Papers by Graham Caldwell
BMC Research Notes
Objective: This paper presents magnetic resonance images of the dorsi-and plantar flexor muscles ... more Objective: This paper presents magnetic resonance images of the dorsi-and plantar flexor muscles for individual young and older healthy adults. Also included are measurements of the volume, proportion, and longitudinal distribution of contractile and non-contractile tissue. This dataset was previously used to quantify age-related differences in these measures, constrain subject-and muscle-specific estimates of dorsi-and plantar flexor maximal isometric force capability, and quantify the degree to which maximal isometric force capability explains the age-related variance in postural control. Data description: The data include contiguous axial magnetic resonance images of the lower leg for 12 young (21-31 years) and 12 older (66-79 years) healthy adults. The data are in the form of MATLAB binary files with a freely distributable custom MATLAB analysis program that allows image viewing and navigation in two and three dimensions, muscle outlining, tissue segmentation, and cross-sectional area calculation. The latter measurements are contained in a set of companion MATLAB binary files, which are included with the image data files. If desired, the magnetic resonance images could be used to identify other anatomical structures, or the MATLAB programs could be used to analyze other image sets.
The Physician and sportsmedicine, 1982
In brief Although squash and racquetball eye protectors are available and many people wear them, ... more In brief Although squash and racquetball eye protectors are available and many people wear them, eye injuries still exist. The authors studied the ability of the 13 eye protectors currently available in Canada to protect the players' eyes. The eye guards were mounted on a headform, and balls were thrown at it at speeds from 50 to 100 mph. This was recorded on high-speed film that was analyzed to determine ball speed, lens or frame deformation, and damage during impact. Eye contact with protectors having lenses was confirmed only once in 54 impacts. All 17 hits to the open eye guards produced ball-eye contact. The authors suggest that standards for eye protectors should be established.
Journal of Applied Biomechanics, 1998
Alterations in kinetic patterns of pedal force and crank torque due to changes in surface grade (... more Alterations in kinetic patterns of pedal force and crank torque due to changes in surface grade (level vs. 8% uphill) and posture (seated vs. standing) were investigated during cycling on a computerized ergometer. Kinematic data from a planar cine analysis and force data from a pedal instrumented with piezoelectric crystals were recorded from multiple trials of 8 elite cyclists. These measures were used to calculate pedal force, pedal orientation, and crank torque profiles as a function of crank angle in three conditions: seated level, seated uphill, and standing uphill. The change in surface grade from level to 8% uphill resulted in a shift in pedal angle (toe up) and a moderately higher peak crank torque, due at least in part to a reduction in the cycling cadence. However, the overall patterns of pedal and crank kinetics were similar in the two seated conditions. In contrast, the alteration in posture from sitting to standing on the hill permitted the subjects to produce different...
Journal of Applied Biomechanics, 1999
Lower extremity joint moments were investigated in three cycling conditions: level seated, uphill... more Lower extremity joint moments were investigated in three cycling conditions: level seated, uphill seated and uphill standing. Based on a previous study (Caldwell, Li, McCole, & Hagberg, 1998), it was hypothesized that joint moments in the uphill standing condition would be altered in both magnitude and pattern. Eight national caliber cyclists were filmed while riding their own bicycles mounted to a computerized ergometer. Applied forces were measured with an instrumented pedal, and inverse dynamics were used to calculate joint moments. In the uphill seated condition the joint moments were similar in profile to the level seated but with a modest increase in magnitude. In the uphill standing condition the peak ankle plantarflexor moment was much larger and occurred later in the downstroke than in the seated conditions. The extensor knee moment that marked the first portion of the down-stroke for the seated trials was extended much further into the downstroke while standing, and the su...
Journal of Applied Biomechanics, 2004
Studies on shock attenuation during running have induced alterations in impact loading by imposin... more Studies on shock attenuation during running have induced alterations in impact loading by imposing kinematic constraints, e.g., stride length changes. The role of shock attenuation mechanisms has been shown using mass-spring-damper (MSD) models, with spring stiffness related to impact shock dissipation. The present study altered the magnitude of impact loading by changing downhill surface grade, thus allowing runners to choose their own preferred kinematic patterns. We hypothesized that increasing downhill grade would cause concomitant increases in both impact shock and shock attenuation, and that MSD model stiffness values would reflect these increases. Ten experienced runners ran at 4.17 m/s on a treadmill at surface grades of 0% (level) to 12% downhill. Accelerometers were placed on the tibia and head, and reflective markers were used to register segmental kinematics. An MSD model was used in conjunction with head and tibial accelerations to determine head/arm/trunk center of mas...
Journal of Applied Biomechanics, 2000
A modified mass-spring-damper model was used to simulate the vertical ground reaction forces of a... more A modified mass-spring-damper model was used to simulate the vertical ground reaction forces of a human runner as stride length was altered. Spring stiffness values were selected by an optimizing routine that altered model parameters to match the model ground reaction force curve to a runner’s actual ground reaction force curve. A mass in series with a spring was used to simulate the behavior of body structures that produce the active portion of the ground reaction force. A second mass in series with a spring-damper system was used to simulate the behavior of those components that cause the impact portion of the ground reaction force. The stiffness of the active spring showed a 51% decrease as subjects increased their stride length. The stiffness value of the impact spring showed a trend opposite that of the active spring, increasing by 20% as strides lengthened. It appears that the impact stiffness plays a role in preventing the support leg from collapsing in response to the increa...
International Journal of Sport Biomechanics, 1985
Differences in the utilization of body segment movements between world-class and recreational cro... more Differences in the utilization of body segment movements between world-class and recreational cross-country skiers which result in a longer stride of the elite were studied using mechanical energy analyses. Nine world-class racers and six recreational skiers (novices) were filmed, the latter while they executed their fastest possible stable diagonal stride on a level track, and the former during competition. A 15-member linked segment model was digitized, the coordinate data filtered at 4.5 Hz and body segment energy curves; mechanical work output and mechanical energy transfers were calculated using the method described by Pierrynowski, Winter, and Norman (1980). The elite skiers exhibited larger exchanges between potential and kinetic energy in all segments during swing phases and all but the upper arm segment during pushing phases. Step-wise discriminant function analysis showed significant differences in the swinging foot, pushing foot, and pushing shank. The differences appear ...
Med Sci Sport Exercise, 1998
Progress in Motor Control Vi, Aug 9, 2007
Medicine and Science in Sports and Exercise, Aug 1, 1984
One female sprinter was filmed at the 100-m mark (speed 6.5 m X S-1) of a 400-m run. Four moments... more 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.
Journal of Motor Behavior, Jun 1, 1995
Med Sci Sport Exercise, 1996
Med Sci Sport Exercise, 1997
Uploads
Papers by Graham Caldwell