David J. Sanderson

Kinematic features of wheelchair propulsion

Three male paraplegics volunteered to push their wheelchairs on a motor driven treadmill, for a total of 80 min each, at a work rate of 60-65% of their VO2 maximum, determined on an earlier test session. At 20 min intervals 16 mm high-speed film of the subjects was taken for three consecutive push cycles. The digitized film was used to compute the angular kinematics of the shoulder and elbow joints, the variations in the position of the trunk (as measured by a marker on the neck) and hand relative to the axle of the rear wheel. There were no intrasubject variations over the 80 min testing period for any of the recorded variables. This was interpreted as implying that at that work rate, fatigue was not exhibited as variations in the kinematics of movement. There were considerable differences between the style of one subject when compared to the other two over all the trials of each subject. This variation in style was most obvious in subject number PT who had a pumping style of push and recovery whereas subjects CA and GW employed a more continuous circular motion. The differences in the amount of forward lean of each subject were related to residual muscle strength. The discussion centered on the influence of the different styles on performance.

The influence of cadence and power output on force application and in-shoe pressure distribution during cycling by competitive and recreational cyclists

The aim of this study was to determine the response of cyclists to manipulations of cadence and power output in terms of force application and plantar pressure distribution. Two groups of cyclists, 17 recreational and 12 competitive, rode at three nominal cadences (60, 80, 100 rev min -1 ) and four power outputs (100, 200, 300, 400 W) while simultaneous force and in-shoe pressure data were collected. Two piezoelectric triaxial force transducers mounted in the right pedal measured components of the pedal force and orientation, and a discrete transducer system with 12 transducers recorded the in-shoe pressures. Force application was characterized by calculating peak resultant and peak effective pedal forces and positive and negative impulses. In-shoe pressures were analysed as peak pressures and as the percent relative load. The force data showed no significant group effect but there was a cadence and power main effect. The impulse data showed a significant three-way interaction. Increased cadence resulted in a decreased positive impulse, while increased power output resulted in an increased impulse. The competitive group produced less positive impulse but the difference became less at higher cadences. Few between-group differences were found in pressure, notable only in the pressure under the first metatarsal region. This showed a consistent pattern of in-shoe pressure distribution, where the primary loading structures were the first metatarsal and hallux. There was no indication that pressure at specific sites influenced the pedal force application. The absence of group differences indicated that pressure distribution was not the result of training, but reflected the intrinsic relationship between the foot, the shoe and the pedal.

The role of external nonrigid ankle bracing in limiting ankle inversion.

The purpose of this study was to measure the effectiveness of the nonrigid subtalar stabilizer (STS) ankle brace under conditions similar to an unexpected fall that could lead to a lateral ligament injury. The calcaneal inversion angles, times, and ground reaction forces were measured when the subjects right foot, bearing body weight, was suddenly inverted to a side slope of 22 degrees. Thirty subjects, 15 women and 15 men, participated in the study. The overall inversion drop was divided into two phases, free fall and loading. Based on the data of this study it is suggested that the major function of a brace is to restrict the amount of foot inversion during the fall before actual landing occurs rather than functioning as a force bypass for the lateral ligaments during loading after foot contact. The results showed that the brace significantly (p < 0.05) reduced the maximum calcaneal inversion angle from 27.4 +/- 6.1 to 18.3 +/- 6.0 degrees for the overall drop, significantly lengthened the inversion time from 0.14 +/- 0.04 to 0.18 +/- 0.04 s for the overall drop, and significantly reduced the calcaneal peak inversion velocity from 324.6 +/- 111.9 to 165.2 +/- 66.5 degrees/s during loading, and from 278.7 +/- 120.0 to 183.0 +/- 108.7 degrees/s for the overall drop. Following exercise, which incorporated lateral movements and sprinting, the STS ankle brace continued to provide significant (p < 0.05) reduction in the calcaneal inversion angle and velocity, although some of its effectiveness was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Varus and Valgus Wedges on Coronal Plane Knee Motion During Steady-Rate Cycling

