Effects of allometric scaling and isokinetic testing methods on the relationship between countermovement jump and quadriceps torque and power     

Yong-Hao Pua  Michael Teik-Hin Koh  Yik-Ying Teo 《Journal of sports sciences》2013,31(4):423-432

Abstract

Determination of the strongest possible relationship between isokinetic quadriceps and functional performance measurements in healthy females would allow sports medicine practitioners to establish normative values when examining muscular performance in injured females. Previous attempts to correlate both measurements have, however, produced inconsistent results. The purpose of this study was to examine the effects of allometric scaling, isokinetic testing velocities, reciprocal and non-reciprocal isokinetic testing on the relationship between countermovement jump (CMJ) and isokinetic quadriceps torque and power in recreational females athletes. Seventeen females (age 21.0 ± 2.0 years, body mass index 19.5 ± 1.0 kg · m^?2) performed isokinetic quadriceps and CMJ tests. Isokinetic peak torque and average power were obtained reciprocally and non-reciprocally at 1.05 and 3.14 rad · s^?1, and were corrected for body mass by allometric modelling. Pearson product–moment correlation (r) was used to assess the relationship between the isokinetic parameters and the CMJ measurements. Coefficients of determination (r ²) were calculated to determine the magnitude of common variance. The r-values for all non-allometrically modelled non-reciprocal parameters were greater (r = 0.58–0.63) than isokinetic parameters obtained reciprocally (r = 0.28–0.47). Using allometric scaling, non-reciprocal isokinetic data accounted for an additional 2–9% of the CMJ height variance, and statistically significant correlations were obtained at both 1.05 and 3.14 rad · s^?1. Allometrically scaled, non-reciprocal isokinetic peak torque and average power at 1.05 rad · s^?1 had the highest correlation with CMJ (r ² = 0.49). At both 1.05 and 3.14 rad · s^?1, non-reciprocal quadriceps parameters correlated more closely with CMJ measurements than do reciprocal contractions. Normalization for body size by allometrically scaling may further improve correlations with CMJ performance.  相似文献   

Fluid balance of elite Brazilian youth soccer players during consecutive days of training     

Rafael P. Silva  Toby Mündel  Antônio J. Natali  Maurício G. Bara Filho  Jorge R. P. Lima  Rita C. G. Alfenas 《Journal of sports sciences》2013,31(7):725-732

Abstract

In this study we investigated pre-training hydration status, fluid intake, and sweat loss in 20 elite male Brazilian adolescent soccer players (mean ± s: age 17.2 ± 0.5 years; height 1.76 ± 0.05 m; body mass 69.9 ± 6.0 kg) on three consecutive days of typical training during the qualifying phase of the national soccer league. Urine specific gravity (USG) and body mass changes were evaluated before and after training sessions to estimate hydration status. Players began the days of training mildly hypohydrated (USG > 1.020) and fluid intake did not match fluid losses. It was warmer on Day 1 (33.1 ± 2.4°C and43.4 ± 3.2% relative humidity; P < 0.05) and total estimated sweat losses (2822 ± 530 mL) and fluid intake (1607 ± 460 mL) were significantly higher (P < 0.001) compared with Days 2 and 3. Data also indicate a significant correlation between the extent of sweat loss and the volume of fluid consumed (Day 1: r = 0.560, P = 0.010; Day 2: r = 0.445, P = 0.049; Day 3: r = 0.743, P = 0.0001). We conclude that young, native tropical soccer players arrive hypohydrated to training and that they exhibit voluntary dehydration; therefore, enhancing athletes' self-knowledge of sweat loss during training might help them to consume sufficient fluid to match the sweat losses.  相似文献   

Prediction of adult height in girls: The Beunen-Malina-Freitas method     

Gaston P. Beunen†  Robert M. Malina  Duarte L. Freitas  Martine A. Thomis  José A. Maia  Albrecht L. Claessens 《Journal of sports sciences》2013,31(15):1683-1691

Abstract

The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10–15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R ² regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-specific coefficients of determination (R ²) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation confirmed the validity of the Beunen-Malina-Freitas method in girls aged 12–15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12–15 years. It is applicable to European populations or populations of European ancestry.  相似文献   

