The relationship between lower limb stiffness and running economy in child soccer players / La relación entre la rigidez de los miembros inferiores y la economía de carrera en jugadores de fútbol infantil / A relação entre rigidez dos membros inferiores e economia de corrida em jogadores de futebol infantil

ABSTRACT Introduction Lower limb stiffness has been shown to be associated with running economy (RE) in adults, but this relationship in children remains unclear. Objectives The purpose of this study was to investigate the relationship between lower limb stiffness, RE, and repeated-sprint ability in child soccer players. Methods Twenty-eight male child soccer players (mean age 11.8 ± 0.9 years) participated in the study. RE was determined by measuring the steady-state oxygen uptake (ml/min/kg) at submaximal running speeds of 8 and 9 km/h. Vertical and leg stiffness were calculated from the flight and contact time data obtained during two submaximal running tests. Additionally, vertical stiffness was measured during the maximal and submaximal hopping tests. All participants performed the repeated sprint test consisting of 10 × 20-m all-out sprints interspersed with 20-s active recovery. Results During both submaximal running tests, vertical (r= -0.505 to -0.472) and leg stiffness (r= -0.484 to -0.459) were significantly correlated with RE (p< 0.05). Maximal (r= -0.450) and submaximal hopping stiffness (r= -0.404) were significantly correlated with RE at 8 km/h (p< 0.05). Maximal hopping stiffness was significantly correlated with the best sprint time (r= -0.439) and mean sprint time (r= -0.496) (p< 0.05). Vertical (r= -0.592 to -0.433) and leg stiffness (r= -0.612 to -0.429) at 8 and 9 km/h and submaximal hopping stiffness (r= -0.394) were significantly correlated with the fatigue index (p< 0.05). Conclusions Current findings indicate that the lower limb stiffness may be an important determinant of both RE and repeated-sprint ability in child soccer players. Level of Evidence II; Diagnostic Studies - Investigating a Diagnostic Test.

RESUMEN Introducción Se ha demostrado que la rigidez de los miembros inferiores está relacionada con la economía de carrera (RE) en los adultos, sin embargo esta relación no es muy clara cuando se trata de niños. Objetivos El objetivo de este estudio fue investigar la relación entre la rigidez de los miembros inferiores, la RE y la capacidad de sprints repetidos en jugadores de fútbol infantil. Métodos Veintiocho jugadores de fútbol infantil de sexo masculino (edad media de 11,8 ± 0,9 años) participaron en el estudio. La determinación de la RE se produjo midiendo el consumo de oxígeno en estado estacionario (ml/min/kg) a velocidades de carrera submáximas de 8 km/h y 9 km/h. El cálculo de la rigidez vertical y de la rigidez de las piernas se basó en los datos de tiempo de vuelo y de contacto obtenidos durante dos tests submáximos de carrera. Además, se midió la rigidez vertical durante los tests submáximos y máximos de salto (hop test). Todos los participantes realizaron el test de sprints repetidos, que consistía en diez repeticiones de sprints a velocidad máxima de 20 m intercalados por una recuperación activa de 20 s. Resultados Durante ambos tests submáximos de carrera, la rigidez vertical (r= -0,505 a -0,472) y la rigidez de las piernas (r= -0,484 a -0,459) se correlacionaron significativamente con la RE (p<0,05). La rigidez de salto máximo (r= -0,450) y la rigidez de salto submáximo (r= -0,404) demostraron una correlación significativa con la RE a 8 km/h (p<0,05). La rigidez de salto máximo se asoció sustancialmente con un mejor tiempo de sprint (r= -0,439) y con el tiempo medio de sprint (r= -0,496) (p< 0,05). La rigidez vertical (r= -0,592 a -0,433), la rigidez de las piernas (r= -0,612 a -0,429) a 8 km/h y 9 km/h y la rigidez de salto submáximo (r= -0,394) se correlacionaron significativamente con el índice de fatiga (p< 0,05). Conclusiones Los hallazgos actuales indican que la rigidez de los miembros inferiores puede ser un determinante clave tanto de RE como de la capacidad de sprints repetidos en jugadores de fútbol infantil. Nivel de evidencia II: Estudios diagnósticos - Investigación de una prueba diagnóstica.

