Force production in the rugby union scrum

In this study, we examined the relationship between anthropometric, strength and power characteristics of rugby forwards, their body position when scrummaging, and their ability to apply force when scrummaging. Force applied to an instrumented scrum machine was measured for 56 players, both individually and as scrum packs. Measurements of body position for individuals were made by digitizing videotape records of the trials. Forty players subsequently had their anthropometry assessed and completed several strength and power tests. Body mass, each component of somatotype, maximal anaerobic power developed on a cycle ergometer, and isokinetic knee extension strength correlated significantly with individual scrummaging force. A regression model (P < 0.001) including body mass, mesomorphy, maximal anaerobic power and hip angle while in the scrummaging position accounted for 45% of the variance in individual scrummaging force. The packs that produced the largest scrummaging forces were, in general, characterized by a greater pack force to sum of individual force ratio than the packs producing lower forces. Our results emphasize the need for a scrum pack to develop technique and coordination as a unit to maximize scrummaging force.     

The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO2max) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45+/-0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12+/-0.47 litres). The ambient temperature was 30.2+/-0.6 degrees C (mean +/- s), with a relative humidity of 71+/-1% and an air speed of approximately 0.7 m x s(-1) on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly (P < 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly (P < 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.     

An analysis of selected kinematic variables in national and elite male and female 100-m and 200-m breaststroke swimmers

The kinematic analysis of competition breaststroke swimming has tended to focus on the mean values of swimming speed, stroke rate and stroke length; values in individual lengths, as well as the start, turns and finish, have largely been ignored. This study includes all such variables and aims to improve the coach's holistic understanding of breaststroke racing by determining the relationships and differences between and within these selected kinematic variables. We also compare 100-m events with 200-m events to determine if there are characteristic differences between them. Competitive breaststroke swimming performances in 100-m events (males: n = 159, finishing time = 65.05 +/- 2.62 s; females: n = 158, finishing time = 74.04 +/- 3.66 s) and 200-m events (males: n = 159, finishing time = 141.47 +/- 6.15 s; females: n = 158, finishing time = 158.66 +/- 7.87 s) were collected and analysed from 12 world, international and national championships. The better 100-m and 200-m breaststroke swimmers were found to demonstrate greater competency in the kinematic variables measured, except stroke kinematics, which were unique to each individual. These findings suggest that coaches should place emphasis on all of the kinematic components in training and that they should attempt to identify the stroke rate to stroke length ratio most appropriate for the individual. Finally, characteristic differences do exist between the 100-m and 200-m events, which has implications for how swimmers might train for each event.     

The effect of two different 18-week walking programmes on aerobic fitness, selected blood lipids and factor XIIa

Forty-nine previously sedentary or low active individuals aged 40-71 years were allocated to three groups. The long walking group participated in an 18-week walking programme which consisted of walks lasting 20-40 min; the repetitive short walking group completed walks of between 10 and 15 min, up to three times a day, with no less than 120 min between each walk; and the control group maintained their low level of activity. Both walking programmes began at a prescribed 60 min x week(-1), which increased steadily up to 200 min x week(-1) by week 12. During the study, the long walking group walked for an estimated 2514 min (139 min x week(-1)), expending an estimated 67.5 MJ (3.72 MJ x week(-1)) at an estimated 73% of their age-predicted maximum heart rate and 68% of their estimated VO2max. The repetitive short walking group walked for an estimated 2476 min (135 min x week(-1)), expending an estimated 58.5 MJ (3.17 MJ x week(-1)) at an estimated 71% of their age-predicted maximum heart rate and 65% of their estimated VO2max. The results showed a statistically significant reduction in heart rate during a standardized step test (pre- vs post-intervention) in both walking groups, indicating an improvement in aerobic fitness, although the control group showed a higher average heart rate during the post-intervention test, indicating reduced fitness. When compared with the male subjects pre-intervention, the females possessed more favourable levels of high-density lipoprotein (HDL) cholesterol (P< 0.001), apolipoprotein (apo) AI (P < 0.001) and ratios of total cholesterol:HDL cholesterol (P< 0.02) and low-density lipoprotein (LDL) cholesterol: HDL cholesterol (P< 0.02). Compared with the controls post-intervention, the walking groups showed no statistically significant changes in total cholesterol, LDL cholesterol, HDL cholesterol, apo AI, apo AII, apo B, or the ratios of total cholesterol: HDL cholesterol, LDL cholesterol: HDL cholesterol, apo AI: apo B or apo AI: apo AII (P > 0.05). Relative to the walking groups, factor XIIa increased in the control group (P < 0.05). We conclude that, although both walking programmes appeared to improve aerobic fitness, there was no evidence of improvements in the blood lipids or associated apolipoproteins of the walking groups. Further analysis indicated that this apparent lack of change may have been related to the subjects' relatively good pre-intervention blood lipid profiles, which restricted the potential for change. The implications of the observed changes in the coagulation/fibrinolytic factors remain unclear.     

Entwicklung gro?er Systeme mit generischen Methoden – Eine übersicht über den Sonderforschungsbereich 501

Ohne Zusammenfassung