Purpose: The purpose of this study was to clarify the effects of three types of mountain bikes upon cyclists' oxygen consumption and changes of blood lactate concentration, with consideration of the test course and bicycle mass. Methods: We tested the same mountain bike with three suspension conditions: without suspension systems (RIG), with a front suspension system (FS) and with front and rear suspension systems (FRS). Five male cyclists participated in the study. First, we investigated the effects of the suspension systems on a motor-driven treadmill through 〓O₂, heart rate and RPE measurements. Next, we conducted time trial tests in the field so that the essential function of suspension systems could be demonstrated. We measured 〓O₂, heart rate, blood lactate concentrations and performance time. Results: There were no significant differences among the suspension conditions in the treadmill tests. In the field bicycling test, 〓O₂ was significantly greater with FRS than with FS. On the other hand, the highest blood lactate concentration was observed with FS. Conclusion: Our off-road tests suggested that the FRS mountain bike attenuated blood lactate accumulations and allowed the participants to exercise more aerobically than the FS bike. FRS might therefore be more suitable for 2-hour long cross-country mountain bike races.

To analyze the state of airflow around ski-jumpers, a measurement technique has been developed. It is based on the surface tuft method and enables us to analyze the airflow in the taking-off of a real jumping trial. First, the distributions of the airflow orientation and its perturbation were measured along the back of the human mannequin that took the crouching position on a running car. Apparent turbulence was found at the back of the neck and behind the hip. Then, this technique was applied to the analysis of airflow in the taking-off phase of real ski-jumping. It was newly found that the airflow around the jumper started being disturbed after the jumper passed the hill edge. In the analysis of this phenomenon and the recorded posture transition of the jumper, the information useful to improve the score in competition was obtained. Through this study, the effectiveness and the usefulness of this technique for aerodynamic analysis in sports was verified.

In various soft-tennis smash techniques, the standing smash (SS) and jumping smash (JS) are considered to be fundamental techniques, but have quite different kinematics. In the present study, SS and JS of eight skilled volleyers were videotaped and the racket-arm dynamics was analyzed using the procedures of 3-D motion analysis. The joint forces/torques along the anatomical axes, the joint powers and the mechanical works at each joint were compared between SS and JS.

All of the joint forces of SS and JS showed considerably similar changes at the all joints; however, the peak value of the anterior force at the elbow joint and the proximal force at the elbow and wrist joints of JS were significantly larger than those of SS. This will be caused by the difference in the movement direction of the body; Since center of the gravity of the whole body moves backward in JS (SS: forward), larger forces act on the joints not to distract the racket arm, which moves forward both in SS and JS. SS and JS also showed similar changes in joint torque; however, an elbow extension torque peak in the early phase of the forward swing was observed only in SS. This torque may do a part to control the arm position toward the impact point, and also to be a trigger that starts extending the elbow joint. The horizontal adduction torque near impact of JS was marginally significantly smaller than that of SS; on the contrary, the adduction torque of JS was not significantly but quite larger in the mean value than that of SS. There are substantial differences in how to utilize the shoulder torque between SS and JS. In contrast with the joint force and joint torque, the joint force powers showed quite different changes between SS and JS, particularly near impact. In JS, additional peaks before impact were found at the shoulder and elbow joints compared with SS. Moreover, the mechanical works done by these joint forces (time integral of joint force power) of JS were smaller than those of SS at the all joints. This seems to meet the result that the kinetic energy of the hand-racket segment at impact was also smaller in JS. In spite of the small energy, the enough racket head velocity in JS may be obtained by the larger rotation of the hand-racket segment. Changes of the joint torque powers of SS and JS showed similar tendencies as a whole. However, a slight peak of the torque power at the elbow joint was observed only in SS. This indicates that the energy generation by muscles actually occurs when the elbow extension torque acts in SS. The positive peak value of the torque power at the wrist joint was a marginally significantly large in JS. Consequently, it will be proper to emphasize the larger wrist motion in the situation of JS coaching. As for the mechanical work done by the elbow joint torque (time integral of joint torque power), both of SS and JS were negative (energy absorption), and the absolute value of JS was marginally significantly larger than that of SS. In conclusion, because changes of the joint force and joint torque are quite similar between SS and JS, players may feel little difference in how to use the racket-arm as a whole. However, investigating more details, delicate differences were clarified at any joint, and these results will reflect the subtle characteristics of each technique.