RESUMO Introdução A rigidez dos membros inferiores demonstrou estar associada à economia de corrida (RE) em adultos, porém essa relação não é muito clara quando se trata de crianças. Objetivos O objetivo deste estudo foi investigar a relação entre a rigidez dos membros inferiores, a RE e a capacidade de sprints repetidos em jogadores de futebol infantil. Métodos Vinte e oito jogadores do sexo masculino de futebol infantil (idade média de 11,8 ± 0,9 anos) participaram do estudo. A determinação da RE ocorreu por meio da medição do consumo de oxigênio em estado estacionário (ml/min/kg) a velocidades submáximas de corrida de 8 km/h e 9 km/h. O cálculo da rigidez vertical e da rigidez das pernas baseou-se nos dados de tempo de voo e tempo de contato obtidos durante dois testes submáximos de corrida. Além disso, mediu-se a rigidez vertical durante os testes máximo e submáximo de salto ( hop test ). Todos os participantes realizaram o teste de sprints repetidos que consistiu em dez repetições de sprints em velocidade máxima de 20 m intercalados por recuperação ativa de 20 s. Resultados Durante ambos os testes submáximos de corrida, a rigidez vertical (r= -0,505 a -0,472) e a rigidez das pernas (r= -0,484 a -0,459) estavam significativamente correlacionadas à RE (p<0,05). A rigidez de salto máximo (r= -0,450) e a de salto submáximo (r= -0,404) demonstraram uma correlação significativa com RE em 8 km/h (p<0,05). A rigidez de salto máximo estava associada, de forma substancial, ao melhor tempo de sprint (r= -0,439) e ao tempo médio de sprint (r= -0,496) (p< 0,05). A rigidez vertical (r= -0,592 a -0,433), a rigidez das pernas (r= -0,612 a -0,429) em 8 km/h e 9 km/h e a rigidez de salto submáximo (r= -0,394) estavam expressivamente correlacionadas ao índice de fadiga (p< 0,05). Conclusões Os achados atuais indicam que a rigidez dos membros inferiores pode ser um determinante fundamental tanto de RE quanto de capacidade de sprints repetidos em jogadores de futebol infantil. Nível de evidência II: Estudos diagnósticos - Investigando um teste diagnóstico.

The relationship between cardiac damage biomarkers and heart rate variability following 60 min of running.

PURPOSE: Endurance exercise may cause transient alterations in cardiac tissue. The number of studies evaluating the relationship between changes in heart rate variability (HRV) and cardiac biomarkers following an endurance event is limited. We hypothesized that there would be a time-dependent correlation between biomarkers of cardiac damage and the reduction in parasympathetic indices of HRV within 24 h after 60 min of running in middle-aged recreational runners. METHODS: The trained, middle-aged runners who participated in this study ran 60 min at a half-marathon pace on a treadmill. Blood samples (before and 0, 4, and 24 h after the running test) and HRV data (before and 0, 1, 4, and 24 h after the running test) were obtained. RESULTS: After running, cardiac biomarkers (total creatine kinase, cardiac isoform of creatine kinase, creatine kinase-index [CK-Index], cardiac troponin [cTnI]) increased significantly, and HRV measures related to parasympathetic nervous system activity decreased significantly; these measures returned to baseline levels within 24 h. Finally, there were significant correlations (all p < 0.05) between the change (4 h post-running vs. pre-running) in the CK-Index and the changes (post- vs pre-running) in time-domain and nonlinear measures of HRV (r - 0.61 to - 0.67). In addition, significant correlations (all p < 0.05) were found between the area under the cTnI curve and change (1-h post- and pre-running) in time-domain and nonlinear measures of HRV (r - 0.48 to - 0.51). CONCLUSIONS: The correlation between HRV and cardiac biomarkers indicates that HRV analysis may be an alternative approach to determine the magnitude of cardiac stress after endurance exercises.

Effect of Regular Aerobic Training on Serum C-Reactive Protein and IL-6 Levels in Obese Women.