Acute responses of biomechanical parameters to different sizes of hand paddles in front-crawl stroke     

Augusto Carvalho Barbosa  Flávio De Souza Castro  Milivoj Dopsaj  Sérgio Augusto Cunha  Orival Andries Júnior 《Journal of sports sciences》2013,31(9):1015-1023

Abstract

This study investigated the acute effects of different sizes of paddles on the force-time curve during tethered swimming and swimming velocity in front-crawl stroke. Fourteen male swimmers (20.0 ± 3.7 years; 100-m best time: 53.70 ± 0.87 s) performed two 10-s maximal efforts in tethered swimming to obtain peak force, average force, impulse, rate of force development, stroke duration and time to peak force. Swimming velocity, stroke rate and stroke length were obtained from two 25-m maximal swims. Both tests were repeated in five conditions: free swimming, wearing small (280 cm ² ), medium (352 cm ² ), large (462 cm ² ) and extra-large (552 cm ² ) hand paddles. Compared to free swimming, paddles provided significant increases of peak force (medium: 11.5%, large: 16.7%, extra-large: 21.7%), impulse (medium: 15.2%, large: 22.4%, extra-large: 30.9%), average force (medium: 5.1%, large: 7.5%), rate of force development (extra-large: 11.3%), stroke duration (medium: 9.3%, large: 11.8%, extra-large: 18.5%), time to peak force (medium: 11.1%, large: 15.9%, extra-large: 22.1%), swimming velocity (medium: 2.2%, large: 3.2%, extra-large: 3.7%) and stroke length (medium: 9.0%, large: 9.0%, extra-large: 14.8%), while stroke rate decreased (medium: –6.2%, large: –5.5%, extra-large: –9.5%). It is concluded that medium, large and extra-large paddles influence the force-time curve and change swimming velocity, suggesting these sizes may be useful for force development in water.  相似文献   

Magnesium status and the physical performance of volleyball players: effects of magnesium supplementation     

Luciana Setaro  Paulo Roberto Santos-Silva  Eduardo Yoshio Nakano  Cristiane Hermes Sales  Newton Nunes  Júlia Maria Greve 《Journal of sports sciences》2013,31(5):438-445

Abstract

The aim of this study was to test the hypothesis that magnesium supplementation influences the physical performance of volleyball players, as the efficacy of this approach remains questionable. Twenty-five professional male volleyball players were assigned randomly to experimental (350 mg Mg · d^–1, 4 weeks) and control groups (500 mg maltodextrin · d^–1, 4 weeks) maintaining inter-group homogeneity of urinary magnesium. Erythrocyte, plasma and urinary magnesium levels, plasma creatine kinase activity, lactate production, maximal oxygen uptake (VO₂ max) and plyometric (squat jump, countermovement jump, countermovement jump with arm swing) and isokinetic (peak torque, potency and total work) performances were evaluated before (T₀) and after (T₁) supplementation. Levels of erythrocyte and urinary magnesium and creatine kinase activity and VO₂ max remained within normal ranges in both groups. Plasma magnesium decreased significantly only within the experimental group. Significant decreases in lactate production and significant increases (of up to 3 cm) in countermovement jump and countermovement jump with arm swing values were detected in the experimental group following magnesium supplementation, but not in the control group at T₁. It is concluded that magnesium supplementation improved alactic anaerobic metabolism, even though the players were not magnesium-deficient.  相似文献   

Physiological responses to maximal intermittent exercise: Differences between endurance‐trained runners and games players     

A.L. Hamilton  M.E. Nevill  S. Brooks  C. Williams 《Journal of sports sciences》2013,31(4):371-382

