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Factors governing the When designing, buying, or building a racing wheelchair optimized for his/her performance, the wheelchair athlete is faced with many important decisions. These decisions include: number and placement of wheels, wheel sizes, wheel camber, hand-rim thickness and diameter, frame construction material, frame geometry, and seating position, to name just a few.
Conclusion There are hundreds of different shoes on the market to meet the very specialized needs of able-bodied athletes in every conceivable sport. However, at this stage we have only three or four basic wheelchair designs to meet the equally diverse needs of athletes with disabilities engaged in the same range of sports. Greater equipment and technique specialization is the wave of the future in wheelchair sports. This can be facilitated by the past and current research available to wheelchair designers and athletes. It can be carried ever farther by ever-expanding future research which focuses on the special needs of wheelchair athletes, and how to design wheelchairs that better help them increase and maximize their performance. |
 | The effects of wheelchair camber on physiological and perceptual responses in younger and older men |
| Wheeling in the wind: The effect of wind velocity and direction on the aerodynamic drag of wheelchairs |
| Physical and physiological characteristics of elite wheelchair marathoners |
| Wheelchair racing: effects of rim diameter and speed on physiology and technique |
| The effect of rear wheel camber in manual wheelchair propulsion |
| Seating and wheeled mobility in the disabled elderly population |
| Wheelchair rider injuries: Causes and consequences for wheelchair design and selection |
| Racing wheelchairs: A comparison of three- and four-wheeled designs |
| A kinematic analysis of wheelchair propulsion techniques in senior male, senior female, and junior male athletes |
| Evaluation of methods for determining rearward static stability of manual wheelchair |
| Effects of wheelchair design on metabolic and heart rate responses during propulsion by persons with paraplegia |
| Wheelchair racquetball: A preliminary time motion analysis |
| Wheelchair stability: Effect of body position |
| Pushing economy and propulsion technique of wheelchair racers at three speeds |
| Intermittent velocity and wheelchair performance characteristics |
Buckley, S. M., & Bhambhani, Y. N. (1998). The effects of wheelchair camber on physiological and perceptual responses in younger and older men. Adapted Physical Activity Quarterly, 15, 15-24.
The purpose of this study was to examine the impact of camber angles (0, 4, and 8 degrees) on the physiological and perceptual responses of younger and older men during manual wheelchair propulsion, and to compare these responses between the two age groups.
The participants consisted of 19 healthy, sedentary males, who had no previous experience with wheelchair propulsion. These men were then assigned to a younger group (n=7), ages 19 to 44, or an older group (n=12), ages 45 to 75 years. Physiological responses examined included absolute oxygen uptake, relative oxygen uptake, heart rate, oxygen pulse, ventilation volume, respiratory exchange ratio, VE/VO2 ratio, and net energy cost. Perceptual responses were divided into central (i.e., related to heart and lungs) and peripheral (i.e., related to the localized muscles ratings of perceived exertion, RPE) responses in the participants, who propelled a wheelchair at 2 kmh (i.e., a constant velocity test of 2 kmh). Each subject completed one testing session that lasted approximately 1 ½ to 2 hours, during which the subject completed three camber angle tests (of 8 min 30 sec each) in random order, with intervening rest periods of 8 minutes used to record the significant physiological and perceptual data. Statistical analyses included a two-way (age by camber) repeated analysis of variance and post hoc Scheffe test conducted at a significance level of p<.05.
The results of this study showed that there was a significant increase in oxygen uptake, heart rate, and oxygen pulse for both younger and older groups as the camber angle increased from 0 degrees to 8 degrees. However, these values were not significantly different between age groups. Ventilation volume did show significant differences as a result of camber angle, as well as between age groups. Central and peripheral RPE was in many cases unchanged as a result of camber angle in both groups. However, central RPE showed significantly higher responses in the older participants than in the younger ones at 0 and 4 degrees camber (but not at 8 degrees). This higher perceptual stress in the older participants may have been caused by their need to use a higher percentage of maximum physiological capacity in their performance.
In any case, the results of this study regarding the effects of wheelchair camber angle tend to differ from the generally held idea that increased rear wheel camber leads to a greater advantage, such as reduction of physiological stress, during wheelchair propulsion because of the increased proximity of the rear wheel to the wheelchair frame. Therefore, future wheelchair design should consider the findings of this research, and perhaps take into account the fact that reducing rear-wheel camber may, contrary to previous belief, actually increase the physiological strain on the user. Future wheelchair designers might thus consider reducing the camber on rear-wheels, if the implications of this research are found to be valid. Although a constant velocity test of 2 kmh was selected in this study, to better extend the results of this study speeds other than 2 kmh should be implemented in future studies. Also, participants in this study, because they are nonwheelchair users, may not have been representative of people who use wheelchairs.
Higgs, C. (1992). Wheeling in the wind: The effect of wind velocity and direction on the aerodynamic drag of wheelchairs. Adapted Physical Activity Quarterly, 9, 74-87.
In wheelchair racing, speed is increased when the forces applied by the athlete to accelerate the wheelchair are greater than the external forces (e.g., rolling resistance of the wheelchair and aerodynamic drag) acting to slow it down. In particular, aerodynamic drag has been shown to have strong effects on decrease in wheelchair speed. However, if the wind is blowing at the right speed in the right direction, it will help rather than hinder the athlete. The purpose of this paper was to examine the impact of wind speed and direction on the aerodynamic drag of wheelchairs, and thus on wheelchair racing performance.