OBJECTIVE: This study's objective was to evaluate interleukin-6 (IL-6) and C-reactive protein (CRP) responses and performance changes in obese women after 8 weeks of aerobic training with an intensity of 50 to 60% of their individual maximum oxygen uptake (VO2). METHODS: A total of 18 sedentary women with an average age of 44.3 (± 1.9) years volunteered for this study. Over a period of 8 weeks, in 4 40-minute sessions per week, the participants walked at an exercise intensity that caused their heart rates to increase to levels corresponding to 50 to 60% of their VO2 peaks. Blood samples were collected from the participants, both when they were at rest and a couple of minutes after the end of the 1st exercise session. Sampling was repeated in the 4th and 8th weeks, before and after the last training sessions. RESULTS: The participants' body mass indices and weights decreased significantly by the end of the 8th week, while their maximum running speeds and VO2 peaks increased significantly. There were no differences in CRP or IL- 6 concentrations between the pre- and post-training sessions, but most of the participants' IL-6 levels dropped below 10 pg/ml after 8 weeks of training. CONCLUSION: Although no significant changes were observed in CRP or IL-6 concentrations, it is important to note that in response to aerobic training, the IL-6 levels of most of the participants fell to what is generally considered acceptable.

The effects of exercise on skeletal and heart muscle citrate synthase and carnitine palmitoyltransferase mRNA expressions in high-calorie fed rats.

In this study, the effect of high-calorie feeding and aerobic exercise on skeletal and cardiac muscle citrate synthase (CS), carnitine palmitoyltransferase-I (CPT-I), and -II (CPT-II) mRNA expressions were evaluated. Genetically non-obese rats were grouped as normal-high calorie and sedentary-exercising. Gastrocnemius-soleus and heart muscles' CS, CPT-I, and CPT-II expressions and skeletal muscles' histopathological characteristics were evaluated. High-fat diet had increased body weight by 10% and aerobic exercise did not make any difference. Skeletal muscle CS expression was increased significantly in normal-calorie exercising group. Exercise and high-fat diet did not change CPT-I and CPT-II expressions in both heart and skeletal muscle. Histopathological evaluations demonstrated increased cytoplasmic lipid droplets in high-calorie fed sedentary rats, and exercise had reduced lipid droplets in skeletal muscle. Also, both mitochondria and nuclei distribution were impaired in high-calorie groups. In conclusion, aerobic exercise without food restriction was not enough to make significant changes in fat transportation mechanism into skeletal and heart muscle.

Effects of training load changes on physical performance and exercise-induced muscle damage / Efeitos das mudanças de carga de treinamento sobre o desempenho físico e dano muscular induzido por exercício / Efectos de los cambios de carga de entrenamiento sobre el desempeño físico y daño muscular inducido por ejercicio

ABSTRACT Introduction There is no previous study examining muscle damage responses from training load changes in individuals trained exclusively with repeated sprint exercise. Objectives The purpose of this study was to examine the effect of training load changes on physical performance and exercise-induced muscle damage in male college athletes who were trained using a 30m repeated sprint protocol. Methods Twelve participants completed the 6-week training period (three sessions/week), which consisted of progressively increasing intensity training in the first 5 weeks. On the first day of the training period, all sprints were performed at 70-80% of maximum effort. In the first session of the 5th week (Maximal intensity training; MIT), all sprints (10×30m sprints) were performed at maximal speed. The sets (10 sprints at maximal speed in each set) were repeated until exhaustion (Exhaustive training; ET) in the first training session of the 6th week, followed by two sessions of the normal training. Isometric strength, 30m sprint performance, flexibility, serum creatine kinase (CK) and cortisol were measured periodically during the examination period. Results Isometric strength, 30m sprint performance, and flexibility were significantly decreased following the ET, and did not recover during the following 9-day period, which consisted of two training sessions and 6 days of recovery. Cortisol was significantly elevated immediately after the ET but was not changed after training on first day and during MIT. CK was significantly elevated after training every week, but the increase at 24 hours after ET was significantly higher than after the first day and MIT. Conclusions Dramatically increasing the volume of maximal intensity repeated sprint exercise results in greater relative muscle damage even in trained individuals, which will significantly limit their performance. Further training sessions, even at normal intensity and volume with insufficient time for muscle recovery, may prolong the duration of fatigue. Level of evidence II; Diagnostic Studies - Investigating a diagnostic test.

