Biomedical subjects

A E Chapman

Publications and source records attributed to A E Chapman.

At least 37 records · Page 2Linked to original sources

PubMed1984

Kinetic sources of lower-limb angular displacement in the recovery phase of sprinting.

One female sprinter was filmed at the 100-m mark (speed 6.5 m X S-1) of a 400-m run. Four moments occurring at each end of the thigh and shank segments during lower-limb recovery were calculated. These were: proximal and distal net muscle moments, a moment due to proximal joint accelerative force and, a moment due to distal joint-force resulting from motion and inertia of the distal connected segment. Individual contributions of each moment to segmental angular displacement were calculated by double integration, and angular velocity at toe-off was multiplied by time to yield its contribution. Contributions of the proximal muscle moments throughout recovery were 21 rad and 7.5 rad for the thigh and shank segments, respectively. Such large angular displacements did not occur because the three remaining moments opposed the proximal muscle moment. These large moments are mutually offsetting and interactive, acceleration of proximal joints provides a substantial moment during contralateral stance, and segmental angular velocity at toe-off is a significant contributor. Consequently, a phenomenon producing a change in any moment (e.g. muscular fatigue, slippery surface) will require modification of other moments for angular displacement to be maintained within reasonable limits.

Biomechanical Phenomena↗

PubMed1984

Kinematic symmetry of the lower limbs.

This study examined the extent of kinematic symmetry of lower limbs when walking. Twelve able-bodied subjects were measured with a device which recorded three-dimensional motion of hip and knee joints bilaterally. Comparisons of right and left sagittal, transverse, and coronal plane motions were conducted in the time and frequency domains, and indices were developed to express these symmetries in each domain. In both domains high levels of symmetry were observed for the sagittal plane motions of hips and knees. High symmetry was also observed for the hip transverse and coronal plane motions, but symmetry was lower for these planes at the knee. Low standard deviations for the group occurred where symmetry was high. Reduced symmetry in the transverse and coronal planes was attributed to the lower signal to noise ratio for these planes. While experimental technique could be improved by better data collection procedures and by different analytic procedures, the study concluded that the able-bodied individual walks with reasonable symmetry at the hips and knees. These data formed a suitable baseline for comparison with pathologic gait data.

Adult↗

PubMed1984

Prostheses alignment: effect on gait of persons with below-knee amputations.

This study investigated the effect on gait of changing prosthetic alignment for five people with amputations. Three-dimensional angular kinematic data were recorded by electrogoniometers positioned at their hips and knees. Indices of symmetry were developed in time and frequency domains for motion data of lower limbs when walking. These measures of symmetry were determined at different prostheses alignment settings and used to assess the possibility of aligning below-knee prostheses on the basis of symmetry of lower limb motion. Optimal or neutral alignment of below-knee prosthesis, as selected by clinically experienced personnel, tended to minimize asymmetry of gait at the hips and knees for persons with below-knee amputations. The indices of symmetry showed that alignment changes to the prosthetic foot disrupt gait to a greater extent than do other alignment changes. Asymmetries of hip flexion-extension motions were more sensitive to alignment changes than were other asymmetries. An index was selected that showed sensitivity to changes in gait caused by changes in prosthetic alignment for below-knee amputations. Refinements and other applications of this index in rehabilitation are suggested.

Artificial Limbs↗

PubMed1983

A new approach to the human muscle model.

Hill's (1938) two component muscle model is used as basis for digital computer simulation of human muscular contraction by means of an iterative process. The contractile (CC) and series elastic (SEC) components are lumped components of structures which produce and transmit torque to the external environment. The CC is described in angular terms along four dimensions as a series of non-planar torque-angle-angular velocity surfaces stacked on top of each other, each surface being appropriate to a given level of muscular activation. The SEC is described similarly along dimensions of torque, angular stretch, overall muscle angular displacement and activation. The iterative process introduces negligible error and allows the mechanical outcome of a variety of normal muscular contractions to be evaluated parsimoniously. The model allows analysis of many aspects of muscle behaviour as well as optimization studies. Definition of relevant relations should also allow reproduction and prediction of the outcome of contractions in individuals.

Computers↗

PubMed1983

Mechanical properties of a single equivalent muscle producing forearm supination.

