4.2 +/- 1.3%, 4.8 +/- 2.4%, 3.6 +/- 1.1%, and 4.6 +/- 1.9% for dlim90, dlim95, dlim100, and dlim105, respectively; P = 0.40). Performances were not improved by a variable pace excepted for the dlim at 105% v.VO(2max) (4.96 +/- 0.6 m.s-1 vs 4.86 +/- 0.5 m.s-1, P = 0.04). Oxygen kinetics and the volume of oxygen consumed were not modified by this (low) variation in velocity. CONCLUSION: These results indicate that for long-distance runners, variable pace modifies neither performance nor the oxygen kinetics in all-out suprathreshold runs.
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Consumo de Oxígeno/fisiología , Educación y Entrenamiento Físico/métodos , Carrera/fisiología , Análisis y Desempeño de Tareas , Adulto , Humanos , Ácido Láctico/sangre , Masculino , Persona de Mediana Edad , Resistencia Física/fisiología , Esfuerzo Físico/fisiología , Distribución Aleatoria , Factores de TiempoRESUMEN
PURPOSE: This study compares the physical and training characteristics of top-class marathon runners (TC), i.e., runners having a personal best of less than 2 h 11 min for males and 2 h 32 min for females, respectively, versus high-level (HL) (< 2 h 16 min and < 2 h 38 min). METHODS: Twenty marathon runners (five TC and HL in each gender) ran 10 km at their best marathon performance velocity (vMarathon) on a level road. This velocity was the target velocity for the Olympic trials they performed 8 wk later. After a rest of 6 min, they ran an all-out 1000-m run to determine the peak oxygen consumption on flat road (.VO(2peak)). RESULTS: Marathon performance time (MPT) was inversely correlated with .VO(2peak). (r = -0.73, P < 0.01) and predicted 59% of the variance of MPT. Moreover, TC male marathon runners were less economical because their energy cost of running (Cr) at marathon velocity was significantly higher than that of their counterparts (212 +/- 17 vs 195 +/- 14 mL.km(-1).kg(-1), P = 0.03). For females, no difference was observed for the energetic characteristics between TC and HL marathon runners. However, the velocity reached during the 1000-m run performed after the 10-km run at vMarathon was highly correlated with MPT (r = -0.85, P < 0.001). Concerning training differences, independent of the gender, TC marathon runners trained for more total kilometers per week and at a higher velocity (velocity over 3000 m and 10,000 m). CONCLUSION: The high energy output seems to be the discriminating factor for top-class male marathon runners who trained at higher relative intensities.
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Educación y Entrenamiento Físico/métodos , Aptitud Física/fisiología , Carrera/fisiología , Análisis y Desempeño de Tareas , Peso Corporal , Metabolismo Energético/fisiología , Femenino , Humanos , Ácido Láctico/sangre , Masculino , Consumo de Oxígeno/fisiología , Factores Sexuales , Factores de TiempoRESUMEN
The main purpose of this study was to investigate the effects of an 8-wk severe interval training program on the parameters of oxygen uptake kinetics, such as the oxygen deficit and the slow component, and their potential consequences on the time until exhaustion in a severe run performed at the same absolute velocity before and after training. Six endurance-trained runners performed, on a 400-m synthetic track, an incremental test and an all-out test, at 93% of the velocity at maximal oxygen consumption, to assess the time until exhaustion. These tests were carried out before and after 8 wk of a severe interval training program, which was composed of two sessions of interval training at 93% of the velocity at maximal oxygen consumption and three recovery sessions of continuous training at 60--70% of the velocity at maximal oxygen consumption per week. Neither the oxygen deficit nor the slow component were correlated with the time until exhaustion (r = -0.300, P = 0.24, n = 18 vs. r = -0.420, P = 0.09, n = 18, respectively). After training, the oxygen deficit significantly decreased (P = 0.02), and the slow component did not change (P = 0.44). Only three subjects greatly improved their time until exhaustion (by 10, 24, and 101%). The changes of oxygen deficit were significantly correlated with the changes of time until exhaustion (r = -0.911, P = 0.01, n = 6). It was concluded that the decrease of oxygen deficit was a potential factor for the increase of time until exhaustion in a severe run performed after a specific endurance-training program.