This study used a computer simulation model rather than actual physical subjects. Using the formula [Drag = (Cd r A V2 )/2, where Cd is the coefficient of form drag, r is the density of air, A is the cross-sectional area of the wheelchair and athlete perpendicular to the directions which they are struck by the wind, and V is the velocity of air flow] for determining the magnitude of aerodynamic drag on the wheelchair, calculations of total drag forces over a range of wheeling speeds between 2 m/sec and 20 m/sec were made for each angle of wind direction between 0° (headwind) and 180° (tailwind), at 1° intervals. The results were formed by a variety of spreadsheet and technical graphing programs.
According to the computer model, the graphs (plotted data) show that the large lateral area of a wheelchair adds considerably to the retarding drag forces at relative wind angles between 0° and 90° , and that while the three-wheeled chair has an advantage for all wind velocities and directions, this advantage decreases as the wind angle approaches 180° . Therefore, the results conclude that the four-wheeled chair has a slight aerodynamic advantage when the relative wind angle exceeds 90° , but under other speed and wind conditions the three-wheeled chair is more efficient.
These results suggest that the wind angle for maximum drag production is a complex function of wheelchair shape, wind direction, and wind velocity in addition to wheeling velocity. In particular, as the two factors in the equations that account for the greatest changes in calculated drag are the cross-sectional area and the relative wind velocity, optimum race performance would occur under zero wind conditions; furthermore, for any combination of wind speed and wind direction, the three-wheeled chair would have a major aerodynamic advantage. Therefore, the evidence suggests that future wheelchair design should consider the complex interaction among race length, wind speed, wind direction, and wheeling speed.
Coutts, K. D. (1984). Physical and physiological characteristics of elite wheelchair marathoners. In C. Sherrill (Ed.), Sport and disabled athletes: The 1984 Olympic scientific congress proceedings (pp.157-161). Champaign, IL: Human Kinetics.
Improved design and engineering of chairs, as well as the improved and increased training of the athletes, has allowed performances in wheelchair marathons to improve dramatically. The purpose of this paper is to compare some of the physical traits and physiological responses to maximal wheelchair exercise of a small group of elite wheelchair marathoners and a group of nonmarathon wheelchair athletes.
Three wheelchair marathoners and three nonmarathon wheelchair athletes (who have competed in basketball and other events) served as subjects for the study. All subjects, aged 24 to 36 years old, were either class IV or class V males. Each athlete completed a battery of tests on a single visit to the laboratory. All subjects had participated in previous studies and were familiar with the test procedures. The tests included skinfold measures, handgrip strength measures and maximal oxygen uptake and associated variables (e.g., power output, heart rate, minute ventilation, oxygen pulse and ventilatory equivalent) during wheelchair ergometry for each subject. Average values for each measure were calculated for both the marathon and nonmarathon subjects.
The results represent a purely descriptive comparison of the two groups of subjects. Several points were noted in this comparison; first, the nonmarathoners were on the average slightly heavier and older with larger skinfold thicknesses at each of the four sites (biceps, triceps, subscapular and suprailiac) than the marathoners. Second, the strength measures indicated that the marathoners had a greater maximal handgrip and higher peak torques for elbow flexion and shoulder extension than nonmarathon subjects. Third, the marathoners displayed a higher maximal oxygen uptake with positive effects on associated variables during wheelchair ergometry.
Marathoners’ higher peak torques, using elbow flexion and shoulder extension, suggest a difference in movement patterns which may also be a consequence of their smaller push-rim. In order to maintain the same time of force application during each push, the marathoner with a smaller diameter push-rim would need to increase the arc when force is applied. In contrast, the normal propulsive movement for the standard or larger diameter push-rim used in most other sports (e.g., basketball) involves elbow extension and shoulder flexion. Wheelchair marathoners were thus found to differ from non-marathon wheelchair athletes in movement patterns and physiological responses involved in their sport. However, wheelchair marathoners were found to have rather similar physiological responses to able-bodied marathoners (i.e., higher maximal oxygen uptake and associated cardiorespiratory responses). This might imply that, for athletes with and without disabilities, the marathon involves a particular level of physiological effort which distinguishes it from other sports. It may also imply that wheelchair design should take into account the specialized physiological and movement needs of wheelchair marathoners.
van der Woude, L., Veeger, H., Rozendal, R., van Ingen Schenau, G., Rooth, F., & van Nierop, P. (1988). Wheelchair racing: Effects of rim diameter and speed on physiology and technique. Medicine and Science in Sports and Exercise, 20(5), 492-500.
The purpose of this study is to investigate the effects of varying hand rim diameters in wheelchair racing by measuring the effects on physiology and technique of wheelchair ambulation at different velocities and hand rim diameters.
Eight male wheelchair athletes participated in this study on a voluntary basis. They each used a similar model racing wheelchair. Five progressive 15-min exercise tests were randomly spaced on three subsequent days. In each exercise test, one of five different hand rim diameters (D1 = 0.3m, D2 = 0.35m, D3 = 0.38m, D4 = 0.47m, and D5 = 0.56m) was mounted to the rear driving wheels. At a constant inclination angle of the treadmill (0.5° ), speed increased every 3 min by 0.83 m× s-1. The test began at 0.83 m× s-1 and built up (in a total of five increments) to 4.17 m× s-1. Prior to testing, the subjects performed a 10-min warm-up followed by a 5-min rest period. There was also an obligatory 1-hr rest period between tests. Physiological responses (oxygen cost, mechanical efficiency, heart rate, ventilation, and respiratory exchange ratio) and propulsion technique parameters (cycle time, push time, recovery time, push angle, and work per cycle) were obtained every third minute, together with the movement pattern of trunk and arm segments. A three-factor analysis of variance (ANOVA) was performed on the data (hand-rim diameter, velocity, and their interaction). The level of significant was p<.05.
