Effectiveness of force application in manual wheelchair propulsion in persons with spinal cord injuries

Effect of handrim diameter on manual wheelchair propulsion: mechanical energy and power flow analysis

BACKGROUND

Wheelchair design parameters such as handrim diameter could affect propulsion. The purpose of this study was to examine the effect of handrim size (0.54, 0.43, and 0.32 m) on mechanical energy and power flow during wheelchair propulsion.

METHODS

Twelve young normal male adults (mean age 23.5 years old) were recruited in this study. Both 3-D kinematic and kinetic data of the upper extremity were collected synchronously using a Hi-Res Expert Vision motion system and an instrumented wheel during wheelchair propulsion.

FINDINGS

The kinetic, potential and total mechanical energy of the upper extremity increased as the handrim size increased. For each upper arm segment, the joint translational power and the rotational power of the proximal joint increased with increasing handrim size. The work done during a complete propulsion cycle with the larger handrim size is significantly larger than that using a smaller handrim (P<0.05).

INTERPRETATION

The increased kinetic, potential and total mechanical energy were due to the increased linear velocity and the elevated positions of the upper extremity segments. The shoulder and trunk flexors increased the magnitude of their concentric contractions during propulsion with the large handrim as increased output power is required. By using mechanical energy and power flow analysis techniques, we evaluated the previously-reported effect of handrim size on mechanical cost and provided insight into the relationship between the two.

Course of Gross Mechanical Efficiency in Handrim Wheelchair Propulsion During Rehabilitation of People With Spinal Cord Injury: A Prospective Cohort Study

OBJECTIVE

To investigate the course of mechanical efficiency of handrim wheelchair propulsion during rehabilitation of subjects with (in)complete paraplegia and tetraplegia.

DESIGN

Subjects were tested at the start of active rehabilitation (t1), 3 months later (t2), and when discharged from inpatient rehabilitation (t3). They performed two 3-minute submaximal treadmill exercise blocks in a wheelchair.

SETTING

Eight rehabilitation centers in the Netherlands.

PARTICIPANTS

Ninety-two people with (in)complete paraplegia and tetraplegia.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Mechanical efficiency values were calculated for each block. The course of mechanical efficiency was investigated using test occasions (t1 -t3), completeness and level (paraplegia or tetraplegia) of the lesion, and power output as independent variables in a multilevel regression analysis.

RESULTS

Mechanical efficiency significantly increased between t1 and t2 only. After adding level and completeness of the lesion and their interactions with time to the model, block 2 showed that subjects with paraplegia had a significantly higher mechanical efficiency than subjects with tetraplegia. Subjects with tetraplegia improved more between t1 and t2 . Differences in mechanical efficiency between subjects with paraplegia and tetraplegia could not be explained by differences in absolute and relative power output levels.

CONCLUSIONS

Results showed a significant improvement in mechanical efficiency during the first 3 months of active rehabilitation. Subjects with paraplegia showed a higher mechanical efficiency than did subjects with tetraplegia, whereas the latter showed more improvement between t1 and t2 .

The intra-push velocity profile of the over-ground racing wheelchair sprint start

The aim of this study was to analyse the first six pushes of a sprint start in over-ground racing wheelchair propulsion. One international male wheelchair athlete (age=28 years; body mass=60.6 kg; racing classification=T4) performed maximal over-ground sprint trials, over approximately 10 m, in his own racing wheelchair fitted with a velocometer. Each trial was filmed at 200 Hz using a "Pan and Tilt" system. Eight trials were manually digitised at 100 Hz. Raw co-ordinate data were smoothed and differentiated using a quintic spline routine. Across the period from pushes one to six the duration of each push cycle decreased (0.82+/-0.02-0.45+/-0.01 s) with the mean duration of the propulsive phase decreasing from 0.62+/-0.02 to 0.21+/-0.01 s and the recovery phase increasing from 0.20+/-0.01 to 0.24+/-0.02 s. The push-rim was contacted progressively closer to top dead centre and released progressively closer to bottom dead centre with each push. The data indicate that peak velocity occurred after release. The main findings of this study support the observation that racing wheelchair sprint propulsion is a complex form of locomotion and cannot be described accurately by using just the established definitions of a propulsive and a recovery phase.

Effects of spinal cord injury level on the activity of shoulder muscles during wheelchair propulsion: an electromyographic study11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To determine the influence of spinal cord injury (SCI) level on shoulder muscle function during wheelchair propulsion.

DESIGN

Fine-wire electromyographic activity of 11 muscles was recorded during wheelchair propulsion.

SETTING

Biomechanics research laboratory.

