The effect of ball carrying method on sprint speed in rugby union football players

Different methods of ball carrying can be used when a player runs with the ball in rugby union. We examined how three methods of ball carrying influenced sprinting speed: using both hands, under the left arm and under the right arm. These methods were compared with running without the ball. Our aim was to determine which method of ball carrying optimizes sprinting speed. Altogether, 48 rugby union players (age 21 +/- 2 years, height 1.83 +/- 0.1 m, body mass 85.3 +/- 12 kg, body fat 14 +/- 5%; mean +/- s) were recruited. The players performed twelve 30-m sprints in total (each player performed three trials under each of three methods of carrying the ball and sprinting without the ball). The design of the study was a form of Latin rectangle, balanced across the trial order for each of the methods and for pairwise combinations of the methods in blocks of four per trial. Each sprint consisted of a 10-m rolling start, followed by a 20-m timed section using electronic timing gates. Compared with sprinting 20 m without the ball (2.58 +/- 0.16 s), using both hands (2.62 +/- 0.16 s) led to a significantly slower time (P < 0.05). Sprinting 20 m with the ball under the left arm (2.61 +/- 0.15 s) or under the right arm (2.60 +/- 0.17 s) was significantly quicker than when using 'both hands' (P < 0.05), and both these methods were significantly slower than when running without the ball (P < 0.05). Accordingly, running with the ball in both hands led to the greatest decrement in sprinting performance, although carrying the ball under one arm also reduced the players' sprinting ability. Our results indicate that to gain a speed advantage players should carry the ball under one arm.     

Comparing the pre- and post-impact ball and racquet kinematics of elite tennis players' first and second serves: a preliminary study

The aim of this study was to compare the pre- and post-impact three-dimensional kinematics of the ball and racquet during first and second serves performed by elite tennis players. Data were collected from four male and four female right-handed professional players during competition using two high-speed cameras (200 Hz). For each player, one first serve and one second serve from the 'deuce' or right service court that landed within the specified target area were analysed. To test for significant differences between the first and second serves, Wilcoxon tests (P < or = 0.05) were performed on selected parameters. The results indicate that the ball travelled forward and to the left during the flight phase of the toss in all but one trial. The average pre-impact ball forward location for the first serve was significantly more in front and had a higher associated forward ball velocity than the corresponding values for the second serve. On average, the decrease in post-impact ball speed from the first to the second serve was 24.1%. No significant differences between the first and second serves were found in the pre-impact racquet head speed and orientation, which was represented as a unit vector perpendicular to the racquet face. The major adjustments made by the players when going from the first to second serve were a decrease in pre-impact ball forward location (P < or = 0.01) and an increase in the pre-impact racquet vertical and lateral velocities (both P < or = 0.05). This implies that the players tossed the ball closer to the body and imparted topspin and sidespin on the ball by changing the racquet vertical and lateral velocities when going from the first to the second serve.     

Differences between the sexes in the three-dimensional angular rotations of the lumbo-pelvic-hip complex during treadmill running

The aims of this experiment were to determine whether there are differences between the sexes in the three-dimensional angular rotations of the lumbo-pelvic-hip complex during running and, if such differences exist, to establish whether factors other than sex can explain the observed differences. A cohort of 44 non-injured runners (22 males, 22 females) who usually ran more than 20 km per week were voluntarily recruited. All trials were conducted on a treadmill at a running speed of 4.0 m x s(-1). Reflective markers were placed over specific anatomical landmarks of the thoraco-lumbar spine, pelvis and femur. Data were captured using a VICON motion analysis system. Females tended to display a greater peak-to-peak oscillation for most of the angular rotations. An offset was the main difference between the male and female group mean waveforms for pelvis anterior-posterior tilt. Forward stepwise regression analysis revealed that sex was the most common variable related to the amplitudes of the angular rotations. Given these results, sport scientists conducting future biomechanical studies using angular data to test hypotheses are advised to be extremely cautious about averaging across male and female participants.     

