This paper deals with the dynamic motion analysis of carving and skidding turns by the measurement of skier gliding on the actual snow field. The measurement system consists of the motion measurement systems installing the inertial and magnetic field sensors, the measurement system of gliding trajectory installing the GPS receiver and the measurement system of reaction force from snow surface installing the 6-axis force sensor. The joint torque of skier is estimated by the information of the measurement systems of motion and reaction force from snow surface. We conducted the measurement experiment of carving and skidding turns by skier gliding on the actual snow field. Then we analyzed the skier's motion using the joint torque. Furthermore, we analyzed about the carving turn and the side skidding of ski using the joint torque and the gliding velocity. The analysis results indicated the method used for the forces of skier in turns and the relation between joint torque and gliding velocity. The proposed method and the analysis results can be used to the detection of ideal turn methods and the evaluation of skier's skill.

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We have developed various kinds of the alpine skiing robot to clarifying the basic elements of a skier's movements, which look complex during turns. The skiing turn is classified roughly into carving turns and skidding turns. The alpine skiing robot is split into two basic types: an active type（with actuator）and a passive type （without actuator）．We have developed active carving-turn models with actuators, skidding-turn models with actuators, and passive carving-turn models without actuators. However, so far the research had not included the conditions and objectives of a passive skidding-turn model without an actuator. So we have developed a passive skidding-turn model of inward lean with inner rotation of the hip Joints, with inner rotation of the hip joints around the femur axes, but with no actuation, and which can snowplow like a skier. In terms of the performance of the passive skidding-turn model, keeping the bilateral hip joints of the skidding-turn model（which are rotated slightly inside with a rectangular double-lever mechanism of the four links of a quadric crank-chain），a sequential skidding-turn could be achieved with energy-less skiing. For the passive skidding-turn model, even if the rudder angle was applied to the top-lifted side, a turn could be achieved. Moreover, the direction of the turns of the skidding-turn model of inward lean with inner rotation of the hip joints corresponded overall to the direction of the steer of a ship.

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Olaf Helset came to Japan to introduce new Nordic skiing techniques in 1928-29. After his extensive activities in Japan, skier's ability developed quickly. As a result the Japanese skier Adachi took eighth place at the 1932 Winter Olympic games held in Lake Placid. Helset's distinguished services were a valuable contribution towards the Japanese ski society. We need to outline his life and career as a benefactor who enabled the further development of Japanese skiing early in the Showa era（1925-1988）． This study informs about his career as follows; 1. Helset grew up having strong patriotism and became an army officer who was active in the Norwegian ski society from the 1920's to 1930's. 2. When Norway was under German rule from 1940 to 1945, Helset led the sports strike as a leader for the movement of resistance against the German army. As a Chief of the Army he organized and trained the Norwegian army within Sweden illegally. 3.After World War-Ⅱ Helset became Chief of the Army and sports society in Norway due to his distinguished services between 1946-1948. When the Labour Party won the national election in 1948, he took a step down from these two positions.

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This study examines the regional pattern of lost and closed ski fields in Japan, analyzing closing trend of all developed ski fields including those equipped only with T-bar lifts. Around 750 ski fields were opened between 1950 and 2003 in the whole country. However, nearly 37 percent of them were already closed or completely disappeared. This trend was dominant around 2000, involving owners' changes of lift companies. Most of the lost fields tend to be very small with one or two ski lifts. Whereas there are many lost ski fields previously operated by urban capital around the metropolitan areas, the outer extent areas from there have many lost ski fields by local governments. The increasing difficulty of the management plays an important role for the closing based on the decrease in the number of active skiers, rather than shortage of snow depth. The changing environment of the management has been affected through the changes in locational conditions for ski fields, the diseconomies of fields' agglomeration in an appropriate region, the very short-term of growth period around 1990, and problems in local municipalities（such as deficit budget and amalgamation）．While the number of active skiers continuously decreased in the last 20 years, especially in snowy regions in eastern Japan, there are some signs for recovering market of skiers now. Operating firms of existing ski fields face various tasks for the sustainable development, including measures against the expanding foreign skiers.