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Consumo de Oxígeno/fisiología , Resistencia Física/fisiología , Carrera/fisiología , Adulto , Aerobiosis , Análisis de Varianza , Humanos , Lactatos/sangre , Matemática , Modelos Biológicos , Fatiga Muscular , Reproducibilidad de los Resultados , Pruebas de Función Respiratoria , Factores de TiempoRESUMEN
The aim of this study was to determine the effect of endurance training on the relationship between mechanical stride descriptors (stride rate and stride rate variability) and the aerobic energy cost that would be decreased by training in an all-out supra-lactate threshold run. Six long distance runners (175 +/- 6 cm; 72 +/- 9 kg; 27 +/- 4 years) performed two identical track tests before and after 8 weeks of supra-lactate threshold training: an incremental test and a constant load test at 50% of the velocity difference between the lactate threshold and *VO2max (vdelta50). During the constant load test, aerobic energy cost (EC), stride rate (SR) and stride rate variability (SRV) were measured. The constant load tests were carried out before and after training at the same absolute intensity, in order to compare stride mechanical descriptors. Our results show that after eight weeks of intermittent running at vdelta50, the velocity associated with *VO2max (v *V02max) increases (p = 0.03) due to the decrease of running economy (RE, p = 0.02), and not due to an increase in *VO2max (p = 0.5). EC remained unchanged with training (p > 0.1), but SRV was significantly reduced (p < 0.03). No relationship was observed before and after training between the stride rate variability and the aerobic energetic cost (rs < 0.5; p > 0.05). This study indicates that because of the initial level of the runners, endurance training has not induced an increased *VO2max but a decrease of the SRV. Further studies have to be conducted with more subjects in order to elucidate the mechanisms underlying this decrease in SRV which is observed with training.
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Metabolismo Energético/fisiología , Ácido Láctico/metabolismo , Resistencia Física/fisiología , Carrera/fisiología , Adulto , Ejercicio Físico/fisiología , Humanos , Consumo de Oxígeno , Factores de TiempoRESUMEN
BACKGROUND: The purpose of this study was to examine the influence of prior intermittent running at VO2max on oxygen kinetics during a continuous severe intensity run and the time spent at VO2max. METHODS: Eight long-distance runners performed three maximal tests on a synthetic track (400 m) whilst breathing through the COSMED K4 portable telemetric metabolic analyser: i) an incremental test which determined velocity at the lactate threshold (vLT), VO2max and velocity associated with VO2max (vVO2max), ii) a continuous severe intensity run at vLT+50% (vdelta50) of the difference between vLT and vVO2max (91.3+/-1.6% VO2max)preceded by a light continuous 20 minute run at 50% of vVO2max (light warm-up), iii) the same continuous severe intensity run at vdelta50 with a prior interval training exercise (hard warm-up) of repeated hard running bouts performed at 100% of vVO2max and light running at 50% of vVO2max (of 30 seconds each) performed until exhaustion (on average 19+/-5 min with 19+/-5 interval repetitions). This hard warm-up speeded the VO2 kinetics: the time constant was reduced by 45% (28+/-7 sec vs 51+/-37 sec) and the slow component of VO2 (deltaVO2 6-3 min) was deleted (-143+/-271 ml x min(-1) vs 291+/-153 ml x min(-1)). In conclusion, despite a significantly lower total run time at vdelta50 (6 min 19+/-0) min 17 vs 8 min 20+/-1 min 45, p=0.02) after the intermittent warm-up at VO2max, the time spent specifically at VO2max in the severe continuous run at vdelta50 was not significantly different.
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Consumo de Oxígeno/fisiología , Carrera/fisiología , Adulto , Algoritmos , Umbral Anaerobio/fisiología , Prueba de Esfuerzo , Tolerancia al Ejercicio/fisiología , Frecuencia Cardíaca/fisiología , Humanos , Lactatos/sangre , Masculino , Oxígeno/sangre , Resistencia Física/fisiología , Estadísticas no Paramétricas , Telemetría/instrumentación , Factores de TiempoRESUMEN
Aggressive non-Hodgkin's lymphona include diffuse large B-cell lymphoma, anaplastic large cell lymphona, and different peripheral T-cell lymphomas. An international prognostic index has been developed including age, serum LDH, performance status, and extranodal involvement. For localized aggressive lymphoma, the preferred treatment is 3-4 CHOP and radiation therapy, with a cure rate of 70-80%. For disseminated aggressive lymphoma, current regimens have a cure rate of less than 40%. Innovative strategies, including dose escalation, autologus stem cell support, new drugs, and immunotherapy are being explored to improve these results.
