Combined metabolic gas analyser and dGPS analysis of performance in cross-country skiing     

Peter Larsson  Karin Henriksson-Larsén 《Journal of sports sciences》2013,31(8):861-870

The purpose of this study was to provide a more detailed analysis of performance in cross-country skiing by combining findings from a differential global positioning system (dGPS), metabolic gas measurements, speed in different sections of a ski-course and treadmill threshold data. Ten male skiers participated in a freestyle skiing field test (5.6?km), which was performed with dGPS and metabolic gas measurements. A treadmill running threshold test was also performed and the following parameters were derived: anaerobic threshold, threshold of decompensated metabolic acidosis, respiratory exchange ratio = 1, onset of blood lactate accumulation and peak oxygen uptake ([Vdot]O_2peak). The combined dGPS and metabolic gas measurements made detailed analysis of performance possible. The strongest correlations between the treadmill data and final skiing field test time were for [Vdot]O_2peak (l?·?min^?1), respiratory exchange ratio = 1 (l?·?min^?1) and onset of blood lactate accumulation (l?·?min^?1) (r = ?0.644 to ??0.750). However, all treadmill test data displayed stronger associations with speed in different stretches of the course than with final time, which stresses the value of a detailed analysis of performance in cross-country skiing. Mean oxygen uptake ([Vdot]O₂) in a particular stretch in relation to speed in the same stretch displayed its strongest correlation coefficients in most stretches when [Vdot]O₂ was presented in units litres per minute, rather than when [Vdot]O₂ was normalized to body mass (ml?·?kg^?1?·?min^?1 and ml?·?min^?1?·?kg^?2/3). This suggests that heavy cross-country skiers have an advantage over their lighter counterparts. In one steep uphill stretch, however, [Vdot]O₂ (ml?·?min^?1?·?kg^?2/3) displayed the strongest association with speed, suggesting that in steep uphill sections light skiers could have an advantage over heavier skiers.  相似文献   

Body fat measurement in elite sport climbers: Comparison of skinfold thickness equations with dual energy X-ray absorptiometry     

Vanesa España Romero  Jonatan R. Ruiz  Francisco B. Ortega  Enrique G. Artero  Germán Vicente-Rodríguez  Luis A. Moreno 《Journal of sports sciences》2013,31(5):469-477

Abstract

The aim of this study was to compare equations for estimating percentage body fat from skinfold thickness in elite sport climbers by assessing their agreement with percentage body fat measured using dual-energy X-ray absorptiometry (DXA). Skinfold thickness was measured in a convenience sample of 19 elite sport climbers [9 women and 10 men; mean age 31.2 years (s = 5.0) and 28.6 years (s = 3.6), respectively]. Percentage body fat was estimated using 17 different equations, and it was also measured by DXA. A significant inter-methods difference was observed for all equations, except for Durnin's equation in men (inter-methods difference: ?0.57% and ?0.29%; 1.96 s: 5.56 and 5.23 for Siri's and Brozek's equation, respectively) and women (inter-methods difference: ?0.67% and ?1.29% for Siri's and Brozek's equation, respectively), and for Wilmore's equation using Siri's body fat equation in women (inter-methods difference: ?1.86%). In women, the limits of agreement were lower when using Durnin's equation compared with Wilmore's equation (1.96 s: 3.86% and 5.13%, respectively). In conclusion, of the 17 studied equations, Durnin's equation was the most accurate in estimating percentage body fat in both male and female elite climbers. Therefore, Durnin's equation could be used to assess percentage body fat in elite sport climbers if more accurate methods are not available. The generalizability of the results is limited by the fact that the sample was not selected at random.  相似文献   

Inter-individual differences in stride frequencies during running obtained from wearable data     

B.T. Van Oeveren  M.J.M. Hoozemans  P.J. Beek  J.H. Van Dieën 《Journal of sports sciences》2013,31(17):1996-2006

ABSTRACT

The purpose of the present study was to identify factors that underlie differences among runners in stride frequency (SF) as a function of running speed. Participants (N = 256; 85.5% males and 14.5% females; 44.1 ± 9.8 years; 181.4 ± 8.4 cm; 75.3 ± 10.6 kg; mean ± SD) shared their wearable data (?Garmin Inc). Individual datasets were filtered to obtain representative relationships between stride frequency (SF) and speed per individual, representing in total 16.128 h of data. The group relationship between SF (72.82 to 94.73 strides · min^?1) and running speed (V) (from 1.64 to 4.68 m · s^?1) was best described with SF = 75.01 + 3.006 V. A generalised linear model with random effects was used to determine variables associated with SF. Variables and their interaction with speed were entered in a stepwise forward procedure. SF was negatively associated with leg length and body mass and an interaction of speed and age indicated that older runners use higher SF at higher speed. Furthermore, run frequency and run duration were positively related to SF. No associations were found with injury incidence, athlete experience or performance. Leg length, body mass, age, run frequency and duration were associated with SFs at given speeds.

KEY POINTS

• On a group level, stride frequency can be described as a linear function of speed: SF (strides · min^?1) = 75.01+ 3.006·speed (m · s^?1) within the range of 1.64 to 4.68 m · s^?1.

• On an individual level, the SF-speed relation is best described with a second order polynomial.

• Leg length and body mass were positively related to stride frequency while age was negatively related to stride frequency.

• Run frequency and run duration were positively related to stride frequency, while running experience, performance and injury incidence were unrelated.

