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Yuki Inaba, Shinsuke Yoshioka, Yoshiaki Iida, Dean C. Hay and Senshi Fukashiro

Lateral quickness is a crucial component of many sports. However, biomechanical factors that contribute to quickness in lateral movements have not been understood well. Thus, the purpose of this study was to quantify 3-dimensional kinetics of hip, knee, and ankle joints in side steps to understand the function of lower extremity muscle groups. Side steps at nine different distances were performed by nine male subjects. Kinematic and ground reaction force data were recorded, and net joint torque and work were calculated by a standard inverse-dynamics method. Extension torques and work done at hip, knee, and ankle joints contributed substantially to the changes in side step distances. On the other hand, hip abduction work was not as sensitive to the changes in the side step distances. The main roles of hip abduction torque and work were to accelerate the center of mass laterally in the earlier phase of the movement and to keep the trunk upright, but not to generate large power for propulsion.

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Hans H.C.M. Savelberg, Ingrid G.L. Van de Port and Paul J.B. Willems

By manipulating trunk angle in ergometer cycling, we studied the effect of body configuration on muscle recruitment and joint kinematics. Changing trunk angle affects the length of muscles that span the hip joint. It is hypothesized that this affects the recruitment of the muscles directly involved, and as a consequence of affected joint torque distributions, also influences the recruitment of more distal muscles and the kinematics of distal joints. It was found that changing the trunk from an upright position to approximately 20 deg forward or backward affected muscle activation patterns and kinematics in the entire lower limb. The knee joint was the only joint not affected by manipulation of the lengths of hip joint muscles. Changes in trunk angle affected ankle and hip joint kinematics and the orientation of the thigh. A similar pattern has been demonstrated for muscle activity: Both the muscles that span the hip joint and those acting on the ankle joint were affected with respect to timing and amplitude of EMG. Moreover, it was found that the association between muscle activity and muscle length was adapted to manipulation of trunk angle. In all three conditions, most of the muscles that were considered displayed some eccentric activity. The ratio of eccentric to concentric activity changed with trunk angle. The present study showed that trunk angle influences muscle recruitment and (inter)muscular dynamics in the entire limb. As this will have consequences for the efficiency of cycling, body configuration should be a factor in bicycle design.

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Akiko Imura, Yoichi Iino and Takeji Kojima

The fouetté turn in classical ballet dancing is a continuous turn with the whipping of the gesture leg and the arms and the bending and stretching of the supporting leg. The knowledge of the movement intensities of both legs for the turn would be favorable for the conditioning of the dancer’s body. The purpose of this study was to estimate the intensities. The hypothesis of this study was that the intensities were higher in the supporting leg than in the gesture leg. The joint torques of both legs were determined in the turns performed by seven experienced female classical ballet dancers with inverse dynamics using three high-speed cine cameras and a force platform. The hip abductor torque, knee extensor and plantar flexor torques of the supporting leg were estimated to be exerted up to their maximum levels and the peaks of the torques were larger than the peaks of their matching torques of the gesture leg. Thus, the hypothesis was partly supported. Training of the supporting leg rather than the gesture leg would help ballet dancers perform many revolutions of the fouetté turn continuously.

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Michael L. Madigan

The purpose of this study was to investigate agerelated differences in muscle power during a surrogate task of trip recovery. Participants included 10 healthy young men (19–23 years old) and 10 healthy older men (65–83). The task involved releasing participants from a forward-leaning posture. After release, participants attempted to recover their balance using a single step of the right foot. Muscle power at the hip, knee, and ankle of the stepping limb were determined from the product of joint angular velocity and joint torque. Muscle powers during balance recovery followed a relatively consistent pattern in both young and older men, and showed effects of both lean and age. Interestingly, the effects of age did not always involve smaller peak power values in the older men as expected from the well-documented loss of muscle power with aging. Older men exhibited smaller peak muscle power at the knee and larger peak muscle power at the ankle and hip compared to young men. The increases in muscle power at the ankle and hip may result from a neuromuscular adaptation aimed at improving balance recovery ability by compensating for the age-related loss of muscle function.

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Hideyuki Ishii, Toshio Yanagiya, Hisashi Naito, Shizuo Katamoto and Takeo Maruyama

The objective of this study was to investigate the factors affecting ball velocity at the final instant of the impact phase (t 1) in full instep soccer kicking. Five experienced male university soccer players performed maximal full instep kicks for various foot impact points using a one-step approach. The kicking motions were captured two dimensionally by a high-speed camera at 2,500 fps. The theoretical equation of the ball velocity at t 1 given in the article was derived based on the impact dynamics theory. The validity of the theoretical equation was verified by comparing the theoretical relationship between the impact point and the ball velocity with the experimental one. Using this theoretical equation, the relationship between the impact point and the ball velocity was simulated. The simulation results indicated that the ball velocity is more strongly affected by the foot velocity at the initial instant of the impact phase than by other factors. The simulation results also indicated that decreasing the ankle joint reaction force during ball impact shifts the impact point that produces the greatest ball velocity to the toe side and decreasing the ankle joint torque during ball impact shifts the impact point that produces the greatest ball velocity to the ankle side.