The results revealed highly significant effects of both hand rim diameter and propelling speed for the physiological parameters. In physiological terms, these results indicated a tendency to be less beneficial with each increase in hand rim diameter. That is, D5 appeared to be the least beneficial, followed by D4. Moreover, increasing rim diameter had a significant negative effect on movement patterns of the sagittal as well as the frontal plane of motion. Hand rim diameter had no effect on cycle time (the reciprocal of cycle frequency) or on its subdivisions: push time, recovery time, and push angle. While timing parameters varied with changing speed, the segmental excursions of the upper limb did not show a "speed-effect".
A clear "hand rim effect" is seen in the physiological results, indicating reduced cardiorespiratory stress with smaller hand rims. This may be related to the decreased segmental excursions of the upper limb, as well as the lower linear hand velocity needed to use smaller rim sizes. Together with its low rolling drag and air resistance, lower heart rate and oxygen cost requirements make the racing wheelchair rather speed effective, and those with smaller rims even more so. The effect of seat height and angle is an as yet insufficiently studied factor of the wheelchair-user interface. Therefore, the possible effect of the seat height and seat angle on cardiorespiratory and propulsion technique parameters needs further study. In addition, to what extent these findings are dependent on training and wheeling expertise needs further clarification.
Veeger, D., van der Woude, L., & Rozendal, R. (1989). The effect of rear wheel camber in manual wheelchair propulsion. Journal of Rehabilitation Research and Development, 26(2), 37-46.
The purpose of this study is to investigate whether increased camber leads to a more efficient level of wheelchair propulsion in terms of physiological and movement pattern parameters.
Eight non-wheelchair users participated in this study. The experiment consisted of four 12-minute wheelchair exercise tests on a motor-driven treadmill, in which camber varied between 0, 3, 6, and 9 degrees. Within each test, the treadmill belt speed increased every three minutes (speeds of 0.56 m/s, 0.83 m/s, 1.11 m/s, and 1.39 m/s). Each test was preceded by a 5-min warm-up (speed 1.11 m/s) and followed by a 5-min rest period. All subjects used a Morrien-Tornado basketball wheelchair. During each test, physiological analysis (oxygen uptake, respiratory exchange ratio, heart rate, and gross mechanical efficiency) was performed on-line and printed out every 30 seconds. Also, in order to facilitate kinematic parameter (push time, recovery time, cycle time, and push angle) analysis, the subjects bore landmarks on the shoulder, elbow, wrist, and hand, and were also monitored by EMG. A two-way ANOVA with repeated measurements was used.
The results indicated that the physiological parameters of oxygen cost, heart rate, and mechanical efficiency were not dependent on camber, but were highly dependent on belt speed. The kinematic parameters of push time, push angle, and abduction (or the angle of the upper arm to a vertical line) did not change with camber. No difference was found between 0 and 9 degrees or between 3 and 9 degrees. However, camber showed a strong difference between 3 degrees and 6 degrees.
On the basis of this study, it could not be generally concluded that, for the group and model of wheelchair studied, rear wheel camber was physiologically advantageous to vertically-placed rear wheels. Furthermore, the kinematic results did not clearly confirm the expectation that increasing camber facilitates arm movements. However, the researchers discussed several alternative explanations for the fact that no effect of camber was found on physiological parameters. They mentioned that the differences between subjects, the fact that they were using basketball wheelchairs, and the low speeds at which the experiments took place might cause these results. In this experiment, the seat was relatively high above the wheel axle, and the shoulder high above the rim, in comparison to a racing wheelchair. It might be possible that at a lower seat height, with a smaller armpit-to-wheel-top distance, differences in physiology and abduction or adduction due to camber will be found. Further study, focusing on the influence of camber using a racing wheelchair with a shorter armpit-to-wheel-top distance, and with a constant top-to-top distance independent of the camber angle, is recommended. If nothing else, it might be possible that although no kinematic advantages were found, a camber angle of 6 degrees could be seen as optimal, as it is the condition in which the largest push angle is reached. This might have implications for better design of basketball wheelchairs at least, and thus make this study a valuable one.
Redford, J. B. (1993). Seating and wheeled mobility in the disabled elderly population. Archives of Physical Medicine and Rehabilitation, 74, 877-885.
Elderly persons represent a particularly large percentage of users of adaptive seating or wheelchairs. This paper is a review of the few studies specifically concerned with seating for the elderly. Though much attention has been given to designing seating components for wheelchairs, little research has been done on wheelchair seating designed specifically for the aged. Seating clinics have been established to prescribe special wheelchairs for young people with serious disabilities, but scant attention has been given to providing such clinics for the disabled elderly. This review describes ways of matching currently available seating technology with the special needs of disabled elderly people.
This review also discusses two major barriers to greater use of new seating technology. The first one is the high cost of durable medical equipment; the money needed to purchase proper equipment is unavailable in many facilities dealing with care for the elderly. The other problem is the failure of most clinicians and institutional administrators to recognize the importance of posture and comfort in providing functional independence for wheelchair users.
