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Isokinetic torques and kicking maximal ball velocity in young soccer players
No full textThe purpose of this study is to assess if there is any correlation between isokinetic testing and field performance of young soccer players. The isokinetic peak torques of the knee extensor muscles in sitting position (T(KE)), and those of the hip flexor muscles in standing position (T(HF)) were measured in 24 junior soccer players. Four angular velocities (ω = 1.05, 3.14, 4.19, 5.23 rad · s-1 or 60, 180, 240, 300 deg · s-1) were used for the knee extensors and three (1.05, 3.14, 4.19 rad · s-1) for the hip flexors. On the field the subjects were asked to kick a stationary soccer ball as fast as possible against a barrier and the mean linear velocity over a 10 m path (v) was measured. T(KE) of the non dominant limb were higher than those of the opposite one at the three highest ω (p < 0.05). On the contrary the T(HF) of the dominant limbs were higher than those of the contralateral, at the two highest ω. When the ball was kicked by the dominant or non dominant limbs, the mean values and standard deviations (±SD) of v were 23.6 (±2.5) and 21.4 (±2.6) m · s-1. Torques and v were always positively correlated to each other; however, only in few cases was this relationship statistically significant. In conclusion the isokinetic torques do not seem to be good predictors of v, one of the several factors which determine the global performances of the soccer players
The effect of range of motion and isometric pre-activation on isokinetic torques
No full textThe effect of an increased angle of excursion and isometric pre-activation on isokinetic torques of knee extensors was investigated in five male subjects, mean age 35.0 years, SD 9.6. Peak torque and isoangular torque at 0.52 rad from full knee extension (FKE) were measured when contractions were carried out at 3.14, 4.19 and 5.24 rad·s-1 starting: 1) from a standard knee angle (SA) of 1.57 rad from FKE, 2) from the same starting angle as SA, plus an isometric preload (P) equivalent to 25% of isometric maximal voluntary contraction and 3) from an increased angle of knee flexion (1A), 2.09 rad from FKE plus P. Surface integrated electromyograms (iEMG) of the vastus lateralis muscle in SA and IA+P were also recorded. The IA+P had the effect of increasing peak torque, as compared to SA, on average by 12.0%, SD 7.5% (P4.19 rad·s-1) was submaximal. The underestimation of torque seemed to be counteracted by starting the contraction from a flexed position and by utilizing a submaximal P. © 1991 Springer-Verlag
Correlations between physiological variables and performance in high level cross country off road cyclists
No full textObjectives: To examine the relations between maximal and submaximal indices of aerobic fitness and off road cycling performance in a homogeneous group of high level mountain bikers. Methods: 12 internationally competitive mountain bikers completed the study. Maximum oxygen uptake (VO2max), peak power output (PPO), power output (PO), and oxygen uptake (VO2) at first (VT) and second (RCT) ventilatory thresholds were measured in the laboratory, and correlated with race time during a cross country circuit race. Results: The only physiological indices of aerobic fitness correlated with off road cycling performance were PO and VO2 at RCT when normalised to body mass (r = -0.63 and r = -0.66, respectively; p<0.05). VT, VO 2max, and PPO were not correlated to performance in this homogeneous group of high level mountain bikers. Conclusions: The results of this study suggest that submaximal indices of aerobic fitness such as PO and VO2 at RCT are more important determinants of off road cycling performance than maximal indices such as PPO and VO2max. This study confirms the importance of body mass for mountain biking performance. As aerobic fitness explained only 40% of the variance, other physiological and technical factors should be investigated, as they may be important determinants of cross country performance among elite mountain bikers
Prediction of time to exhaustion from blood lactate response during submaximal exercise in competitive cyclists
No full textThe aim of this investigation was to develop and validate a new method to predict time to exhaustion (pTE) from blood lactate variables measured during a submaximal non-exhaustive constant workload cycling test in professional cyclists. A multiple regression equation to estimate pTE from blood lactate variables measured within the first 10 min of a submaximal test and TE was determined in 40 competitive cyclists. Predicted TE reliability [individual coefficient of variation (CV)] was calculated in eight amateur cyclists who repeated the proposed test three times. Seasonal variations of pTE were monitored in 12 professional cyclists. Validity of pTE was determined by the known-group difference method in 49 professional cyclists. The prediction equation was: lognTE = 4.2067 - 0.8221(logn B) - 0.2519(logn C), where B is the lactate concentration at the 10th minute of the constant workload test and C is the lactate slope calculated between the 5th and 10th minute (adjusted r2 = 0.83, root mean square error in cross validation = 23.1%). Predicted TE CV was 11.7%. The pTE obtained at the beginning of the season and the best and worst tests performed during the competitive season, resulted 162, 224 and 103% higher than the basic period test, respectively (P< 0.05). Predicted TE was the only parameter discriminating elite from subelite professional cyclists. In conclusion, this study demonstrates that pTE is a valid and practical alternative to incremental tests and direct measures of endurance capacity requiring exhaustive efforts for the evaluation of competitive cyclists. © Springer-Verlag 2006
Exercise intensity during off-road cycling competitions
No full textPurpose: This study was designed to quantify and describe the intensity profile of cross-country mountain-biking races using heart rate (HR) recorded during competitions. Methods: Nine mountain bikers participated in four cross-country circuit races of international and national levels. Each cyclist was tested before the competitions to determine lactate threshold (LT), the onset of blood lactate accumulation (OBLA4), and the relationship between percentage of maximum HR and percentage of VO2max. Results: To control for intersubject variability, only the five off-road cyclists who completed all four competitions were included in the statistical analysis. The four races' mean absolute and relative time expressed in percentage of race duration (147 ± 15 min) spent in the EASYZONE (HR below LT) were 27 ± 16 min and 18 ± 10%, in the MODERATEZONE (HR between LT and OBLA4) were 75 ± 19 min and 51 ± 9%, and in the HARDZONE (HR above OBLA4) were 44 ± 21 min and 31 ± 16%. The average HR was 171 ± 6 beats·min-1, corresponding to 90 ± 3% of maximum (84 ± 3% of VO2max). Conclusion: This study shows that cross-country events are conducted at very high intensity, especially at the start of the race. Coaches must take into account the distribution of the effort and the high exercise intensity characteristic of mountain-biking cross-country events when prescribing specific training programs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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