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Relationship between physiological parameters and performance during a half-ironman triathlon in the heat     

Juan Del Coso  Cristina González  Javier Abian-Vicen  Juan José Salinero Martín  Lidon Soriano  Francisco Areces 《Journal of sports sciences》2013,31(18):1680-1687

Abstract

Triathlon is a popular outdoor endurance sport performed under a variety of environmental conditions. The aim of this study was to assess physiological variables before and after a half-ironman triathlon in the heat and to analyse their relationship with performance. Thirty-four well-trained triathletes completed a half-ironman triathlon in a mean dry temperature of 29 ± 3ºC. Before and within 1 min after the end of the race, body mass, core temperature, maximal jump height and venous blood samples were obtained. Mean race time was 315 ± 40 min, with swimming (11 ± 1%), cycling (49 ± 2%) and running (40 ± 3%) representing different amounts of the total race time. At the end of the competition, body mass changed by ?3.8 ± 1.6% and the change in body mass correlated positively with race time (r = 0.64; P < 0.001). Core temperature increased from 37.5 ± 0.6ºC to 38.8 ± 0.7ºC (P < 0.001) and post-race core temperature correlated negatively with race time (r = ?0.47; P = 0.007). Race time correlated positively with the decrease in jump height (r = 0.38; P = 0.043), post-race serum creatine kinase (r = 0.55; P = 0.001) and myoglobin concentrations (r = 0.39; P = 0.022). In a half-ironman triathlon in the heat, greater reductions in body mass and higher post-competition core temperatures were present in faster triathletes. In contrast, slower triathletes presented higher levels of muscle damage and decreased muscle performance.  相似文献   

Detecting Bouts of Physical Activity in a Field Setting     

Louise C. Mâsse  Janet E. Fulton  Kathleen L. Watson  Kristiann C. Heesch  Harold W. Kohl III  Steven N. Blair 《Research quarterly for exercise and sport》2013,84(3):212-219

Abstract

The purposes of this study were to assess the TRITRAC® and CSA® for: (a) interaccelerometer agreement; (b) agreement in detecting patterns of moderate-intensity physical activity; and (c) agreement in detecting walking patterns recorded in a diary. Thirty-one women wore both the TRITRAC® and CSA® accelerometers for three consecutive days. Interaccelerometer agreement (measured with generalizability coefficients) ranged from .88 to .99. In total, 71.3% of the accelerometers' patterns agreed in length, with CSA® patterns being on average significantly longer. Interaccelerometer agreement in detecting patterns of brisk walking, as recorded in a diary, was comparable (69.4%). Interaccelerometer discrepancies may be related in part to the threshold employed by each instrument for classifying moderate intensity patterns.  相似文献   

The Mechanics of Batting: Analysis of Ground Reaction Forces and Selected Lower Extremity Kinematics     

Stephen P. Messier  Marjorie G. Owen 《Research quarterly for exercise and sport》2013,84(2):138-143

Abstract

The purpose of this study was to examine variations in ground reaction forces and selected lower extremity kinematics during the stride and swing phases of batting. High speed photography (100 fps) employing direct linear transformation methodology and a force plate were used to record three-dimensional kinematic and kinetic data for 7 female fast pitch softball batters. Mean vertical forces (F_z) of the right or rear foot increased to approximately 1 BW during the stride. Once the left or forward foot made contact with the ground after completion of the stride, right F_z forces decreased to .43 BW while left F_z forces rapidly increased to 1.6 BW at contact. The mean decrease in right F_z forces from peak force until contact was 55%, and the ratio of left to right F_z forces; at impact was 3.67:1. Right mediolateral forces (F_x) were exerted laterally, away from the batter, and were responsible for initiating movement of the body toward the pitched ball. As the left foot made contact with the ground at completion of the stride, left F_x forces were exerted laterally toward the pitched ball. The reaction to these forces retarded the batter's forward momentum, increased stability, and caused the left hip and knee to extend as contact approached. Right and left anteroposterior forces (F_y) acted in opposite directions (right foot pushing backward, left foot pushing forward), and were responsible for rotating the hips and upper body in a counterclockwise direction toward the pitched ball. Horizontal angular deceleration of both thighs just prior to contact was due, in part, to a decrease in these forces. These data may prove helpful when attempting to identify atypical batting patterns, and when considering improvements in shoe design. In the latter instance, force production and stability may be enhanced by aligning the cleats along the lines of action of the applied resultant shear forces.  相似文献   

Teaching and learning in the Arab World     

Ali Ait Si Mhamed 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2012,58(2):303-307

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The Role of Multicultural Personality in Predicting University Adjustment of International Students in Turkey     

Dilek Yelda Ka?n?c? 《International journal for the advancement of counseling》2012,34(2):174-184

The study examined how particular demographic and multicultural personality variables might predict university adjustment of international students in Turkey. One hundred and twenty-one international students from five geographical regions, including Middle Central Asia, the Balkans, the Middle East, the Kafkasia Region, and the Russian Federations, studying in a main university in İzmir, Turkey, participated in the study. The Multicultural Personality Questionnaire (Van der Zee and Van Oudenhoven, 2000) and a demographic information questionnaire were used to collect data, which were examined in regard to responses to the University Life Scale (Aladağ, Kağnıcı, Tuna and Tezer, 2003). According to the results, while demographic variables did not significantly predict the university adjustment of international students, multicultural personality variables did. Social initiative, emotional stability, open-mindedness and cultural empathy were found to be significant predictors of university adjustment.  相似文献   

Development and trialling of a graduated descriptors tool for Australian pharmacy students     

Ieva Stupans  Susanne Owen  Leigh McKauge  Lisa Pont  Greg Ryan  Jim Woulfe 《Assessment & Evaluation in Higher Education》2012,37(7):829-845

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Sexual force at sexual debut. Swedish adolescents with disabilities at higher risk than adolescents without disabilities     

Brunnberg E  Boström ML  Berglund M 《Child abuse & neglect》2012,36(4):285-295

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