Abstract

Six games players (GP) and six endurance‐trained runners (ET) completed a standardized multiple sprint test on a non‐motorized treadmill consisting often 6‐s all‐out sprints with 30‐s recovery periods. Running speed, power output and oxygen uptake were determined during the test and blood samples were taken for the determination of blood lactate and pH. Games players tended to produce a higher peak power output (GP vs ET: 839 ± 114 vs 777 ± 89 W, N.S.) and higher peak speed (GP vs ET: 7.03 ± 0.3 vs 6.71 ± 0.3 m s^‐1, N.S.), but had a greater decrement in mean power output than endurance‐trained runners (GP vs ET: 29.3 ± 8.1% vs 14.2 ± 11.1%, P < 0.05). Blood lactate after the test was higher for the games players (GP vs ET: 15.2 ± 1.9 vs 12.4 ± 1.7 mM, P < 0.05), but the decrease in pH was similar for both groups (GP vs ET: 0.31 ± 0.08 vs 0.28 ± 0.08, N.S.). Strong correlations were found between peak blood lactate and peak speed (r = 0.90, P < 0.01) and between peak blood lactate and peak power fatigue (r = 0.92, P<0.01). The average increase in oxygen uptake above pre‐exercise levels during the sprint test was greater for endurance‐trained athletes than for the games players (ET vs GP: 35.0 ± 2.2 vs 29.6 ± 3.0 ml kg^‐1 min^‐1 , P < 0.05), corresponding to an average oxygen uptake per sprint (6‐s sprint and 24 s of subsequent recovery) of 67.5 ± 2.9% and 63.0 ± 4.5% VO ₂ max respectively (N.S.). A modest relationship existed between the average increase in oxygen uptake above pre‐exercise values during the sprint test and mean speed fatigue (r = ‐0.68, P < 0.05). Thus, the greater decrement in performance for the games players may be related to higher glycolytic rates as reflected by higher lactate concentrations and to their lower oxygen uptake during the course of the 10 sprints.  相似文献   

The Relationship of Isokinetic Torque at Two Speeds to the Vertical Jump     

Susan E. Genuario  Forrest A. Dolgener 《Research quarterly for exercise and sport》2013,84(4):593-598

Abstract

The relationship between the ability to develop leg torque and performance in the vertical jump was investigated in 29 female athletes. Each subject's leg flexion, leg extension, and foot plantar flexion peak torque was determined isokinetically on a Cybex at angular velocities of 30 degrees/second and 180 degrees/second. The vertical jump was determined for each subject and correlations among the measures of torque and the vertical jump were calculated. Although the ability to produce leg power as exemplified by the vertical jump was significantly correlated with peak torque at the fast angular velocity but was not significantly correlated with peak torque at the slow angular velocity, the correlations were so low it was concluded that there was little if any relationship between torque at a fast or slow angular velocity and the ability to vertically jump.  相似文献   

Comparison of the Criterion-Related Validity of Sit-and-Reach Tests with and without Limb Length Adjustment in Asian Adults     

Sai Chuen Hui  Pak Y. Yuen  James R. Morrow Jr.  Allen W. Jackson 《Research quarterly for exercise and sport》2013,84(4):401-406

Abstract

The stages of motivational readiness as conceptualized by the Transtheoretical Model have been widely used among adult samples to assess readiness for adopting exercise behavior. To date, little research has been conducted using a staging framework with adolescent samples. There is a need for validation of the staging framework prior to a substantial amount of research with this age group. The current article presents two studies assessing stage and reported exercise behavior (Study 1: n = 819; M age = 15.0 years, SD = 1.2; 51 % men; Study 2: n = 184; M age = 18.6 years, SD = .5; 45 % men). As hypothesized in both studies, reported exercise consistently varied as a function of stage classification; those in earlier stages of readiness reported less exercise than those in later stages. Staging algorithms showed good sensitivity to detect reported exercise; however, specificity was distinctly better with the algorithm that used a specific activity criterion and immediate intention, as opposed to irregular behavior, in defining the preparation stage. Results support the validity of the staging framework for measuring motivational readiness for exercise behavior among North American adolescents.  相似文献   

Taiwan and the 2001 Baseball World Cup: The National Impact of a World Sporting Event     

Chien-Yu Lin  Chih-Fu Cheng 《国际体育史杂志》2013,30(13):2234-2254

National identity is one of the most contentious issues in Taiwan. This paper examines the relationship between the staging of the 2001 Baseball World Cup (BWC) and wider issues such as that of Taiwanese nationalism and broader sociopolitical values in Taiwan. It attempts to explain the impact on Taiwanese nationalism of hosting such a sports mega-event. The paper argues that baseball in general, and the 2001 BWC in particular, was a political vehicle utilised by the ‘new’ government to promote social integration/national identity; and it evaluates the responses of the Taiwanese to baseball used for this purpose.