Hermann-Altrock-Stipendium Ausschreibung 2003

Deutscher Sportbund

Hermann-Altrock-Stipendium Ausschreibung 2003     

Impact absorption of tennis shoe-surface combinations

The aim of this study was to investigate, for typical shoes and surfaces used in tennis, the relative role of the shoe and surface in providing cushioning during running. Five test surfaces ranging from concrete to artificial turf were selected, together with two shoe models. Impact absorbing ability was assessed mechanically using drop test procedures and biomechanically using peak magnitude and rate of loading of impact force and peak in-shoe pressure data at the lateral heel. Differences in biomechanical variables between shoe-surface combinations were identified using a two-way ANOVA (p < 0.05). Mechanical test results were found to rank the surfaces in the same order regardless of the shoe model, suggesting that the surface is influential in providing cushioning. However, for all mechanical and biomechanical (p < 0.05) variables representing impact absorbing ability, it was found that the difference between shoes was markedly greater than the differences between surfaces. The peak heel pressure data were found to rank the surfaces in the same order as the mechanical tests, while impact force data were not as sensitive to the changes in surface. Correlations between mechanical and biomechanical impact absorption highlighted the importance of testing the shoe-surface combination in mechanical tests, rather than the surface alone. In conclusion, mechanical testing of the shoe-surface combination was found to provide a strong predictor of the impact absorbing ability during running if pressure data were used. In addition, for typical shoe-surface combinations in tennis, the shoe was found to have more potential than the surface to influence impact loading during running. Finally, in-shoe pressure data were found to be more sensitive than force plate data to changes in material cushioning.     

Do you Mini-Med School? Leveraging library resources to improve Internet consumer health information literacy

Popular for engaging public interest in medical science while promoting health awareness, Mini-Med School (MMS) programs also afford important if largely unrealized opportunities to improve the health information literacy of attendees. With a growing population using the Internet to make health decisions, needed venues for improving Internet Consumer Health Information (CHI) literacy may be found in the MMS platform. Surveyed directors of MMS programs understand the need to include CHI, and successful programs at SUNY Stony Brook and elsewhere demonstrate the potential for collaboration with affiliated health sciences libraries to integrate CHI instruction into MMS curricula.     

Do oarsmen have asymmetries in the strength of their back and leg muscles?

The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring: quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring: quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side (P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.     

Season-of-birth bias in association football

In this longitudinal study, we assessed the frequency of birth dates for boys selected for the Football Association National School. Birthdays were divided into three periods of the year: January to April, May to August and September to December. We compared data over a 5 year period and concluded that there is indeed a bias towards selecting older children. Furthermore, analysis of separate data revealed a shift of bias when comparing two different start dates, namely September and January. Our findings show that the youngest children from the January start date (born September to December) are selected significantly more often than the youngest children from the September start date (born May to August). Interestingly, even when the influence of body mass was reduced, the selection bias towards the older players remained.     

Effects of active, passive or no warm-up on metabolism and performance during high-intensity exercise

The aim of this study was to determine the influence of type of warm-up on metabolism and performance during high-intensity exercise. Eight males performed 30 s of intense exercise at 120% of their maximal power output followed, 1 min later, by a performance cycle to exhaustion, again at 120% of maximal power output. Exercise was preceded by active, passive or no warm-up (control). Muscle temperature, immediately before exercise, was significantly elevated after active and passive warm-ups compared to the control condition (36.9 +/- 0.18 degrees C, 36.8 +/- 0.18 degrees C and 33.6 +/- 0.25 degrees C respectively; mean +/- sx) (P< 0.05). Total oxygen consumption during the 30 s exercise bout was significantly greater in the active and passive warm-up trials than in the control trial (1017 +/- 22, 943 +/- 53 and 838 +/- 45 ml O2 respectively). Active warm-up resulted in a blunted blood lactate response during high-intensity exercise compared to the passive and control trials (change = 5.53 +/- 0.52, 8.09 +/- 0.57 and 7.90 +/- 0.38 mmol x l(-1) respectively) (P < 0.05). There was no difference in exercise time to exhaustion between the active, passive and control trials (43.9 +/- 4.1, 48.3 +/- 2.7 and 46.9 +/- 6.2 s respectively) (P= 0.69). These results indicate that, although the mechanism by which muscle temperature is elevated influences certain metabolic responses during subsequent high-intensity exercise, cycling performance is not significantly affected.