RESUMO Introdução Não existe nenhum estudo anterior que tenha analisado as respostas às lesões musculares decorrentes das alterações da carga de treinamento em indivíduos treinados exclusivamente com exercícios repetitivos de corrida. Objetivos A proposta deste estudo foi examinar o efeito das alterações da carga de treinamento sobre o desempenho físico e as lesões musculares induzidas pelo exercício em atletas universitários do sexo masculino que foram treinados usando um protocolo de sprint (treinamento de alta intensidade) de 30 metros repetido. Métodos Doze participantes concluíram o período de treinamento de 6 semanas (três sessões/semana), que consistiu em aumentar progressivamente o treinamento de intensidade nas primeiras 5 semanas. No primeiro dia do período de treinamento, todos os sprints foram realizados com 70% a 80% do esforço máximo. Na primeira sessão da 5ª semana (treinamento de intensidade máxima, TIM), todos os sprints (10 × 30 m) foram realizados na velocidade máxima. As séries (10 sprints na velocidade máxima em cada série) foram repetidas até a exaustão (treinamento exaustivo, TE) na primeira sessão de treinamento da 6ª semana, seguidas de duas sessões de treinamento normal. A força isométrica, o desempenho no sprint de 30 metros, a flexibilidade, a creatina quinase sérica (CK) e o cortisol foram medidos periodicamente durante o período de treinamento. Resultados A força isométrica, o desempenho no sprint de 30 metros e a flexibilidade diminuíram significativamente depois do TE e não foram recuperados durante o período de 9 dias seguintes, que consistiu em duas sessões de treinamento e 6 dias de recuperação. O cortisol teve elevação significativa imediatamente após o TE, mas não teve alteração depois do treinamento no primeiro dia e durante o TIM. A CK teve aumento significativo depois do treinamento em cada semana, mas o aumento 24 horas depois de TE foi expressivamente maior do que depois do primeiro dia e do TIM. Conclusões O aumento drástico da intensidade máxima do exercício de sprint repetido resulta em maior dano muscular relativo, mesmo em indivíduos treinados, o que limitará substancialmente seu desempenho. Outras sessões de treinamento, mesmo em intensidade e volume normais, com tempo insuficiente para recuperação muscular, podem prolongar a duração da fadiga. Nível de evidência II; Estudos Diagnósticos - Investigação de exame diagnóstico.

RESUMEN Introducción No existe ningún estudio anterior que haya analizado las respuestas a las lesiones musculares provenientes de las alteraciones de la carga de entrenamiento en individuos entrenados exclusivamente con ejercicios repetitivos de carrera. Objetivos La propuesta de este estudio fue examinar el efecto de las alteraciones de la carga de entrenamiento sobre el desempeño físico y las lesiones musculares inducidas por el ejercicio en atletas universitarios del sexo masculino que fueron entrenados usando un protocolo de sprint (entrenamiento de alta intensidad) de 30 metros repetido. Métodos Doce participantes concluyeron el período de entrenamiento de seis semanas (tres sesiones/semana), que consistió en aumentar progresivamente el entrenamiento de intensidad en las primeras cinco semanas. En el primer día del período de entrenamiento, todos los sprints fueron realizados con 70% a 80% del esfuerzo máximo. En la primera sesión de la 5ª semana (entrenamiento de intensidad máxima, EIM), todos los sprints (10 × 30 m) fueron realizados en la velocidad máxima. Las series (10 sprints en la velocidad máxima en cada serie) fueron repetidas hasta la extenuación (entrenamiento exhaustivo, EE) en la primera sesión de entrenamiento de la 6ª semana, seguidas de dos sesiones de entrenamiento normal. La fuerza isométrica, el desempeño en el sprint de 30 metros, la flexibilidad, la creatina quinasa sérica (CK) y el cortisol fueron medidos periódicamente durante el período de entrenamiento. Resultados La fuerza isométrica, el desempeño en el sprint de 30 metros y la flexibilidad disminuyeron significativamente después del EE y no fueron recuperados durante el período de 9 días siguientes, que consistió en dos sesiones de entrenamiento y seis días de recuperación. El cortisol tuvo elevación significativa inmediatamente después del EE, pero no tuvo alteración después del entrenamiento en el primer día y durante el EIM. La CK tuvo aumento significativo después del entrenamiento en cada semana, pero el aumento 24 horas después de EE fue expresivamente mayor que después del primer día y del EIM. Conclusiones El aumento drástico de la intensidad máxima del ejercicio de sprint repetido resulta en mayor daño muscular relativo, aún en individuos entrenados, lo que limitará sustancialmente su desempeño. Otras sesiones de entrenamiento, aún en intensidad y volumen normales, con tiempo insuficiente para recuperación muscular, pueden prolongar la duración de la fatiga. Nivel de evidencia II; Estudios Diagnósticos - Investigación de examen diagnóstico.

