Reproducibility of an isokinetic eccentric muscle endurance task

Abstract

Despite the widespread use of isokinetic eccentric muscle endurance protocols, no research has examined the absolute and relative reliability of such tests. The aim of this study was to examine the reliability of an isokinetic eccentric knee muscle endurance task. Fifteen healthy untrained males volunteered to take part in the study and written informed consent was obtained. The procedures received approval from the University Research Ethics Committee. Participants visited the laboratory on three separate occasions: 2 weeks before testing to familiarize them with the experimental procedures, and on two separate occasions, 2 weeks apart and at the same time of day. Isokinetic eccentric knee extension and flexion movements of the dominant limb were performed using a calibrated dynamometer (Biodex System 3). Range of motion during testing was set using voluntary maximal full extension (0 rad) to 1.57 rad of knee flexion and testing was conducted at 1.56 rad · s^?1. Participants performed four maximal efforts to determine maximal peak torque. After 2 min rest, participants completed the all-out endurance test of 50 continuous eccentric repetitions. Data were gravity corrected and windowed to only include constant velocity periods. Repeated-measures analyses of variance were used to examine differences in maximal peak extension and flexion torque and the maximal torque measurement recorded during the endurance test. Absolute and relative reliability of the torque fatigue index, work fatigue index, and total work were assessed through calculation of intra-class correlation coefficients, coefficients of variation, and absolute 95% limits of agreement using the methods described by Bland and Altman (1986). Differences between the strength test and the endurance trial for peak torque were found to be non-significant for both quadriceps (323 vs. 323 N · m) and hamstrings (183 vs. 178 N · m). The intra-class correlation coefficients revealed significant (P<0.05) positive moderate to strong correlations (r=0.44–0.94) across repeated trials for all parameters except hamstring torque fatigue (P=0.11) and hamstring work fatigue index (P=0.08). Coefficients of variation ranged from 6% to 48% and were large for the work fatigue index and torque fatigue index but acceptable for total work for both the extensors and flexors. The 95% limits of agreement indicated systematic bias in repeated trials for both the work fatigue index and torque fatigue index for extensors and flexors, ranging from ?3% to ?10%, with less fatigue evident in the second test. There was also systematic bias for total work, with more work being performed during the second than the first test for both extensors and flexors. The random error was large for all variables and there was greater random error in the hamstrings compared with the quadriceps. Together with moderate to strong intra-class correlation coefficients and large coefficients of variation, the data suggest that there is small systematic bias in repeated eccentric muscle actions for both the quadriceps and hamstrings, although the random error was large despite habituation procedures. Therefore, data from an isokinetic eccentric muscle endurance task should be viewed with some caution even when participants receive considerable habituation before assessment.     

Effect of tapering period on plasma hormone concentrations,mood state,and performance of elite male cyclists

Abstract

In this study, we investigated the effect of 1- and 3-week tapering periods on concentrations of plasma testosterone (T), cortisol (C), T/C ratio, mood state, and performance in elite male cyclists. After 8 weeks of progressive training, cyclists were randomly assigned to a control group (n=12) who continued performing intense training for a further 3 weeks, or a taper group (n=12) who continued with a 50% reduction in training volume. Blood testosterone and cortisol concentrations were assayed and the T/C ratio calculated from analysis obtained via standard ELISA. Mood state was determined using the Profile of Mood States (POMS) questionnaire. All data were collected immediately after a 40-km time-trial performed before, during, and after the 8-week training protocol and after the 1- and 3-week tapering/training periods. In the taper group, 40-km time-trial time decreased significantly (P<0.01) and equally for both the 1- and 3-week taper periods relative to the control group. There were significant elevations in T/C ratio (P<0.001) and reductions in cortisol concentrations and POMS scores in the taper group relative to the control groups at the end of both the 1- and 3-week tapering periods. Hence, taper periods are effective in improving performance and mood state and elevating the blood T/C ratio.     

Prophylactic effect of hot pack on symptoms of eccentric exercise-induced muscle damage of the wrist extensors

Abstract

This study investigated whether hot pack treatment could provide prophylactic effects on muscle damage induced by eccentric exercise of the wrist extensors. Twenty-eight healthy men (age 21±1 years, weight 65±16 kg, height 171±6 cm) were randomly placed into hot pack (n = 14) and control (n = 14) groups. All participants performed an exercise consisting of 300 maximal eccentric contractions of the wrist extensors of the non-dominant arm using an isokinetic dynamometer. A hot pack was applied for 20 min to the wrist extensors of the exercised arm before the exercise for the hot pack group. The control group received no treatment before the exercise. Measured variables included pain intensity assessed by a visual analogue scale and a modified Likert's scale, cold thermal pain threshold, pressure pain threshold (PPT), range of motion in active wrist flexion (ROM-AF) and extension (ROM-AE), range of motion in passive wrist flexion (ROM-PF) and extension (ROM-PE), grip strength, and wrist extension strength. Changes in these variables before, immediately after, and 1 to 8 days following the exercise were compared between groups by a two-way repeated measures ANOVA. All outcome measures from both groups (except for the cold thermal pain threshold of the hot pack group) demonstrated a significant change within the first 2–3 days following exercise. Significant differences between groups were only found at a single point in time for PPT, ROM-PF, ROM-PE and ROM-AE, and the changes were smaller for the hot pack group in comparison to the control group. These results suggest that the prophylactic effects of hot pack treatment on eccentric exercise-induced muscle damage of the wrist extensors are limited.     