Maintenance of stable seating positions may be a problem for elderly patients, who tend to slide out of the chair, or who can not maintain position because of muscle weakness. Elderly persons need special seating for comfort and postural accommodation. Most elderly users need to be matched to chairs on the basis of their individual functional mobility. This review classifies elderly persons into 4 types: (a) the nonmobile and dependent, who may be safety risks and who are without enough energy or ability to wheel or walk by themselves; (b) mobile, nonambulatory; (c) ambulatory, but with special wheelchair needs; and (d) ambulatory frail. Next, this review discusses the necessity of research regarding wheeled mobility in a number of areas: better matching of mobility to function, cheaper and more effective cushions, more modular seating systems, and better lifting and transfer devices.
The fact that such crucial areas are still in great need of further research indicates the distance that has yet to be traveled in designing wheelchair and seating systems that take the special needs of the elderly into account. This paper’s listing of the as yet insufficiently researched and developed areas of adaptive seating and wheelchairs for the elderly sets a challenge for clinicians, institutional administrators, and all those who assist the elderly in leading fulfilling lives.
Gaal, R. P., Rebholtz, N., Hotchkiss. R. D., & Pfaelzer, P. F. (1997). Wheelchair rider injuries: Causes and consequences for wheelchair design and selection. Journal of Rehabilitation Research and Development, 34(1), 58-71.
An understanding of the adverse incidents and injuries sustained by active wheelchair users is needed to improve safety through better wheelchair design, selection, and configuration. The purpose of this study was to examine the causes of incidents and injuries suffered by active riders, both indoors and outdoors.
Interviews, using a questionnaire comprised of 130 specific questions reflecting the current state of wheelchair design, were conducted with 109 active wheelchair riders (at least 18 years old) who had experienced incidents during the 5 years prior to the interview. To obtain detailed incident reports, three engineers and two assistants trained in wheelchair use conducted the interviews, mostly by phone. These interviews lasted from 30 minutes to 1 hour, and were conducted over an 8-month period. Demographic descriptions, wheelchair specifications (manual or powered, make, model, age, wheel types and sizes, and the type of control used), the type and severity of any injuries, and riding situations (rough or smooth, level or sloping up, down, or to the side, etc) were recorded. The chi-square test and Fisher’s exact test were used to evaluate associations between outcomes (i.e., incident types, injury severity and type, and the number of incidents per participant) and potential causative factors (i.e., characteristics of the rider, wheelchair, and riding situation), noting statistical significance at p<.05.
Participants reported n=253 incidents (53% in powered wheelchairs, 47% manual) occurring within a 5-year period. These incidents were comprised of 106 (42%) tips and falls, 84 (33%) component failures, and 63 (25%) other events. Sixty-eight (27%) of the incidents caused injuries requiring medical attention, including 13 hospitalizations. The results showed that the direction of the tip or fall was correlated to the type of wheelchair (manual or powered), injury severity, and different riding surface. Also, in manual wheelchairs, the number of tips and falls was related to caster wheel size and type. Additionally, twice as many component failures occurred in powered chairs as did in manual wheelchairs.
The authors discussed that aspects of wheelchair stability, particularly the effects of wheelchair configuration and of different riding surfaces, are important engineering issues affecting wheelchair safety. They also made following recommendations regarding safety-related design to prevent tips and falls and component failures: (a) moving the center of gravity downward; (b) moving the center of gravity horizontally; (c) improving the ability to negotiate obstacles; and (d) improved product testing/measuring. It should be noted that because participants were asked to report from memory all the incidents they had experienced during a 5-year period, it is possible that they inadvertently emphasized injurious experiences and underreported more mundane incidents. However, if nothing else, insights have been given into the actual experiences of wheelchair users, most if not all of which are doubtless true, and the results of this study could have implications for potential design improvements in wheelchair stability mechanics as seen above.
Higgs, C. (1992). Racing wheelchairs: A comparison of three- and four-wheeled designs. Palaestra, 8(4), 28-36.
To design, buy, or build a racing wheelchair optimized for his/her performance, the wheelchair athlete is faced with many important decisions including number and placement of wheels, wheel sizes, wheel camber, hand-rim thickness and diameter, frame construction material, frame geometry, and seating position, to list just a few. However, the most fundamental decision concerns the number of wheels. This study dealt with the shift from classic four-wheeled wheelchairs to the now widely accepted three-wheeled design, and also reviewed the relative strengths and weaknesses of three- or four-wheeled wheelchairs.
The author indicates that the two major factors affecting wheelchair energy losses (i.e., slowing down the wheelchair) are rolling resistance and aerodynamic drag. Rolling resistance can be calculated as the product of the wheel’s coefficient of rolling resistance and weight supported by that wheel. As weight supported by the wheels is the total weight of the athlete plus the chair itself, the three-wheeled chair is lighter than the four-wheeled; furthermore, the lighter weight of the three-wheeler also gives the advantage of lower rolling resistance. Resistance of athlete and wheelchair to passage through air is caused by two distinct types of aerodynamic drag (form drag and surface drag). Form drag is caused by an imbalance in air pressure between front and rear of the wheelchair; for most athletes, it is the most trouble one type of drag, and that which streamlining seeks to overcome. Surface drag is the slowing effect caused by adhesion of air molecules to exposed surfaces of wheelchair and athlete. Neither is particularly aerodynamic, but the sharper front and end on the three-wheeled chair appears to cut more cleanly into the airflow, so that three-wheeled chairs may have a slight advantage in wheelchair speed. In addition, because the surface area of three-wheeled wheelchairs is decreased, the three wheeled design produces increased wheelchair performance and speed.