A Comparison of the Maximal Fat Oxidation Rates of Three Different Time Periods in The Fatmax Stage.

This study aimed to compare the maximal fat oxidation (MFO) rates obtained from the stage average, last 2 min average, and highest value in the Fatmax stage determined with a 6 min step protocol. A total of 35 overweight, sedentary healthy men (age: 25.4 ± 0.7 years, body mass index: 26.0 ± 0.6 kg/m2) participated in the study. Substrate oxidation was calculated using breath-by-breath gas exchange data for each stage. When the change in the fat oxidation rate for every min throughout the Fatmax stage was evaluated, the average value of the 4th min was significantly lower than that of the 2nd and 3rd min (p < 0.01). In addition, the 5th and 6th min fat oxidation rates were significantly lower than the rates of the 1st, 2nd, 3rd, and 4th min (0.30 ± 0.01 and 0.29 ± 0.01 g/min for the 5th and 6th min, respectively, vs. 0.35 ± 0.02, 0.34 ± 0.02, 0.33 ± 0.02, and 0.31 ± 0.01 g/min for the 1st, 2nd, 3rd, and 4th min, respectively; p < 0.01). Most of the participants had MFO rates in the 1st min of the stage (16/35 participants), and the MFO rates of the remaining participants were observed in the 2nd, 3rd, and 4th min (7/35, 4/35, and 8/35 participants, respectively). None of the participants had MFO rates in the 5th or 6th min. The individual MFO rate (highest fat oxidation rate during Fatmax) was significantly higher than the fat oxidation rate calculated with the last 2 min average values (0.36 ± 0.02 and 0.30 ± 0.01 g/min, respectively; p < 0.05). In conclusion, the calculation of the fat oxidation rate by averaging the last portion of the Fatmax stage data may cause the underestimation of the MFO rate, which probably occurs earlier in the Fatmax stage.

Determination of an Optimal Threshold Value for Muscle Activity Detection in EMG Analysis.

It is commonly agreed that one needs to use a threshold value in the detection of muscle activity timing in electromyographic (EMG) signal analysis. However, the algorithm for threshold determination lacks an agreement between the investigators. In this study we aimed to determine a proper threshold value in an incremental cycling exercise for accurate EMG signal analysis. Nine healthy recreationally active male subjects cycled until exhaustion. EMG recordings were performed on four low extremity muscle groups; gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SOL) and vastus medialis (VM). We have analyzed our data using three different threshold levels: 25%, 35% and 45% of the mean RMS EMG value. We compared the appropriateness of these threshold values using two criteria: (1) significant correlation between the actual and estimated number of bursts and (2) proximity of the regression line of the actual and estimated number of bursts to the line of identity. It had been possible to find a significant correlation between the actual and estimated number of bursts with the 25, 35 and 45% threshold values for the GL muscle. Correlation analyses for the VM muscle had shown that the number of bursts estimated with the 35% threshold value was found to be significantly correlated with the actual number of bursts. For the GM muscle, it had been possible to predict the burst number by using either the 35% or 45% threshold value and for the SOL muscle the 25% threshold value was found as the best predictor for actual number of burst estimation. Detailed analyses of the actual and estimated number of bursts had shown that success of threshold estimation may differ among muscle groups. Evaluation of our data had clearly shown that it is important to select proper threshold values for correct EMG signal analyses. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. Key pointsα priori accepted threshold value may cause erroneous results in EMG analysis.Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results.The investigators may need to use different threshold selection strategies for different workloads.The investigators have to justify the choice of threshold selection with valid arguments before detailed EMG signal analyses.