Dynamics of the game in soccer: Detection of T-patterns

Abstract

Traditional approaches to the quantification of team sports have proved to be limited in their ability to identify complex structural regularities that, despite being unobservable, nonetheless underlie the development of the sporting contest between opposing teams. This paper describes a method for detecting the dynamics of play in professional soccer through the analysis of temporal patterns (T-patterns). The observation instrument used was SOF-5, which is especially designed for studying the dynamics of the game in soccer. The recording consisted of within-session monitoring using the MATCH VISION STUDIO 3.0 software, while the THEME software was used to detect and analyse T-patterns. These T-patterns revealed regularities in the playing style of the observed team, FC Barcelona. The structures detected included a ball possession pattern, whereby the ball was first kept in the central zone before being played forward, through several moves, into the zones closest to the opposing team's goal in order to disrupt the latter's equilibrium. The results obtained show that it is possible to identify stable temporal structures that provide information about concurrent interaction contexts with respect to lateral position and zone. As such, the proposed methodology appears to be useful in detecting complex structures within the game of soccer, structures which may help coaches to design attacking and defensive strategies.     

Precision of the optimized carbon monoxide rebreathing method to determine total haemoglobin mass and blood volume

Abstract

The aim of this study was to evaluate the influence of different apparatuses, procedures and calculations on the precision of the optimized carbon monoxide method. Total haemoglobin mass was determined twice on consecutive days in 11 subjects using both venous and capillary blood samples. To estimate loss of carbon monoxide due to exhalation, carbon monoxide concentration was measured by two portable carbon monoxide analysers (Fluke CO-220, Fluke, Norwich, UK and Pac 7000 Carbon Monoxide, Draeger Safety, Northumberland, UK) and alveolar ventilation was specified using an automated metabolic gas analysis system (Cosmed Quark b2, Cosmed, Rome, Italy). Blood volume was derived from total haemoglobin mass using haemoglobin concentration and haematocrit obtained in both the supine and the seated position. Two different formulae to calculate blood volume were also compared. Precision was good for both total haemoglobin mass and blood volume measurements performed on consecutive days (typical error < 2%). Using Fluke CO-220 analyser, an estimated alveolar ventilation and capillary blood, total haemoglobin mass (917±136 g) was similar when compared to the Pac 7000 Draeger CO-analyser (904±137 g; mean bias –13 g with 95% limits of agreement –26 to + 1 g, P=0.76), specified alveolar ventilation (911±132 g, mean bias –6 g with 95% limits of agreement –18 g to + 6 g, P =0.87) and venous blood (917±134 g, mean bias 0 g with 95% limits of agreement –38 to + 38 g, P=0.99), respectively. Blood volume determination was also not significantly affected by the supine vs. seated position (6.7±0.8 l vs. 6.6±0.8 l, P=0.56) but can deviate by ~0.6 l (P=0.01) depending on the formula applied. Thus, the good precision of the assessment of total haemoglobin mass and blood volume using the optimized carbon monoxide rebreathing method is not significantly influenced by the make of CO analyser, method of obtaining alveolar ventilation, blood sampling method and subject position, but should for longitudinal monitoring purposes use the same formula.     

Determination of thigh volume in youth with anthropometry and DXA: Agreement between estimates

Abstract

This study examined the agreement between estimates of thigh volume (TV) with anthropometry and dual-energy x-ray absorptiometry (DXA) in healthy school children. Participants (n=168, 83 boys and 85 girls) were school children 10.0–13.9 years of age. In addition to body mass, height and sitting height, anthropometric dimensions included those needed to estimate TV using the equation of Jones & Pearson. Total TV was also estimated with DXA. Agreement between protocols was examined using linear least products regression (Deming regressions). Stepwise regression of log-transformed variables identified variables that best predicted TV estimated by DXA. The regression models were then internally validated using the predicted residual sum of squares method. Correlation between estimates of TV was 0.846 (95%CI: 0.796–0.884, S_y·x=0.152L). It was possible to obtain an anthropometry-based model to improve the prediction of TVs in youth. The total volume by DXA was best predicted by adding body mass and sum of skinfolds to volume estimated with the equation of Jones & Pearson (R=0.972; 95%CI: 0.962–0.979; R ²=0.945).     