While a three-wheeled wheelchair is faster, the price of this increase in speed is decreased wheelchair stability. In three-wheeled chairs, shifting the center of gravity forward moves it to a position where the base of support is narrower. This makes the chair less stable so that the three-wheeled chair is inherently more likely to tip or falling over, particularly in road racing when an athlete is traveling at high speed, downhill, and attempts to make a turn. On the other hand, properly designed four-wheeled chairs have the advantage of greater stability, and therefore safety; this advantage is of tactical importance in road racing where it bestows on the athlete an ability to take corners at higher speeds. However, the author mentions that three-wheeled chairs also have a performance advantage in wet conditions and crosswind, as well as increased drafting performances.
Wheelchair design which minimizes energy losses contributes to successful athletic performances. The author suggests that, on the road, where speeds are higher and corners tighter, three-wheeled wheelchairs should be used only by those with skill and experience in controlling them. On the other hand, beginners would be well advised to start with a more stable four-wheeled design. Thus, the author points out that wheelchair design may have important implications for racing strategy and performance, and that wheelchair athletes should take these factors into account when selecting the wheelchair they will use.
Goosey, V. L., Fowler, N. E., & Campbell, I. G. (1997). A kinematic analysis of wheelchair propulsion techniques in senior male, senior female, and junior male athletes. Adapted Physical Activity Quarterly, 14, 156-165.
A number of studies have examined the propulsion techniques of wheelchair users. However, no research has compared the propulsion techniques of junior and senior athletes. Thus, the purpose of this study was to examine and compare the wheelchair propulsion techniques of senior male, senior female, and junior athletes, and to examine the relationship between kinematic variables and performance in an 800 m race.
Twenty-three wheelchair racers (classified as T3 and T4) participating in the 800 m finals at the British Wheelchair National Track Championships were filmed through a two-dimensional video (50 Hz) analysis. They were the 800 m event finalists from the senior male (n=8), ages 18 to 41, senior female (n=8), ages 18 to 33, and junior male (n=7), ages 15 to 17 years, categories. The kinematic variables (e.g., the angle of lean, elbow angle, and the cycle dynamics) found in each group of athletes were determined. A Pearson correlation coefficient was used to determine the relationship between the selected kinematic variables and 800 m performance time. Also, a one-way analysis of variance (ANOVA) was used to assess differences between groups, and a Tukey post hoc test (if significant F-ratios were found) was applied. An alpha level of .05 was used to determine statistical significance.
The results of this study showed that the senior male athletes were found to achieve faster 800 m performance times when compared to both the senior female and junior male athletes. The cycle velocity for the senior male athletes was found to be faster than that of either the senior female or junior male athletes, resulting in a greater distance covered during one push cycle. The results also showed differences in trunk movement between the groups. The junior athletes adopted an upright position 5° greater than the senior athletes, and spent less time in contact with the hand-rim. No differences in the maximum and minimum values of the elbow angle were found during the propulsion and recovery phase of the push cycle. A moderate correlation was found between the cycle distance and performance (r=-.68; p<.01). However, correlation coefficients between the elbow, angle of lean, the range of both these variables, and performance time were low (r<.40;n.s).
The authors note that the greater velocity achieved by the senior male athletes indicates that the senior athletes had a greater amount of time to apply force to the hand-rim. In addition, because junior athletes tended to retain a more upright posture in the chair, their propulsion technique may result in greater aerodynamic drag. In this study, there were no differences in the elbow angle during the propulsion and recovery phase of the push cycle, because all groups adopted a similar arm movement pattern. Therefore, it seems feasible that different amounts of effective force were applied to the hand-rim by the three groups of athletes. Future study might want to examine this possibility, as well as the effect of hand-rim size on all the above-mentioned aspects of performance.
Cooper, R. A., Stewart, K. J., & VanSickle, D. P. (1994). Evaluation of methods for determining rearward static stability of manual wheelchairs. Journal of Rehabilitation Research and Development, 31(2), 144-147.
Wheelchair standards have been under development for several years. Although a set of tests has been developed and approved by the American National Standards Institute (ANSI) and by the International Standards Organization (ISO), continuous refinement is needed. In particular, as static stability is one of the indicators used to evaluate manual wheelchairs, this study focuses on some needed improvements in the determination of rearward static stability, which is determined by placing a loaded wheelchair on a platform which is then tilted. The current test procedure using a block behind the rear wheels may yield different results than those from simply using the brakes alone. Thus, this study proposed a new method, using a belt. It was hypothesized that the belt and brake alone (without a block) would yield similar results, whereas using the block would yield different results.
The rearward static tip angle for each of eight manual wheelchairs was measured, using three load cases (55kg person with paraplegia, 100kg ambulatory person, and a 100kg ISO test dummy). Measurements were made with three different restraints: (a) the wheelchair brakes; (b) a flexible belt fixed to the rising edge of the platform, the other end of which was attached to the backrest of the wheelchair after being wrapped around the rear wheels; (c) a block behind the rear wheel. In all cases, the brakes were activated. Only backward tip angle was measured with the axle in the farthest rearward position in all cases. The static tip angle was measured using a machinist protractor and level and was determined as the point when a standard piece of paper could pass under the front wheels without turning them. During the tests, each test load was positioned as far as possible to the back of the seat, equidistant from either side. Results of statistical analysis [a three-factor analysis of variance (load device, chair type, and test condition), and Scheffe post-hoc test] were used in terms of significance (p<.05).