Suppression of the tumorigenicity of B-16V melanoma cells via lysozyme gene.

OBJECTIVE: The aim of this study was to evaluate the effects of lysozyme on the tumorigenicity of B-16V melanoma cells. METHODS: After performing a series of molecular biology applications, including mRNA isolation, reverse transcriptase polymerase chain reaction, restriction digestions and ligations, recombinant pHM6 vector harboring mouse lysozyme gene (pHM6mLys) was constructed. B-16V melanoma cells were transfected with plasmid DNAs (pHM6 and pHM6mLys). Transfected cells (B-16VpHM6 and B-16VpHM6mLys) were selected in media containing geneticin. B-16V, B-16VpHM6, and B-16VpHM6mLys cells were then injected subcutaneously (s.c.) to the three groups of C57BL/6 inbred mice (30 mice/group). These mice were examined every 3 days for s.c. tumor development over 41 days. The results were evaluated by using statistical methods. RESULTS: Tumor formation was observed in all mice injected with B-16V and B-16VpHM6 cells in the first 8-12 days. However, tumor didn't develop in 16 of 30 of the mice injected with B-16VpHMmLys cells. Tumor-free animals (16 mice) in this group were reinjected with B-16V cells, and 9 of them died during the first 10 days of observation. Tumor development was not observed in the remaining 7 mice over 60 days of the experimental period. Results were statistically significant (p values < or = 0.05). CONCLUSIONS: These findings indicate that lysozyme expressed by B-16VpHMmLys cells may suppress the tumorigenicity of these cells and may help development of protective immunity against B-16V melanoma cells.

Effect of pulsed magnetic field on regenerating rat sciatic nerve: an in-vitro electrophysiologic study.

Some experimental studies report that low-frequency pulsed electromagnetic field (PEMF) stimulation may accelerate regeneration in peripheral nerves. In the present study, effects of PEMF on the regeneration of the crushed rat sciatic nerves were investigated with histological and in-vitro electrophysiological methods (sucrose-gap). After crush injury of the sciatic nerves, rats were divided into 5, 15, 25, 38 day-groups and exposed to PEMF (1.5 h/day, intensity; 1.5 mT, consecutive frequency; 10-40-100 Hz). In the 15th day post crush, compound action potential (CAP) amplitude was measured as 5.5+/-1 mV (crush group) and 5.4+/-1.2 mV (crush+PEMF group). In addition, half width of CAP extended ~3 fold in both groups and frequency-dependent amplitude inhibition (FDI) decreased approximately 20% at 100 Hz. In the 38th day, amplitude of CAP, half width of CAP and FDI were measured nearly intact nerve values in both groups. In histological examinations, Wallerian degeneration was observed similar progress between both groups. The results were compared between crush and crush + PEMF groups, it was found that the effect of PEMF was not significant. The authors conclude that PEMF were ineffective on rat sciatic nerve regeneration.

Conduction blocks of lidocaine on crushed rat sciatic nerve: an in-vitro study.

The effects of lidocaine on the action potential of crushed sciatic nerves were investigated. The sciatic nerves of the rats were removed 5, 15, 25, and 38 days after the crushing and the compound action potentials were recorded with sucrose gap technique. The nerves were treated with 1 mM lidocaine and the conduction blocks of nonfrequency dependent block (NFDB) and frequency depended block (FDB) at 10, 40, and 100 Hz were determined. In intact nerves, the NFDB effect of lidocaine was 38.4 +/- 0.7 %. On the 15th day after the crush, the NFDB was increased to 60.1 +/- 1.3%. On the 38th day NFDB was decreased to 46.0 +/- 0.8%. The following days after the crushing, lidocaine caused a very high rate of FDB with 10, 40, and 100 Hz stimulation. The high NFDB ratios approached normal levels with the improvement of regeneration, but FDB ratios continued to stay at high levels. The results showed that the ratios of FDB and NFDB were increased on the crushed nerve. It was concluded that, in the regeneration conditions of crushed rat sciatic nerves, the sensitivity to local anesthetic increases more than in intact nerves.

Analysis of isokinetic knee extension / flexion in male elite adolescent wrestlers.