Childhood practice and play as determinants of adolescent intrinsic and extrinsic motivation among elite youth athletes

Abstract

The study empirically tested the postulate of the Developmental Model of Sport Participation (DMSP; Côté, J., Baker, J., & Abernethy, B. (2007). Practice and play in the development of sport expertise. In R. Eklund & G. Tenenbaum (Eds.), Handbook of sport psychology (pp. 184–202). Hoboken, NJ: Wiley) that diversified childhood self-led sport play will beneficially affect future, adolescent intrinsic motivation. Participants were 178 elite youth athletes (age 15.3?±?1.5 years) from several game and non-game sports; 117 were members of the federal state or national junior squad in their respective sport. A questionnaire measured current (adolescent) intrinsic and extrinsic motivation of the youth athletes using the Sport Motivation Scale (Pelletier, L. G., Fortier, M. S., Vallerand, R. J., Tuson, K. M., Brière, N. M., & Blais, M. R. (1995). Towards a new measure of intrinsic motivation, extrinsic motivation, and amotivation in sports: The sport motivation scale (SMS). Journal of Sport & Exercise Psychology, 17, 35–53) and their earlier volume of childhood engagement (through 12 years) in coach-led practice and self-led play in their respective main sport and other sports. Analyses revealed that adolescent intrinsic motivation was not significantly correlated with earlier childhood self-led sport activities, self-led play in particular, or childhood sports diversification. Furthermore, considering all different types of childhood sport activities together in multiple regression analyses, they did not provide meaningful explanatory power regarding adolescent intrinsic or extrinsic motivation. In summary, the results did not provide support for the postulate of the DMSP among elite youth athletes. The findings suggest that future research may seek to enable more robust empirical substantiation of the DMSP postulate.     

The differential effects of PNF versus passive stretch conditioning on neuromuscular performance

Abstract

The effects of flexibility conditioning on neuromuscular and sensorimotor performance were assessed near to full knee extension (25°). Eighteen males who were randomly assigned into two groups underwent eight weeks (three-times per week) of flexibility conditioning (hip region/knee flexor musculature; dominant limb) involving either proprioceptive neuromuscular facilitation (PNF) (n=9) or passive stretching (PASS) (n=9). Both modes of flexibility conditioning are popular within contemporary exercise and clinical settings and have demonstrated efficacy in improving range of motion. The contralateral limb and a prior ‘no exercise’ condition were used as controls. The PNF and PASS modes of conditioning improved passive hip flexibility to a similar extent (mean 19.3% vs. baseline, intervention limb, p<0.01) but did not alter knee flexor strength (overall mean 309.6±81 N) or sensorimotor performance (force and positional errors: 2.3±8.2% and 0.48±7.1%). Voluntary and magnetically evoked electromechanical delays (EMD_V and EMD_E, respectively) were increased but to a greater extent following PASS compared to PNF (PASS: 10.8% and 16.9% lengthening of EMD_V and EMD_E, respectively vs. PNF: 3.2% and 6.2%, p<0.01).The attenuated change to electromechanical delay (EMD) performance during PNF conditioning suggests a preserved capability for rapid muscle activation, which is important in the maintenance of dynamic joint stability. That PNF was also equally efficacious in flexibility conditioning would suggest that this mode of flexibility training should be used over passive to help preserve dynamic joint stability capabilities at this extended and vulnerable joint position.     

武则天“扼婴”事件考疑

武则天“扼婴”成为这位杰出女皇一生最残忍的罪恶,使她不仅不能成为伟大女性,而且连普通母亲都不配。在历史上,她成为一个最残忍的母亲,为了政治向上爬,甚至亲手扼杀自己的亲生幼女,连起码的人性都可以不要。从1300多年来的史籍中,这似乎已经成为铁定事实。其实,历史记载有许多不可解释的疑问和矛盾,实际上这只不过是封建文人对这位女皇的强加之罪,原因就在于她是我国历史上唯一的伟大的超凡女皇,这是封建社会男子中心社会所不允许的。通过对多种史料的考证,事件过程的对比,用确切的史实证明,考疑这实在是历史上一件天大冤案：女皇武则天不是一位残忍至极失去母性的人。     

发展小区体育 推动全民健身

摘要川、区是城市社区的构成单元,是家庭和居民的聚居地,发展小区体育对推动全民健身具有重要意义。小区体育的现状,是通过小区体育设施、体育项目、体育地点和体育目的体现出来。要大力发展小区体育,就要切实加强组织管理、加强宣传教育、充分利用现有设施和因人而异开展体育活动。