Effects of weighted vests and sled towing on sprint kinematics

In this study, we compared sprint kinematics of sled towing and vest sprinting with the same relative loads. Twenty athletes performed 30-m sprints in three different conditions: (a) un-resisted, (b) sled towing, and (c) vest sprinting. During sled towing and vest sprinting, external loads of 15% and 20% of body mass were used. Sprint times were recorded over 10 and 30 m. Sagittal-plane high-speed video data were recorded at 5, 15, and 25 m from the start. Relative to the un-resisted condition, sprint time increased (7.5 to 19.8%) in both resisted conditions, resulting mainly from decreased step length (-5.2 to -16.5%) with small decreases in step frequency (-2.7 to -6.1%). Sled towing increased stance phase duration (14.7 to 26.0%), trunk angle (12.5 to 71.5%), and knee angle (10.3 to 22.7%), and decreased swing phase duration (-4.8 to -15.2%) relative to the un-resisted condition. Vest sprinting increased stance phase duration (12.8 to 24.5%) and decreased swing phase duration (-8.4 to -14.4%) and trunk angle (-1.7 to -13.0%). There were significant differences between the two resisted conditions in trunk, thigh, and knee angles. We conclude that sled towing and vest sprinting have different effects on some kinematics and hence change the overload experienced by muscle groups.     

Simulation to clarify the effect of paddling motion on the hull behavior of a single kayak in a sprint race

The cause and effect relationship between the paddling motion and the hull behavior of a kayak in a sprint race has not been sufficiently investigated. The objective of this study was to investigate the effect of the paddling motion on the hull behavior by numerical simulation. A dynamic simulation model of a paddler, paddle and hull in a single kayak, which was previously developed, was used for the simulation. One standard paddling motion and three modified motions were prepared for the simulation. Three modified motions were created based on suggestions by coaches of the Japan Olympic team. These motions were thought to be often seen in paddlers of lower skill level and, therefore, empirically considered to be typically bad motions. From the simulation results, the following findings were obtained: in the simulation of the standard paddling motion, the averaged hull velocity was 5.4 m/s. This was consistent with the actual hull velocity of 5.5 m/s. Typically bad motions which induced undesirable hull fluctuations reduced the propulsive efficiency.     

Intercultural Encounters as Religious Education: Japanese Students at a Christian University and their Religious Transformation

It is commonly acknowledged by many that Japanese teenagers in general hold very negative views of organized religions. However the researcher, as an educator at a Christian University in California, observed every year a great number of Japanese international students becoming persons who paint positive pictures of religion. A study done on those students, utilizing the method of grounded theory, uncovered the following. One, their cross-cultural experiences created crisis situations, which became a catalyst to question their uncritical beliefs about religion. Two, their positive personal encounters with religious people in the United Sates caused them to experience transformation.     

Effects of weighted sled towing on ground reaction force during the acceleration phase of sprint running

Abstract

Athletes use weighted sled towing to improve sprint ability, but little is known about its biomechanics. The purpose of this study was to investigate the effect of weighted sled towing with two different loads on ground reaction force. Ten physically active men (mean ± SD: age 27.9 ± 1.9 years; stature 1.76 ± 0.06 m; body mass 80.2 ± 9.6 kg) performed 5 m sprints under three conditions; (a) unresisted, (b) towing a sled weighing 10% of body mass (10% condition) and (c) towing a sled weighing 30% of body mass (30% condition). Ground reaction force data during the second ground contact after the start were recorded and compared across the three conditions. No significant differences between the unresisted and 10% conditions were evident, whereas the 30% condition resulted in significantly greater values for the net horizontal and propulsive impulses (P < 0.05) compared with the unresisted condition due to longer contact time and more horizontal direction of force application to the ground. It is concluded that towing a sled weighing 30% of body mass requires more horizontal force application and increases the demand for horizontal impulse production. In contrast, the use of 10% body mass has minimal impact on ground reaction force.