PARTICIPANTS

Convenience sample of 69 men, in 4 groups by SCI level (low paraplegia, n=17; high paraplegia, n=19; C7-8 tetraplegia, n=16; C6 tetraplegia, n=17).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Timing of muscle activity onset, cessation, and duration, and time of peak intensity for each functional group were compared with 1-way analysis of variance. Median electromyographic intensity was also compared.

RESULTS

Two functional synergies were observed: push (anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, biceps) and recovery (middle and posterior deltoid, supraspinatus, subscapularis, middle trapezius, triceps). Push phase activity began in late recovery and ceased in early to late push. Recovery phase muscles functioned from late push to late recovery. Recruitment patterns for the groups with paraplegia were remarkably similar. For subjects with tetraplegia, pectoralis major activity was significantly prolonged compared with subjects with paraplegia (P<.05). Subscapularis activity shifted from a recovery pattern in subjects with paraplegia to a push pattern in persons with tetraplegia.

CONCLUSIONS

Level of SCI significantly affected the shoulder muscle recruitment patterns during wheelchair propulsion. Differences in rotator cuff and pectoralis major function require specific considerations in rehabilitation program design.

Submaximal physical strain and peak performance in handcycling versus handrim wheelchair propulsion

STUDY DESIGN

Experimental study in subjects with paraplegia and nondisabled subjects.

OBJECTIVE

To compare submaximal physical strain and peak performance in handcycling and handrim wheelchair propulsion in wheelchair-dependent and nondisabled control subjects

SETTING

Amsterdam, The Netherlands.

METHODS

Nine male subjects with paraplegia and 10 nondisabled male subjects performed two exercise tests on a motor-driven treadmill using a handrim wheelchair and attach-unit handcycle system. The exercise protocol consisted of two 4-min submaximal exercise bouts at 25 and 35 W, followed by 1-min exercise bouts with increasing power output until exhaustion.

RESULTS

Analysis of variance for repeated measures showed a significantly lower oxygen uptake (VO2), ventilation (Ve), heart rate (HR), rate of perceived exertion and a higher gross efficiency for handcycling at 35 W in both subject groups, while no significant differences were found at 25 W. Peak power output and peak VO2, Ve and HR were significantly higher during handcycling in both groups. The differences between handcycling and wheelchair propulsion were the same in subjects with paraplegia and the nondisabled subjects.

CONCLUSIONS

Handcycling induces significantly less strain at a moderate submaximal level of 35 W, and shows noticeably higher maximal exercise responses than wheelchair propulsion, which is consistent in subjects with paraplegia and nondisabled controls. These results demonstrate that handcycling is beneficial for mobility in daily life of wheelchair users.

Hand rim configuration: effects on physical strain and technique in unimpaired subjects?

OBJECTIVE

Hand rim wheelchair propulsion is inefficient and physically straining. To evaluate the possibly advantageous role in this respect of three different prototype hand rim configurations (a rubber foam-coated cylindrical (II) hand rim and two profiled rubber foam-coated hand rims (wide and narrow: III, IV)), a group of 10 unimpaired subjects conducted four submaximal discontinuous wheelchair exercise tests on a computer-controlled wheelchair ergometer, thus allowing a comparison with a standard hand rim (chromium-plated round hand rim (I)).

METHODS

Apart from physiological measures (oxygen uptake, heart rate (HR), ventilation, mechanical efficiency (ME)), a subjective score for the rating of each of the hand rims was determined, as well as characteristics of the force application in the propulsion phase during each test condition. Timing parameters of the push and recovery phase were determined. Each exercise test was conducted with one of the four hand rim configurations in a counter-balanced order.

RESULTS

Analysis of variance with repeated measures (hand rim configuration, power output) revealed no significant effects (P>0.05) on any of the physiological parameters and force application characteristics for the main factor 'hand rim configuration'. Only the subjective score (scale 0-10) for rating of the hand rims proved significantly different between the round rubber (7.5+/-0.53) coated hand rim-receiving the highest score-versus the narrow rubber-coated flat profiled hand rim (5.5+/-1.72).

DISCUSSION

In this subject group and under the selected tasks and submaximal conditions of wheelchair propulsion, the studied hand rim configurations did not introduce critical shifts in the technique of (de-)coupling and power production in the push phase. As a consequence, no systematic shifts in ME are found among the different hand rim configurations. It is suggested that the biological constraints of the task overrule the possible effects of small design variations of the different hand rim configurations within the studied subject group and under the limited test conditions. The hand rim design characteristics may however be much more critical in (1) experienced wheelchair users, (2) especially those subjects with a limited hand-arm and/or trunk function and/or (3) under much more extreme conditions of daily wheelchair ambulation (i.e. turning, stopping/starting, negotiating a slope) or during peak performance. These issues clearly require continued future research. As such, the current results can be viewed as preliminary results only.

