Yu-Sheng Yang

A kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces

The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces. Eleven manual wheelchairs were fitted with a SMART(Wheel) and their users were asked to push on a course consisting of high- and low-pile carpet, indoor tile, interlocking concrete pavers, smooth level concrete, grass, hardwood flooring, and a sidewalk with a 5-degree grade. Peak resultant force, wheel torque, mechanical effective force, and maximum resultant force rate of rise were analyzed during start-up for each surface and normalized relative to their steady-state values on the smooth level concrete. Additional variables included peak velocity, distance traveled, and number of strokes in the first 5 s of the trial. We compared biomechanical data between surfaces using repeated-measures mixed models and paired comparisons with a Bonferroni adjustment. Applied resultant force (p = 0.0154), wheel torque (p < 0.0001), and mechanical effective force (p = 0.0047) were significantly different between surfaces. The kinetic values for grass, interlocking pavers, and ramp ascent were typically higher compared with tile, wood, smooth level concrete, and high- and low-pile carpet. Users were found to travel shorter distances up the ramp and across grass (p < 0.0025) and had a higher stroke count on the ramp (p = 0.0124). While peak velocity was not statistically different, average velocity was slower for the ramp and grass, which indicates greater wheelchair/user deceleration between strokes. The differences noted between surfaces highlight the importance of evaluating wheelchair propulsion ability over a range of surfaces.

Multisite comparison of wheelchair propulsion kinetics in persons with paraplegia

A multisite collaborative study is being conducted on the association between propulsion biomechanics and upper-limb injuries. This substudy compared subject characteristics and pushrim kinetics across three sites and identified early on in the main study any differences that could affect interpretation of the findings or data pooling. A total of 42 manual wheelchair users with paraplegia (14 from each site) performed 0.9 m/s and 1.8 m/s steady state propulsion trials and an acceleration-brake-coastdown trial on a wheelchair dynamometer while propulsion forces and moment about the hub were measured with a SmartWheel. Significant differences between two sites were found in peak and average resultant force (p < 0.05), peak and average moment at the slower steady state speed (p < 0.005), and peak and average torque at the faster steady state speed (p = 0.06). Subjects at the site with significantly lower forces and torques had a slower deceleration rate during coastdown compared with the subjects at the other two sites (p < 0.001). These results imply that rolling resistance is lower at one of the sites and likely due to differences in dynamometer properties. A mechanical method was used to site-normalize the data and enable data pooling for future analyses.

Biomechanical Analysis of Functional Electrical Stimulation on Trunk Musculature During Wheelchair Propulsion

Background. The objective of this study was to examine how surface electrical stimulation of trunk musculature influences the kinematic, kinetic, and metabolic characteristics, as well as shoulder muscle activity, during wheelchair propulsion. Methods. Eleven participants with spinal cord injury propelled their own wheelchairs on a dynamometer at a speed of 1.3 m/s for three 5-minute trials. During a propulsion trial, 1 of 3 stimulation levels (HIGH, LOW, and OFF) was randomly applied to the participant’s abdominal and back muscle groups with a surface functional electrical stimulation device. Propulsion kinetics, trunk kinematics, metabolic responses, and surface electromyographic (EMG) activity of 6 shoulder muscles were collected synchronously. Kinetic, kinematic, and EMG variables were recorded during 3 time intervals (30 seconds each) within a 5-minute trial. Metabolic variables were recorded through the entire 5-minute trial. Results. Participants with HIGH stimulation increased their gross mechanical efficiency (P = .05) during wheelchair propulsion. No differences were found in shoulder EMG activity, energy expenditure, and trunk motion between stimulation levels. Conclusion. Functional electrical stimulation on the trunk musculature has potential advantages in helping manual wheelchair users with spinal cord injury improve propulsion efficiency without placing additional demands on shoulder musculature.