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This research aims to provide an overview of the present situation of master ski by clarifying the characteristics of the participants and the competitions' performances. The author based the analysis mainly on the results of the questionnaire survey made to Prefectural Ski Associations as well as all the individual data from the SAJ Data Bank published on the homepage of SAJ and approached the findings as follows: 1）the master ski participants increased 2.2 times after 01/02 seasons, but this number has been kept at the same level in the recent three seasons. 2）Female master ski participants occupied about 11～13％ of the total, less than the male participants. 3）The Ski Association of every prefecture is expecting to develop master ski as a「Lifelong Sport」， therefore「safety」becomes the top issue in running the Master Ski Tournaments. And finally the author concluded that it is necessary to discuss the supporting strategies to further promote the Master Ski program.

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This paper proposes a measurement system of reaction force from snow surface using compact force sensors for snowboarding. This system can measure the 3-axis force and the 3-axis moment components from the outputs of three 3-axis compact force sensors installing to this system. We established the calculation method of moment component using three 3-axis force sensors, and this measurement system was lighter than that used in previous studies. We conducted the verification experiment to evaluate the system accuracy, and the results indicated the high accuracy. The measurement experiment of snowboarder installing the system was conducted on the actual snow field. The reaction force from snow surface obtained by the experiment indicated the major features of snowboard turns. The proposed system can be used to clarify the mechanism of snowboard turn and the skill rating of snowboarder.

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The purpose of this study was to determine whether or not occlusal force had any relation to power type on anaerobic output. The relations of anaerobic power and occlusal force was tested using 14 alpine skiers（nationally ranked within the top 200）．Anaerobic power and occlusal force were measured at the same time using a Power Max V II stationary bike and occlusal force（dental prescale）．Subjects were then classified as strength type or speed type depending on their power profiles. The range of anaerobic power for the subjects was from 14.28 watt/kg to 14.63 watt/kg which are within the expected range for alpine skiers. Strength type and speed type subjects showed very pronounced differences in their occlusal force tests; strength type subjects occlusal force decreased rapidly during the three stages of the Power Max test while the speed type subjects showed no significant decreases at all. There is significant difference of two group to occlusal force at power max test in three stage（p<0.05）．In conclusion, we found a significant relation between anaerobic power profile and occlusal force. Future studies will be done to generate more detailed occlusal force contact profiles to determine whether or not force values in specific areas of the mouth can be used to determine power type.

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The aim of this study was to investigate the seasonal variation of bone metabolism and bone mineral density in male alpine skiers. Ten alpine skiers（male 20.6±1.6 year）were measured body weight, percent body fat, lean body mass, body mass index（BMI），body mineral density（BMD），serum levels of osteocalcin（OC）， bone alkaline phosphatase（BAP），tartrate-resistant acid phosphatase 5b（TRACP-5b），parathormone, and 25- hydroxyvitamin D（25（OH）D）．Measurements were conducted in pre-competitive season（T1），competitive season（T2），post-competitive season（T3），and second pre-competitive season（T4）．Percent body fat was significantly increased from T1 to T3 and T4, BMI was also significantly increased from T1 to T4. Although no significant differences were observed BMD, BAP and OC were significantly decreased from T1 to T2 and T3, TRACP-5b was significantly decreased from T2 to T4. The coupling index of bone metabolism, which means the ratio of bone resorption and bone formation were also significantly decreased from T1 to T2 and T3. Since bone formation and coupling index were significantly decreased from T1 to T3, we suggest that bone metabolism of male alpine skiers was close to severe condition because of consecutive competitions. We conclude that skiers, it is necessary for male alpine to monitor the bone metabolism markers with BMD throughout the year.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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