Taiwan et la Coupe du Monde de baseball de 2001 : l'impact national d'un événement sportif mondial

L'identité nationale est l'un des questions les plus litigieuses à Taïwan. Cet article examine les relations entre l'accueil de la Coupe du monde de base-ball 2001 (BWC) et d'autres aspects plus généraux comme ceux du nationalisme taïwanais et plus largement des valeurs sociopolitiques à Taïwan. Il tente d'expliquer l'impact de l'accueil d'un tel méga-événement sportif sur le nationalisme taïwanais; L'article soutient que le base-ball en général et la coupe du monde de 2001 en particulier furent un véhicule politique utilisé par ‘le nouveau’ gouvernement pour promouvoir l'intégration sociale et l'identité nationale et il évalue les réponses des Taïwanais dans le base-ball à cette fin.

Taiwan y el Mundial de Béisbol de 2001: impacto nacional de un acontecimiento deportivo mundial

Una de las cuestiones más controvertidas en Taiwan es la de la identidad nacional. Este artículo examina las relaciones entre la celebración del Mundial de Béisbol de 2001 y otros aspectos más generales como el nacionalismo taiwanés y los valores sociopolíticos en Taiwán. Intenta explicar el impacto que tuvo sobre el nacionalismo taiwanés el hecho de albergar un acontecimiento deportivo de este nivel. El artículo postula que el béisbol en general, y el Mundial de 2001 en concreto, fueron un instrumento político utilizado por el “nuevo” gobierno para promover la integración social y la identidad nacional, y valora las respuestas de los taiwaneses al uso del béisbol con este propósito.

Taiwan und die Baseball Weltmeisterschaft 2001: Der nationale Einfluss einer Weltsportveranstaltung

Die nationale Identität ist eine der umstrittensten Angelegenheiten in Taiwan. Diese Arbeit untersucht die Beziehung zwischen der Ausrichtung der Baseball Weltmeisterschaft (BWC) im Jahre 2001 und weitreichenderen Problemfeldern wie dem des Nationalismus und allgemeineren soziopolitischen Werten in Taiwan. Es wird versucht, den Einfluss eines derartigen sportlichen Großereignisses auf den taiwanesischen Nationalismus zu erklären. Die Abhandlung zeigt, dass Baseball allgemein, besonders aber die Weltmeisterschaft 2001 als politisches Werkzeug von der ?neuen” Regierung benutzt wurde, um die soziale Integration/nationale Identitätsstiftung voranzutreiben. Darüberhinaus werden die Reaktionen der Taiwanesen auf den zu diesem Zweck verwendeten Baseballsport untersucht.

  相似文献   

A Failed Project in Turkey's Sports History: The Law on Physical Education of 1938     

Sait Tarakçıoğlu 《国际体育史杂志》2014,31(14):1807-1819

The aim of this article is to analyse the Law on Physical Education of 1938 to demonstrate the state interventions in Turkey's sport history. The Law was claimed to be the first one in the world which made physical education (PE) and sports obligatory to its citizens and was created on the verge of the Second World War. It was prepared by Carl Diem under the direction of Atatürk, the founder of the Republic of Turkey. According to the Law, male citizens aged between 12 and 45 years, and female citizens between 12 and 30 years would be required to perform PE and sports regularly. For the execution of the Law, a General Directorate of Physical Education was founded. Many grand plans such as creating sports complexes, and training teachers and staff were made without taking the socio-economic conditions of the country into consideration. Ultimately, due to the effects of the economic and political conditions of the nation and the wider world, the Law failed to fulfil the expectations of its creators. Two government-supported journals named Beden Terbiyesi ve Spor and Ülkü are examined here as primary sources to see how the Law was enforced and how they reflected the Law and the period.  相似文献