The purpose of this study was to investigate kinetic characteristics of distance running on the uphill. Six varsity distance runners were asked to run on the slopes of different inclinations (0, 3.2, 6.4, and 9.1 %) at three running speeds (5.0, 4.2, and 3.3 m/s) on the overground. Subjects were videotaped with a high speed video camera. Ground reaction forces (GRF) were measured with two force platforms mounted in a specially-made runway, 12 m in length, on the slope. Two dimensional coordinates of body segment endpoints were obtained by a panning DLT method. Joint torques and joint torque powers of the lower limb joints were calculated on a planar link model. GRF data normalized by the support time and the joint torque and joint torque power normalized by the time of one running cycle were averaged.

In the steep slopes (6.4% and 9.1%), the vertical impact force just after the foot contact was small and the maximum loading rate was significantly smaller than the level condition. There was no significant difference in the impulse and the peak value of the vertical and horizontal GRF among four inclinations. The hip extensors' torque just before the foot contact and the hip positive power before and after the foot contact significantly increased as the inclination increased. The hip flexors' torque and the positive power just after toe-off significantly increased as the inclination increased. These results reveal that, the impact shock just after the foot contact was smaller and hip torque power during the swing phase was enhanced in the uphill running. In the support phase, there was little difference in the peak value and the pattern of the joint torques among the inclinations. However, the positive powers of the lower limb joints during the second half of the support phase increased in the uphill running due to larger extension velocities of the lower limb joints.

The kip maneuver is one of the principal skills of apparatus exercise at the horizontal bar, but it is difficult for beginners to execute the maneuver. Most of the studies on the kip maneuver compared successful trials with unsuccessful ones, or the trials of skilled subjects with that of unskilled ones. Although skill training is mandatory for beginners to successfully complete the kip maneuver, there is no study on the process of learning and the effect of skill training on the changes in biomechanical parameters in the kip maneuver. The purpose of this study was to investigate effects of skill training for the kip maneuver on the shoulder and hip joint torques in the learning process. The kip maneuver of ten male varsity club gymnasts was videotaped and analyzed two-dimensionally to make the motion model of the kip maneuver of the skilled subjects. Three male subjects with no experience of performing the kip maneuver were selected as unskilled subjects. They participated in skill training for 5 to 12 days to learn the kip maneuver. All trials of the unskilled subjects were videotaped during the training. We selected every five trials to analyze changes in joint angles, torques of the shoulder and hip joints, and mechanical work done by the joints.

The number of trials the unskilled subjects needed to successfully complete the kip ranged from 47 to 108. Movements of the shoulder and hip joints in the trials in the second half of training were similar to those of the successful trials of all unskilled subjects. The range of the hip movement gradually increased with the number of trials. In the skilled subjects, immediately after the reversal point of the swing, i.e. the forward to the backward swing, the shoulder extension torque was increased rapidly with the extension of the shoulder joint, while the hip extension torque was exerted continuously in the same phase. This may indicate that the skilled subjects extended the shoulder joint strongly and intentionally. In the first trial of the unskilled subjects, the shoulder joint torque had three peaks. The hip extension torque was very small, whereas in the trials from the midpoint of the training, one of the peaks of the shoulder joint torque disappeared and hip extension torque was developed during the backward swing. In the unskilled subjects, the maximal hip extension torque significantly related to the number of trials in subjects B (y = 158.5 + 0.99 x, p < 0.05, where y is the maximal hip extension torque and x is the number of trials) and C (y = 145.3 + 1.09 x, p < 0.05, y and x respectively). The mechanical work done by the shoulder joint showed no significant relation to the number of trials in all subjects. Although the mechanical work done by the hip joint significantly related to the number of trials (subj. A: y = 150.2 + 2.15 x, p < 0.05; subj. B: y = 164.3 + 1.30 x, p < 0.05; subj. C: y = 196.7 + 1.22 x, p < 0.05, where y is the mechanical work and x is the number of trials). These results may suggest that it is essential for the unskilled subjects of the kip maneuver to increase the hip extension torque and the mechanical work done by the hip joint as well as to exert the shoulder extension torque.