The push force pattern in manual wheelchair propulsion as a balance between cost and effect

We investigate the hypothesis that the direction of the propulsion force in manual wheelchair propulsion can be interpreted as a result of the balance between the mechanical task requirements and the driver's biomechanical possibilities. We quantify the balance at the joint level in the form of an effect-cost criterion, from which we predict the force direction that results in an optimal compromise. Kinematic and dynamic data were collected from nine habitual wheelchair users driving at four velocities (0.83, 1.11, 1.39, 1.67 m/s) and three external power levels (10, 20, 30 W). Experimental data and predictions are in good agreement in the middle and final part of the push; the effect-cost value in this region approximates the achievable maximum. Early in the push the effect-cost criterion predicts an upwards propulsion force whereas the experimental force is downwards, the difference probably being mainly attributable to the force generation dynamics of the muscles. As a result of the geometric features of large-rim manual wheelchairs, the mechanically required and biomechanically preferred force directions are not in accordance during a substantial part of the push, making even the best compromise a poor one. This may contribute to the low mechanical efficiency of manual wheelchair propulsion and the high incidence of shoulder complaints.

Wheelchair propulsion technique and mechanical efficiency after 3 wk of practice

PURPOSE

Differences in gross mechanical efficiency between experienced and inexperienced wheelchair users may be brought about by differences in propulsion technique. The purpose of this experiment was to study changes in propulsion technique (defined by force application, left-right symmetry, intercycle variability, and timing) and gross mechanical efficiency during a 3-wk wheelchair practice period in a group of novice able-bodied nonwheelchair users.

METHODS

Subjects were randomly divided over an experimental group (N = 10) and a control group (N = 10). The experimental group received a 3-wk wheelchair practice period (3.wk-1, i.e., 9 practice trials) on a computer-controlled wheelchair ergometer, whereas the control group only participated in trials 1 and 9. During all nine practice trials, propulsion technique variables and mechanical efficiency were measured.

RESULTS

No significant differences between the groups were found for force application, left-right symmetry, and intercycle variability. The push frequency and negative power deflection at the start of the push phase diminished significantly in the experimental group in contrast to the control group (P < 0.05). Work per cycle, push time, cycle time, and mechanical efficiency increased.

CONCLUSION

The practice period had a favorable effect on some technique variables and mechanical efficiency, which may indicate a positive effect of improved technique on mechanical efficiency. Although muscle activation and kinematic segment characteristics were not measured in the present study, they may also impact mechanical efficiency. No changes occurred over time in most force application parameters, left-right symmetry, and intercycle variability during the 3-wk practice period; however, these variables may change on another time scale.

Consequence of feedback-based learning of an effective hand rim wheelchair force production on mechanical efficiency

OBJECTIVE

Investigation of the effect of visual feedback on effective hand rim wheelchair force production and the subsequent effect on gross mechanical efficiency.

DESIGN

Ten subjects in an experimental group and 10 subjects in a control group practised three weeks (3.wk(-1), i.e., a pre-test and 8 trials) on a computer-controlled wheelchair ergometer. Every trial consisted of two blocks of 4 min at 0.15 and 0.25 W.kg(-1) at 1.11 m.s(-1). On three trials an additional block at 0.40 W.kg(-1) was performed. The experimental group practised with and the control group practised without visual feedback on the effectiveness of force production.

BACKGROUND

In mechanical terms, the low gross mechanical efficiency of hand rim wheelchair propulsion may be the result of ineffective force production.

METHODS

During all trials oxygen uptake, power output, forces and torque on the hand rims were measured.

RESULTS

In comparison with the control group, the experimental group at trial 8 had a significantly more effective force production compared to the control group (90-97% vs. 79-83%, respectively), but showed a significantly lower mechanical efficiency (5.5-8.5% vs. 5.9-9.9%, respectively).

CONCLUSION

Findings indicate that the most effective force production from a mechanical point of view is not necessarily the most efficient way--in terms of energy cost-- from a biological point of view and that force direction is based on an optimization of cost and effect.

RELEVANCE

Learning a more effective force production by visual feedback is not useful for increasing the mechanical efficiency of hand rim wheelchair propulsion.

Biomechanics of manual wheelchair propulsion in elderly: system tilt and back recline angles

OBJECTIVE

To investigate the effects of the system tilt and back recline angles on the biomechanics of wheelchair propulsion for a group of older, disabled patients. It was hypothesized that increasing both the system tilt and backrest recline angles would have a positive effect on the biomechanical efficiency of manual wheelchair propulsion.