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John H. Lawrence III and T. Richard Nichols

Muscle actions are often defined with respect to a single anatomical reference plane based on a “predominant” functional activity. Yet animals must control posture and movement within a three-dimensional (3-D) environment, exerting control over more than one reference plane when responding to a 3-D array of perturbing forces. Consequently, enhanced knowledge concerning the 3-D torque capabilities of certain appendicular muscles might provide for greater understanding of the biomechanical basis for motor control. We propose that the cat postural control mechanism utilizes the inherent 3-D mechanical actions of ankle flexors and extensors to maintain extra-saggital joint stiffness. We used a 6 degree-of-freedom force-moment sensor to assess the effect of ankle joint orientation on the 3-D nature of isometric joint torques evoked by electrical stimulation of muscles crossing the AJC in the deeply anesthetized cat. An orthogonal axis system was established at the designated ankle rotation center, such that pitch (defining flexion-extension), yaw (abduction-adduction), and roll (inversion-eversion) axis torques were calculated. Experimental results show that the classical cat ankle flexor and extensors evoke large extra-sagittal torques as well. Also, the hind limb levering system stabilizes the AJC against large yaw and roll rotations away from the control position.

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Julien Jacquier-Bret, Arnaud Faupin, Nasser Rezzoug and Philippe Gorce

The aim of this study was to propose a new index called Postural Force Production Index (PFPI) for evaluating the force production during handcycling. For a given posture, it assesses the force generation capacity in all Cartesian directions by linking the joint configuration to the effective force applied on the handgrips. Its purpose is to give insight into the force pattern of handcycling users, and could be used as ergonomic index. The PFPI is based on the force ellipsoid, which belongs to the class of manipulability indices and represents the overall force production capabilities at the hand in all Cartesian directions from unit joint torques. The kinematics and kinetics of the arm were recorded during a 1-min exercise test on a handcycle at 70 revolutions per minute performed by one paraplegic expert in handcycling. The PFPI values were compared with the Fraction Effective Force (FEF), which is classically associated with the effectiveness of force application. The results showed a correspondence in the propulsion cycle between FEF peaks and the most favorable postures to produce a force tangential to the crank rotation (PFPI). This preliminary study opens a promising way to study patterns of force production in the framework of handcycling movement analysis.

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Stephanie E. Forrester and Matthew T.G. Pain

This study aimed to identify areas of reduced surface EMG amplitude and changed frequency across the phase space of a maximal dynamic knee extension task. The hypotheses were that (1) amplitude would be lower for eccentric contractions compared with concentric contractions and unaffected by fiber length and (2) mean frequency would also be lower for eccentric contractions and unaffected by fiber length. Joint torque and EMG signals from the vasti and rectus femoris were recorded for eight athletic subjects performing maximum knee extensions at 13 preset crank velocities spanning ±300°⋅s−1. The instantaneous amplitude and mean frequency were calculated using the continuous wavelet transform time–frequency method, and the fiber dynamics were determined using a muscle model of the knee extensions. The results indicated that (1) only for the rectus femoris were amplitudes significantly lower for eccentric contractions (p = .019) and, for the vasti, amplitudes during eccentric contractions were less than maximal but this was also the case for concentric contractions due to a significant reduction in amplitude toward knee extension (p = .023), and (2) mean frequency increased significantly with decreasing fiber length for all knee extensors and contraction velocities (p = .029). Using time–frequency processing of the EMG signals and a muscle model allowed the simultaneous assessment of fiber length, velocity, and EMG.

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Taku Wakahara, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga and Toshimasa Yanai

The purpose of this study was to examine the relationship between muscle architecture of the triceps brachii (TB) and joint performance during concentric elbow extensions. Twenty-two men performed maximal isometric and concentric elbow extensions against various loads. Joint torque and angular velocity during concentric contractions were measured, and joint power was calculated. Muscle length, cross-sectional areas, and volume of TB were measured from magnetic resonance images. Pennation angle (PA) of TB at rest was determined by ultrasonography. The PA was significantly correlated with the maximal isometric torque (r = .471), but not to the torque normalized by muscle volume (r = .312). A significant correlation was found between PA and the angular velocity at 0 kg load (r = .563), even when the angular velocity was normalized by the muscle length (r = .536). The PA was significantly correlated with the maximal joint power (r = .519), but not with the power normalized by muscle volume (r = .393). These results suggest that PA has a positive influence on the muscle shortening velocity during an unloaded movement, but does not have a significant influence on the maximum power generation in untrained men.

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Robert J. Neal and Barry D. Wilson

Three-dimensional kinematics and kinetics for a double pendulum model golf swing were determined for 6 subjects, who were filmed by two phase-locked Photosonics cameras. The film was digitally analyzed. Abdel-Aziz and Karara's (1971) algorithm was used to determine three-dimensional spatial coordinates for the segment endpoints. Linear kinematic and kinetic data showed similarities with previous studies. The orientation of the resultant joint force at the wrists was in the direction of motion of the club center of gravity for most of the downswing. Such an orientation of the force vector would tend to prevent wrist uncocking. Indeterminate peak angular velocities for rotations about the X axis were reported. However, these peaks were due to computational instabilities that occurred when the club was perpendicular to the YZ plane. Furthermore, the motion of the club during the downswing was found to be nonplanar. Wrist uncocking appeared to be associated with the resultant joint torque and not the resultant joint force at the wrists. Torques reported in this study were consistent with those reported by Vaughan (1981).