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Linfoma no Hodgkin/terapia , Adulto , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Terapia Combinada , Trasplante de Células Madre Hematopoyéticas , Humanos , Linfoma no Hodgkin/patología , Linfoma no Hodgkin/fisiopatología , Terapia RecuperativaRESUMEN
Interval training consisting of brief high intensity repetitive runs (30 s) alternating with periods of complete rest (30 s) has been reported to be efficient in improving maximal oxygen uptake (VO2max) and to be tolerated well even by untrained persons. However, these studies have not investigated the effects of the time spent at VO2max which could be an indicator of the benefit of training. It has been reported that periods of continuous running at a velocity intermediate between that of the lactate threshold (vLT) and that associated with VO2max (vVO2max) can allow subjects to reach VO2max due to an additional slow component of oxygen uptake. Therefore, the purpose of this study was to compare the times spent at VO2max during an interval training programme and during continuous strenuous runs. Eight long-distance runners took part in three maximal tests on a synthetic track (400 m) whilst breathing through a portable, telemetric metabolic analyser: they comprised firstly, an incremental test which determined vLT, VO2max [59.8 (SD 5.4) ml.min-1; kg-1], vVO2max [18.5 (SD 1.2) km.h-1], secondly, an interval training protocol consisting of alternately running at 100% and at 50% of vVO2max (30 s each); and thirdly, a continuous high intensity run at vLT + 50% of the difference between vLT and vVO2max [i.e. v delta 50: 16.9 (SD 1.00) km.h-1 and 91.3 (SD 1.6)% vVO2max]. The first and third tests were performed in random order and at 2-day intervals. In each case the subjects warmed-up for 15 min at 50% of vVO2max. The results showed that in more than half of the cases the v delta 50 run allowed the subjects to reach VO2max, but the time spent specifically at VO2max was much less than that during the alternating low/high intensity exercise protocol [2 min 42 s (SD 3 min 09 s) for v delta 50 run vs 7 min 51 s (SD 6 min 38 s) in 19 (SD 5) interval runs]. The blood lactate responses were less pronounced in the interval runs than for the v delta 50 runs, but not significantly so [6.8 (SD 2.2) mmol.l-1 vs 7.5 (SD 2.1) mmol.l-1]. These results do not allow us to speculate as to the chronic effects of these two types of training at VO2max.
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Consumo de Oxígeno , Carrera/fisiología , Adulto , Ejercicio Físico/fisiología , Humanos , Cinética , Ácido Láctico/sangre , Masculino , Factores de TiempoRESUMEN
Syntheses of N-(2-dialkylaminoethyl)-(5-chloro-4-methyl-2-[(4-butyl or isobutyl -4H-1,2,4-triazol-3-yl)aminosulfonyl]phenylthio) alkanecarboxyamides [VII-X] and hydrochlorides [VIIa-Xa, XI-XIII] are described. Results of preliminary pharmacological examination such as acute toxicity and influence on the circulatory system of compounds [VIIa, IXa, Xa, XIII, XIV] are presented. The antiarrhythmic effect of the most active [IXa] was comparable to the reference procainamide.
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Antiarrítmicos/síntesis química , Sulfonamidas/síntesis química , Triazoles/síntesis química , Alquilación , Animales , Antiarrítmicos/farmacología , Evaluación Preclínica de Medicamentos , Ratones , Ratas , Relación Estructura-Actividad , Sulfonamidas/farmacología , Triazoles/farmacologíaRESUMEN
ATP level, cell motility and viability, oxygen uptake, pyruvate kinase activity, and ultra-weak photon emission (UPE) induced by red-ox Fe(2+)-ascorbate cycling system were studied in fresh, in previously equilibrated in a glycerol diluent, and in cryopreserved bull spermatozoa, exposed to thermal stress by incubation of the cells at 44 degrees C. A sharp drop in motility and viability of fresh spermatozoa and even more so, of equilibrated and cryopreserved cells was accompanied by accumulation of ATP. When cell movement was totally inhibited, ATP utilization was decreased, while chemical energy continued to be produced by cell pyruvate kinase, one of the key glycolytic enzymes, which in spermatozoa is very active (6500 IU/g protein) and insensitive to feed-back inhibition by excess of ATP and L-cysteine. Accumulation of ATP during incubation at 44 degrees C in 0.9% NaCl was accompanied by rapid decrease in oxygen consumption by fresh spermatozoa and an increase in Fe(2+)-ascorbate induced UPE, followed by a sharp decrease in ATP level observed at the end of induced UPE measurement. The increase in photon emission due to lipid peroxidation was highly correlated with the increase in cell ATP level caused by thermal stress.