BRAKING FORCES DURING BICYCLE PEDALING: AN EXAMINATION OF THE FULL CRANK ROTATION

Pedalling skills are evaluated using angular impluse of negative crank torque (INCT) that occurs in pulling phase (180-360° of crank rotation that 0° is top dead center. INCT has the effect of inhibit crank rotation (“braking force“). The aim of study was to obtain findings to reduce INCT for improving cyclists\u27 pedalling skills. We examined the relationship between INCT and kinetic pedalling data through the full crank rotation. Fifteen male cyclists performed constant pedalling at 80%Vo2max and 90rpm. Kinetic and kinematic pedalling data were measured by the pedal-shaped force platform (KISTLER) and by a 3D motion capture system (VICON). A negative correlation was indicated 80-250° of crank rotation between horizontal pedal force (Fh) and INCT (pNCT occurring in pulling phase was affected by amount of Fh in pushing phase

Kinematic analysis of punt kick in football goalkeepers based on the level of kick effort

In the present study, we aimed to investigate the differences in punt kicks by football goalkeepers based on the level of effort required. Twelve experienced goalkeepers participated in the study. The participants were instructed to kick the ball as far as possible in the maximum distance trial (100% trial) and to have a more controlled approach for the 80% and 60% trials. Each punt kick was divided into three events: release of the ball from the left hand (BR), pivot foot ground-contact (LFC), and ball impact (IMP). Right lower limb joint velocity, right hip and knee joint angles, flight distance, ball velocity, and kick angle were calculated. The 80% and 100% trials yielded almost the same velocity for each part of the right leg; however, in the 60% trial, the level of kicking effort was managed by adjusting the velocity of the right ankle joint, starting from BR, in addition to adjustment of the velocity of the right knee joint at LFC. Compared to punt kicks with a lower level of effort, the punt kicks with a higher level of effort involved an increase in the hip joint extension angle for the right leg during the backswing and the lowering of the knee joint angle of the right leg at the start of the forward swing, thus producing forward swing velocity for the right foot

スキーにおける基礎回転技術の重要性について －プルークボーゲン･プルークターンの動作解析データより－

本研究ではカービングスキーを用いた基礎回転技術の重要性を確認するための客観的データを取得すると共に､今後の技術指導の一助となる基礎データを蓄積することを目的とした｡カービングスキーが普及して以降､スキー滑走時のスピードコントロールが非常に難しくなってきている｡これはカービングスキーの特性と少なからず関連があると思われ､回転初期へのターン導入が容易になったといわれるカービングスキーではあるが､その一方ターン後半の横滑りが少なくなりスピードコントロールが難しくなっているためではないかと考えられる｡本編では筆者らが2008年に発表した｢スキー技術の関連性に関する研究｣を元に､スキー指導における基礎回転技術の重要性について再検討を試みた｡そこで､これまでの先行研究ではあまり注目されなかった基礎回転技術のプルークボーゲン(PFB)やプルークターン(PFT)に注目し､滑走時の重心位置やスキー板の動きから､2つの技術がスキー滑走時に重要な回転時のスライド(横滑り)を習得するためのものであることが確認された｡またスキー用具の変化にとらわれず基礎技術を習得することの重要さを再認識することができた｡研究論

Hormonal and metabolic responses to repeated cycling sprints under different hypoxic conditions

OBJECTIVE: Sprint exercise and hypoxic stimulus during exercise are potent factors affecting hormonal and metabolic responses. However, the effects of different hypoxic levels on hormonal and metabolic responses during sprint exercise are not known. Here, we examined the effect of different hypoxic conditions on hormonal and metabolic responses during sprint exercise. DESIGN: Seven male subjects participated in three experimental trials: 1) sprint exercise under normoxia (NSE); 2) sprint exercise under moderate normobaric hypoxia (16.4% oxygen) (HSE 16.4); and 3) sprint exercise under severe normobaric hypoxia (13.6% oxygen) (HSE 13.6). The sprint exercise consisted of four 30s all-out cycling bouts with 4-min rest between bouts. Glucose, free fatty acids (FFA), blood lactate, growth hormone (GH), epinephrine (E), norepinephrine (NE), and insulin concentrations in the HSE trials were measured before exposure to hypoxia (pre 1), 15 min after exposure to hypoxia (pre 2), and at 0, 15, 30, 60, 120, and 180 min after the exercise performed in hypoxia. The blood samples in the NSE trial were obtained in normoxia at the same time points as the HSE trials. RESULTS: Circulating levels of glucose, FFA, lactate, GH, E, NE, and insulin significantly increased after all three exercise trials (P < 0.05). The area under the curve (AUC) for GH was significantly higher in the HSE 13.6 trial than in the NSE and HSE 16.4 trials (P < 0.05). A maximal increase in FFA concentration was observed at 180 min after exercise and was not different between trials. CONCLUSION: These findings suggest that severe hypoxia may be an important factor for the enhancement of GH response to all-out sprint exercise