Muscles involved in forearm supination in man were analyzed in terms of a two component muscle model. The properties of the contractile component and series elastic component were determined by a series of dynamic contractions at four levels of perceived exerted effort. Generally characteristics were found to be highly non-linear, however at submaximal effort levels mechanical relationships contained long linear segments. This was interpreted as an attempt to make muscle behaviour more linear and thus more predictable. The outlined method is not limited to forearm supination, and allows description not only of muscle properties, but also of strategies employed in the use of muscles. When determined muscle characteristics were used in a validated muscle model, accurate prediction of contractions for individual subjects was possible.

Biomechanical Phenomena↗

PubMed1983

Factors determining changes in lower limb energy during swing in treadmill running.

This investigation determined the manner in which the lower limb is supplied with mechanical energy in the recovery phase of treadmill sprinting. This was done by following energy input to each limb segment through joint force power and muscle moment power. Joint force power and concentric muscle moment power at the hip are responsible for changes in limb energy although eccentric knee muscle moment power continually reduces total limb energy. In early recovery energy is transmitted distally to raise all segmental energies. In late recovery energy lost from shank and foot is transmitted proximally to the hip without loss in thigh energy. Interlimb exchanges of energy indicate that energy lost in late recovery is transmitted across the pelvis to provide a gain in energy in the opposite limb in early recovery. Much of the loss in limb energy appears to result from the presence of two joint muscles.

Biomechanical Phenomena↗

PubMed1983

Kinetic limitations of maximal sprinting speed.

One runner was filmed when sprinting at a variety of speeds on a treadmill and a variety of kinetic and kinematic variables was calculated during leg recovery. Peak total leg energy increased at lower speeds but changed little between penultimate and maximal speed. Consequently successful completion of recovery occurred at high speeds by delaying the reduction of total leg energy prior to foot strike. The extent of this delay appeared to be limiting between penultimate and maximal speed, and eccentric muscle moment at the knee appears to be the factor which limits this delay. This necessitated spending more time in the airborne phase of recovery and resulted in a modification of the relationship between stride length and stride frequency at high speeds. The fixed proportion of energy removed from the recovery leg at all speeds during contralateral stance was related to the action of two-joint muscles.

Biomechanical Phenomena↗

PubMed1983

Mechanical resonance of the human body during voluntary oscillations about the ankle joint.

Viscoelastic models of the musculoskeletal system suggest resonant frequencies of oscillatory movement at which maximal output is realized with minimal energy expenditure. To investigate this, resonance at the human ankle joint was explored by comparing predicted and experimental gain/frequency and phase frequency functions. These functions were predicted from viscous (B) and elastic (K) coefficients of ankle extensors which were determined from the damped sinusoidal force produced after landing with muscles in sustained contraction (B = 3986 kg/s, K = 31,898 kg/s2). Experimental input/output functions were determined from Fourier analysis of force (output) and rectified, filtered EMG (input) obtained during voluntary sinusoidal oscillations of ground reaction force of a specified magnitude and frequency. Correlations between predicted and experimental functions were significant (p less than 0.02) in four of five subjects. The average resonant frequency was 3.33 +/- 0.15 Hz. The mechanical properties of muscle are considered to be as important as the nervous system in determining the choice of both the movement pattern and the strategy which is adopted in response to changing conditions.

Ankle Joint↗

PubMed1982

Hierarchy of changes induced by fatigue in sprinting.

Five female sprinters ran 400m. on successive occasions during which they were filmed at 100m. (initial) and 380m. (final). Times and ranges of motion for specific segments of the running cycle were obtained and their changes from initial to final stages of the runs were analyzed. A hierarchical approach was taken in which a gross change was broken down into its separate parts for subjects individually and the group as a whole. The decrease in velocity with fatigue resulted from different combinations of changes in step length and cycle time. Different hierarchical patterns of temporal and kinematic variables were observed among subjects with the result that the hierarchical pattern for the group frequently obscured significant individual changes. It is suggested that the hierarchical approach be taken for the establishment of both present status and effects of training on the individual athlete.

Biomechanical Phenomena↗

PubMed1980

The effect of a "wind-up" on forearm rotational velocity.

Subjects performed supination and pronation of the forearm against an inertial load with maximal voluntary effort, from either rest or when arresting the opposite motion of the load (a wind-up). The angular velocities produced at the mid-range of forearm movement were significantly greater with wind-up than without. The angle from which the movement began was significantly increased by wind-up. Isometric contractions produced torques which varied a great deal through the range of motion. While it was not possible to identify the physiology effects of wind-up, consideration was given to techniques which would achieve this aim. Wind-up was discussed in the context of skilled activity where sustained maximal contractions are unlikely throughout the activity.

Biomechanical Phenomena↗

PubMed1977