Significant differences were found among the three types of load device. The data for the 55kg person and the 100kg person were significantly different from that of the ISO dummy, with that for the dummy being the more conservative measurement. Also, there were significant differences found between test conditions. The rearward tip angle in both the test using the wheelchair brakes and the belts is significantly different from that using the brakes alone. However, no differences in rearward tip angle were found between chair types.
Wheelchair standards help manufacturers compare their products on a quantitative basis with other manufacturers’ products and establish minimum design criteria. Also, consumers benefit by being able to evaluate wheelchairs before making a purchase. The results indicate that there is no difference between the rearward static tip angle when measured using the wheelchair brakes or when using a flexible belt around the rear wheels, but a significant difference is seen when a block is used. Therefore, this study implies that, instead of the block method (which doubles and biases the rear static tip angle), the method of obtaining the standard for rear static tip angle should be changed to use the belt or flexible membrane method.
Hilbers, P. A., & White, T. P. (1987). Effects of wheelchair design on metabolic and heart rate responses during propulsion by persons with paraplegia. Physical Therapy, 67(9), 1355-1358.
In the last decade, the wheelchair industry has offered consumers several extensively engineered wheelchairs. Some new models have been developed and classified initially as "sports wheelchairs," with the unfortunate result that considerable documentation is required to substantiate the need for a sports wheelchair, especially in cases where third-party payers are providing assistance with purchase costs. The purpose of this study was to examine and compare the metabolic and heart rate responses of individuals with paraplegia to propulsion in a conventional wheelchair and in a sports wheelchair. It was hypothesized that there would be no difference between the two wheelchair designs in metabolic efficiency during propulsion.
Nine (8 men and 1 woman) wheelchair users with paraplegia, aged 26 to 38 years, participated in this study. All nine subjects were asymptomatic with respect to cardiovascular disease and impairment, and were devoid of upper extremity deformities. Each subject propelled both a conventional and a sports wheelchair on a level wooden surface (in an oval configuration of 220 m circumference), at four velocities ranging from 1 to 3 m/sec. During the first half of the oval course, a constant velocity was established. During the last 110 m of each trial, expired gas was collected for a certain interval of time (50-90 seconds), thus allowing determination of Oxygen consumption (Vo2), carbon dioxide production (Vco2), and respiratory exchange ratio (R). Also, immediate postexercise heart rate (HR) was measured by palpation. Furthermore, work rate for each trial was used in this study. For statistical analysis, linear regression analyses were performed between work rate and velocity, as well as between velocity and Vo2, Vco2, R, and HR for the both wheelchair designs.
The results revealed no difference between wheelchair designs in the relationship between velocity and work rate. However, the relationship of measured physiological variables (Vo2 and HR) to wheelchair velocity did show differences in efficiency of energy use in propulsion between the wheelchair designs. The energetic cost of propelling the sports wheelchair at any given submaximal velocity was 17% less than that of the conventional wheelchair. Furthermore, the immediate post-exercise HR measured after the sports wheelchair use was 24% less than that of the conventional chair.
This study makes an unique contribution in regard to the effects of wheelchair design on physiological adaptations to propulsion. From these results, the authors rejected the null hypothesis, and discovered the increased efficiency of the sports wheelchair relative to the conventional wheelchair. The authors explain that the greater efficiency of the sports chair can be attributed to design factors other than the smaller mass of the sports wheelchair. The sitting posture, cambered wheels, and narrow, highly inflated tires of the sports wheelchair may play important roles in increasing its efficiency. These finding might have the implication that, if nothing else, wheelchair designers at least incorporate elements of sports wheelchair design into the design of conventional wheelchairs as much as possible.
Higgs, C. (1990). Wheelchair racquetball: A preliminary time motion analysis. Adapted Physical Activity Quarterly, 7(4), 370-384.
Wheelchair racquetball is an innovation within a sport itself recently developed for able-bodied participants. It is played in the same court, with the same equipment (except of course the wheelchair), and with only minor modifications to the rules. The modifications are that the position of the wheelchair's wheels, rather than the player's feet, determine whether the player is in a legal position to serve or receive the ball, and a rally is ended when the ball touches the floor for the third, not the second time. The purpose of the study was to provide a preliminary description of the demands of the game of wheelchair racquetball at the developmental and elite levels of performance.
Wheelchair racquetball players in the A and B divisions (the A-level players being more proficient) of the 1989 Canadian Racquetball Championship were videotaped from a point beyond the rear of the court through the glass back wall. The following aspects of their performances were noted: (a) time at the start and end of each rally; (b) time at the start and end of each pause between rallies; (c) the number of forehand and backhand shots taken by each player during each rally; (d) the number and magnitude of changes in wheelchair direction during each minute of the games; and (e) the position on the court at which the receiver made, or attempted to make, contact with each serve. From the position and time data, distances covered and players' speed of movement were calculated.
The athletes had an exercise-to-pause ratio of 1:1.5 at the A level and 1:2.3 at the B level. Rallies were slightly longer at the higher level, with substantially longer pause periods at the B level. There was a higher percentage of longer rallies at the A level, although both divisions of play had a comparable percentage of forehand and backhand shots. A-level players demonstrated greater distances covered per rally, greater wheelchair speed, and a higher degree of wheelchair maneuverability, as measured by the number and magnitude of directional changes. In particular, A-level players showed a greater tendency to use small directional corrections, in particular, turns to the right of less than 45° .
