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Biomedical subjects

R J Gregor

Publications and source records attributed to R J Gregor.

40 records · Page 3Linked to original sources
PubMedDate not supplied

Relationship between ankle muscle and joint kinetics during the stance phase of locomotion in the cat.

The purpose of this study was to examine the relationship between internal force production in selected skeletal muscles and the externally calculated joint moment during overground locomotion in the adult cat. Hindlimb segments were modelled as a linked system of rigid bodies and a generalized muscle moment (GMM), the sum over all active and passive tissues acting about the joint, was calculated using principles of inverse dynamics. Moments produced by individual muscles were calculated using tendon transducers implanted in freely moving cats and muscle moment arm information. Results indicated that the externally measured variables of peak ground reaction force and joint position were equally important to the determination of peak ankle GMM. Examination of peak moments revealed that increases in peak ankle GMM were met by increases in medial (MG) and lateral (LG) gastrocnemius output. Peak soleus (SOL) moments did not change significantly as a function of peak ankle GMM. The role of the plantaris (PLT) was less clear, with peak moments increasing significantly as a function of peak ankle GMM in one cat. All four ankle extensors were important to the attainment of peak ankle GMM early in stance. Subsequently, SOL and PLT contributed substantially to the ankle GMM throughout stance, LG moments declined to near zero, soon after peak ankle GMM; and MG moments demonstrated a substantial but more gradual decline. The relative contributions of these individual muscles to the ankle GMM were supported by their respective architecture, uniarticular versus multiarticular function, and physiological profiles.

Animals↗
PubMedDate not supplied

Three-dimensional cinematographic analysis of water polo throwing in elite performers.

Thirteen members of the United States Men's Water Polo Team were filmed using two synchronized cameras while shooting at a goal. Three-dimensional (3D) coordinates of the throwers' shoulder, elbow, wrist, and the ball were used to estimate elbow angle, elbow angular velocity, and ball velocity at release. Ball release velocities ranged from 14.5 to 25.8 m/sec, with peak elbow angular velocities averaging 1137 degrees/sec. Peak elbow angular velocity typically was reached just prior (x = 28 msec) to release as the elbow approached full extension. Results are significant in establishing the efficacy of 3D techniques in evaluating throwing mechanics and may prove useful in: identifying characteristics of superior performers, assessing differences in throwing technique between injured and non-injured populations, and providing a kinematic data base for further studies of throwing kinetics and potential injury mechanisms.

Adult↗
PubMedDate not supplied

Kinematic analysis of human upper extremity movements in boxing.

Using two synchronized cameras, four experienced boxers were filmed while they threw a series of punches at a practice bag. Three-dimensional (3D) coordinates of each boxer's shoulder, elbow, wrist, and glove were used to estimate linear and angular kinematics of the upper extremity. Average velocities at contact ranged from 5.9 to 8.2 m/s with peak velocities of 6.6 to 12.5 m/s reached 8 to 21 ms prior to hand/grove contact with the bag. Significant differences in shoulder and wrist velocitie, elbow angle excursions, and elbow angular velocities were seen when comparing hooks and jabs. Few differences were evident when comparing the kinematics of gloved versus bare-handed punches. Results are significant in providing kinematic data characteristic of experienced performers, which may be used in a kinetic model of punch impact and its relationship to potential injury mechanisms.

Adult↗