Wrestling requires strength of the upper and lower body musculature which is critical for the athletic performance. Evaluation of the adolescent's skeletal muscle is important to understand body movement, especially including those involved in sports. Strength, power and endurance capacity are defined as parameters of skeletal muscle biomechanical properties. The isokinetic dynamometer is an important toll for making this type of evaluation. However, load range phase of range of motion has to be considered to interpret the data correctly. With this in mind we aimed to investigate the lover body musculature contractile characteristics of adolescent wrestlers together with detailed analyses of load range phase of motion. Thirteen boys aged 12 - 14 years participated to this study. Concentric load range torque, work and power of knee extension and flexion were measured by a Cybex Norm dynamometer at angular velocities from 450°/sec to 30°/sec with 30°/sec decrements for each set. None of the wrestlers were able to attain load range for angular velocities above 390°/sec and 420°/sec for extension and flexion respectively. Detailed analyses of the load range resulted in statistically significant differences in the normalized load range peak torque for extension at 270°/sec (1.44 ± 0.28 Nm·kg(-1) and 1.14 ± 0.28 Nm·kg(-1) for total and load range peak torque respectively, p < 0.05), and for flexion at 300°/sec (1.26 ± 0.28 Nm·kg(-1) and 1.03 ± 0.23 Nm·kg(-1) for total and load range peak torque respectively, p < 0.05), compared to total peak torque data. Similarly, the significant difference was found for the work values at 90°/sec (1.91 ± 0.23 Nm·kg(-1) and 1.59 ± 0.24 Nm·kg(-1) for total and load range work respectively for extension and 1.73 ± 0.21 Nm·kg(-1) and 1.49 ± 0.19 Nm·kg(-1) for total and load range work respectively for flexion, p < 0.05), and was evident at higher angular velocities (p < 0.001) for both extension and flexion. At extension, load range power values were significantly smaller than total power for all angular velocities except 150°/sec (p < 0.05 for 120 and 180°/sec, p < 0.001 for others). Finally, load range flexion power was found to be higher than total power with statistically significance (p < 0.05 for 60, 120, 150, 180, 210, 270 and 300°/sec, p < 0.001 for 240 °/sec). Extra caution is required for correct interpretation of load range data in terms of considering the load range during limb movement. Evaluation of muscle performance of these adolescent wrestlers at regular intervals may give us an opportunity to obtain a healthy maturation profile of these adolescent wrestlers. Key PointsConsideration of load range for peak torque, work and power calculation resulted significant differences in the data presented by isokinetic dynamometer. Therefore evaluation of the dynamometer data required consideration of the load range for correct analysis and interpretation.Contraction velocity has critical importance in determining the load range attaining ability for a moving limb during load range evaluation. In fact alterations in contraction speed may be due to a number of changes in muscle morphology, subjects' age and the ratio between type I and type II muscle fiber area.

Differential contributions of right and left brains to paw skill in right- and left-pawed female rats.

Paw preference and paw frequency was studied in female rats. Paw preference was assessed using a modified version of food reaching task in quadrupedal position. Of 68 rats, 56 (82.4%) were right-handed, 7 (10.3%) were left-handed, and 5 (7.4%) were mixed-handed. There were significantly more right-handers than left-handers. The distribution of right minus left (L) paw reach (R + L = 50) was not U-shaped, it was J-shaped like in humans. Estrus cycle was a significant factor influencing the right-paw entry scores: most of left-handers were in estrus and proestrus, most of left -handers were in estrus, and most of mixed-handers were in postestrus. In right- and non-right- handers, the frequency of right-paw usage (right-hand skill) increased linearly with testing days, but the frequency of left-hand usage (left-hand skill) did not show significant changes with the successive testing days. Controlling for body weight and estrus only accentuated these results. It was concluded that distribution of hand preference in rats is J-shaped and there is a right-sided population bias in handedness in rats like in humans. The results suggested that motor learning in paw skill is mainly involved the left brain in right- and mixed-handed rats, not the right brain: only the left brain has the inbuilt capacity for motor learning in female rats. Such an asymmetric cognitive control in an animal model may have a major impact in many aspects of biology in respect to normal functioning, superior talents, and disease (see Geschwind, 1985).