The performances of wheelchair racquetball players were analyzed in this study. These results, therefore, provided a preliminary description of the demands of the game of wheelchair racquetball at the developmental and elite levels of performance. Future study needs to more specifically investigate time motion and perform further game analysis. Finally, this might have the implication of allowing wheelchair manufacturers and/or designers to recognize potential design related performance limitations, and by considering necessary and effective movements, to improve the motion time of wheelchair racquetball and perhaps other athletes as well.
Kirby, R. L., Sampson, M. T., Thoren, F. A. V., & MacLeod, D. A. (1995). Wheelchair stability: Effect of body position. Journal of Rehabilitation Research and Development, 32(4), 367-372.
General knowledge holds that when a wheelchair user reaches and leans, static stability decreases in the direction of the lean and increases in the opposite direction. However, there are no reports in the published literature that document the extent of this important effect. Therefore, the purpose of this study was to fill this gap by demonstrating how body position affects wheelchair stability
Because some wheelchair users (e.g., those with amputations or with heavily muscled upper bodies) have variations in their body composition that affect stability, twenty-one adults without disabilities (11 females and 10 males) participated in this study. Each participant used the same representative 15.9 kg wheelchair, and tightened the lap belt around his/her waist to a comfortably tolerable extent. Static stability was measured, according to the methods of the International Organization for Standardization (ISO), on a tilting platform. In a randomly balanced order, forward (i.e., the chair faced downhill and the casters trailed backward), rear (i.e., the chair faced uphill and the casters trailed backward), and lateral stability (i.e., the chair faced 90° to the direction of tilt, and the casters trailed uphill) positions were tested. Three stability values (neutral, forward, and away from the expected tip) were tested for each participant. Comparisons among the stability values for each of the four settings (forward, rear-locked, rear-unlocked, and lateral stability) were made by means of single-tailed matched-pairs t-tests (at a significant level of .05).
The results of this study showed that reaching forward had a greater effect on stability than did reaching back or to the side. Reaching and leaning away from the tip added stability, with mean increases ranging from 9.1% to 124.3 % of the neutral-position values, whereas reaching and leaning toward the tip reduced stability, with mean decreases ranging from 25.2 % to 52.3 %. The stability range (leaning away minus leaning toward), expressed as a percentage of the neutral-position values, varied from 52.4 % to 149.5 %. Also, rear stability was greater without brakes than with the brakes locked; the mean differences in the neutral, away, and toward positions were 8.4° , 16.9° , and 6.1° respectively.
From these results, the authors conclude that wheelchair users with the ability to control their body position can profoundly affect the stability of their wheelchairs, and reaching and leaning forward have the greatest effect on stability. The authors propose that this may have been due to the fact that reaching forward allows both arms to be used, whereas reaching behind or to the side allows only one arm to be used. This is an implicative factor that should be considered in wheelchair design and in the process of wheelchair selection and training.
Goosey, V. L., & Campbell, I. G. (1998). Pushing economy and propulsion technique of wheelchair racers at three speeds. Adapted Physical Activity Quarterly, 15(1), 36-50.
Pushing economy is defined as the energy cost (i.e., oxygen uptake) of wheelchair propulsion at a constant fixed speed. To lead to changes in the performance of wheelchair racers, some researchers have, recently, suggested the importance of making pushing economy more efficient. Therefore, the purpose of this study was (a) to describe kinematic patterns at a range of wheelchair propulsion speeds, (b) to examine pushing economy at a range of speeds, and (c) to determine relationships between wheelchair propulsion mechanics and pushing economy.
The participants consisted of 8 paraplegic wheelchair athletes (7 male and 1 female), from 22 to 38 years old, with body masses ranging from 56.7 to 79.3 kg. Each athlete was examined in an exercise that included speed increments of 6.0, 6.5 and 7.0 m/s at an incline of 0.7% on a motorized treadmill. During the test period all participants used their own racing chairs, but all wheelchairs were fitted with 0.70 m (diameter) spoked wheels, with the hand rim sizes varying from 0.37 to 0.39 m. Sagittal view kinematic data were collected by a video camera for two-dimensional analysis. Pushing economy (as measured by the collection of expired air) was determined at three speed levels. Results of statistical analysis, consisting of a one-way repeated analysis of variance and a Tukey post hoc test to identify kinematic changes across speeds, and Pearson correlations to determine the association between pushing economy and each kinematic variable at three speeds, were used in terms of significance (p<.05).
In respect to kinematic patterns across speeds, the results of this study showed that as propulsion speed increased from 6.0 to 7.0 m/s, there was: (a) a reduction in cycle time; (b) an increase in push rate; and (c) a greater flexion of the elbow. Further, at each speed there were large differences in pushing economy among the 8 participants. The relationship between pushing economy and selected kinematic variables revealed that pushing economy was significantly associated with body mass (r<.83), a greater range of elbow movement (r<-.63), and a lower push rate (r<.63) at each speed. However, the remaining variables (e.g., maximum elbow angle, angle of lean, and range of trunk motion) did not correlate significantly with pushing economy.
From these results, it can be concluded that adaptations to speed changes occur, initially by a decrease in cycle time and an increase in cycle rate, and later by an increase in the flexion of the elbow. Also, differences in propulsion technique appear to influence oxygen uptake. In terms of pushing economy, lighter athletes with a greater range of elbow movement and a lower push rate had the advantage. The variations in pushing economy were not accounted for by variation in the kinematic variables examined (elbow angle and angle of lean), but were partly explained differences in body mass. Furthermore, as the speed increased from 6.0 to 7.0 m/s, the relationships between pushing economy and the kinematic variables (push rate, minimum elbow angle, and elbow range) were reduced.