Effect of Backrest Height on Wheelchair Propulsion Biomechanics for Level and Uphill Conditions

OBJECTIVE To evaluate the effect of backrest height on wheelchair propulsion kinematics and kinetics. DESIGN An intervention study with repeated measures. SETTING University laboratory. PARTICIPANTS Convenience sample included manual wheelchair users (N=36; 26 men and 10 women) with spinal cord injuries ranging from T8 to L2. INTERVENTION Participants propelled on a motor-driven treadmill for 2 conditions (level and slope of 3°) at a constant speed of 0.9 m/s while using in turn a sling backrest fixed at 40.6 cm (16 in) high (high backrest) and a lower height set at 50% trunk length (low backrest). MAIN OUTCOME MEASURES Cadence, stroke angle, peak shoulder extension angle, shoulder flexion/extension range of motion, and mechanical effective force. RESULTS Pushing with the low backrest height enabled greater range of shoulder motion (P<.01), increased stroke angle (P<.01), push time (P<.01), and reduced cadence (P=.01) regardless of whether the treadmill was level or sloped. CONCLUSIONS A lower cadence can be achieved when pushing with a lower backrest, which decreases the risk of developing upper-limb overuse related injuries. However, postural support, comfort, and other activities of daily living must also be considered when selecting a backrest height for active, long-term wheelchair users. The improvements found when using the low backrest were found regardless of slope type. Pushing uphill demanded significantly higher resultant and tangential force, torque, mechanical effective force, and cadence.

The effect of cushion properties on skin temperature and humidity at the body-support interface

ABSTRACT The purpose of this study is to explore the effects of various cushions on skin temperature and moisture at the body–seat interface during a 2-hour period of continuous sitting. Seventy-eight participants were randomly assigned to sit on one of the three types of wheelchair cushions for unrelieved sitting for over 2 hours. Skin temperature and relative humidity (RH) were measured under the subjects’ ischial tuberosities and thighs bilaterally with digital temperature and humidity sensors. Data were collected before sitting and at 15-minute intervals thereafter. Participants sitting on foam–fluid hybrid cushions showed significantly lower skin temperatures than those sitting on air-filled and foam cushions (p < 0.05), but RH did not differ significantly among the cushions (p = 0.97). The three cushions produced a similar increasing trend in RH over time and RH reached a plateau during the 2-hour sitting period. To select the appropriate wheelchair cushion, the microclimate (heat and moisture control) between the body–seat interface should be considered as well as pressure distribution. In comparison with foam–fluid hybrid cushions, the air-filled rubber and foam cushions tended to increase skin temperature by several degrees after prolonged sitting. However, cushion materials did not have significant differences in moisture accumulations.

Effect of a Wheelie Training Method With the Front Wheels on a Ramp in Novice Able-Bodied Participants: A Randomized Controlled Trial.

The objective of this study was to determine if wheelie training that begins with learning how to balance with the front wheels on a ramp would increase the success rate, reduce the training time, and improve retention rates. A randomized controlled trial design was used to evaluate the effectiveness of wheelie training on a ramp setting (ramp group, n = 26) and conventional training (conventional group, n = 26). The main outcome measures were success rates in achieving wheelie competence, training time, and the retention rate in 7 and 30 days respectively. The results showed that the success rate for each training group both reached 100%. The mean training times for the conventional group and the ramp group were 86.0 ± 35.7 and 76.0 ± 25.8 minutes. Training time was not significantly affected by the training method (p = 0.23), but it was affected by gender, with women requiring an average of 92.0 ± 31.4 minutes in comparison with 70.0 ± 27.5 minutes for men (p = 0.01). The skill retention rate after 7 and 30 days was 100% for both groups. Neither success rate nor training time for wheelie skill acquisition by learners were improved by learning wheelie balance on a ramp. However, a high retention rate of wheelie skills for both training groups was found, which implies that success can be achieved by training on a ramp used in this study.

SURFACE EMG ANALYSIS ON SHOULDER MUSCLE DURING PROLONGED WHEELCHAIR PROPULSION

Yu-Sheng Yang, PhD, Alicia M. Koontz PhD, RET, Ronald J. Triolo PhD, Rory A. Cooper, PhD, Michael L. Boninger MD. Human Engineering Research Laboratories, VA Medical Center, Pittsburgh, PA, USA Cleveland FES Center, Louis Stokes Cleveland VA Medical Center, Cleveland OH, USA Department of Occupational therapy, Kaohsiung Medical University, Kaohsiung City, Taiwan email:yusheng@kmu.edu.tw, web: www.ot.kmu.edu.tw