DESIGN

Three kinetic variables were estimated during a 10-m, steady-state propulsion between 0.96 m/sec and 1.01 m/sec. The fraction of the mechanical effective force is defined by the ratio between the tangential and the total force applied to the pushrim: It expresses the directionality of force application. The mechanical use is defined as the ratio between the total force generated during wheelchair propulsion and that generated during maximal isometric contraction. The biomechanical efficiency is defined as the product of mechanical effective force and the mechanical use.

RESULTS

On average, the fraction of the mechanical effective force was found to be low when compared with other studies. Tilting the system by 10 degrees and reclining the back by 10 degrees increase significantly the biomechanical efficiency of the subject by 10%. The biomechanical efficiency variable was more sensitive to the system tilt than to the back recline adjustment.

CONCLUSIONS

The results of this study confirm the hypothesis that system tilt angle but not back recline significantly affects biomechanical efficiency. The findings of this study will help in designing and adjusting a wheelchair intended for self-propelled, older people.

Mechanical efficiency and user power requirement with a pushrim activated power assisted wheelchair

The objective of this study was to quantify the difference in mechanical efficiency and user power generation between traditional manual wheelchairs and a pushrim activated power assisted wheelchair (PAPAW). Ten manual wheelchair users were evaluated in a repeated measures design trial with and without the PAPAW for propulsion efficiency. Subjects propelled a Quickie GP equipped with the PAPAW and their own chair on a computer controlled wheelchair dynamometer at five different resistance levels. Power output, user power with the PAPAW hubs, subjects' oxygen consumption per minute and mechanical efficiency were analyzed. Metabolic energy and user power were significantly lower (p<0.05), and mechanical efficiency significantly higher with the PAPAW than with subjects' own chairs. Subjects needed to generate on average 3.65 times more power when propelling their own wheelchairs as compared to PAPAW. Mean mechanical efficiency over all trials was 80.33% higher with the power assisted hubs. PAPAW provides on average 73% of the total power when subjects propel with power assistance. Significantly increased efficiency and reduced requirement of user power is achieved using the PAPAW. With use, the PAPAW may contribute to delaying secondary injuries of manual wheelchair users. In addition, it may be suitable for people who have (or at risk for) upper extremity joint degeneration, reduced exercise capacity, low strength or endurance who currently use electric powered wheelchairs.

Biomechanics and physiology in active manual wheelchair propulsion

Manual wheelchair propulsion in daily life and sports is increasingly being studied. Initially, an engineering and physiological perspective was taken. More recently a concomitant biomechanics interest is seen. Themes of biomechanical and physiological studies today are performance enhancing aspects of wheelchair use and the ergonomics of wheelchair design. Apart from the propulsion technique the focus of biomechanics research of manual wheelchair propulsion is mainly towards injury mechanisms, especially phenomena of overuse to the upper extremity. Obviously, the vehicle mechanics of wheelchairs must be included within this biological framework. Scientific research is progressing, but is still hampered by methodological limitations, such as the heterogeneity and small numbers of the population at study as well as the inconsistency of employed technologies and methodologies. There is a need for consensus regarding methodology and research strategy, and a strong need for collaboration to improve the homogeneity and size of subject groups and thus the power of the experimental results. Thus a sufficiently strong knowledge database will emerge, leading to an evidence-base of performance enhancing factors and the understanding of the risks of wheelchair sports and long-term wheelchair use. In the light of the current biomechanical and physiological knowledge of manual wheelchair propulsion there seems to be a need for the stimulation of other than hand rim propelled manual wheelchairs.

The effect of level of spinal cord injury on shoulder joint kinetics during manual wheelchair propulsion

OBJECTIVE

The effects of spinal cord injury level on shoulder kinetics during manual wheelchair propulsion were studied.

DESIGN

Single session data collection in a laboratory environment.

METHODS

Male subjects were divided into four groups: low level paraplegia (n=17), high level paraplegia (n=19), C7 tetraplegia (C7, n=16) and C6 tetraplegia (C6, n=17). Measurements were recorded using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and wheelchair ergometer. Shoulder joint forces and moments were calculated using the inverse dynamics approach.

RESULTS

Mean self-selected propulsion velocity was higher in the paraplegic (low paraplegia=90.7 m/min; high paraplegia=83.4 m/min) than tetraplegic (C7=66.5 m/min; C6=47.0 m/min) groups. After covarying for velocity, no significant differences in shoulder joint moments were identified. However, superior push force in subjects with tetraplegia (C7=21.4 N; C6=9.3 N) was significantly higher than in those with high paraplegia (7.3 N), after covarying velocity.