Therefore, the authors suggested that effects of lesion level and wheelchair design may be more important than differences in propulsion technique (i.e., kinematic variables) in explaining differences in pushing economy. This might have the implication of emphasizing the importance of allocating more time and effort to improved wheelchair design in order to improve the performance of wheelchair athletes.
Gehlsen, G. M., Davis, R. W., & Bahamonde, R. (1990). Intermittent velocity and wheelchair performance characteristics. Adapted Physical Activity Quarterly, 7(3), 219-230.
Mechanical inefficiency values in wheelchair propulsion may be attributed to the intermittent exertion characteristics of wheelchair propulsion. Thus, the purpose of this study was to describe the intermittent velocity variation of wheelchair propulsion, and to determine the relationship between selected wheelchair propulsive characteristics (i.e., hand and body positions) and peak velocity.
The subjects in this study consisted of 11 (10 male and 1 female) wheelchair track and field athletes who participated in the 1988 Paralympics. Four subjects were male quadriplegics; the remaining seven were paraplegics. Each subject’s personal racing chair was mounted on rollers so that the center of the wheel axis and the center of the roller axis were vertically placed over one other. The subjects were given 3 to 5 minutes to familiarize themselves with the roller propulsion. Data collection began at the subject’s convenience. Intermittent velocity was ascertained by a tach-generator. A stationary 16-mm camera was used to photograph the subject’s sagittal plane propulsive movements. A sonic digitizer was used to digitize three complete propulsive cycles for each subject.
Regarding hand-rim contact and release points relative to the velocity/time curve, the film data showed that the mean time from the point of contact to the start of acceleration was .06 seconds for the paraplegic subjects and .05 seconds for the quadriplegic subjects. Paraplegic and quadriplegic subjects’ stroke frequency mean values were 2.27 and 1.80 Hz, respectively. Examination of the relation between peak velocity and contact time indicated significant correlation (r =-.71, p<.05). Also, significant correlations were indicated between the computer-generated peak velocity values and the mean values for the angle of hand position relative to the hand-rim for the contact, start of acceleration, peak velocity, and release portions of the propulsive cycle. In addition, the results showed differences of joint motion range between paraplegic and quadriplegic subjects during the propulsive cycle. The paraplegic subjects never allowed the upper arm to move in front of the trunk. In contrast, the quadriplegic subjects moved the upper arm to a maximum of 10° in front of the trunk.
From these results, the variables most influencing peak velocity are the contact position of the hand relative to the hand-rim (hand-rim contact angle), and the trunk angle. It can be suggested that a lean of the trunk and a hand-rim contact angle of 30-40° forward of that reported elsewhere allows the athlete to apply maximum force further around the rim, and thereby enhance force application. Therefore, as pointed out in this study, trunk position and the hand-rim contact position are vital contributors to the speed of the competitive wheelchair athlete. Finally, paraplegic athletes are able to propel themselves and require less coordination of the trunk and upper extremities than their quadriplegic counterparts. This might remind wheelchair designers of the need to design wheelchairs which allow the most efficient hand-rim contact and trunk lean angles to be easily achieved.
Buckley, S. M., & Bhambhani, Y. N. (1998). The effects of wheelchair camber on physiological and perceptual responses in younger and older men. Adapted Physical Activity Quarterly, 15, 15-24.
Frank, T., & Abel, E. (1993). Drag forces in wheelchairs. In L. van der Woude, P. Meijs, B. van der Grunten, & Y. de Boer (Eds.), Ergonomics of manual wheelchair propulsion (pp. 255-267). Amsterdam: IOS Press.
Higgs, C. (1983). An analysis of racing wheelchairs used at the 1980 Olympic games for the disabled. Research Quarterly for Exercise and Sport, 54, 229-233.
Higgs, C. (1992). Racing wheelchairs: A comparison of three- and four-wheeled designs. Palaestra, 8(4), 28-36.
Higgs, C. (1995). Enhancing wheelchair sport performance. In J. P. Winnick (Ed.), Adapted physical education and sport (pp.421-433). Champaign, IL: Human Kinetics.
Kirby, R. L., Sampson, M. T., Thoren, F. A. V., & MacLeod, D. A. (1995). Wheelchair stability: Effect of body position. Journal of Rehabilitation Research and Development, 32(4), 367-372.
LaMere, T. J., & Labanowich, S. (1984). The history of sport wheelchairs- Part III: The racing wheelchair 1976-1983. Sports’n Spokes, 10(2), 12-16.
Redford, J. B. (1993). Seating and wheeled mobility in the disabled elderly population. Archives of Physical Medicine and Rehabilitation, 74, 877-885.
Traut, L. (1989). Gestaltung ergonoisch relevanter Konstruktionshparameter am Antriebssysteem des Greifreifenrollstuhls-Teil 1. Orthopedaedie Technik, 7, 394-398.
van der Woude, L., Veeger, H., Rozendal, R., van Ingen Schenau, G., Rooth, F., & van Nierop, P. (1988). Wheelchair racing: effects of rim diameter and speed on physiology and technique. Medicine and Science in Sports and Exercise, 20(5), 492-500.
Veeger, D., van der Woude, L., & Rozendal, R. (1989). The effect of rear wheel camber in manual wheelchair propulsion. Journal of Rehabilitation Research and Development, 26(2), 37-46.
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