AbstractThe aim of this experiment was to quantify the effect of a wedge placed between the cycling shoe and the pedal on the kinematics of coronal-plane knee motion during steady-rate cycling. The subjects (n = 28) were filmed in the frontal plane as they rode their own bicycles mounted on stationary trainer. The pedaling rate was 90 rpm, and the load was adjusted to be similar to a moderate training pace. The subjects were divided into two groups. The first group (n = 15) rode a single time with the pedals in their normal position, whereas the second group (n = 13) made three rides: one with the pedal in its normal orientation, one with a 10° varus wedge between the pedal and shoe, and one with a 10° valgus wedge between the pedal and shoe. The paths of high-contrast markers (placed on each tibial tuberosity and one on the center of each pedal, as seen from the front) were recorded using 16-mm film. These data were digitized, and a value for the range of excursion and the axis of movement of the tibial marker on the left and right legs was determined. A repeated measures analysis of variance (ANOVA) indicated that there was no significant difference in the range of motion across the three conditions. A repeated measures ANOVA of the shift in the vertical axis of the knee path was significant for one side but not the other. The data indicated that the wedge had the desired effect of moving the vertical axis of knee motion either away from or closer to the frame. It was concluded that wedging the foot on the pedal would not necessarily produce the desired results, as each rider might choose a different adjustment.

The effect of mass on the kinematics of steady state wheelchair propulsion in adults and children with spinal cord injury

A recent trend in wheelchair design has been the reduction of the mass of wheelchairs. The purpose of this study was to examine the effect of mass on the kinematics of steady state wheelchair propulsion. The mass of test chairs (9 .3 kg) was manipulated by mass additions (5 and 10 kg) in two, neurologically matched, groups (n=10) of adults and children with spinal cord injury . Three dimensional video analysis was used to determine the movement of upper body angles (elbow, shoulder, trunk, and shoulder abduction) . Statistical analysis were multiple univariate, repeated measures analysis of variance (ANOVA) and analysis of covariance (ANCOVA) with significance set at adjusted p values <0 .05. The average mass and age of the pediatric group was much smaller than the adult group (37.4 kg and 11 .3 years versus 68 .5 kg and 33 .5 years) . The averaged group wheeling velocities were 2 .26 m/sec (pediatric) and 2 .38 m/sec (adult) . A two-(groups)-by-four-(conditions) ANOVA of the actual wheeling velocities showed a significant groups effect and a nonsignificant interaction effect . The two groups spent comparable proportions of the wheeling cycle in propulsion (pediatric -= 24.45 %, adult = 24 .41 %) . A two-(groups)-by-four(conditions) ANCOVA of the % propulsion data showed that both the groups effect and the groups-by-condition interaction effect were not significantly different . A two-(groups)-by-four-(conditions)-by-six-(portion of wheeling cycle, first 25%) ANCOVA of the angular data (with velocity as the covariate) showed significant differences for three (elbow, shoulder, and shoulder abduction) of the four angular parameters and nonsignificant groups-by-conditions effects. These results, based on a test sample of chairs and subjects, indicate that mass additions did not affect the angular kinematics, % propulsion or wheeling velocities of two groups of subjects with spinal cord injury in steady state, short distance, level wheelchair propulsion . The pediatric group did show significant absolute angular differences from the adult group, but the angular changes over time and across experimental conditions were the same in both groups .

The effect of subject grouping on the kinematic assessment of wheelchair propulsion

FINGERTIP IMPACT LOADING DURING KEYBOARD USE D. Rempel, J.T. Dennerlein, C.D. Mote, Jr., and T. Armstrong Ergonomics Laboratory, University of California, San Francisco Department of Mechanical Engineering, University of California, Berkeley Department of Industrial Engineering, University of Michigan Building 112, 1301 South 46th Street, Richmond, CA 94804 Measuring the fingertip loads during keyboard use is a necessary first step to understanding the biomechanics of keying. A single keycap from a standard keyboard was instrumented with a piezoelectric load cell and fingertip motion was recorded with a high-speed video motion analysis system. Fingertip force histories were collected while four typists typed standard text for five minutes. Each keystroke force history contained three distinct phases: key switch compression (I), finger impact (II), and fingertip pulp compression and release (III). The subject mean peak forces ranged from 167.3 to 542.3 gm. Subject mean peak fingertip velocities ranged from 0.28 to 0.66 m/s. Motion analysis combined with high-speed force measurements indicate a ballistic process of finger motion during typing on a computer keyboard.