CONCLUSIONS

The superior push force in the tetraplegic groups coupled with weakness of thoraco-humeral depressors increases susceptibility of the subacromial structures to compression.

RELEVANCE

Increased vertical force at the shoulder joint, coupled with reduced shoulder depressor strength, may contribute to shoulder problems in subjects with tetraplegia. Wheelchair design modifications, combined with strength and endurance retention, should be considered to prevent shoulder pain development.

Wheelchair propulsion biomechanics: implications for wheelchair sports

The aim of this article is to provide the reader with a state-of-the-art review on biomechanics in hand rim wheelchair propulsion, with special attention to sport-specific implications. Biomechanical studies in wheelchair sports mainly aim at optimising sport performance or preventing sport injuries. The sports performance optimisation question has been approached from an ergonomic, as well as a skill proficiency perspective. Sports medical issues have been addressed in wheelchair sports mainly because of the extremely high prevalence of repetitive strain injuries such as shoulder impingement and carpal tunnel syndrome. Sports performance as well as sports medical reflections are made throughout the review. Insight in the underlying musculoskeletal mechanisms of hand rim wheelchair propulsion has been achieved through a combination of experimental data collection under realistic conditions, with a more fundamental mathematical modelling approach. Through a synchronised analysis of the movement pattern, force generation pattern and muscular activity pattern, insight has been gained in the hand rim wheelchair propulsion dynamics of people with a disability, varying in level of physical activity and functional potential. The limiting environment of a laboratory, however, has hampered the drawing of sound conclusions. Through mathematical modelling, simulation and optimisation (minimising injury and maximising performance), insight in the underlying musculoskeletal mechanisms during wheelchair propulsion is sought. The surplus value of inverse and forward dynamic simulation of hand rim stroke dynamics is addressed. Implications for hand rim wheelchair sports are discussed. Wheelchair racing, basketball and rugby were chosen because of the significance and differences in sport-specific movement dynamics. Conclusions can easily be transferred to other wheelchair sports where movement dynamics are fundamental.

The effect of handgrip position on upper extremity neuromuscular responses to arm cranking exercise

The purpose of this study was to determine if handgrip position during arm cranking exercise influences the neuromuscular activity of muscles biceps brachii (BB), lateral head of triceps brachii (TB), middle deltoid (DT), infraspinatus (IS) and brachioradialis (BR). Fifteen participants cranked an arm ergometer using three different handgrip positions (supinated, pronated, and neutral). Electromyographic (EMG) data were recorded from the aforementioned muscles, and relative duration of EMG activation and amplitude were quantified for the first and second 180 degrees of crank angle. EMG measures were analyzed with MANOVA and follow-up univariate procedures; alpha was set at 0.01. The relative durations of EMG activation did not differ between handgrip positions. Muscle IS exhibited 36% less amplitude in the supinated versus neutral handgrip position (second half-cycle), and muscle BR displayed 63% greater amplitude across cycles in the neutral versus supinated and pronated handgrip positions. The greater BR activity displayed in the neutral handgrip position may reflect its anatomical advantage as an elbow flexor when the forearm is in neutral position. Muscle IS exhibited less activity in the supinated position and may be clinically relevant if it allows arm cranking to occur without subsequent shoulder pain, which is often the aim of shoulder rehabilitation.

A kinetic analysis of trained wheelchair racers during two speeds of propulsion

The purpose of the study was to investigate the propulsion kinetics of wheelchair racers at racing speeds and to assess how these change with an increase in speed. It was hypothesised that propulsive force would increase in proportion to speed, to accommodate the additional work required. Six wheelchair racers volunteered to participate in this study which required each athlete to push a racing wheelchair at 4.70 and 5.64 m s(-1) on a wheelchair ergometer (WERG). Eight pairs (16 in total) of strain gauges, mounted on four bars attached to the hand-rim of a racing wheelchair wheel, measured the medio-lateral and tangential forces applied to the hand-rim. Kinetic data were sampled at 200 Hz while a single on-line (ELITE) infrared camera operating at 100 Hz was positioned perpendicular to the WERG to record the location of the hand with respect to the hand-rim. In general, peak tangential force occurred when the hand was positioned on the hand-rim between 140 and 180 degrees. With the increase in speed, the peak hand-rim forces applied tangentially increased from 132 to 158 N and those applied medio-laterally increased from 90 to 104 N. The ratio of tangential to total measured force was similar at both speeds (80 and 82%, respectively). In conclusion, these data indicate that wheelchair racers adopt a different propulsion strategy than that employed in everyday chairs and that the forces increase in proportion to propulsion speed.